8-bit AVR Microcontroller
ATtiny1614 / ATtiny1616 / ATtiny1617
Introduction
®
The ATtiny1614/1616/1617 is a member of the tinyAVR 1-series of microcontrollers, using the 8-bit AVR
processor with hardware multiplier, running at up to 20MHz and with 16KB Flash, 2KB of SRAM and
256B of EEPROM in a 14-, 20- and 24-pin package. The tinyAVR 1-series uses the latest technologies
with a flexible and low power architecture including Event System and SleepWalking, accurate analog
features and advanced peripherals. Capacitive touch interfaces with proximity sensing and driven shield
®
are supported with the integrated QTouch peripheral touch controller.
Features
•
•
•
CPU
®
– AVR 8-bit CPU
– Running at up to 20MHz
– Single cycle I/O access
– Two-level interrupt controller
– Two-cycle hardware multiplier
Memories
– 16KB In-system self-programmable Flash memory
– 256B EEPROM
– 2KB SRAM
System
– Power-on Reset (POR)
– Brown-out Detection (BOD)
– Internal and external clock options:
• 16/20MHz low power RC oscillator
• 32.768kHz Ultra Low Power (ULP) internal RC oscillator with ±10% accuracy, ±2%
calibration step size
• 32.768kHz external crystal oscillator
• External clock input
– Single pin programming and debugging interface (UPDI)
– Three sleep modes:
• Idle with all peripherals running for immediate wake up
• Standby
– Configurable operation of selected peripherals
– SleepWalking peripherals
• Power Down with limited wake-up functionality
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 1
8-bit AVR Microcontroller
•
•
•
•
Peripherals
– One 16-bit Timer/Counter type A with dedicated period register, 3 compare channels (TCA)
– Two 16-bit Timer/Counter type B with input capture (TCB)
– One 12-bit Timer/Counter type D optimized for control applications (TCD)
– 16-bit Real Time Counter (RTC) running from external crystal or internal RC oscillator
– One USART with fractional baud rate generator, autobaud, and start-of-frame detection
– Master/slave Serial Peripheral Interface (SPI)
– Master/slave I2C with dual address match
• Standard mode (Sm, 100kHz)
• Fast mode (Fm, 400kHz)
• Fast mode plus (Fm+, 1MHz)
– Configurable Custom Logic (CCL) with two programmable Lookup Tables (LUT)
– Three Analog Comparators (AC) with low propagation delay
– Two 10-bit 115ksps Analog to Digital Converters (ADC)
– Three 8-bit Digital to Analog Converters (DAC) with one external channel
– Five selectable internal voltage references: 0.55V, 1.1V, 1.5V, 2.5V and 4.3V
– Automated CRC memory scan
– Window Watchdog Timer (WDT) with separate on-chip oscillator
– Peripheral Touch Controller (PTC)
• Capacitive touch buttons, sliders and wheels
• Wake-up on touch
• Driven shield for improved moisture and noise handling performance
• Up to 14 self-capacitance and up to 49 mutual capacitance channels
– External interrupt on all general purpose pins
I/O and Packages:
– 12 to 22 programmable I/O lines
– 14-pin SOIC150
– 20-pin QFN 3x3 and SOIC300
– 24-pin QFN 4x4
Temperature Ranges:
– -40°C to 105°C
– -40°C to 125°C Temperature Device Options available
Speed Grades:
– 0-5MHz @ 1.8V – 5.5V
– 0-10MHz @ 2.7V – 5.5V
– 0-20MHz @ 4.5V – 5.5V
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 2
Table of Contents
Introduction......................................................................................................................1
Features.......................................................................................................................... 1
1. tinyAVR 1-Series Overview......................................................................................10
1.1.
Configuration Summary..............................................................................................................11
2. Ordering Information................................................................................................12
2.1.
ATtiny161x..................................................................................................................................12
3. Block Diagram......................................................................................................... 13
4. Pinout...................................................................................................................... 14
4.1.
4.2.
4.3.
4.4.
14-pin SOIC................................................................................................................................14
20-pin SOIC................................................................................................................................15
20-pin QFN.................................................................................................................................16
24-pin QFN.................................................................................................................................17
5. I/O Multiplexing and Considerations........................................................................18
5.1.
Multiplexed Signals.................................................................................................................... 18
6. Memories.................................................................................................................20
6.1.
6.2.
6.3.
6.4.
6.5.
6.6.
6.7.
6.8.
Overview.................................................................................................................................... 20
Memory Map.............................................................................................................................. 21
In-System Reprogrammable Flash Program Memory................................................................21
SRAM Data Memory.................................................................................................................. 21
EEPROM Data Memory............................................................................................................. 22
User Row....................................................................................................................................22
I/O Memory.................................................................................................................................22
FUSES - Configuration and User Fuses.................................................................................... 22
7. Peripherals and Architecture................................................................................... 33
7.1.
7.2.
Peripheral Module Address Map................................................................................................ 33
Interrupt Vector Mapping............................................................................................................ 34
8. AVR CPU................................................................................................................. 36
8.1.
8.2.
8.3.
8.4.
8.5.
8.6.
8.7.
Features..................................................................................................................................... 36
Overview.................................................................................................................................... 36
Architecture................................................................................................................................ 36
ALU - Arithmetic Logic Unit........................................................................................................ 38
Functional Description................................................................................................................39
Register Summary - CPU...........................................................................................................44
Register Description................................................................................................................... 44
9. NVMCTRL - Non Volatile Memory Controller.......................................................... 47
9.1.
Features..................................................................................................................................... 47
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Datasheet Preliminary
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8-bit AVR Microcontroller
9.2.
9.3.
9.4.
9.5.
Overview.................................................................................................................................... 47
Functional Description................................................................................................................48
Register Summary - NVMCTRL................................................................................................. 54
Register Description................................................................................................................... 54
10. CLKCTRL - Clock Controller................................................................................... 58
10.1.
10.2.
10.3.
10.4.
10.5.
Features..................................................................................................................................... 58
Overview.................................................................................................................................... 58
Functional Description................................................................................................................60
Register Summary - CLKCTRL.................................................................................................. 66
Register Description................................................................................................................... 66
11. SLPCTRL - Sleep Controller................................................................................... 73
11.1.
11.2.
11.3.
11.4.
11.5.
Features..................................................................................................................................... 73
Overview.................................................................................................................................... 73
Functional Description................................................................................................................74
Register Summary - SLPCTRL.................................................................................................. 77
Register Description................................................................................................................... 77
12. RSTCTRL - Reset Controller...................................................................................78
12.1.
12.2.
12.3.
12.4.
12.5.
Features..................................................................................................................................... 78
Overview.................................................................................................................................... 78
Functional Description................................................................................................................79
Register Summary - RSTCTRL..................................................................................................81
Register Description................................................................................................................... 81
13. CPUINT - CPU Interrupt Controller......................................................................... 83
13.1.
13.2.
13.3.
13.4.
13.5.
Features..................................................................................................................................... 83
Overview.................................................................................................................................... 83
Functional Description................................................................................................................85
Register Summary - CPUINT..................................................................................................... 91
Register Description................................................................................................................... 91
14. EVSYS - Event System........................................................................................... 94
14.1.
14.2.
14.3.
14.4.
14.5.
Features..................................................................................................................................... 94
Overview.................................................................................................................................... 94
Functional Description................................................................................................................97
Register Summary - EVSYS...................................................................................................... 99
Register Description................................................................................................................... 99
15. PORTMUX - Port Multiplexer................................................................................ 107
15.1. Overview.................................................................................................................................. 107
15.2. Register Summary - PORTMUX.............................................................................................. 108
15.3. Register Description................................................................................................................. 108
16. PORT - I/O Pin Configuration.................................................................................111
16.1. Features....................................................................................................................................111
16.2. Overview...................................................................................................................................111
16.3. Functional Description.............................................................................................................. 113
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8-bit AVR Microcontroller
16.4.
16.5.
16.6.
16.7.
Register Summary - PORT.......................................................................................................117
Register Description - Ports......................................................................................................117
Register Summary - VPORT.................................................................................................... 123
Register Description - Virtual Ports.......................................................................................... 123
17. BOD - Brownout Detector......................................................................................125
17.1.
17.2.
17.3.
17.4.
17.5.
Features................................................................................................................................... 125
Overview.................................................................................................................................. 125
Functional Description..............................................................................................................127
Register Summary - BOD.........................................................................................................129
Register Description................................................................................................................. 129
18. VREF - Voltage Reference.................................................................................... 133
18.1.
18.2.
18.3.
18.4.
18.5.
Features................................................................................................................................... 133
Overview.................................................................................................................................. 133
Functional Description..............................................................................................................133
Register Summary - VREF.......................................................................................................135
Register Description................................................................................................................. 135
19. WDT - Watchdog Timer......................................................................................... 138
19.1.
19.2.
19.3.
19.4.
19.5.
Features................................................................................................................................... 138
Overview.................................................................................................................................. 138
Functional Description..............................................................................................................140
Register Summary - WDT........................................................................................................ 144
Register Description................................................................................................................. 144
20. TCA - 16-bit Timer/Counter Type A....................................................................... 146
20.1.
20.2.
20.3.
20.4.
20.5.
20.6.
20.7.
Features................................................................................................................................... 146
Overview.................................................................................................................................. 146
Functional Description..............................................................................................................150
Register Summary - TCA in Normal Mode (CTRLD.SPLITM=0)............................................. 160
Register Description - Normal Mode........................................................................................ 161
Register Summary - TCA in Split Mode (CTRLD.SPLITM=1).................................................. 173
Register Description - Split Mode.............................................................................................173
21. TCB - 16-bit Timer/Counter Type B....................................................................... 182
21.1.
21.2.
21.3.
21.4.
21.5.
Features................................................................................................................................... 182
Overview.................................................................................................................................. 182
Functional Description..............................................................................................................184
Register Summary - TCB......................................................................................................... 193
Register Description................................................................................................................. 193
22. TCD - 12-bit Timer/Counter Type D.......................................................................200
22.1.
22.2.
22.3.
22.4.
22.5.
Features................................................................................................................................... 200
Overview.................................................................................................................................. 200
Functional Description..............................................................................................................204
Register Summary - TCD......................................................................................................... 226
Register Description................................................................................................................. 227
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 5
8-bit AVR Microcontroller
23. RTC - Real Time Counter...................................................................................... 239
23.1. Features................................................................................................................................... 239
23.2. Overview.................................................................................................................................. 239
23.3. RTC Functional Description..................................................................................................... 241
23.4. PIT Functional Description....................................................................................................... 242
23.5. Events...................................................................................................................................... 243
23.6. Interrupts.................................................................................................................................. 243
23.7. Sleep Mode Operation............................................................................................................. 244
23.8. Synchronization........................................................................................................................244
23.9. Configuration Change Protection............................................................................................. 244
23.10. Register Summary - RTC.........................................................................................................245
23.11. Register Description................................................................................................................. 245
24. USART - Universal Synchronous and Asynchronous Receiver and Transmitter.. 254
24.1.
24.2.
24.3.
24.4.
24.5.
Features................................................................................................................................... 254
Overview.................................................................................................................................. 254
Functional Description..............................................................................................................258
Register Summary - USART.................................................................................................... 272
Register Description................................................................................................................. 272
25. SPI - Serial Peripheral Interface............................................................................ 283
25.1.
25.2.
25.3.
25.4.
25.5.
Features................................................................................................................................... 283
Overview.................................................................................................................................. 283
Functional Description..............................................................................................................285
Register Summary - SPI...........................................................................................................290
Register Description................................................................................................................. 290
26. TWI - Two Wire Interface.......................................................................................295
26.1.
26.2.
26.3.
26.4.
26.5.
Features................................................................................................................................... 295
Overview.................................................................................................................................. 295
Functional Description..............................................................................................................297
Register Summary - TWI..........................................................................................................310
Register Description................................................................................................................. 310
27. CRCSCAN - Cyclic Redundancy Check Memory Scan........................................ 324
27.1.
27.2.
27.3.
27.4.
27.5.
Features................................................................................................................................... 324
Overview.................................................................................................................................. 324
Functional Description..............................................................................................................326
Register Summary - CRCSCAN...............................................................................................329
Register Description................................................................................................................. 329
28. CCL – Configurable Custom Logic........................................................................ 332
28.1.
28.2.
28.3.
28.4.
28.5.
Features................................................................................................................................... 332
Overview.................................................................................................................................. 332
Functional Description..............................................................................................................334
Register Summary - CCL......................................................................................................... 343
Register Description................................................................................................................. 343
29. AC – Analog Comparator...................................................................................... 348
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Datasheet Preliminary
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8-bit AVR Microcontroller
29.1.
29.2.
29.3.
29.4.
29.5.
Features................................................................................................................................... 348
Overview.................................................................................................................................. 348
Functional Description..............................................................................................................350
Register Summary - AC........................................................................................................... 353
Register Description................................................................................................................. 353
30. ADC - Analog to Digital Converter.........................................................................356
30.1.
30.2.
30.3.
30.4.
30.5.
Features................................................................................................................................... 356
Overview.................................................................................................................................. 356
Functional Description..............................................................................................................360
Register Summary - ADC.........................................................................................................368
Register Description................................................................................................................. 368
31. DAC - Digital to Analog Converter.........................................................................378
31.1.
31.2.
31.3.
31.4.
31.5.
Features................................................................................................................................... 378
Overview.................................................................................................................................. 378
Functional Description..............................................................................................................380
Register Summary - DAC.........................................................................................................382
Register Description................................................................................................................. 382
32. PTC - Peripheral Touch Controller.........................................................................383
32.1.
32.2.
32.3.
32.4.
32.5.
32.6.
Overview.................................................................................................................................. 383
Features................................................................................................................................... 383
Block Diagram.......................................................................................................................... 384
Signal Description.................................................................................................................... 384
System Dependencies............................................................................................................. 385
Functional Description..............................................................................................................386
33. UPDI - Unified Program and Debug Interface....................................................... 387
33.1.
33.2.
33.3.
33.4.
33.5.
Features................................................................................................................................... 387
Overview.................................................................................................................................. 387
Functional Description..............................................................................................................390
Register Summary - UPDI........................................................................................................410
Register Description................................................................................................................. 410
34. Instruction Set Summary....................................................................................... 417
35. Conventions...........................................................................................................423
35.1.
35.2.
35.3.
35.4.
Numerical Notation...................................................................................................................423
Memory Size and Type.............................................................................................................423
Frequency and Time.................................................................................................................423
Registers and Bits.................................................................................................................... 424
36. Acronyms and Abbreviations.................................................................................425
37. Electrical Characteristics ATtiny1614/1616/1617.................................................. 428
37.1. Disclaimer.................................................................................................................................428
37.2. Absolute Maximum Ratings .....................................................................................................428
37.3. General Operating Ratings ......................................................................................................428
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Datasheet Preliminary
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8-bit AVR Microcontroller
37.4. Power Consumption................................................................................................................. 429
37.5. Wake-Up Time..........................................................................................................................431
37.6. Peripherals Power Consumption..............................................................................................431
37.7. BOD and POR Characteristics................................................................................................. 432
37.8. External Reset Characteristics................................................................................................. 433
37.9. Oscillators and Clocks..............................................................................................................433
37.10. I/O Pin Characteristics............................................................................................................. 436
37.11. USART..................................................................................................................................... 437
37.12. SPI........................................................................................................................................... 438
37.13. TWI...........................................................................................................................................440
37.14. Bandgap and VREF................................................................................................................. 442
37.15. ADC..........................................................................................................................................443
37.16. DAC..........................................................................................................................................446
37.17. AC............................................................................................................................................ 447
37.18. Programming Time...................................................................................................................447
38. Typical Characteristics...........................................................................................449
38.1.
38.2.
38.3.
38.4.
38.5.
38.6.
38.7.
38.8.
Power Consumption................................................................................................................. 449
GPIO........................................................................................................................................ 456
VREF Characteristics............................................................................................................... 463
BOD Characteristics.................................................................................................................465
ADC Characteristics................................................................................................................. 467
AC Characteristics....................................................................................................................477
OSC20M Characteristics..........................................................................................................479
OSCULP32K Characteristics................................................................................................... 481
39. Package Drawings.................................................................................................482
39.1.
39.2.
39.3.
39.4.
14-pin SOIC150........................................................................................................................482
20-pin SOIC..............................................................................................................................483
20-pin VQFN............................................................................................................................ 484
24-pin QFN...............................................................................................................................485
40. Errata ....................................................................................................................486
40.1. Die Revision A..........................................................................................................................486
41. Datasheet Revision History................................................................................... 489
41.1. Rev.B - 03/2017........................................................................................................................489
41.2. Rev.A - 03/2017........................................................................................................................489
The Microchip Web Site.............................................................................................. 490
Customer Change Notification Service........................................................................490
Customer Support....................................................................................................... 490
Product Identification System...................................................................................... 491
Microchip Devices Code Protection Feature............................................................... 491
Legal Notice.................................................................................................................491
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Datasheet Preliminary
DS40001893B-page 8
8-bit AVR Microcontroller
Trademarks................................................................................................................. 492
Quality Management System Certified by DNV...........................................................492
Worldwide Sales and Service......................................................................................493
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 9
8-bit AVR Microcontroller
1.
tinyAVR 1-Series Overview
™
Figure 1-1 shows the tinyAVR 1-series, laying out pin count variants and memory sizes:
•
•
Vertical migration can be done upwards without code modification, since these devices are pin
compatible and provide the same or even more features. Downward migration may require code
modification due to fewer available instances of some peripherals.
Horizontal migration to the left reduces the pin count and therefore also the available features.
Figure 1-1. tinyAVR 1-Series Overview
Flash
32KB
16KB
ATtiny1614
ATtiny1616
ATtiny1617
8KB
ATtiny814
ATtiny816
ATtiny817
ATtiny417
4KB
2KB
8
14
20
24
32
Pins
Devices with different Flash memory size typically also have different SRAM and EEPROM.
The name of a device of the series contains information as depicted below:
Figure 1-2. Device Designations
AT tiny1617 - MNR
Carrier Type
Package up to 24 pins
Flash size in KB
tinyAVR series
Pin count
R=Tape & Reel
Temperature Range
N=-40°C to +105°C
F=-40°C to +125°C
Package Type
7=24 pins
6=20 pins
4=14 pins
© 2017 Microchip Technology Inc.
M=QFN
S=SOIC300
SS=SOIC150
Datasheet Preliminary
DS40001893B-page 10
8-bit AVR Microcontroller
1.1
Configuration Summary
1.1.1
Peripheral Summary
Table 1-1. Peripheral Summary
ATtiny1614
ATtiny1616
ATtiny1617
Pins
14
20
24
SRAM
2KB
2KB
2KB
Flash
16KB
16KB
16KB
EEPROM
256B
256B
256B
Max. frequency (MHz)
20
20
20
16-bit Timer/Counter type A (TCA)
1
1
1
16-bit Timer/Counter type B (TCB)
2
2
2
12-bit Timer/Counter type D (TCD)
1
1
1
Real Time Counter (RTC)
1
1
1
USART
1
1
1
SPI
1
1
1
1
1
1
ADC
2
2
2
ADC channels
10+4
12+8
12+12
DAC
3
3
3
3
3
3
1
1
1
TWI
(I2C)
AC
Peripheral Touch Controller
(PTC)(1)
PTC number of self-capacitance
channels(1)
6XY
12XY
14XY
PTC number of mutual-capacitance channels(1)
9
36
49
Custom Logic/Configurable Lookup Tables
1
1
1
Window Watchdog
1
1
1
Event System channels
6
6
6
General purpose I/O
12
18
22
External interrupts
12
18
22
CRCSCAN
1
1
1
Note:
1. The PTC takes control over the ADC0 while the PTC is used.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 11
8-bit AVR Microcontroller
2.
Ordering Information
2.1
ATtiny161x
Table 2-1. ATtiny1617 Ordering Codes
Ordering
Code(1)
Flash Package Type
(GPC)
Leads Power
Supply
Operational Range
Carrier Type
ATtiny1617-MNR 16KB QFN (ZHA)
24
1.8V - 5.5V
Industrial (-40°C to
+105°C)
Tape & Reel
ATtiny1617-MFR
24
1.8V - 5.5V
Industrial (-40°C to
+125°C)
Tape & Reel
16KB QFN (ZHA)
Table 2-2. ATtiny1616 Ordering Codes
Ordering
Code(1)
Flash Package Type Leads Power Supply Operational Range
(GPC)
Carrier Type
ATtiny1616-MNR 16KB QFN (ZCL)
20
1.8V - 5.5V
Industrial (-40°C to
+105°C)
Tape & Reel
ATtiny1616-MFR 16KB QFN (ZCL)
20
1.8V - 5.5V
Industrial (-40°C to
+125°C)
Tape & Reel
ATtiny1616-SNR
16KB SOIC300
(SRJ)
20
1.8V - 5.5V
Industrial (-40°C to
+105°C)
Tape & Reel
ATtiny1616-SFR
16KB SOIC300
(SRJ)
20
1.8V - 5.5V
Industrial (-40°C to
+125°C)
Tape & Reel
Table 2-3. ATtiny1614 Ordering Codes
Ordering
Code(1)
Flash Package Type
(GPC)
Leads Power
Supply
Operational Range
Carrier Type
ATtiny1614SSNR
16KB SOIC150
(SVQ)
14
1.8V - 5.5V
Industrial (-40°C to
+105°C)
Tape & Reel
ATtiny1614SSFR
16KB SOIC150
(SVQ)
14
1.8V - 5.5V
Industrial (-40°C to
+125°C)
Tape & Reel
Note:
1. Pb-free packaging complies to the European Directive for Restriction of Hazardous Substances
(RoHS directive). Also Halide free and fully Green.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 12
8-bit AVR Microcontroller
3.
Block Diagram
Figure 3-1. ATtiny1614/1616/1617 Block Diagram
analog peripherals
analog
peripherals
digital peripherals
analog
peripherals
core components
UPDI
UPDI / RESET
CRC
CPU
analog
peripherals
clocks/generators
OCD
To
detectors
M
M
Flash
M
S
SRAM
BUS Matrix
S
EEPROM
S
S
AINP[3:0]
AINN[1:0]
OUT
OUT
AIN[11:0]
X[13:0]
Y[13:0]
DS[1:0]
REFA
AIN[11:0]
LUTn-IN[2:0]
LUTn-OUT
WO[5:0]
WO
PORTS
AC [2:0]
GPIOR
DAC [2:0]
ADC0 / PTC
ADC1
CCL
TCA0
TCB[1:0]
NVMCTRL
E
V
E
N
T
R
O
U
T
I
N
G
N
E
T
W
O
R
K
D
A
T
A
B
U
S
CPUINT
I
N
/
O
U
T
D
A
T
A
B
U
S
System
Management
MISO
MOSI
SCK
SS
SPI0
SDA
SCL
TWI0
BOD
VLM
SLPCTRL
Clock generation
CLKOUT
OSC20M
OSC32K
TOSC1
XOSC32K
TOSC2
EXTCLK
© 2017 Microchip Technology Inc.
POR
CLKCTRL
RTC
USART0
RST
Bandgap
TCD0
RXD
TXD
XCK
XDIR
Detectors/
References
RSTCTRL
WDT
WO[A,B,C,D]
PA[7:0]
PB[7:0]
PC[5:0]
EVSYS
Datasheet Preliminary
EXTINT
EVOUT[n:0]
DS40001893B-page 13
8-bit AVR Microcontroller
4.
Pinout
4.1
14-pin SOIC
VDD
1
14
GND
PA4
2
13
PA3/EXTCLK
PA5
3
12
PA2
PA6
4
11
PA1
PA7
5
10
PA0/RESET/UPDI
TOSC1/PB3
6
9
PB0
TOSC2/PB2
7
8
PB1
Input supply
Programming, Debug, Reset
Ground
Clock, crystal
GPIO VDD power domain
Digital function only
Analog function
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Datasheet Preliminary
DS40001893B-page 14
8-bit AVR Microcontroller
4.2
20-pin SOIC
VDD
1
20
GND
PA4
2
19
PA3/EXTCLK
PA5
3
18
PA2
PA6
4
17
PA1
PA7
5
16
PA0/RESET/UPDI
PB5
6
15
PC3
PB4
7
14
PC2
TOSC1/PB3
8
13
PC1
TOSC2/PB2
9
12
PC0
PB1
10
11
PB0
Input supply
Programming, Debug, Reset
Ground
Clock, crystal
GPIO VDD power domain
Digital function only
Analog function
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Datasheet Preliminary
DS40001893B-page 15
8-bit AVR Microcontroller
PA1
PA0/RESET/UPDI
PC3
PC2
PC1
20
19
18
17
16
20-pin QFN
3
13
PB1
VDD
4
12
PB2/TOSC2
PA4
5
11
PB3/TOSC1
10
GND
PB4
PB0
9
14
PB5
2
8
EXTCLK /PA3
PA7
PC0
7
15
PA6
1
6
PA2
PA5
4.3
Input supply
Programming, Debug, Reset
Ground
Clock, crystal
GPIO VDD power domain
Digital function only
Analog function
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 16
8-bit AVR Microcontroller
PA1
PA0/RESET/UPDI
PC5
PC4
PC3
PC2
24
23
22
21
20
19
24-pin QFN
PB0
VDD
4
15
PB1
PA4
5
14
PB2/TOSC2
PA5
6
13
PB3/TOSC1
12
16
PB4
3
11
GND
PB5
PC0
10
17
PB6
2
9
EXTCLK /PA3
PB7
PC1
8
18
PA7
1
7
PA2
PA6
4.4
Input supply
Programming, Debug, Reset
Ground
Clock, crystal
GPIO VDD power domain
Digital function only
Analog function
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 17
8-bit AVR Microcontroller
5.
I/O Multiplexing and Considerations
5.1
Multiplexed Signals
QFN 24-pin
QFN 20-pin
SOIC 20-pin
SOIC 14-pin
Table 5-1. PORT Function Multiplexing
Pin
Other/ ADC0 ADC1 PTC(3) AC0
Name Specia
(1,2)
l
23
19
16
10
PA0
RESE
AC1
AC2
DAC0 USAR SPI0
T0
TWI0
TCA0
TCBn TCD0
AIN0
CCL
LUT0IN0
T
UPDI
24
20
17
11
PA1
BREA AIN1
K
TXD
MOSI
SDA
LUT0IN1
1
1
18
12
PA2
EVOU AIN2
T0
RxD
MISO
SCL
LUT0IN2
2
2
19
13
PA3
EXTCL AIN3
K
XCK
SCK
WO3
3
3
20
14
GND
4
4
1
1
VDD
5
5
2
2
PA4
AIN4
AIN0
X0/Y0
XDIR
SS
WO4
6
6
3
3
PA5
VREFA AIN5
AIN1
X1/Y1 OUT
7
7
4
4
PA6
AIN6
AIN2
X2/Y2 AINN0 AINP1 AINP0 OUT
8
8
5
5
PA7
AIN7
AIN3
X3/Y3 AINP0 AINP0 AINN0
9
PB7
AIN4
10
PB6
AIN5
11
9
6
PB5
CLKO AIN8
UT
AINN0
WO5
TCB1
WO
WOA
TCB0
WO
LUT0OUT
WOB
LUT1OUT
AINN1 AINP3
X12/Y1
AINP3
AINN1
AINP1
AINP2
WO2
2
12
10
7
13
11
8
PB4
6
PB3
AIN9
WO1
X13/Y1 AINN1 AINP3
3
OUT
TOSC
RxD
WO0
TxD
WO2
LUT0OUT
1
14
12
9
7
PB2
15
13
10
8
PB1
AIN10
X4/Y4 AINP2
16
14
11
9
PB0
AIN11
X5/Y5
17
15
12
PC0
AIN6
X6/Y6
SCK
18
16
13
PC1
AIN7
X7/Y7
MISO
19
17
14
PC2
AIN8
X9/Y8
MOSI
20
18
15
PC3
AIN9
X9/Y9
SS
21
PC4
22
PC5
TOSC
2,
EVOU
T1
OUT
EVOU
T2
BREAK
© 2017 Microchip Technology Inc.
AINP2 AINP1
XCK
SDA
WO1
XDIR
SCL
WO0
TCB0
WO
WOD
WO3
AIN10 X10/Y1
0
WO4
AIN11 X11/Y1
1
WO5
Datasheet Preliminary
WOC
LUT1OUT
LUT1IN0
TCB1
WO
LUT1IN1
LUT1IN2
DS40001893B-page 18
8-bit AVR Microcontroller
Note:
1. Pins names are of type Pxn, with x being the PORT instance (A,B) and n the pin number. Notation
for signals is PORTx_PINn. All pins can be used as event input.
2. All pins can be used for external interrupt, where pins Px2 and Px6 of each port have full
asynchronous detection.
3. Every PTC line can be configured as X-line or Y-line.
Tip: Signals on alternative pin locations are in typewriter font.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 19
8-bit AVR Microcontroller
6.
Memories
6.1
Overview
The main memories are SRAM data memory, EEPROM data memory, and Flash program memory. In
addition, the peripheral registers are located in the I/O memory space.
Table 6-1. Physical Properties of EEPROM
Property
ATtiny1617/1616/1614
Size
256B
Page size
32B
Number of pages
8
Start address
0x1400
Table 6-2. Physical Properties of SRAM
Property
ATtiny1617/1616/1614
Size
2KB
Start address
0x3800
Table 6-3. Physical Properties of Flash Memory
Property
ATtiny1617/1616/1614
Size
16KB
Page size
64B
Number of pages
256
Start address
0x8000
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Datasheet Preliminary
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8-bit AVR Microcontroller
6.2
Memory Map
Figure 6-1. Memory Map ATtiny1617/ATtiny1616/ATtiny1614
64 I/O Registers
0x0000 – 0x003F
960 Ext I/O Registers
0x0040 – 0x0FFF
NVM I/O registers and data
0x1000 – 0x13FF
EEPROM 256B
0x1400 – 0x14FF
(Reserved)
Internal SRAM
2KB
0x3C00 – 0x3FFF
(Reserved)
Boot
Flash
16KB
0x8000 - BOOTEND
Application
code
App data
APPEND
0xBFFF
(Reserved)
0xFFFF
6.3
In-System Reprogrammable Flash Program Memory
The ATtiny1614/1616/1617 contains 16KB On-Chip In-System Reprogrammable Flash memory for
program storage. Since all AVR instructions are 16 or 32 bits wide, the Flash is organized as 4K x 16. For
write protection, the Flash Program memory space can be divided into three sections: Boot Loader
section, Application code section and Application data section, with restricted access rights among them.
The program counter is 13 bits wide to address the whole program memory. The procedure for writing
Flash memory is described in detail in the documentation of the Non-Volatile Memory Controller
(NVMCTRL) peripheral.
The entire Flash memory is mapped in the memory space and is accessible with normal LD/ST
instructions as well as the LPM instruction. For LD/ST instructions, the Flash is mapped from address
0x8000. For the LPM instruction, the Flash start address is 0x0000.
The ATtiny1614/1616/1617 also has a CRC module that is a master on the bus. If the CRC is configured
to run in the background it will read the Flash memory and can affect the program timing.
Related Links
Configuration Summary
NVMCTRL - Non Volatile Memory Controller
6.4
SRAM Data Memory
The 2KB SRAM is used for data storage and stack.
Related Links
AVR CPU
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 21
8-bit AVR Microcontroller
Stack and Stack Pointer
6.5
EEPROM Data Memory
The ATtiny1614/1616/1617 has 256 bytes of EEPROM data memory, see Memory Map. The EEPROM
memory supports single byte read and write. The EEPROM is controlled by the Non-Volatile Memory
Controller (NVMCTRL).
Related Links
NVMCTRL - Non Volatile Memory Controller
BOD - Brownout Detector
6.6
User Row
In addition to the EEPROM, the ATtiny1614/1616/1617 has one extra page of EEPROM memory that can
be used for firmware settings, the User Row (USERROW). This memory supports single byte read and
write as the normal EEPROM. The CPU can write and read this memory as normal EEPROM and the
UPDI can write and read it as a normal EEPROM memory if the part is unlocked. The User Row can also
be written by the UPDI when the part is locked. USERROW is not affected by a chip erase.
Related Links
NVMCTRL - Non Volatile Memory Controller
UPDI - Unified Program and Debug Interface
6.7
I/O Memory
All ATtiny1614/1616/1617 I/Os and peripherals are located in the I/O space. The I/O address range from
0x00 to 0x3F can be accessed in a single cycle using IN and OUT instructions. The Extended I/O space
from 0x0040 - 0x0FFF can be accessed by the LD/LDS/LDD and ST/STS/STD instructions, transferring
data between the 32 general purpose working registers and the I/O space.
I/O Registers within the address range 0x00 - 0x1F are directly bit-accessible using the SBI and CBI
instructions. In these registers, the value of single bits can be checked by using the SBIS and SBIC
instructions. Refer to the Instruction Set section for more details.
For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O
memory addresses should never be written.
Some of the interrupt flags are cleared by writing a '1' to them. On ATtiny1614/1616/1617 devices, the
CBI and SBI instructions will only operate on the specified bit, and can therefore be used on registers
containing such interrupt flags. The CBI and SBI instructions work with registers 0x00 - 0x1F only.
General Purpose I/O Registers
The ATtiny1614/1616/1617 devices provide four General Purpose I/O Registers. These registers can be
used for storing any information, and they are particularly useful for storing global variables and interrupt
flags. General Purpose I/O Registers, which recide in the address range 0x1C - 0x1F, are directly bitaccessible using the SBI, CBI, SBIS, and SBIC instructions.
6.8
FUSES - Configuration and User Fuses
Fuses are part of the non-volatile memory and holds factory calibration data and device configuration.
The fuses are available from device power-up. The fuses can be read by the CPU or the UPDI, but can
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 22
8-bit AVR Microcontroller
only be programmed or cleared by the UPDI. The configuration and calibration values stored in the fuses
are written to their respective target registers at the end of the start-up sequence.
The content of the Signature Row fuses (SIGROW) is pre-programmed, and cannot be altered. SIGROW
holds information such as device ID, serial number, and calibration values.
The fuses for peripheral configuration (FUSE) are pre-programmed, but can be altered by the user.
Altered values in the configuration fuses will be effective only after a Reset.
This device also provides a User Row fuse area (USERROW) that can hold application data. The
USERROW can be programmed on a locked device by the UPDI. This can be used for final configuration
without having programming or debugging capabilities enabled.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
6.8.1
Signature Row Summary - SIGROW
Offset
Name
Bit Pos.
0x00
DEVICEID0
7:0
DEVICEID[7:0]
0x01
DEVICEID1
7:0
DEVICEID[7:0]
0x02
DEVICEID2
7:0
DEVICEID[7:0]
0x03
SERNUM0
7:0
SERNUM[7:0]
0x04
SERNUM1
7:0
SERNUM[7:0]
0x05
SERNUM2
7:0
SERNUM[7:0]
0x06
SERNUM3
7:0
SERNUM[7:0]
0x07
SERNUM4
7:0
SERNUM[7:0]
0x08
SERNUM5
7:0
SERNUM[7:0]
0x09
SERNUM6
7:0
SERNUM[7:0]
0x0A
SERNUM7
7:0
SERNUM[7:0]
0x0B
SERNUM8
7:0
SERNUM[7:0]
0x0C
SERNUM9
7:0
SERNUM[7:0]
TEMPSENSE[7:0]
0x0D
...
Reserved
0x1F
0x20
TEMPSENSE0
7:0
0x21
TEMPSENSE1
7:0
TEMPSENSE[7:0]
0x22
OSC16ERR3V
7:0
OSC16ERR3V[7:0]
0x23
OSC16ERR5V
7:0
OSC16ERR5V[7:0]
0x24
OSC20ERR3V
7:0
OSC20ERR3V[7:0]
0x25
OSC20ERR5V
7:0
OSC20ERR5V[7:0]
6.8.2
Signature Row Description
6.8.2.1
Device ID n
Each device has a Device ID, identifying the device and its properties, such as memory sizes, pin count,
and die revision. This can be used to identify a device and hence, the available features by software. The
Device ID consists of three bytes: SIGROW.DEVICEID[2:0].
Name: DEVICEIDn
Offset: 0x00 + n*0x01 [n=0..2]
Reset: [Device ID]
Property:
Bit
7
6
5
4
3
2
1
0
DEVICEID[7:0]
Access
R
R
R
R
R
R
R
R
Reset
x
x
x
x
x
x
x
x
Bits 7:0 – DEVICEID[7:0]: Byte n of the Device ID
6.8.2.2
Serial Number Byte n
Each device has an individual serial number, representing a unique ID. This can be used to identify a
specific device in the field. The serial number consists of ten bytes: SIGROW.SERNUM[9:0].
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Datasheet Preliminary
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8-bit AVR Microcontroller
Name: SERNUMn
Offset: 0x03 + n*0x01 [n=0..9]
Reset: [device serial number]
Property:
Bit
7
6
5
4
3
2
1
0
SERNUM[7:0]
Access
R
R
R
R
R
R
R
R
Reset
x
x
x
x
x
x
x
x
Bits 7:0 – SERNUM[7:0]: Serial Number Byte n
6.8.2.3
Temperature Sensor Calibration n
These registers contain correction factors for temperature measurements by the ADC.
SIGROW.TEMPSENSE0 is a correction factor for the gain/slope (unsigned), SIGROW.TEMPSENSE1 is
a correction factor for the offset (signed).
Name: TEMPSENSEn
Offset: 0x20 + n*0x01 [n=0..1]
Reset: [Temperature sensor calibration value]
Property:
Bit
7
6
5
4
Access
R
R
R
R
Reset
0
0
0
0
3
2
1
0
R
R
R
R
0
0
0
0
2
1
0
TEMPSENSE[7:0]
Bits 7:0 – TEMPSENSE[7:0]: Temperature Sensor Calibration Byte n
Related Links
Temperature Measurement
6.8.2.4
OSC16 error at 3V
Name: OSC16ERR3V
Offset: 0x22
Reset: [Oscillator frequency error value]
Property:
Bit
7
6
5
4
3
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
OSC16ERR3V[7:0]
Bits 7:0 – OSC16ERR3V[7:0]: OSC16 error at 3V
This registers contain the signed oscillator frequency error value when running at internal 16MHz at 3V,
as measured during production.
6.8.2.5
OSC16 error at 5V
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 25
8-bit AVR Microcontroller
Name: OSC16ERR5V
Offset: 0x23
Reset: [Oscillator frequency error value]
Property:
Bit
7
6
5
4
3
2
1
0
OSC16ERR5V[7:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 7:0 – OSC16ERR5V[7:0]: OSC16 error at 5V
This registers contain the signed oscillator frequency error value when running at internal 16MHz at 5V,
as measured during production.
6.8.2.6
OSC20 error at 3V
Name: OSC20ERR3V
Offset: 0x24
Reset: [Oscillator frequency error value]
Property:
Bit
7
6
5
4
Access
R
R
R
R
Reset
0
0
0
0
3
2
1
0
R
R
R
R
0
0
0
0
OSC20ERR3V[7:0]
Bits 7:0 – OSC20ERR3V[7:0]: OSC20 error at 3V
This registers contain the signed oscillator frequency error value when running at internal 20MHz at 3V,
as measured during production.
6.8.2.7
OSC20 error at 5V
Name: OSC20ERR5V
Offset: 0x25
Reset: [Oscillator frequency error value]
Property:
Bit
7
6
5
4
3
2
1
0
OSC20ERR5V[7:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 7:0 – OSC20ERR5V[7:0]: OSC20 error at 5V
This registers contain the signed oscillator frequency error value when running at internal 20MHz at 5V,
as measured during production.
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Datasheet Preliminary
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8-bit AVR Microcontroller
6.8.3
Fuse Summary - FUSE
Offset
Name
Bit Pos.
0x00
WDTCFG
7:0
0x01
BODCFG
7:0
0x02
OSCCFG
7:0
OSCLOCK
0x03
Reserved
0x04
TCD0CFG
7:0
CMPDEN
0x05
SYSCFG0
7:0
0x06
SYSCFG1
7:0
0x07
APPEND
7:0
APPEND[7:0]
0x08
BOOTEND
7:0
BOOTEND[7:0]
0x09
Reserved
0x0A
LOCKBIT
7:0
LOCKBIT[7:0]
WINDOW[3:0]
LVL[2:0]
CRCBOOTDI
S
PERIOD[3:0]
SAMPFREQ
ACTIVE[1:0]
SLEEP[1:0]
FREQSEL[1:0]
CMPCEN
CMPBEN
CRCAPPDIS
CMPAEN
RESERVED[1:0]
CMPD
CMPC
RSTPINCFG[1:0]
CMPB
CMPA
RESERVED
EESAVE
SUT[2:0]
6.8.4
Fuse Description
6.8.4.1
Watchdog Configuration
Name: WDTCFG
Offset: 0x00
Reset: Property:
Bit
7
6
5
4
3
2
Access
R
Reset
0
1
0
R
R
R
R
R
0
0
0
0
R
R
0
0
0
WINDOW[3:0]
PERIOD[3:0]
Bits 7:4 – WINDOW[3:0]: Watchdog Window Timeout Period
This value is loaded into the WINDOW bit field of the Watchdog Control A register (WDT.CTRLA) during
Reset.
Bits 3:0 – PERIOD[3:0]: Watchdog Timeout Period
This value is loaded into the PERIOD bit field of the Watchdog Control A register (WDT.CTRLA) during
Reset.
6.8.4.2
BOD Configuration
Name: BODCFG
Offset: 0x01
Reset: Property:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 27
8-bit AVR Microcontroller
Bit
7
6
5
LVL[2:0]
4
3
SAMPFREQ
2
1
ACTIVE[1:0]
0
SLEEP[1:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 7:5 – LVL[2:0]: BOD Level
This value is loaded into the LVL bit field of the BOD Control B register (BOD.CTRLB) during Reset.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
BODLEVEL0
BODLEVEL1
BODLEVEL2
BODLEVEL3
BODLEVEL4
BODLEVEL5
BODLEVEL6
BODLEVEL7
Description
1.8V
2.15V
2.60V
2.95V
3.30V
3.70V
4.00V
4.30V
Bit 4 – SAMPFREQ: BOD Sample Frequency
This value is loaded into the SAMPFREQ bit of the BOD Control A register (BOD.CTRLA) during Reset.
Value
0x0
0x1
Description
Sample frequency is 1kHz
Sample frequency is 125Hz
Bits 3:2 – ACTIVE[1:0]: BOD Operation Mode in Active and Idle
This value is loaded into the ACTIVE bit field of the BOD Control A register (BOD.CTRLA) during Reset.
Value
0x0
0x1
0x2
0x3
Description
Disabled
Enabled
Sampled
Enabled with wake-up halted until BOD is ready
Bits 1:0 – SLEEP[1:0]: BOD Operation Mode in Sleep
This value is loaded into the SLEEP bit field of the BOD Control A register (BOD.CTRLA) during Reset.
Value
0x0
0x1
0x2
0x3
6.8.4.3
Description
Disabled
Enabled
Sampled
Reserved
Oscillator Configuration
Name: OSCCFG
Offset: 0x02
Reset: 0x00
Property:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 28
8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
OSCLOCK
0
FREQSEL[1:0]
Access
R
R
R
Reset
0
1
0
Bit 7 – OSCLOCK: Oscillator Lock
This fuse bit is loaded to LOCK in CLKCTRL.OSC20MCALIBB during reset.
Value
0
1
Description
Calibration registers of the 20 MHz oscillator are accessible
Calibration registers of the 20 MHz oscillator are locked
Bits 1:0 – FREQSEL[1:0]: Frequency Select
These bits selects the operation frequency of the 16/20MHz internal oscillator (OSC20M), and determine
the respective factory calibration values to be written to CAL20M in CLKCTRL.OSC20MCALIBA and
TEMPCAL20M in CLKCTRL.OSC20MCALIBB.
Value
0x1
0x2
Other
6.8.4.4
Description
Run at 16MHz with corresponding factory calibration
Run at 20MHz with corresponding factory calibration
Reserved
Timer Counter Type D Configuration
The bit values of this fuse register are written to the corresponding bits in the TCD.FAULTCTRL register
of TCD0 at start-up.
The CMPEN and CMP settings of the TCD will only be reloaded from the FUSE values after a Power-On
Reset. For all other resets the corresponding TCD settings of the device will remain unchanged.
Name: TCD0CFG
Offset: 0x04
Reset: Property:
Bit
7
6
5
4
3
2
1
0
CMPDEN
CMPCEN
CMPBEN
CMPAEN
CMPD
CMPC
CMPB
CMPA
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 4, 5, 6, 7 – CMPAEN, CMPBEN, CMPCEN, CMPDEN: Compare x Enable
Value
0
1
Description
Compare x output on Pin is disabled
Compare x output on Pin is enabled
Bits 0, 1, 2, 3 – CMPA, CMPB, CMPC, CMPD: Compare x
This bit selects the default state of Compare x after Reset, or when entering debug if FAULTDET is '1'.
Value
0
1
Description
Compare x default state is 0
Compare x default state is 1
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
6.8.4.5
System Configuration 0
Name: SYSCFG0
Offset: 0x05
Reset: Property:
Bit
7
6
5
4
3
2
1
0
CRCBOOTDIS
CRCAPPDIS
RESERVED[1:0]
RSTPINCFG[1:0]
RESERVED
EESAVE
Access
R
R
R
R
R
R
R
R
Reset
1
1
1
1
0
1
1
0
Bit 7 – CRCBOOTDIS: CRC of Boot Section in Reset Disable
See CRC description for more information about the functionality.
Value
0
1
Description
Boot section undergoing a CRC before Reset releases
No CRC of the boot section before Reset releases
Bit 6 – CRCAPPDIS: CRC of Application Code Section in Reset Disable
See CRC description for more information about the functionality.
Value
0
1
Description
Application code section undergoing a CRC before Reset releases
No CRC of the application code section before Reset releases
Bits 5:4 – RESERVED[1:0]
Bits 3:2 – RSTPINCFG[1:0]: Reset Pin Configuration
These bits select the Reset/UPDI pin configuration.
Value
0x0
0x1
0x2
0x3
Description
GPIO
RESET
UPDI
For 24-pin device: UPDI, with external Reset on alternate location.
Reserved for lower pin-counts.
Bit 1 – RESERVED
Bit 0 – EESAVE: EEPROM Save during chip erase
Note: If the device is locked the EEPROM is always erased by a chip erase, regardless of this bit.
Value
0
1
6.8.4.6
Description
EEPROM erased during chip erase
EEPROM not erased under chip erase
System Configuration 1
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Name: SYSCFG1
Offset: 0x06
Reset: Property:
Bit
7
6
5
4
3
2
1
0
SUT[2:0]
Access
R
R
R
Reset
1
1
1
Bits 2:0 – SUT[2:0]: Start Up Time Setting
These bits selects the start-up time between power-on and code execution.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
6.8.4.7
Description
0ms
1ms
2ms
4ms
8ms
16ms
32ms
64ms
Application Code End
Name: APPEND
Offset: 0x07
Reset: Property:
Bit
7
6
5
4
3
2
1
0
APPEND[7:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 7:0 – APPEND[7:0]: Application Code Section End
These bits set the end of the application code section in blocks of 256 bytes. The end of the application
code section should be set as BOOT size + application code size. The remaining Flash will be application
data. A value of 0x00 defines the Flash from BOOTEND*256 to end of Flash as application code. When
both FUSE.APPEND and FUSE.BOOTEND are 0x00, the entire Flash is BOOT section.
6.8.4.8
Boot End
Name: BOOTEND
Offset: 0x08
Reset: Property:
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Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
BOOTEND[7:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 7:0 – BOOTEND[7:0]: Boot Section End
These bits set the end of the boot section in blocks of 256 bytes. A value of 0x00 defines the whole Flash
as BOOT section. When both FUSE.APPEND and FUSE.BOOTEND are 0x00, the entire Flash is BOOT
section.
6.8.4.9
Lock Bits
Name: LOCKBIT
Offset: 0x0A
Reset: Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
LOCKBIT[7:0]
Access
Reset
Bits 7:0 – LOCKBIT[7:0]: Lock Bits
When the part is locked, UPDI cannot access the system bus, so it cannot read out anything but CSspace.
Value
0xC5
other
Description
The device is open
The device is locked
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Datasheet Preliminary
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8-bit AVR Microcontroller
7.
Peripherals and Architecture
7.1
Peripheral Module Address Map
The address map show the base address for each peripheral. For complete register description and
summary for each peripheral module, refer to the respective module chapters.
Table 7-1. Peripheral Module Address Map
Base Address
Name
Description
0x0000
VPORTA
Virtual Port A
0x0004
VPORTB
Virtual Port B
0x0008
VPORTC
Virtual Port C
0x001C
GPIO
General Purpose IO registers
0x0030
CPU
CPU
0x0040
RSTCTRL
Reset Controller
0x0050
SLPCTRL
Sleep Controller
0x0060
CLKCTRL
Clock Controller
0x0080
BOD
Brown-Out Detector
0x00A0
VREF
Voltage Reference
0x0100
WDT
Watchdog Timer
0x0110
CPUINT
Interrupt Controller
0x0120
CRCSCAN
Cyclic Redundancy Check Memory Scan
0x0140
RTC
Real Time Counter
0x0180
EVSYS
Event System
0x01C0
CCL
Configurable Custom Logic
0x0200
PORTMUX
Port Multiplexer
0x0400
PORTA
Port A Configuration
0x0420
PORTB
Port B Configuration
0x0440
PORTC
Port C Configuration
0x0600
ADC0
Analog to Digital Converter/Peripheral Touch Controller
0x0640
ADC1
Analog to Digital Converter instance 1
0x0680
AC0
Analog Comparator 0
0x0688
AC1
Analog Comparator 1
0x0690
AC2
Analog Comparator 2
0x06A0
DAC0
Digital to Analog Converter 0
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Datasheet Preliminary
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8-bit AVR Microcontroller
7.2
Base Address
Name
Description
0x06A8
DAC1
Digital to Analog Converter 1
0x06B0
DAC2
Digital to Analog Converter 2
0x0800
USART0
Universal Synchronous Asynchronous Receiver Transmitter
0x0810
TWI0
Two Wire Interface
0x0820
SPI0
Serial Peripheral Interface
0x0A00
TCA0
Timer/Counter Type A instance 0
0x0A40
TCB0
Timer/Counter Type B instance 0
0x0A50
TCB1
Timer/Counter Type B 1
0x0A80
TCD0
Timer/Counter Type D instance 0
0x0F00
SYSCFG
System Configuration
0x1000
NVMCTRL
Non Volatile Memory Controller
0x1100
SIGROW
Signature Row
0x1280
FUSES
Device specific fuses
0x1300
USERROW
User Row
Interrupt Vector Mapping
Each of the 26 interrupt vectors is connected to one peripheral instance, as shown in the table below. A
peripheral can have one or more interrupt sources, see the 'Interrupt' section in the 'Functional
Description' of the respective peripheral for more details on the available interrupt sources.
When the interrupt condition occurs, an Interrupt Flag (nameIF) is set in the Interrupt Flags register of the
peripheral (peripheral.INTFLAGS).
An interrupt is enabled or disabled by writing to the corresponding Interrupt Enable bit (nameIE) in the
peripheral's Interrupt Control register (peripheral.INTCTRL).
The naming of the registers may vary slightly in some peripherals.
An interrupt request is generated when the corresponding interrupt is enabled and the Interrupt Flag is
set. The interrupt request remains active until the Interrupt Flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear Interrupt Flags.
Interrupts must be enabled globally for interrupt requests to be generated.
Table 7-2. Interrupt Vector Mapping
Vector Number
Base Address
Peripheral source
0
0x00
RESET
1
0x02
NMI - Non Maskable Interrupt
from CRC
2
0x04
VLM - Voltage Level Monitor
3
0x06
PORTA - Port A
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Datasheet Preliminary
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8-bit AVR Microcontroller
Vector Number
Base Address
Peripheral source
4
0x08
PORTB - Port B
5
0x0A
PORTC - Port C
6
0x0C
RTC - Real Time Counter
7
0x0E
PIT - Periodic Interrupt Timer (in
RTC peripheral)
8
0x10
TCA0 - Timer Counter Type A
13
0x1A
TCB0 - Timer Counter Type B
14
0x1C
TCB1 - Timer Counter Type B
15
0x1E
TCD0 - Timer Counter Type D
17
0x22
AC0 – Analog Comparator
18
0x24
AC1 – Analog Comparator
19
0x26
AC2 – Analog Comparator
20
0x28
ADC0 – Analog-to-Digital
Converter / PTC
22
0x2C
ADC1 – Analog-to-Digital
Converter
24
0x30
TWI0 - Two Wire Interface / I2C
26
0x34
SPI0 - Serial Peripheral Interface
27
0x36
USART0 - Universal
Asynchronous ReceiverTransmitter
30
0x3C
NVM - Non Volatile Memory
Related Links
NVMCTRL - Non Volatile Memory Controller
PORT - I/O Pin Configuration
RTC - Real Time Counter
SPI - Serial Peripheral Interface
USART - Universal Synchronous and Asynchronous Receiver and Transmitter
TWI - Two Wire Interface
CRCSCAN - Cyclic Redundancy Check Memory Scan
TCA - 16-bit Timer/Counter Type A
TCB - 16-bit Timer/Counter Type B
TCD - 12-bit Timer/Counter Type D
AC – Analog Comparator
ADC - Analog to Digital Converter
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
8.
AVR CPU
8.1
Features
•
•
•
•
•
•
•
•
8.2
8-bit, high-performance AVR RISC CPU
– 135 instructions
– Hardware multiplier
32 8-bit registers directly connected to the ALU
Stack in RAM
Stack pointer accessible in I/O memory space
Direct addressing of up to 64KB of unified memory
– Entire Flash accessible with all LD/ST instructions
True 16/24-bit access to 16/24-bit I/O registers
Efficient support for 8-, 16-, and 32-bit arithmetic
Configuration Change Protection for system-critical features
Overview
All AVR devices use the 8-bit AVR CPU. The CPU is able to access memories, perform calculations,
control peripherals, and execute instructions in the program memory. Interrupt handling is described in a
separate section.
Related Links
Memories
NVMCTRL - Non Volatile Memory Controller
CPUINT - CPU Interrupt Controller
8.3
Architecture
In order to maximize performance and parallelism, the AVR CPU uses a Harvard architecture with
separate buses for program and data. Instructions in the program memory are executed with single-level
pipelining. While one instruction is being executed, the next instruction is pre-fetched from the program
memory. This enables instructions to be executed on every clock cycle.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Figure 8-1. AVR CPU Architecture
Register file
R31 (ZH)
R29 (YH)
R27 (XH)
R25
R23
R21
R19
R17
R15
R13
R11
R9
R7
R5
R3
R1
R30 (ZL)
R28 (YL)
R26 (XL)
R24
R22
R20
R18
R16
R14
R12
R10
R8
R6
R4
R2
R0
Program
counter
Flash program
memory
Instruction
register
Instruction
decode
Data memory
Stack
pointer
Status
register
ALU
The Arithmetic Logic Unit (ALU) supports arithmetic and logic operations between registers or between a
constant and a register. Single-register operations can also be executed in the ALU. After an arithmetic
operation, the status register is updated to reflect information about the result of the operation.
The ALU is directly connected to the fast-access register file. The 32 8-bit general purpose working
registers all have single clock cycle access time allowing single-cycle arithmetic logic unit operation
between registers or between a register and an immediate. Six of the 32 registers can be used as three
16-bit address pointers for program and data space addressing, enabling efficient address calculations.
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8-bit AVR Microcontroller
The program memory bus is connected to Flash, and the first program memory Flash address is 0x0000.
The data memory space is divided into I/O registers, SRAM, EEPROM and Flash.
All I/O status and control registers reside in the lowest 4KB addresses of the data memory. This is
referred to as the I/O memory space. The lowest 64 addresses are accessed directly with single cycle
IN/OUT instructions, or as the data space locations from 0x00 to 0x3F. These addresses can also be
accessed using load (LD/LDS/LDD) and store (ST/STS/STD) instructions. The lowest 32 addresses can
even be accessed with single cycle SBI/CBI instructions and SBIS/SBIC instructions. The rest is the
extended I/O memory space, ranging from 0x0040 to 0x0FFF. I/O registers here must be accessed as
data space locations using load and store instructions.
Data addresses 0x1000 to 0x1800 are reserved for memory mapping of fuses, the NVM controller and
EEPROM. The addresses from 0x1800 to 0x7FFF are reserved for other memories, such as SRAM.
The Flash is mapped in the data space from 0x8000 and above. The Flash can be accessed with all load
and store instructions by using addresses above 0x8000. The LPM instruction accesses the Flash as in
the code space, where the Flash starts at address 0x0000.
For a summary of all AVR instructions, refer to the Instruction Set Summary. For details of all AVR
instructions, refer to http://www.microchip.com/design-centers/8-bit.
Related Links
NVMCTRL - Non Volatile Memory Controller
Memories
Instruction Set Summary
8.4
ALU - Arithmetic Logic Unit
The Arithmetic Logic Unit supports arithmetic and logic operations between registers, or between a
constant and a register. Single-register operations can also be executed.
The ALU operates in direct connection with all 32 general purpose registers. Arithmetic operations
between general purpose registers or between a register and an immediate are executed in a single clock
cycle, and the result is stored in the register file. After an arithmetic or logic operation, the Status register
(CPU.SREG) is updated to reflect information about the result of the operation.
ALU operations are divided into three main categories – arithmetic, logical, and bit functions. Both 8- and
16-bit arithmetic is supported, and the instruction set allows for efficient implementation of 32-bit
arithmetic. The hardware multiplier supports signed and unsigned multiplication and fractional format.
8.4.1
Hardware Multiplier
The multiplier is capable of multiplying two 8-bit numbers into a 16-bit result. The hardware multiplier
supports different variations of signed and unsigned integer and fractional numbers:
•
•
•
•
Multiplication of signed/unsigned integers
Multiplication of signed/unsigned fractional numbers
Multiplication of a signed integer with an unsigned integer
Multiplication of a signed fractional number with an unsigned one
A multiplication takes two CPU clock cycles.
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Datasheet Preliminary
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8-bit AVR Microcontroller
8.5
Functional Description
8.5.1
Program Flow
After Reset, the CPU will execute instructions from the lowest address in the Flash program memory,
0x0000. The program counter (PC) address the next instruction to be fetched.
Program flow is supported by conditional and unconditional jump and call instructions, capable of
addressing the whole address space directly. Most AVR instructions use a 16-bit word format, and a
limited number uses a 32-bit format.
During interrupts and subroutine calls, the return address PC is stored on the stack as a word pointer.
The stack is allocated in the general data SRAM, and consequently the stack size is only limited by the
total SRAM size and the usage of the SRAM. After Reset, the stack pointer (SP) points to the highest
address in the internal SRAM. The SP is read/write accessible in the I/O memory space, enabling easy
implementation of multiple stacks or stack areas. The data SRAM can easily be accessed through the
five different addressing modes supported by the AVR CPU.
8.5.2
Instruction Execution Timing
The AVR CPU is clocked by the CPU clock, CLK_CPU. No internal clock division is applied. The Figure
below shows the parallel instruction fetches and instruction executions enabled by the Harvard
architecture and the fast-access register file concept. This is the basic pipelining concept enabling up to
1MIPS/MHz performance with high efficiency.
Figure 8-2. The Parallel Instruction Fetches and Instruction Executions
T1
T2
T3
T4
clkCPU
1st Instruction Fetch
1st Instruction Execute
2nd Instruction Fetch
2nd Instruction Execute
3rd Instruction Fetch
3rd Instruction Execute
4th Instruction Fetch
The following Figure shows the internal timing concept for the register file. In a single clock cycle, an ALU
operation using two register operands is executed, and the result is stored in the destination register.
Figure 8-3. Single Cycle ALU Operation
T1
T2
T3
T4
clkCPU
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
8.5.3
Status Register
The Status register (CPU.SREG) contains information about the result of the most recently executed
arithmetic or logic instruction. This information can be used for altering program flow in order to perform
conditional operations.
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Datasheet Preliminary
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8-bit AVR Microcontroller
CPU.SREG is updated after all ALU operations, as specified in the Instruction Set Summary. This will in
many cases remove the need for using the dedicated compare instructions, resulting in faster and more
compact code. CPU.SREG is not automatically stored/restored when entering/returning from an interrupt
service routine. Maintaining the status register between context switches must therefore be handled by
user defined software. CPU.SREG is accessible in the I/O memory space.
Related Links
Instruction Set Summary
8.5.4
Stack and Stack Pointer
The Stack is used for storing return addresses after interrupts and subroutine calls. It can also be used
for storing temporary data. The Stack Pointer (SP) always point to the top of the Stack. The SP is defined
by the Stack Pointer bits (SP) in the Stack Pointer register (CPU.SP). CPU.SP is implemented as two 8bit registers that are accessible in the I/O memory space.
Data is pushed and popped from the Stack using the PUSH and POP instructions. The Stack grows from
higher to lower memory locations. This implies that pushing data onto the Stack decreases the SP, and
popping data off the Stack increases the SP. The Stack Pointer is automatically set to the highest address
of the internal SRAM after Reset. If the Stack is changed, it must be set to point above address 0x2000,
and it must be defined before both any subroutine calls are executed and before interrupts are enabled.
During interrupts or subroutine calls, the return address is automatically pushed on the Stack as a word
pointer and the SP is decremented by '2'. The return address consists of two bytes and the least
significant byte is pushed on the Stack first (at the higher address). As an example, a byte pointer return
address of 0x0006 is saved on the Stack as 0x0003 (shifted one bit to the right), pointing to the fourth 16bit instruction word in the program memory. The return address is popped off the Stack with RETI (when
returning from interrupts) and RET (when returning from subroutine calls) and the SP is incremented by
'2'.
The SP is decremented by '1' when data is pushed on the Stack with the PUSH instruction, and
incremented by '1' when data is popped off the Stack using the POP instruction.
To prevent corruption when updating the Stack pointer from software, a write to SPL will automatically
disable interrupts for up to four instructions or until the next I/O memory write.
8.5.5
Register File
The register file consists of 32 8-bit general purpose working registers with single clock cycle access time.
The register file supports the following input/output schemes:
•
•
•
•
One 8-bit output operand and one 8-bit result input
Two 8-bit output operands and one 8-bit result input
Two 8-bit output operands and one 16-bit result input
One 16-bit output operand and one 16-bit result input
Six of the 32 registers can be used as three 16-bit address register pointers for data space addressing,
enabling efficient address calculations.
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Datasheet Preliminary
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8-bit AVR Microcontroller
Figure 8-4. AVR CPU General Purpose Working Registers
R0
R1
R2
Addr.
0x00
0x01
0x02
R13
R14
R15
R16
R17
0x0D
0x0E
0x0F
0x10
0x11
R26
R27
R28
R29
R30
R31
0x1A
0x1B
0x1C
0x1D
0x1E
0x1F
0
7
...
...
X-register Low Byte
X-register High Byte
Y-register Low Byte
Y-register High Byte
Z-register Low Byte
Z-register High Byte
The register file is located in a separate address space and is therefore not accessible trough instructions
operation on data memory.
8.5.5.1
The X-, Y-, and Z- Registers
Registers R26...R31 have added functions besides their general-purpose usage.
These registers can form 16-bit address pointers for addressing data memory. These three address
registers are called the X-register, Y-register, and Z-register. Load and store instructions can use all X-, Yand Z-registers, while the LPM instructions can only use the Z-register. Indirect calls and jumps (ICALL
and IJMP) also use the Z-register.
Please refer to the instruction set or instruction set summary for more information about how the X-, Yand Z-registers are used.
Figure 8-5. The X-, Y- and Z-registers
Bit (individually)
7
X-register
15
Bit (individually)
7
Y-register
Bit (individually)
7
R29
15
7
R31
8
7
0
7
0
0
R28
0
YL
8
7
0
7
ZH
15
R26
XL
YH
Z-register
Bit (Z-register)
0
XH
Bit (X-register)
Bit (Y-register)
R27
0
R30
0
ZL
8
7
0
The lowest register address holds the least-significant byte (LSB), and the highest register address holds
the most-significant byte (MSB). In the different addressing modes, these address registers function as
fixed displacement, automatic increment, and automatic decrement.
Related Links
Instruction Set Summary
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
8.5.6
Accessing 16-bit Registers
The AVR data bus is 8 bits wide, and so accessing 16-bit registers requires atomic operations. These
registers must be byte-accessed using two read or write operations. 16-bit registers are connected to the
8-bit bus and a temporary register using a 16-bit bus.
For a write operation, the low byte of the 16-bit register must be written before the high byte. The low byte
is then written into the temporary register. When the high byte of the 16-bit register is written, the
temporary register is copied into the low byte of the 16-bit register in the same clock cycle.
For a read operation, the low byte of the 16-bit register must be read before the high byte. When the low
byte register is read by the CPU, the high byte of the 16-bit register is copied into the temporary register
in the same clock cycle as the low byte is read. When the high byte is read, it is then read from the
temporary register.
This ensures that the low and high bytes of 16-bit registers are always accessed simultaneously when
reading or writing the register.
Interrupts can corrupt the timed sequence if an interrupt is triggered and accesses the same 16-bit
register during an atomic 16-bit read/write operation. To prevent this, interrupts can be disabled when
writing or reading 16-bit registers.
The temporary registers can also be read and written directly from user software.
8.5.6.1
Accessing 24-bit Registers
For 24-bit registers, the read and write access is done in the same way as described for 16-bit registers,
except there are two temporary registers for 24-bit registers . The least-significant byte must be written
first when doing a write, and read first when doing a read.
8.5.7
CCP - Configuration Change Protection
System critical I/O register settings are protected from accidental modification. Flash self-programming
(via store to NVM controller) is protected from accidental execution. This is handled globally by the
configuration change protection (CCP) register.
Changes to the protected I/O registers or bits, or execution of protected instructions, are only possible
after the CPU writes a signature to the CCP register. The different signatures are listed in the description
of the CCP register (CPU.CCP).
There are two modes of operation: one for protected I/O registers, and one for the protected selfprogramming.
Related Links
CCP
8.5.7.1
Sequence for Write Operation to Configuration Change Protected I/O Registers
In order to write to registers protected by CCP, these steps are required:
1.
2.
The software writes the signature that enables change of protected I/O registers to the CCP bit field
in the CPU.CCP register.
Within four instructions, the software must write the appropriate data to the protected register.
Most protected registers also contain a write enable/change enable/lock bit. This bit must be written
to '1' in the same operation as the data are written.
The protected change is immediately disabled if the CPU performs write operations to the I/O
register or data memory, if load or store accesses to Flash, NVMCTRL, EEPROM are conducted,
or if the SLEEP instruction is executed.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
8.5.7.2
Sequence for Execution of Self-Programming
In order to execute self-programming (the execution of writes to the NVM controller's command register),
these steps are required:
1.
2.
The software temporary enables self-programming by writing the SPM signature to the CCP
register (CPU.CCP).
Within four instructions, the software must execute the appropriate instruction. The protected
change is immediately disabled if the CPU performs accesses to the Flash, NVMCTRL, or
EEPROM, or if the SLEEP instruction is executed.
Once the correct signature is written by the CPU, interrupts will be ignored for the duration of the
configuration change enable period. Any interrupt request (including non-maskable interrupts) during the
CCP period will set the corresponding interrupt flag as normal, and the request is kept pending. After the
CCP period is completed, any pending interrupts are executed according to their level and priority.
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Datasheet Preliminary
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8-bit AVR Microcontroller
8.6
Register Summary - CPU
Offset
Name
Bit Pos.
0x04
CCP
7:0
CCP[7:0]
7:0
SP[7:0]
0x05
...
Reserved
0x0C
0x0D
SP
0x0E
0x0F
15:8
SREG
SP[15:8]
7:0
I
T
8.7
Register Description
8.7.1
Configuration Change Protection
H
S
V
N
Z
C
Name: CCP
Offset: 0x04
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
CCP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – CCP[7:0]: Configuration Change Protection
Writing the correct signature to this bit field allows changing protected I/O registers or executing protected
instructions within the next four CPU instructions executed.
All interrupts are ignored during these cycles. After these cycles, interrupts will automatically be handled
again by the CPU, and any pending interrupts will be executed according to their level and priority.
When the protected I/O register signature is written, CCP[0] will read as '1' as long as the CCP feature is
enabled.
When the protected self-programming signature is written, CCP[1] will read as '1' as long as the CCP
feature is enabled.
CCP[7:2] will always read as zero.
Value
0x9D
0xD8
8.7.2
Name
SPM
IOREG
Description
Allow Self-Programming
Un-protect protected I/O registers
Stack Pointer
The CPU.SP holds the Stack Pointer (SP) that points to the top of the Stack. After Reset, the Stack
Pointer points to the highest internal SRAM address.
Only the number of bits required to address the available data memory including external memory (up to
64KB) is implemented for each device. Unused bits will always read as zero.
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Datasheet Preliminary
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8-bit AVR Microcontroller
The CPU.SPL and CPU.SPH register pair represents the 16-bit value, CPU.SP. The low byte [7:0] (suffix
L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset + 0x01. For
more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
To prevent corruption when updating the Stack Pointer from software, a write to CPU.SPL will
automatically disable interrupts for the next four instructions or until the next I/O memory write.
Name: SP
Offset: 0x0D
Reset: 0xxxxx
Property:
Bit
15
14
13
12
11
10
9
8
SP[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
x
x
x
x
x
x
x
x
Bit
7
6
5
4
3
2
1
0
SP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
x
x
x
x
x
x
x
x
Bits 15:8 – SP[15:8]: Stack Pointer high byte
These bits hold the MSB of the 16-bit register.
Bits 7:0 – SP[7:0]: Stack Pointer low byte
These bits hold the LSB of the 16-bit register.
8.7.3
Status Register
The Status register contains information about the result of the most recently executed arithmetic or logic
instruction. For details about the bits in this register and how they are affected by the different
instructions, see the Instruction Set Summary.
Name: SREG
Offset: 0x0F
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
3
2
1
0
I
T
H
S
V
N
Z
C
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 – I: Global Interrupt Enable
Writing a '1' to this bit enable interrupts on the device.
Writing a '0' to this bit disables interrupts on the device, independent of the individual interrupt enable
settings of the peripherals.
This bit is not cleared by hardware after an interrupt has occurred.
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This bit can be set and cleared by software with the SEI and CLI instructions.
Changing the I flag through the I/O-register result in a one-cycle wait state on the access.
Bit 6 – T: Bit Copy Storage
The bit copy instructions bit load (BLD) and bit store (BST) use the T bit as source or destination for the
operated bit.
A bit from a register in the register file can be copied into this bit by the BST instruction, and this bit can
be copied into a bit in a register in the register file by the BLD instruction.
Bit 5 – H: Half Carry Flag
This bit indicates a half carry in some arithmetic operations. Half carry is useful in BCD arithmetic.
Bit 4 – S: Sign Bit, S = N ⊕ V
The sign bit (S) is always an exclusive or (xor) between the negative flag (N) and the two’s complement
overflow flag (V).
Bit 3 – V: Two’s Complement Overflow Flag
The two’s complement overflow flag (V) supports two’s complement arithmetic.
Bit 2 – N: Negative Flag
The negative flag (N) indicates a negative result in an arithmetic or logic operation.
Bit 1 – Z: Zero Flag
The zero flag (Z) indicates a zero result in an arithmetic or logic operation.
Bit 0 – C: Carry Flag
The carry flag (C) indicates a carry in an arithmetic or logic operation.
Related Links
Interrupts
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8-bit AVR Microcontroller
9.
NVMCTRL - Non Volatile Memory Controller
9.1
Features
•
•
•
•
•
•
9.2
Unified memory
In-system programmable
Self-programming and boot loader support
Configurable sections for write protection:
– Boot section for boot loader code or application code
– Application code section for application code
– Application data section for application code or data storage
Signature Row for factory-programmed data:
– ID for each device type
– Serial number for each device
– Calibration bytes for factory calibrated peripherals
User Row for application data:
– 32 bytes in size
– Can be read and written from software
– Can be written from UPDI on locked device
– Content is kept after chip erase
Overview
The NVM Controller (NVMCTRL) is the interface between the device, the Flash, and the EEPROM. The
Flash and EEPROM are reprogrammable memory blocks that retain their values even when not powered.
The Flash is mainly used for program storage, but can also be used for data storage. The EEPROM is
used for data storage and can be programmed while the CPU is running the program from the Flash.
9.2.1
Block Diagram
Figure 9-1. NVMCTRL Block Diagram
NVM Block
Program Memory Bus
Flash
NVMCTRL
Data Memory Bus
EEPROM
Signature Row
User Row
9.2.2
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
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Table 9-1. NVMCTRL System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
Yes
CPUINT
Events
No
-
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
Interrupts
9.2.2.1
Clocks
This peripheral always runs on the CPU clock (CLK_CPU). It will request this clock also in sleep modes if
a write/erase is ongoing.
Related Links
CLKCTRL - Clock Controller
9.2.2.2
I/O Lines and Connections
Not applicable.
9.2.2.3
Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
9.2.2.4
Events
Not applicable.
9.2.2.5
Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in debugging
mode will halt normal operation of the peripheral.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
UPDI - Unified Program and Debug Interface
9.3
Functional Description
9.3.1
Memory Organization
9.3.1.1
Flash
The Flash is divided into a set of pages. A page is the basic unit addressed when programming the Flash.
It is only possible to write or erase a whole page at a time. One page consists of several words.
The Flash can be divided into three sections in blocks of 256 bytes for different security. The three
different sections are BOOT, application code (APPCODE) and application data (APPDATA).
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Figure 9-2. Flash Sections
FLASHSTART: 0x8000
BO OT
BOOTEND>0: 0x8000+BOOTEND*256
AP PL ICA TIO N
CO DE
APPEND>0: 0x8000+APPEND*256
AP PL ICA TIO N
DA TA
Section Sizes
The sizes of these sections are set by the Boot Section End fuse (FUSE.BOOTEND) and Application
Code Section End fuse (FUSE.APPEND).
The fuses select the section sizes in blocks of 256 bytes. As shown in Figure 9-2, the BOOT section
stretches from the start of the Flash until BOOTEND. The APPCODE section runs from BOOTEND until
APPEND. The remaining area is the APPDATA section. If APPEND is written to 0, the APPCODE section
runs from BOOTEND to the end of Flash (removing the APPDATA section). If BOOTEND and APPEND
are written to 0, the entire Flash is regarded as BOOT section. APPEND should either be set to 0 or a
value greater or equal than BOOTEND.
Table 9-2. Setting up Flash sections
BOOTEND APPEND
BOOT section
APPCODE section
APPDATA section
0
0
0 to FLASHEND
-
-
>0
0
0 to 256*BOOTEND
256*BOOTEND to
FLASHEND
-
>0
==
BOOTEND
0 to 256*BOOTEND
-
256*BOOTEND to
FLASHEND
>0
>
BOOTEND
0 to 256*BOOTEND
256*BOOTEND to
256*APPEND
256*APPEND to
FLASHEND
Note:
•
Also see BOOTEND and APPEND descriptions.
•
Interrupt vectors are by default located after the BOOT section. This can be changed in the
interrupt controller. Refer to Interrupt Vector Locations
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If FUSE.BOOTEND is written to 0x04 and FUSE.APPEND is written to 0x08, the first
4*256 bytes will be BOOT, the next 4*256 bytes will be APPCODE, and the remaining
Flash will be APPDATA.
Inter-Section Write Protection
Between the three Flash sections, a directional write protection is implemented:
•
Code in the BOOT section can write to APPCODE and APPDATA.
•
Code in APPCODE can write to APPDATA
•
Code in APPDATA cannot write to Flash or EEPROM.
Boot Section Lock and Application Code Section Write Protection
The two lock bits (APCWP and BOOTLOCK in NVMCTRL.CTRLB) can be set to lock further updates of
the respective APPCODE or BOOT section until the next Reset.
The CPU can never write to the BOOT section. NVMCTRL_CTRLB.BOOTLOCK prevents reads and
execution of code from the BOOT section.
9.3.1.2
EEPROM
The EEPROM is divided into a set of pages where one page consists of multiple bytes. The EEPROM
has byte granularity on erase write. Within one page, only the bytes marked to be updated will be erased/
written. The byte is marked by writing a new value to the page buffer for that address location.
9.3.1.3
User Row
The User Row is one extra page of EEPROM. This page can be used to store various data, such as
calibration/configuration data and serial numbers. This page is not erased by a chip erase. The User Row
is written as normal EEPROM, but in addition it can be written through UPDI on a locked device.
9.3.2
Memory Access
9.3.2.1
Read
Reading of the Flash and EEPROM is done by using a load instructions with address according to the
memory map. Reading any of the arrays while a write or erase is in progress will result in a bus wait, and
the instruction will be suspended until the ongoing operation is complete.
9.3.2.2
Page Buffer Load
The page buffer is loaded by writing directly to the memories as defined in the memory map. Flash,
EEPROM and User Row share the same page buffer so only one section can be programmed at one
time. The least significant bits of the address are used to select where in the page buffer the data is
written. The resulting data will be a binary AND operation between the new and the previous content of
the page buffer. The page buffer will automatically be erased (all bits set) after:
•
a device reset
•
any page write or erase operation
•
a clear page buffer command
•
the device wakes up from any sleep mode
9.3.2.3
Programming
For page programming, filling the page buffer and writing the page buffer into Flash, User Row and
EEPROM are two separate operations.
Before programming a flash page with the data in the page buffer, the flash page must be erased. The
page buffer is also erased when the device enter sleep mode. Programming an un-erased flash page will
corrupt its content.
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The flash can either be written with the erase and write separately or one command handling both:
Alternative 1:
•
Fill the page buffer
•
Write the page buffer to flash with the erase-write page command
Alternative 2:
•
Write to a location in the page to set up the address
•
Perform a erase page command
•
•
Fill the page buffer
Perform a write page command
The NVM command set supports both a single erase and write operation, and split page erase and page
write commands. This split commands enable shorter programming time for each command, and the
erase operations can be done during non-time-critical programming execution.
The EEPROM programming is similar, but only the bytes updated in the page buffer will be written or
erased in the EEPROM.
9.3.2.4
Commands
Reading of the Flash/EEPROM and writing of the page buffer is handled with normal load/store
instructions. Other operations, such as writing and erasing the memory arrays, are handled by commands
in the NVM.
To execute a command in the NVM:
1. Write the NVM command unlock to the Configuration Change Protection register in the CPU
(CPU.CCP).
2. Write the desired command value to the CMD bits in the Control A register (NVMCTRL.CTRLA)
within the next 4 instructions.
Write Command
The write command of the Flash controller writes the content of the page buffer to the Flash or
EEPROM.
If the write is to the Flash, the CPU will stop executing code as long as the Flash is busy with the write
operation. If the write is to the EEPROM, the CPU can continue executing code while the operation is
ongoing.
The page buffer will be automatically cleared after the operation is finished.
Erase Command
The erase command erases the current page. There must be one byte written in the page buffer for the
erase command to take effect.
For erasing the Flash, first write to one address in the desired page, then execute the command. The
whole page in the Flash will then be erased. The CPU will be halted while the erase is ongoing.
For the EEPROM, only the bytes written in the page buffer will be erased when the command is
executed. To erase a specific byte, write to its corresponding address before executing the command. To
erase a whole page all the bytes in the page buffer has to be updated before executing the command.
The CPU can continue running code while the operation is ongoing.
The page buffer will be automatically cleared after the operation is finished.
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Erase-Write Operation
The erase-write command is a combination of the erase and write command, but without clearing
the page buffer after the erase command: The erase-write operation first erases the selected page,
then it writes the content of the page buffer to the same page.
When executed on the Flash, the CPU will be halted when the operations are ongoing. When executed
on EEPROM, the CPU can continue executing code.
The page buffer will be automatically cleared after the operation is finished.
Page Buffer Clear Command
The page buffer clear command clears the page buffer. The contents of the page buffer will be allones after the operation. The CPU will be halted when the operation executes (7 CPU cycles).
Chip Erase Command
The chip erase command erases the Flash and the EEPROM. The EEPROM is unaltered if the
EEPROM Save During Chip Erase (EESAVE) fuse in FUSE.SYSCFG0 is set. The memory will be allones after the operation.
EEPROM Erase Command
The EEPROM erase command erases the EEPROM. The EEPROM will be all-ones after the operation.
The CPU will be halted while the EEPROM is being erased.
Fuse Write Command
The fuse write command writes the fuses. It can only be used by the UPDI, the CPU cannot start this
command.
Follow this procedure to use this command:
•
Write the address of the fuse to the Address register (NVMCTRL.ADDR)
•
Write the data to be written to the fuse to the Data register (NVMCTRL.DATA)
•
Execute the fuse write command.
•
After the fuse is written, a Reset is required for the updated value to take effect.
For reading fuses, use a regular read on the memory location.
9.3.3
Preventing Flash/EEPROM Corruption
During periods of low VDD, the Flash program or EEPROM data can be corrupted if the supply voltage is
too low for the CPU and the Flash/EEPROM to operate properly. These issues are the same as for board
level systems using Flash/EEPROM, and the same design solutions should be applied.
A Flash/EEPROM corruption can be caused by two situations when the voltage is too low: First, a regular
write sequence to the Flash requires a minimum voltage to operate correctly. Also, the CPU itself can
execute instructions incorrectly when the supply voltage is too low. See the Electrical Characteristics
chapter for Maximum Frequency vs. VDD.
Flash/EEPROM corruption can be avoided by these measures:
Keep the device in reset during periods of insufficient power supply voltage. This can be done by enabling
the internal Brown-Out Detector (BOD).
The voltage level monitor in the BOD can be used to prevent starting a write to the EEPROM close to the
BOD level.
If the detection levels of the internal BOD does not match the required detection level, an external lowVDD-reset protection circuit can be used. If a Reset occurs while a write operation is ongoing, the write
operation will be aborted.
Related Links
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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General Operating Ratings
BOD - Brownout Detector
9.3.4
Interrupts
Table 9-3. Available Interrupt Vectors and Sources
Offset Name
Vector Description
Conditions
0x00
NVM
The EEPROM is ready for new write/erase operations.
EEREADY
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Interrupt Flags register
of the peripheral (NVMCTRL.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding bit in the peripheral's Interrupt
Enable register (NVMCTRL.INTEN).
An interrupt request is generated when the corresponding interrupt source is enabled and the Interrupt
Flag is set. The interrupt request remains active until the Interrupt Flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear Interrupt Flags.
9.3.5
Sleep Mode Operation
If there is no ongoing write operation, the NVMCTRL will enter sleep mode when the system enters sleep
mode.
If a write operation is ongoing when the system enters a sleep mode, the NVM block, the NVM Controller
and the system clock will remain on until the write is finished. This is valid for all sleep modes, including
Power Down sleep mode.
The EEPROM Ready interrupt will wake up the device only from Idle sleep mode.
The page buffer is cleared when waking up from sleep.
9.3.6
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
Table 9-4. NVMCTRL - Registers under Configuration Change Protection
Register
Key
NVMCTRL.CTRLA
SPM
Related Links
Sequence for Execution of Self-Programming
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9.4
Register Summary - NVMCTRL
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
STATUS
7:0
0x03
INTCTRL
7:0
EEREADY
0x04
INTFLAGS
7:0
EEREADY
0x05
Reserved
0x06
DATA
0x07
0x08
ADDR
0x09
CMD[2:0]
BOOTLOCK
WRERROR
7:0
DATA[7:0]
15:8
DATA[15:8]
7:0
ADDR[7:0]
15:8
ADDR[15:8]
9.5
Register Description
9.5.1
Control A
EEBUSY
APCWP
FBUSY
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property: Configuration Change Protection
Bit
7
6
5
4
3
2
1
0
CMD[2:0]
Access
Reset
R/W
R/W
R/W
0
0
0
Bits 2:0 – CMD[2:0]: Command
Write this bit field to issue a command. The Configuration Change Protection key for self-programming
(SPM) has to be written within four instructions before this write.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
9.5.2
Name
WP
ER
ERWP
PBC
CHER
EEER
WFU
Description
No command
Write page buffer to memory (NVMCTRL.ADDR selects which memory)
Erase page (NVMCTRL.ADDR selects which memory)
Erase and write page (NVMCTRL.ADDR selects which memory)
Page buffer clear
Chip erase: erase Flash and EEPROM (unless EESAVE in FUSE.SYSCFG is '1')
EEPROM Erase
Write fuse (only accessible through UPDI)
Control B
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Name: CTRLB
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
Access
Reset
1
0
BOOTLOCK
APCWP
R/W
R/W
0
0
Bit 1 – BOOTLOCK: Boot Section Lock
Writing a '1' to this bit locks the boot section from read and instruction fetch.
If this bit is '1', a read from the boot section will return '0'. A fetch from the boot section will also return 0
as instruction.
This bit can only be written from the boot section. It can only be cleared to '0' by a Reset.
This bit will only take effect when the boot section is left the first time after the bit is written.
Bit 0 – APCWP: Application Code Section Write Protection
Writing a '1' to this bit protects the application code section from further writes.
This bit can only be written to '1', it is cleared to '0' only by Reset.
9.5.3
Status
Name: STATUS
Offset: 0x02
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
WRERROR
EEBUSY
FBUSY
Access
R
R
R
Reset
0
0
0
Bit 2 – WRERROR: Write Error
This bit will read '1' when a write error has happened. A write error could be writing to different sections
before doing a page write or writing to a protected area. This bit is valid for the last operation.
Bit 1 – EEBUSY: EEPROM Busy
This bit will read '1' when the EEPROM is busy with a command.
Bit 0 – FBUSY: Flash Busy
This bit will read '1' when the Flash is busy with a command.
9.5.4
Interrupt Control
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Name: INTCTRL
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
EEREADY
Access
R/W
Reset
0
Bit 0 – EEREADY: EEPROM Ready Interrupt
Writing a '1' to this bit enables the interrupt which indicates that the EEPROM is ready for new write/erase
operations.
This is a level interrupt that will be triggered only when the EEREADY flag in the INTFLAGS register is set
to zero. Thus, the interrupt should not be enabled before triggering an NVM command, as the EEREADY
flag will not be set before the NVM command issued. The interrupt should be disabled in the interrupt
handler.
9.5.5
Interrupt Flags
Name: INTFLAGS
Offset: 0x04
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
EEREADY
Access
R/W
Reset
0
Bit 0 – EEREADY: EEREADY Interrupt Flag
Interrupt flag for the EEPROM interrupt. This bit is cleared by writing a '1' to it. When this interrupt is
enabled, it will immediately request an interrupt, and it will continue to request interrupts continuously even if no EEPROM writes are initiated.
9.5.6
Data
The NVMCTRL.DATAL and NVMCTRL.DATAH register pair represents the 16-bit value,
NVMCTRL.DATA. The low byte [7:0] (suffix L) is accessible at the original offset. The high byte [15:8]
(suffix H) can be accessed at offset + 0x01. For more details on reading and writing 16-bit registers, refer
to Accessing 16-bit Registers.
Name: DATA
Offset: 0x06
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
15
14
13
12
11
10
9
8
DATA[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
DATA[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:0 – DATA[15:0]: Data Register
This register is used by the UPDI for fuse write operations.
9.5.7
Address
The NVMCTRL.ADDRL and NVMCTRL.ADDRH register pair represents the 16-bit value,
NVMCTRL.ADDR. The low byte [7:0] (suffix L) is accessible at the original offset. The high byte [15:8]
(suffix H) can be accessed at offset + 0x01. For more details on reading and writing 16-bit registers, refer
to Accessing 16-bit Registers.
Name: ADDR
Offset: 0x08
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
R/W
R/W
R/W
R/W
Reset
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
ADDR[15:8]
Access
ADDR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:0 – ADDR[15:0]: Address
The Address register contains the address to the last memory location that has been updated.
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8-bit AVR Microcontroller
10.
CLKCTRL - Clock Controller
Related Links
Clocks
10.1
Features
•
•
•
•
10.2
All clocks and clock sources are automatically enabled when requested by peripherals
Internal oscillators:
– 16/20MHz oscillator (OSC20M)
– 32KHz Ultra Low Power oscillator (OSCULP32K)
External clock options:
– 32.768kHz crystal oscillator (XOSC32K)
– External clock
Main clock features:
– Safe run-time switching
– Prescaler with 1x to 64x division in 12 different settings
Overview
The Clock Controller peripheral (CLKCTRL) controls, distributes, and prescales the clock signals from the
available oscillators. The CLKCTRL supports internal and external clock sources.
The CLKCTRL is based on an automatic clock request system, implemented in all peripherals on the
device. The peripherals will automatically request the clocks needed. If multiple clock sources are
available, the request is routed to the correct clock source.
The Main Clock (CLK_MAIN) is used by the CPU, RAM, and the IO bus. The Main Clock source can be
selected and prescaled. Some peripherals can share the same clock source as the Main Clock, or run
asynchronously to the Main Clock domain.
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10.2.1
Block Diagram - CLKCTRL
Figure 10-1. CLKCTRL Block Diagram
NVM
RAM
CPU
Other
Peripherals
CLKOUT
WDT
RTC
BOD
TCD
INT
PRESCALER
CLK_CPU
CLK_PER
CLK_RTC
CLK_WDT
CLK_BOD
CLK_TCD
TCD
CLKCSEL
Main Clock Prescaler
CLK_MAIN
RTC
CLKSEL
Main Clock Switch
DIV32
XOSC32K
OSCULP32K
OSC20M
XOSC32K
SEL
OSC20M
int. Oscillator
32KHz ULP
Int. Oscillator
32.768kHz
ext. Crystal Osc.
TOSC2
TOSC1
EXTCLK
The clock system consists of the Main Clock and other asynchronous clocks:
•
Main Clock
This clock is used by the CPU, RAM, Flash, the IO bus and all peripherals connected to the IO bus.
It is always running in Active and Idle sleep mode, and can be running in Standby sleep mode if
requested.
•
The main clock CLK_MAIN is prescaled and distributed by the Clock Controller:
•
CLK_CPU is used by the CPU, SRAM and the NVMCTRL peripheral to access the nonvolatile memory
•
CLK_PER is used by all peripherals that are not listed under asynchronous clocks.
Clocks running asynchronously to the Main Clock domain:
– CLK_RTC is used by the RTC/PIT. It will be requested when the RTC/PIT is enabled. The
clock source for CLK_RTC should only be changed if the peripheral is disabled.
– CLK_WDT is used by the WDT. It will be requested when the WDT is enabled.
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–
CLK_BOD is used by the BOD. It will be requested when the BOD is enabled in Sampled
Mode.
CLK_TCD is used by the TCD. It will be requested when the TCD is enabled. The clock
source can only be changed if the peripheral is disabled.
–
The clock source for the for the Main Clock domain is configured by writing to the Clock Select bits
(CLKSEL) in the Main Clock Control A register (CLKCTRL.MCLKCTRLA). The asynchronous clock
sources are configured by registers in the respective peripheral.
10.2.2
Signal Description
Signal
Type
Description
CLKOUT
Digital output
CLK_PER output
Related Links
I/O Multiplexing and Considerations
10.3
Functional Description
10.3.1
Sleep Mode Operation
When a clock source is not used/requested it will turn off. It is possible to request an clock source directly
by writing a '1' to the Run Standby bit (RUNSTDBY) in the respective oscillator's Control A register
(CLKCTRL.[osc]CTRLA). This will cause the oscillator to run constantly, except for Power Down sleep
mode. Additionally, when this bit is written to '1' the oscillator start-up time is eliminated when the clock
source is requested by a peripheral.
The Main Clock will always run in Active and Idle sleep mode. In Standby sleep mode, the Main Clock will
only run if any peripheral is requesting it, or the Run in Standby bit (RUNSTDBY) in the respective
oscillator's Control A register (CLKCTRL.[osc]CTRLA) is written to '1'.
In Power Down sleep mode, the Main Clock will stop after all NVM operations are completed.
10.3.2
Main Clock Selection and Prescaler
All internal oscillators can be used as the Main Clock source for CLK_MAIN. The Main Clock source is
selectable from software, and can be safely changed during normal operation.
Built-in hardware protection prevents unsafe clock switching:
Upon selection of an external clock source, a switch to the chosen clock source will only occur if edges
are detected, indicating it is stable. Until a sufficient number of clock edges are detected, the switch will
not occur and it will not be possible to change to another clock source again without executing a Reset.
An ongoing clock source switch is indicated by the System Oscillator Changing flag (SOSC) in the Main
Clock Status register (CLKCTRL.MCLKSTATUS). The stability of the external clock sources is indicated
by the respective status flags (EXTS and XOSC32KS in CLKCTRL.MCLKSTATUS).
Caution: If an external clock source fails while used as CLK_MAIN source, only the WDT can
provide a mechanism to switch back via System Reset.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
CLK_MAIN is fed into a prescaler before it is used by the peripherals (CLK_PER) in the device. The
prescaler divide CLK_MAIN by a factor from 1 to 64.
Figure 10-2. Main Clock and Prescaler
OSC20M
32kHz Osc.
CLK_MAIN
Main Clock Prescaler
(Div 1, 2, 4, 8, 16, 32,
64, 6, 10, 24, 48)
32.768kHz crystal Osc.
External clock
CLK_PER
The Main Clock and Prescaler configuration registers (CLKCTRL.MCLKCTRLA,
CLKCTRL.MCLKCTRLB) are protected by the Configuration Change Protection Mechanism, employing a
timed write procedure for changing these registers.
Related Links
CCP - Configuration Change Protection
10.3.3
Main Clock after Reset
After any Reset, CLK_MAIN is provided by the 16/20MHz oscillator (OSC20M) and with a Prescaler
division factor of 6. Since the actual frequency of the OSC20M is determined by the Frequency Select
bits (FREQSEL) of the Oscillator Configuration fuse (FUSE.OSCCFG), these frequencies are possible
after Reset:
Table 10-1. Peripheral Clock Frequencies after Reset
CLK_MAIN
as per FREQSEL in FUSE.OSCCFG
Resulting CLK_PER
16MHz
2.66MHz
20MHz
3.33MHz
See the OSC20M description for further details.
Related Links
16/20MHz Oscillator (OSC20M)
10.3.4
Clock Sources
All internal clock sources are enabled automatically when they are requested by a peripheral. The crystal
oscillator, based on an external crystal, must be enabled by writing a '1' to the ENABLE bit in the 32KHz
Crystal Oscillator Control A register (CLKCTRL.XOSC32KCTRLA) before it can serve as clock source.
The respective Oscillator Status bits in the Main Clock Status register (CLKCTRL.MCLKSTATUS) indicate
whether the clock source is running and stable.
Related Links
FUSES - Configuration and User Fuses
CCP - Configuration Change Protection
10.3.4.1 Internal Oscillators
The internal oscillators do not require any external components to run. See the related links for accuracy
and electrical characteristics.
16/20MHz Oscillator (OSC20M)
This oscillator can operate at multiple frequencies, selected by the value of the Frequency Select bits
(FREQSEL) in the Oscillator Configuration fuse (FUSE.OSCCFG). The center frequencies are:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
•
•
16MHz
20MHz
After a System Reset, FUSE.OSCCFG determines the initial frequency of CLK_MAIN.
During Reset the calibration values for the OSC20M are loaded from fuses . There are two different
calibration bit fields. The Calibration bit field (CAL20M) in the Calibration A register
(CLKCTRL.OSC20MCALIBA) enables calibration around the current center frequency. The Oscillator
Temperature Coefficient Calibration bit field (TEMPCAL20M) in the Calibration B register
(CLKCTRL.OSC20MCALIBB) enables adjustment of the slope of the temperature drift compensation.
For applications requiring more fine-tuned frequency setting than the oscillator calibration provides,
factory stored frequency error after calibrations are available. There are 4 errors, measured at different
settings, available in Signature Row as signed byte values.
•
•
SIGROW.OSC16ERR3V is the frequency error from 16MHz measured at 3V
SIGROW.OSC16ERR5V is the frequency error from 16MHz measured at 5V
•
•
SIGROW.OSC20ERR3V is the frequency error from 20MHz measured at 3V
SIGROW.OSC20ERR5V is the frequency error from 20MHz measured at 5V
The example code below, demonstrates how to apply this value for more accurate USART baud rate:
/* Baud rate compensated with factory stored frequency error */
/* Synchronous communication without Auto-baud (Sync Field) */
/* 16MHz Clock, 3V and 600 BAUD
*/
int8_t sigrow_value
int32_t baud
= SIGROW.OSC16ERR3V;
= 600;
baud *= (1024 + sigrow_value);
baud /= 1024;
USART0.BAUD = (int16_t) baud;
// read signed error
// ideal baud rate
// sum resolution + error
// divide by resolution
// set adjusted baud rate
The oscillator calibration can be locked by the Oscillator Lock (OSCLOCK) fuse (FUSE.OSCCFG). When
this fuse is '1', it is not possible to change the calibration. The calibration is also locked if this oscillator is
used as Main Clock source and the Lock Enable bit (LOCKEN) in the Control B register
(CLKCTRL.OSC20MCALIBB) is '1'.
The calibration bits are also protected by the Configuration Change Protection Mechanism, requiring a
timed write procedure for changing the Main Clock and Prescaler settings.
The start-up time of this oscillator is analog start-up time plus 4 oscillator cycles. Refer to Electrical
Characteristics chapter for the start-up time.
When changing oscillator calibration value, the frequency may overshoot. If the oscillator is used as the
main clock (CLK_MAIN) it is recommended to change the main clock prescaler so that the main clock
frequency does not exceed ¼ of the maximum operation main clock frequency as described in the
General Operating Ratings. The system clock prescaler can be changed back after the oscillator
calibration value has been updated.
Related Links
FUSES - Configuration and User Fuses
Configuration Change Protection
General Operating Ratings
Main Clock after Reset
Oscillators and Clocks
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Datasheet Preliminary
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8-bit AVR Microcontroller
OSC20M Stored Frequency Error Compensation
This oscillator can operate at multiple frequencies, selected by the value of the Frequency Select bits
(FREQSEL) in the Oscillator Configuration fuse (FUSE.OSCCFG) at Reset. As previously mentioned
appropriate calibration values are loaded to adjust to center frequency (OSC20M), and temperature drift
compensation (TEMPCAL20M), meeting the specifications defined in the Internal Oscillator
Characteristics. For applications requiring wider operating range, the relative factory stored frequency
error after calibrations can be used. The 4 errors are measured at different setting and are available in
Signature Row as signed byte values.
•
•
•
•
SIGROW.OSC16ERR3V is the frequency error from 16MHz measured at 3V
SIGROW.OSC16ERR5V is the frequency error from 16MHz measured at 5V
SIGROW.OSC20ERR3V is the frequency error from 20MHz measured at 3V
SIGROW.OSC20ERR5V is the frequency error from 20MHz measured at 5V
The Error is stored as a compressed Q1.10 fixed point 8 bit value, in order not to lose resolution, where
the MSB is the sign bit and the 7 LSBs the lower bits of the Q.10.
BAUDact��� = BAUD����� +
BAUD����� * �����������
1024
The example below, demonstrates how to use this factory stored error value for more accurate USART
baud rates:
/* Baud rate compensated with factory stored frequency error */
/* Synchronous communication without Auto-baud (Sync Field) */
/* 16MHz Clock, 3V and 600 BAUD register value
*/
int8_t sigrow_val
int32_t baud_reg_val
= SIGROW.OSC16ERR3V;
= 600;
baud_reg_val *= (1024 + sigrow_value);
baud_reg_val /= 1024;
USART0.BAUD = (int16_t) baud_reg_val;
// read signed error
// ideal baud rate
// sum resolution + error
// divide by resolution
// set adjusted baud rate
Related Links
USART - Universal Synchronous and Asynchronous Receiver and Transmitter
Features
Overview
Signal Description
System Dependencies
Clocks
Events
Debug Operation
Block Diagram
Oscillators and Clocks
32KHz Oscillator (OSCULP32K)
The 32KHz oscillator is optimized for Ultra Low Power (ULP) operation. Power consumption is decreased
at the cost of decreased accuracy compared to an external crystal oscillator.
This oscillator also provides the 1KHz signal for the Real Time Counter (RTC), the Watchdog Timer
(WDT), and the Brownout Detector (BOD).
The start-up time of this oscillator is the oscillator start-up time plus 4 oscillator cycles. Refer to Electrical
Characteristics chapter for the start-up time.
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Datasheet Preliminary
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8-bit AVR Microcontroller
Related Links
BOD - Brownout Detector
WDT - Watchdog Timer
RTC - Real Time Counter
10.3.4.2 External Clock Sources
These external clock sources are available:
•
External clock from pin. (EXTCLK).
•
The TOSC1 and TOSC2 pins are dedicated to driving a 32.768kHz crystal oscillator (XOSC32K).
•
Instead of a crystal oscillator, TOSC1 can be configured to accept an external clock source.
32.768kHz Crystal Oscillator (XOSC32K)
This oscillator supports two input options: Either a crystal is connected to the pins TOSC1 and TOSC2, or
an external clock running at 32KHz is connected to TOSC1. The input option must be configured by
writing the Source Select bit (SEL) in the XOSC32K Control A register (CLKCTRL.XOSC32KCTRLA).
The XOSC32K is enabled by writing a '1' to its ENABLE bit in CLKCTRL.XOSC32KCTRLA. When
enabled, the configuration of the GPIO pins used by the XOSC32K is overridden as TOSC1, TOSC2 pins.
The Enable bit needs to be set for the oscillator to start running when requested.
The start-up time of a given crystal oscillator can be accommodated by writing to the Crystal Start-up
Time bits (CSUT) in CLKCTRL.XOSC32KCTRLA.
When XOSC32K is configured to use an external clock on TOSC1, the start-up time is fixed to 2 cycles.
External Clock (EXTCLK)
The External Clock is taken directly from the pin. This GPIO pin is automatically configured for EXTCLK if
any peripheral is requesting this clock.
This clock source has a start-up time of 2 cycles when first requested.
10.3.5
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
Table 10-2. CLKCTRL - Registers under Configuration Change Protection
Register
Key
CLKCTRL.MCLKCTRLB
IOREG
CLKCTRL.MCLKLOCK
IOREG
CLKCTRL.XOSC32KCTRLA
IOREG
CLKCTRL.MCLKCTRLA
IOREG
CLKCTRL.OSC20MCTRLA
IOREG
CLKCTRL.OSC20MCALIBA
IOREG
CLKCTRL.OSC20MCALIBB
IOREG
CLKCTRL.OSC32KCTRLA
IOREG
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Related Links
Sequence for Write Operation to Configuration Change Protected I/O Registers
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
10.4
Register Summary - CLKCTRL
Offset
Name
Bit Pos.
0x00
MCLKCTRLA
7:0
0x01
MCLKCTRLB
7:0
0x02
MCLKLOCK
7:0
0x03
MCLKSTATUS
7:0
CLKOUT
CLKSEL[1:0]
PDIV[3:0]
PEN
LOCKEN
EXTS
XOSC32KS
OSC32KS
OSC20MS
SOSC
0x04
...
Reserved
0x0F
0x10
OSC20MCTRLA
7:0
0x11
OSC20MCALIBA
7:0
0x12
OSC20MCALIBB
7:0
RUNSTDBY
CAL20M[5:0]
LOCK
TEMPCAL20M[3:0]
0x13
...
Reserved
0x17
0x18
OSC32KCTRLA
7:0
RUNSTDBY
0x19
...
Reserved
0x1B
0x1C
XOSC32KCTRLA
7:0
CSUT[1:0]
10.5
Register Description
10.5.1
Main Clock Control A
SEL
RUNSTDBY
ENABLE
Name: MCLKCTRLA
Offset: 0x00
Reset: 0x00
Property: Configuration Change Protection
Bit
7
6
5
4
3
2
1
CLKOUT
Access
Reset
0
CLKSEL[1:0]
R/W
R
R
R
R
R
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 – CLKOUT: System Clock Out
When this bit is written to '1', the system clock is output to CLKOUT pin.
When the device is in a sleep mode, there is no clock output unless a peripheral is using the system
clock.
Bits 1:0 – CLKSEL[1:0]: Clock Select
This bit field selects the source for the Main Clock (CLK_MAIN).
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8-bit AVR Microcontroller
Value
0x0
0x1
0x2
0x3
10.5.2
Name
OSC20M
OSCULP32K
XOSC32K
EXTCLK
Description
16/20MHz internal oscillator
32KHz internal Ultra Low Power oscillator
32.768kHz external crystal oscillator
External clock
Main Clock Control B
Name: MCLKCTRLB
Offset: 0x01
Reset: 0x11
Property: Configuration Change Protection
Bit
7
6
5
4
3
2
1
Access
R
R
R
R/W
Reset
0
0
0
1
0
R/W
R/W
R/W
R/W
0
0
0
1
PDIV[3:0]
PEN
Bits 4:1 – PDIV[3:0]: Prescaler Division
If the Prescaler Enable (PEN) bit is written to '1', these bits define the division ratio of the Main Clock
prescaler.
These bits can be written during run-time to vary the clock frequency of the system to suit the application
requirements.
User software must ensure a correct configuration of input frequency (CLK_MAIN) and Prescaler settings,
such that the resulting frequency of CLK_PER never exceeds the allowed maximum (see Electrical
Characteristics).
Value
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x8
0x9
0xA
0xB
0xC
other
Description
Division
2
4
8
16
32
64
6
10
12
24
48
Reserved
Bit 0 – PEN: Prescaler Enable
This bit must be written '1' to enable the prescaler. When enabled, the division ratio is selected by the
PDIV bit field.
When this bit is written to '0', the Main Clock will pass through undivided (CLK_PER=CLK_MAIN),
regardless of the value of PDIV.
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Datasheet Preliminary
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8-bit AVR Microcontroller
10.5.3
Main Clock Lock
Name: MCLKLOCK
Offset: 0x02
Reset: 0x00
Property: Configuration Change Protection
Bit
7
6
5
4
3
2
1
0
LOCKEN
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
x
Bit 0 – LOCKEN: Lock Enable
Writing this bit to '1' will lock the CLKCTRL.MCLKCTRLA and CLKCTRL.MCLKCTRLB registers, and, if
applicable, the calibration settings for the current Main Clock source from further software updates. Once
locked, the CLKCTRL.MCLKLOCK registers cannot be accessed until the next hardware Reset.
This provides protection for the CLKCTRL.MCLKCTRLA and CLKCTRL.MCLKCTRLB registers and
calibration settings for the Main Clock source from unintentional modification by software.
10.5.4
Main Clock Status
Name: MCLKSTATUS
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
EXTS
XOSC32KS
OSC32KS
OSC20MS
3
2
1
0
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
SOSC
Bit 7 – EXTS: External Clock Status
Value
0
1
Description
EXTCLK has not started
EXTCLK has started
Bit 6 – XOSC32KS: XOSC32K Status
The status bit will only be available if the source is requested as the main clock or by another module. If
the oscillators RUNSTDBY bit is set but the oscillator is unused/not requested this bit will be 0.
Value
0
1
Description
XOSC32K is not stable
XOSC32K is stable
Bit 5 – OSC32KS: OSCULP32K Status
The status bit will only be available if the source is requested as the main clock or by another module. If
the oscillators RUNSTDBY bit is set but the oscillator is unused/not requested this bit will be 0.
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Datasheet Preliminary
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8-bit AVR Microcontroller
Value
0
1
Description
OSCULP32K is not stable
OSCULP32K is stable
Bit 4 – OSC20MS: OSC20M Status
The status bit will only be available if the source is requested as the main clock or by another module. If
the oscillators RUNSTDBY bit is set but the oscillator is unused/not requested this bit will be 0.
Value
0
1
Description
OSC20M is not stable
OSC20M is stable
Bit 0 – SOSC: Main Clock Oscillator Changing
Value
0
1
10.5.5
Description
The clock source for CLK_MAIN is not undergoing a switch.
The clock source for CLK_MAIN is undergoing a switch, and will change as soon as the new
source is stable.
16/20MHz Oscillator Control A
Name: OSC20MCTRLA
Offset: 0x10
Reset: 0x00
Property: Configuration Change Protection
Bit
7
6
5
4
3
2
1
0
RUNSTDBY
Access
R
R
R
R
R
R
R/W
R
Reset
0
0
0
0
0
0
0
0
Bit 1 – RUNSTDBY: Run Standby
This bit force the oscillator on in all modes, even when unused by the system. In standby sleep mode this
can be used to ensure immediate wake-up and not waiting for oscillator start-up time.
When not requested by peripherals, no oscillator output is provided.
It takes 4 oscillator cycles to open the clock gate after a request but the oscillator analog start-up time will
be removed when this bit is set.
10.5.6
16/20MHz Oscillator Calibration A
Name: OSC20MCALIBA
Offset: 0x11
Reset: Based on FREQSEL in FUSE.OSCCFG
Property: Configuration Change Protection
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Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
CAL20M[5:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
x
x
x
x
x
x
Bits 5:0 – CAL20M[5:0]: Calibration
These bits change the frequency around the current center frequency of the OSC20M for fine tuning.
At Reset factory calibrated values are loaded based on FREQSEL bits in FUSE.OSCCFG.
10.5.7
16/20MHz Oscillator Calibration B
Name: OSC20MCALIBB
Offset: 0x12
Reset: Based on FUSE.OSCCFG
Property: Configuration Change Protection
Bit
7
6
5
4
3
LOCK
2
1
0
TEMPCAL20M[3:0]
Access
R
R/W
R/W
R/W
R/W
Reset
x
x
x
x
x
Bit 7 – LOCK: Oscillator Calibration Locked by Fuse
When this bit is set, the calibration settings in CLKCTRL.OSC20MCALIBA and
CLKCTRL.OSC20MCALIBB cannot be changed.
The Reset value is loaded from the OSCLOCK bit in the Oscillator Configuration fuse (FUSE.OSCCFG).
Bits 3:0 – TEMPCAL20M[3:0]: Oscillator Temperature Coefficient Calibration
These bits tune the slope of the temperature compensation.
At Reset factory calibrated values are loaded based on FREQSEL bits in FUSE.OSCCFG.
10.5.8
32KHz Oscillator Control A
Name: OSC32KCTRLA
Offset: 0x18
Reset: 0x00
Property: Configuration Change Protection
Bit
7
6
5
4
3
2
1
0
RUNSTDBY
Access
R
R
R
R
R
R
R/W
R
Reset
0
0
0
0
0
0
0
0
Bit 1 – RUNSTDBY: Run Standby
This bit force the oscillator on in all modes, even when unused by the system. In standby sleep mode this
can be used to ensure immediate wake-up and not waiting for oscillator start-up time.
When not requested by peripherals, no oscillator output is provided.
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8-bit AVR Microcontroller
It takes 4 oscillator cycles to open the clock gate after a request but the oscillator analog start-up time will
be removed when this bit is set.
10.5.9
32.768kHz Crystal Oscillator Control A
The SEL and CSUT bits cannot be changed as long as the ENABLE bit is set or the XOSC32K Stable bit
(XOSC32KS) in CLKCTRL.MCLKSTATUS is high.
To change settings in a safe way: write a '0' to the ENABLE bit and wait until XOSC32KS is '0' before reenabling the XOSC32K with new settings.
Name: XOSC32KCTRLA
Offset: 0x1C
Reset: 0x00
Property: Configuration Change Protection
Bit
7
6
5
4
3
CSUT[1:0]
2
1
0
SEL
RUNSTDBY
ENABLE
Access
R
R
R/W
R/W
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 5:4 – CSUT[1:0]: Crystal Start-Up Time
These bits select the start-up time for the XOSC32K. It is write protected when the oscillator is enabled
(ENABLE=1).
If SEL=1, the start-up time will not be applied.
Value
0x0
0x1
0x2
0x3
Name
1K
16K
32K
64K
Description
1k cycles
16k cycles
32k cycles
64k cycles
Bit 2 – SEL: Source Select
This bit select the external source type. It is write protected when the oscillator is enabled (ENABLE=1).
Value
0
1
Description
External crystal
External clock on TOSC1 pin
Bit 1 – RUNSTDBY: Run Standby
Writing this bit to '1' starts the crystal oscillator and forces the oscillator on in all modes, even when
unused by the system if the ENABLE bit is set. In standby sleep mode this can be used to ensure
immediate wake-up and not waiting for oscillator start-up time. When this bit is '0', the crystal oscillator is
only running when requested and the ENABLE bit is set.
The output of XOSC32K is not sent to other peripherals unless it is requested by one or more peripherals.
When the RUNSTDBY bit is set there will only be a delay of two to three crystal oscillator cycles after a
request until the oscillator output is received, if the initial crystal start-up time already has completed.
According to RUNSTBY bit, the oscillator will be turned on all the time if the device is in Active, Idle or
Standby sleep mode, or only be enabled when requested.
This bit is I/O protected to prevent unintentional enabling of the oscillator.
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8-bit AVR Microcontroller
Bit 0 – ENABLE: Enable
When this bit is written to '1', the configuration of the respective input pins is overridden to TOSC1 and
TOSC2. Also, the Source Select bit (SEL) and Crystal Start-Up Time (CSUT) become read-only.
This bit is I/O protected to prevent unintentional enabling of the oscillator.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
11.
SLPCTRL - Sleep Controller
11.1
Features
•
•
•
11.2
Three sleep modes:
– Idle
– Standby
– Power Down
Configurable Standby sleep mode where peripherals can be configured as on or off.
SleepWalking in Standby sleep mode, where the PTC can start running on an Event without waking
up the device.
Overview
Sleep modes are used to shut down peripherals and clock domains in the device in order to save power.
The Sleep Controller (SLPCTRL) controls and handles the transitions between active mode and sleep
mode.
There are in total four modes available, one active mode in which software is executed, and three sleep
modes. The available sleep modes are: Idle, Standby and Power Down.
When the device enters a sleep mode, program execution is stopped, and depending on the entered
sleep mode, different peripherals and clock domains are turned off.
To enter a sleep mode, the SLPCTRL must be enabled and the desired sleep mode must be stated. The
software decides when to enter that sleep mode by using a dedicated sleep instruction (SLEEP).
Interrupts are used to wake up the device from sleep. The available Interrupt wake-up sources depend on
the configured sleep mode. When an interrupt occurs, the device will wake up and execute the interrupt
service routine before continuing normal program execution from the first instruction after the sleep
instruction. Any Reset will also take the device out of a sleep mode.
11.2.1
Block Diagram
Figure 11-1. Sleep Controller in System
Sleep instruction
SLPCTRL
Interrupt request
CPU
Sleep state
Interrupt request
Peripheral
11.2.2
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Table 11-1. SLPCTRL System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
no
-
Events
No
-
Debug
Yes
UPDI
11.2.2.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
CLKCTRL - Clock Controller
11.2.2.2 I/O Lines and Connections
Not applicable.
11.2.2.3 Interrupts
Not applicable.
11.2.2.4 Events
Not applicable.
11.2.2.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. The SLPCTRL is only affected
by a break in debug operation: If the SLPCTRL is in a sleep mode when a break occurs, the device will
wake up and the SLPCTRL will go to active mode, even if there are no pending interrupt requests.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
11.3
Functional Description
11.3.1
Initialization
To put the device into a sleep mode, follow these steps:
•
Configure and enable the interrupts that should wake up the device from sleep. Also enable global
interrupts.
Warning: If there are no interrupts enabled when going to sleep, the device cannot wake
up again. Only a reset will allow the device to continue operation.
•
Select the sleep mode to be entered and enable the Sleep Controller by writing to the Sleep Mode
bits (SMODE) and the Enable bit (SEN) in the Control A register (SLPCTRL.CTRLA). A SLEEP
instruction must be run to make the device actually go to sleep.
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8-bit AVR Microcontroller
11.3.2
Operation
11.3.2.1 Sleep Modes
In addition to Active mode, there are three different sleep modes, with decreasing power consumption
and functionality.
Idle
The CPU stops executing code, no peripherals are disabled.
All interrupt sources can wake up the device.
Standby
The user can configure peripherals to be enabled or not, using the respective RUNSTBY bit.
This means that the power consumption is highly dependent on what functionality is enabled,
and thus may vary between the Idle and Power Down levels.
SleepWalking is available for the ADC module.
The wake-up sources are Pin interrupts, TWI address match, UART Start-of-Frame interrupt
(if USART is enabled to run in Standby), ADC window interrupt (if PTC enabled to run in
Standby), RTC interrupt (if RTC enabled to run in Standby), and TCB interrupt.
Only the WDT and the PIT (component of the RTC) are active.
The only wake-up sources are the pin change interrupt and TWI address match.
Power
Down
Table 11-2. Sleep Mode Activity Overview
Group
Peripheral
Active in Sleep Mode
Clock
Active Clock
Domain
Oscillators
Wake-Up
Sources
Idle
Standby
Power Down
CPU
CLK_CPU
Peripherals
CLK_PER
X
RTC
CLK_RTC
X
X*
ADC/PTC
CLK_PER
X
X*
PIT (RTC)
CLK_RTC
X
X
X
WDT
CLK_WDT
X
X
X
Main Clock Source
X
X*
RTC Clock Source
X
X*
WDT Oscillator
X
X
X
INTn and pin change
X
X
X
TWI address match
X
X
X
Periodic Interrupt Timer
X
X
X
UART start of frame
X
X*
ADC/PTC window
X
X*
RTC interrupt
X
X*
All other interrupts
X
Note:
•
X means active. X* indicates that the RUNSTBY bit of the corresponding peripheral must be set to
enter active state.
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8-bit AVR Microcontroller
11.3.2.2 Wake-Up Time
The normal wake-up time for the device is 6 Main Clock cycles (CLK_PER), plus the time it takes to start
up the Main Clock source:
•
In Idle sleep mode the Main Clock source is kept running so it will not be any extra wake-up time.
•
In Standby sleep mode the Main Clock might be running, so it depends on the peripheral
configuration.
•
In Power Down sleep mode only the ULP 32KHz oscillator and RTC clock may be running, if it is
used by the BOD or WDT. All other clock sources will be off.
Table 11-3. Sleep modes and Start-up time
Sleep mode
Start-up time
IDLE
6 CLK
Standby
6 CLK + OSC start-up
Power Down
6 CLK + OSC start-up
The start-up time for the different clock sources is described in the Clock Controller (CLKCTRL) section.
In addition to the normal wake-up time it is possible to make the device wait until the BOD is ready before
executing code. This is done by writing 0x3 to the BOD Operation Mode in Active and Idle bits (ACTIVE)
in the BOD Configuration fuse (FUSE.BODCFG). If the BOD is ready before the normal wake-up time, the
net wake-up time will be the same. If the BOD takes longer than the normal wake-up time, the wake-up
time will be extended until the BOD is ready. This is ensures correct supply voltage whenever code is
executed.
11.3.3
Configuration Change Protection
Not applicable.
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8-bit AVR Microcontroller
11.4
Register Summary - SLPCTRL
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
SMODE[1:0]
11.5
Register Description
11.5.1
Control A
SEN
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
SMODE[1:0]
SEN
Access
R
R
R
R
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 2:1 – SMODE[1:0]: Sleep Mode
Writing these bits selects the sleep mode entered when the Sleep Enable bit (SEN) is written to '1' and
the SLEEP instruction is executed.
Value
0x0
0x1
0x2
other
Name
IDLE
STANDBY
PDOWN
-
Description
Idle sleep mode enabled
Standby sleep mode enabled
Power Down sleep mode enabled
Reserved
Bit 0 – SEN: Sleep Enable
This bit must be written to '1' before the SLEEP instruction is executed to make the MCU enter the
selected sleep mode.
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8-bit AVR Microcontroller
12.
RSTCTRL - Reset Controller
12.1
Features
•
•
•
Reset the device and set it to an initial state.
Reset Flag register for identifying the Reset source in software.
Multiple Reset sources:
–
–
12.2
Power supply Reset sources: Brownout Detect (BOD), Power On Reset (POR)
User Reset sources: External Reset pin (RESET), Watchdog Reset (WDT), Software Reset
(SW) and UPDI Reset.
Overview
The Reset Controller (RSTCTRL) manages the Reset of the device. It issues a device Reset, sets the
device to its initial state, and allows the Reset source to be identified by software.
12.2.1
Block Diagram
Figure 12-1. Reset System Overview
RESET SOURCES
TCD pin
override settings
(Loaded from fuses)
POR
VDD
Pull-up
resistor
RESET
RESET CONTROLLER
BOD
FILTER
UPDI
External Reset
WDT
All other
Peripherals
UPDI
CPU (SW)
12.2.2
Signal Description
Signal
Description
Type
RESET
External Reset (active low)
Digital input
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8-bit AVR Microcontroller
12.3
Functional Description
12.3.1
Initialization
The Reset Controller (RSTCTRL) is always enabled, but some of the Reset sources must be enabled
(either by fuses or by software) before they can request a Reset.
After any Reset, the Reset source that caused the Reset is found in the Reset Flag register
(RSTCTRL.RSTFR).
After a Power-On Reset, only the POR flag will be set.
The flags are kept until they are cleared by writing a '1' to them.
During a Power-On Reset, all registers that are loaded from fuses are reloaded.
12.3.2
Operation
12.3.2.1 Reset Sources
There are two kind of sources for Resets:
•
Power supply Resets, which are caused by changes in the power supply voltage: Power-on Reset
(POR) and Brownout Detector (BOD).
•
User Resets, which are issued by the application, by debug operation or by pin changes (Software
Reset, Watchdog Reset, UPDI Reset and external Reset pin RESET).
Power-On Reset (POR)
A power-on-reset (POR) is generated by an on-chip detection circuit. The POR is activated when the VDD
rises until it reach the POR treshold voltage. The POR is always enabled and will also detect when the
VDD falls below the treshold voltage.
All logic is reset on POR and registers that are loaded with fuse values will be reloaded during the reset
sequence.
Brownout Detector (BOD) Reset Source
The on-chip Brown-out Detection circuit will monitor the VDD level during operation by comparing it to a
fixed trigger level. The trigger level for the BOD can be selected by fuses. If BOD is unused in application
it is forced on to a minimum level in order to guarantee safe operation during internal reset and chip
erase.
A BOD Reset will reset all logic.
Related Links
BOD - Brownout Detector
Software Reset
The software reset makes it possible to issue a system reset from software. The reset is generated by
writing a '1' to the Software Reset Enable bit (SWRE) in the Software Reset register (RSTCTRL.SWRR).
The reset will take place immediately after the bit is written and the device will be kept in reset until the
reset sequence is completed. All logic is reset on software reset, with exception for UPDI, TCD fuse
configuration and BOD configuration.
External Reset
The External Reset is enabled by fuse (see fuse map).
When enabled, the External Reset requests a Reset as long as the RESET pin is low. The device will
stay in Reset until RESET is high again. An External Reset resets the entire device except the UPDI,
TCD pin override settings and BOD settings.
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8-bit AVR Microcontroller
Related Links
FUSES - Configuration and User Fuses
Watchdog Reset
The watchdog timer (WDT) is a system function for monitoring correct program operation. If the WDT is
not reset from software according to the programmed timeout period, a watchdog reset will be issued.
See the WDT documentation for further details.
A WDT reset will reset all logic except UPDI, TCD pin override settings and BOD settings.
Related Links
WDT - Watchdog Timer
Universal Program Debug Interface (UPDI) Reset
The UPDI contains a separate reset source that is used to reset the device during external programming
and debugging. The reset source is accessible only from external debuggers and programmers. The
UPDI reset will reset all logic except the UPDI itself, TCD pin override settings and BOD settings. See
UPDI chapter on how to generate a UPDI reset request.
Related Links
UPDI - Unified Program and Debug Interface
12.3.2.2 Reset time
The reset time can be split in two.
The first part is when any of the Reset sources are active. This part depends on the input to the Reset
sources. The external reset is active as long as the RESET pin is low, the power-on-reset (POR) and
Brownout detector (BOD) is active as long as the supply voltage is below reset source threshold.
When all the Reset sources are released an Internal reset initialization of the device is done. The time it
take to do the Internal reset initialization is typical 250 µs. This time will be increased with the Start Up
time given by the Start Up time fuse setting (SYSCFG1.SUT). The Internal reset initialization time will also
increase if the CRC source is setup to run (SYSCFG0.CRCSRC). The additional Internal reset time will
increase by 500 µs for each KB of memory that is checked.
12.3.3
Sleep Mode Operation
The Reset Controller continues to operate in all active and sleep modes.
12.3.4
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
Table 12-1. RSTCTRL - Registers under Configuration Change Protection
Register
Key
RSTCTRL.SWRR
IOREG
Related Links
Sequence for Write Operation to Configuration Change Protected I/O Registers
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
12.4
Register Summary - RSTCTRL
Offset
Name
Bit Pos.
0x00
RSTFR
7:0
0x01
SWRR
7:0
UPDIRF
SWRF
WDRF
EXTRF
BORF
PORF
SWRE
12.5
Register Description
12.5.1
Reset Flag Register
All flags are cleared by writing a '1' to them. They are also cleared by a Power-on Reset, with the
exception of the Power-On Reset Flag (PORF).
Name: RSTFR
Offset: 0x00
Reset: 0xXX
Property:
Bit
7
6
5
4
3
2
1
0
UPDIRF
SWRF
WDRF
EXTRF
BORF
PORF
Access
R
R
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
x
x
x
x
x
x
Bit 5 – UPDIRF: UPDI Reset Flag
This bit is set if a UPDI Reset occurs.
Bit 4 – SWRF: Software Reset Flag
This bit is set if a Software Reset occurs.
Bit 3 – WDRF: Watchdog Reset Flag
This bit is set if a Watchdog Reset occurs.
Bit 2 – EXTRF: External Reset Flag
This bit is set if an External reset occurs.
Bit 1 – BORF: Brownout Reset Flag
This bit is set if a Brownout Reset occurs.
Bit 0 – PORF: Power-On Reset Flag
This bit is set if a Power-on Reset occurs.
This flag is only cleared by writing a '1' it.
After a POR, only the POR flag is set and all other flags are cleared. No other flag can be set before a full
system boot is run after the POR.
12.5.2
Software Reset Register
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Datasheet Preliminary
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8-bit AVR Microcontroller
Name: SWRR
Offset: 0x01
Reset: 0x00
Property: Configuration Change Protection
Bit
7
6
5
4
3
2
1
0
SWRE
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
Bit 0 – SWRE: Software Reset Enable
When this bit is written to '1', a software reset will occur.
This bit will always read as '0'.
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8-bit AVR Microcontroller
13.
CPUINT - CPU Interrupt Controller
Related Links
Interrupts
13.1
Features
•
•
•
•
•
•
•
•
•
13.2
Short and predictable interrupt response time
Separate interrupt configuration and vector address for each interrupt
Interrupt prioritizing by level and vector address
Two interrupt priority levels: 0 (normal) and 1 (high)
Higher priority for one interrupt
Optional round-robin priority scheme for priority level 0 interrupts
Non-maskable interrupts (NMI) for critical functions
Interrupt vectors optionally placed in the application section or the boot loader section
Selectable compact vector table
Overview
An interrupt request signals a change of state inside a peripheral, and can be used to alter program
execution. Peripherals can have one or more interrupts, and all are individually enabled and configured.
When an interrupt is enabled and configured, it will generate an interrupt request when the interrupt
condition occurs.
The CPU Interrupt Controller (CPUINT) handles and prioritizes interrupt requests. When an interrupt is
enabled and the interrupt condition occurs, the CPUINT will receive the interrupt request. Based on the
interrupt's priority level and the priority level of any ongoing interrupts, the interrupt request is either
acknowledged or kept pending until it has priority. When an interrupt request is acknowledged by the
CPUINT, the program counter is set to point to the interrupt vector. The interrupt vector is normally a jump
to the interrupt handler (i.e., the software routine that handles the interrupt). After returning from the
interrupt handler, program execution continues from where it was before the interrupt occurred. One
instruction is always executed before any pending interrupt is served.
The CPUINT Status register (CPUINT.STATUS) contains state information that ensures that the CPUINT
returns to the correct interrupt level when the RETI (interrupt return) instruction is executed at the end of
an interrupt handler. Returning from an interrupt will return the CPUINT to the state it had before entering
the interrupt. CPUINT.STATUS is not saved automatically upon an interrupt request.
By default, all peripherals are priority level 0. It is possible to set one single interrupt vector to the higher
priority level 1. Interrupts are prioritized according to their priority level and their interrupt vector address.
Priority level 1 interrupts will interrupt level 0 interrupt handlers. Among priority level 0 interrupts, the
priority is determined from the interrupt vector address, where the lowest interrupt vector address has the
highest interrupt priority.
Optionally, a round-robin scheduling scheme can be enabled for priority level 0 interrupts. This ensures
that all interrupts are serviced within a certain amount of time.
Interrupt generation must be globally enabled by writing a '1' to the Global Interrupt Enable bit (I) in the
CPU Status register (CPU.SREG). This bit is not cleared when an interrupt is acknowledged.
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8-bit AVR Microcontroller
13.2.1
Block Diagram
Figure 13-1. CPUINT Block Diagram
Interrupt Controller
Priority
Decoder
Peripheral 1
INT REQ
CPU "RETI"
CPU INT ACK
CPU
INT LEVEL
Peripheral
n
INT REQ
CPU INT REQ
INT REQ
INT ACK
STATUS
LVL0PRI
LVL1VEC
Global
Interrupt
Enable
Wake-up
CPU.SREG
Sleep
Controller
13.2.2
Signal Description
Not applicable.
13.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 13-1. CPUINT System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
No
-
Events
No
-
Debug
Yes
UPDI
Related Links
Debug Operation
Clocks
13.2.3.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
System Dependencies
CLKCTRL - Clock Controller
13.2.3.2 I/O Lines and Connections
Not applicable.
13.2.3.3 Interrupts
Not applicable.
13.2.3.4 Events
Not applicable.
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Datasheet Preliminary
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8-bit AVR Microcontroller
13.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in debugging
mode will halt normal operation of the peripheral.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
System Dependencies
UPDI - Unified Program and Debug Interface
13.3
Functional Description
13.3.1
Initialization
An interrupt must be initialized in the following order:
1.
Configure the CPUINT if the default configuration is not adequate (optional):
– Vector handling is configured by writing to the respective bits (IVSEL and CVT) in the Control
A register (CPUINT.CTRLA).
–
2.
3.
13.3.2
Vector prioritizing by round-robin is enabled by writing a '1' to the Round-Robin Priority Enable
bit (LVL0RR) in CPUINT.CTRLA.
– Select the priority level 1 vector by writing its address to the Interrupt Vector (LVL1VEC) in the
Level 1 Priority register (CPUINT.LVL1VEC).
Configure the interrupt conditions within the peripheral, and enable the peripheral's interrupt.
Enable interrupts globally by writing a '1' to the Global Interrupt Enable bit (I) in the CPU Status
register (CPU.SREG).
Operation
13.3.2.1 Enabling, Disabling, and Resetting
Global enabling of interrupts is done by writing a '1' to the Global Interrupt Enable bit (I) in the CPU Status
register (CPU.SREG). To disable interrupts globally, write a '0' to the I bit in CPU.SREG.
The desired interrupt lines must also be enabled in the respective peripheral, by writing to the peripheral's
Interrupt Control register ([peripheral].INTCTRL).
Interrupt flags are not automatically cleared after the interrupt is executed. The respective INTFLAGS
register descriptions provide information on how to clear specific flags.
13.3.2.2 Interrupt Vector Locations
The table below shows Reset addresses and Interrupt vector placement, dependent on the value of
Interrupt Vector Select bit (IVSEL) in the Control A register (CPUINT.CTRLA).
If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular program
code can be placed at these locations.
Table 13-2. Reset and Interrupt Vector Placement
IVSEL
Reset address
Interrupt vectors start address
0
0x0000
Application start address +
Interrupt vector offset address
1
0x0000
Interrupt vector offset address
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8-bit AVR Microcontroller
13.3.2.3 Interrupt Response Time
The minimum interrupt response time for all enabled interrupts is three CPU clock cycles: one cycle to
finish the ongoing instruction, and two cycles to store the program counter to the stack. After the program
counter is pushed on the stack, the program vector for the interrupt is executed. See also figure below,
first diagram.
The jump to the interrupt handler takes three clock cycles. If an interrupt occurs during execution of a
multicycle instruction, this instruction is completed before the interrupt is served. See also figure below,
second diagram.
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8-bit AVR Microcontroller
Figure 13-2. Interrupt Execution of a Single Cycle Instruction, Multicycle Instruction and from
Sleep
Single Cycle Instruction
Multicycle Instruction
Sleep
If an interrupt occurs when the device is in sleep mode, the interrupt execution response time is
increased by five clock cycles. In addition, the response time is increased by the start-up time from the
selected sleep mode.
A return from an interrupt handling routine takes four to five clock cycles, depending on the size of the
program counter. During these clock cycles, the program counter is popped from the stack and the stack
pointer is incremented. See also figure above, bottom diagram.
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8-bit AVR Microcontroller
13.3.2.4 Interrupt Level
The interrupt level is default on level 0 (normal) for all interrupt sources. It is possible to select one
interrupt source to level 1 (high) by writing interrupt address to CPUINT.LVL1VEC register. This source
will have higher priority than normal level interrupts.
An interrupt request from a level 1 source will interrupt any ongoing interrupt handler from a level 0
interrupt. When returning from the level 1 interrupt handler, the execution of the level 0 interrupt handler
will continue.
13.3.2.5 Interrupt Priority
NMI - Non-Maskable Interrupts
An NMI will be executed regardless of the setting of the I bit in CPU.SREG, and it will never change the I
bit. No other interrupt can interrupt a NMI handler. If more than one NMI is requested at the same time,
priority is static according to the interrupt vector address, where the lowest address has highest priority.
Which interrupts are non-maskable is device-dependent and not subject to configuration. Non-maskable
interrupts must be enabled before they can be used. Refer to the Interrupt Vector Mapping of the device
for available NMI lines.
Related Links
Interrupt Vector Mapping
Static Priority
Interrupt vectors (IVEC) are located at fixed addresses. For static priority, the interrupt vector address
decides the priority within normal interrupt level, where the lowest interrupt vector address has the
highest priority. Refer to the Interrupt Vector Mapping of the device for available interrupt lines and their
base address offset.
Figure 13-3. Static Priority
Lowest Address
IVEC 0
Highest Priority
:
:
:
IVEC x
IVEC x+1
:
:
:
Highest Address
IVEC n
Lowest Priority
Related Links
Interrupt Vector Mapping
Round-Robin Scheduling
To avoid "starvation" for priority level 0 (LVL0) interrupt requests with static priority, i.e. some interrupts
might never be served, the CPUINT offers round-robin scheduling for LVL0 interrupts.
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8-bit AVR Microcontroller
Round-robin scheduling for LVL0 interrupt requests is enabled by writing a '1' to the Round-Robin Priority
Enable bit (LVL0RR) in the Control A register (CPUINT.CTRLA).
When round-robin scheduling is enabled, the interrupt vector address for the last acknowledged LVL0
interrupt will have the lowest priority the next time one or more LVL0 interrupts are requested, as
illustrated in the figure below.
Figure 13-4. Round-Robin Scheduling
IVEC x last acknowledge
interrupt
IVEC x+1 last acknowledge
interrupt
IVEC 0
IVEC 0
:
:
:
:
:
:
IVEC x
Lowest Priority
IVEC x
IVEC x+1
Highest Priority
IVEC x+1
Lowest Priority
IVEC x+2
Highest Priority
:
:
:
IVEC n
:
:
:
IVEC n
Compact Vector Table
The Compact Vector Table (CVT) is a feature to allow for writing of compact code.
When CVT is enabled by writing a '1' to the CVT bit in the Control A register (CPUINT.CTRLA), the vector
table contains these three interrupt vectors:
1. The non-maskable interrupts (NMI) at vector address 1
2. The priority level 1 (LVL1) interrupt at vector address 2
3. All priority level 0 (LVL0) interrupts share vector address 3.
This feature is most suitable for applications using a small number of interrupt generators.
13.3.3
Events
Not applicable.
13.3.4
Sleep Mode Operation
Not applicable.
13.3.5
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
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Datasheet Preliminary
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8-bit AVR Microcontroller
Table 13-3. INTCTRL - Registers under Configuration Change Protection
Register
Key
IVSEL in CPUINT.CTRLA
IOREG
CVT in CPUINT.CTRLA
IOREG
Related Links
Sequence for Write Operation to Configuration Change Protected I/O Registers
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
13.4
Register Summary - CPUINT
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
STATUS
7:0
0x02
LVL0PRI
7:0
LVL0PRI[7:0]
0x03
LVL1VEC
7:0
LVL1VEC[7:0]
IVSEL
CVT
LVL0RR
NMIEX
13.5
Register Description
13.5.1
Control A
LVL1EX
LVL0EX
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property: Configuration Change Protection
Bit
7
Access
Reset
6
5
IVSEL
CVT
4
3
2
1
LVL0RR
0
R/W
R/W
R/W
0
0
0
Bit 6 – IVSEL: Interrupt Vector Select
If boot section is defined, it will be placed before application section. The actual start address of the
application section is determined by the BOOTEND Fuse.
This bit is protected by the Configuration Change Protection mechanism.
Value
0
1
Description
Interrupt vectors are placed at the start of the application section of the Flash.
Interrupt vectors are placed at the start of the boot section of the Flash.
Bit 5 – CVT: Compact Vector Table
This bit is protected by the Configuration Change Protection mechanism.
Value
0
1
Description
Compact Vector Table function is disabled
Compact Vector Table function is enabled
Bit 0 – LVL0RR: Round-Robin Priority Enable
This bit is not protected by the Configuration Change Protection mechanism.
Value
0
1
13.5.2
Description
Priority is fixed for priority level 0 interrupt requests: The lowest interrupt vector address has
highest priority.
Round Robin priority scheme is enabled for priority level 0 interrupt requests.
Status
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Name: STATUS
Offset: 0x01
Reset: 0x00
Property:
Bit
1
0
NMIEX
7
6
5
4
3
2
LVL1EX
LVL0EX
Access
R
R
R
Reset
0
0
0
Bit 7 – NMIEX: Non-Maskable Interrupt Executing
This flag is set if a non-maskable interrupt is executing. The flag is cleared when returning (RETI) from
the interrupt handler.
Bit 1 – LVL1EX: Level 1 Interrupt Executing
This flag is set when a priority level 1 interrupt is executing, or when the interrupt handler has been
interrupted by an NMI. The flag is cleared when returning (RETI) from the interrupt handler.
Bit 0 – LVL0EX: Level 0 Interrupt Executing
This flag is set when a priority level 0 interrupt is executing, or when the interrupt handler has been
interrupted by a priority level 1 interrupt or an NMI. The flag is cleared when returning (RETI) from the
interrupt handler.
13.5.3
Interrupt Priority Level 0
Name: LVL0PRI
Offset: 0x02
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
LVL0PRI[7:0]
Access
Reset
Bits 7:0 – LVL0PRI[7:0]: Interrupt Priority Level 0
When Round Robin is enabled (LVL0RR bit in CPUINT.CTRLA is '1'), this bit field stores the vector of the
last acknowledged priority level 0 (LVL0) interrupt. The stored vector will have the lowest priority next time
one or more LVL0 interrupts are pending.
If Round Robin is disabled (LVL0RR in CPUINT.CTRLA is '0'), the vector address based priority scheme
(lowest address has highest priority) is governing the priorities of LVL0 interrupt requests.
If a system Reset is asserted, the lowest interrupt vector address will have highest priority within the
LVL0.
13.5.4
Interrupt Vector with Priority Level 1
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Name: LVL1VEC
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
LVL1VEC[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – LVL1VEC[7:0]: Interrupt Vector with Priority Level 1
This bit field contains the address of the single vector with increased priority level 1 (LVL1).
If this bit field has the value 0x00, no vector has LVL1. Consequently, the LVL1 interrupt is disabled.
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
14.
EVSYS - Event System
14.1
Features
•
•
•
•
•
•
•
•
14.2
System for direct peripheral-to-peripheral signaling
Peripherals can directly produce, use, and react to peripheral events
Short and guaranteed response time
Up to six parallel Event channels available; 4 asynchronous- and 2 synchronous
Channels can be configured to have one triggering peripheral action and multiple peripheral users
Peripherals can directly trigger and react to Events from other peripherals
Events can be sent and/or received by most peripherals, and by software
Works in active mode and standby sleep mode
Overview
The Event System (EVSYS) enables direct peripheral-to-peripheral signaling. It allows a change in one
peripheral (the Event Generator) to trigger actions in other peripherals (the Event Users) through Event
channels, without using the CPU. It is designed to provide short and predictable response times between
peripherals, allowing for autonomous peripheral control and interaction, and also for synchronized timing
of actions in several peripheral modules. It is thus a powerful tool for reducing the complexity, size, and
execution time of the software.
A change of the Event Generator's state is referred to as an Event, and usually corresponds to one of the
peripheral's interrupt conditions. Events can be directly forwarded to other peripherals using the
dedicated Event routing network. The routing of each channel is configured in software, including event
generation and use.
Only one trigger from an Event generator peripheral can be routed on each channel, but multiple
channels can use the same generator source. Multiple peripherals can use events from the same
channel.
A channel path can be either asynchronous or synchronous to the main clock. The mode must be
selected based on the requirements of the application.
The Event System can directly connect analog and digital converters, analog comparators, I/O port pins,
the real-time counter, timer/counters, and the configurable custom logic peripheral. Events can also be
generated from software and the peripheral clock.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
14.2.1
Block Diagram
Figure 14-1. Block Diagram
Sync user x
Sync event channel ”k”
Sync event channel 0
Sync source 0
Sync source 1
Sync user 0
Sync source n
SYNCCH
SYNCSTROBE
..
.
..
.
..
.
Async source m
ASYNCCH
SYNCUSER
Async user y
Async user 0
Async event channel ”l”
Async event channel 0
Async source 0
Async source 1
To sync user
..
.
..
.
ASYNCSTROBE
To async user
ASYNCUSER
Figure 14-2. Example of Event Source, Generator, User, and Action
Event Generator
Event User
Timer/Counter
ADC
Compare Match
Over-/Underflow
|
Event
Routing
Network
Error
Channel Sweep
Single
Conversion
Event Action Selection
Event Source
Event Action
Note:
1. For an overview of peripherals supporting Events, refer the Block Diagram of the device.
2. For a list of Event Generators, refer to the Channel n Generator Selection registers
(EVSYS.SYNCCH and EVSYS.ASYNCCH).
3. For a list of Event Users, refer to the User Channel n Input Selection registers
(EVSYS.SYNCUSER and EVSYS.ASYNCUSER).
Related Links
SYNCCH0, SYNCCH1
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
ASYNCCH0, ASYNCCH1, ASYNCCH2, ASYNCCH3
SYNCUSER0, SYNCUSER1
ASYNCUSER0, ASYNCUSER1, ASYNCUSER2, ASYNCUSER3, ASYNCUSER4, ASYNCUSER5,
ASYNCUSER6, ASYNCUSER7, ASYNCUSER8, ASYNCUSER9, ASYNCUSER10
14.2.2
Signal Description
Internal Event Signaling
The Event signaling can either happen synchronously to the main clock (CLK_MAIN), or asynchronously
to it.
Depending on the underlying event, the Event signal can be a pulse with a duration of 1 clock cycle, or a
level signal (similar to a status flag).
Event Output to Pin
Signal
Type
Description
EVOUT[2:0]
Digital output
Event output
Related Links
I/O Lines
Block Diagram - CLKCTRL
14.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 14-1. EVSYS System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORTMUX
Interrupts
No
-
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
14.2.3.1 Clocks
The EVSYS uses the peripheral clock for I/O registers and software events. When set up correctly, the
routing network can be used also in sleep modes without any clock. Software Events will not work in
sleep modes where the peripheral clock is halted.
Related Links
CLKCTRL - Clock Controller
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
14.2.3.2 I/O Lines
The EVSYS can output three event channels asynchronously on pins. The output signals are called
EVOUT[2:0].
1. Configure which event channel (one of SYNCCH[1:0] or ASYNCCH[3:0]) is output on which the
EVOUTn by writing to EVSYS.ASYNCUSER10, EVSYS.ASYNCUSER9 or EVSYS.ASYNCUSER8
respectively.
2. Optional: configure the pin properties using the PORT peripheral.
3. Enable the pin output by writing '1' to the respective EVOUTn bit in the Control A register of the
PORTMUX peripheral (PORTMUX.CTRLA).
Related Links
PORTMUX - Port Multiplexer
PORT - I/O Pin Configuration
ASYNCUSER0, ASYNCUSER1, ASYNCUSER2, ASYNCUSER3, ASYNCUSER4, ASYNCUSER5,
ASYNCUSER6, ASYNCUSER7, ASYNCUSER8, ASYNCUSER9, ASYNCUSER10
14.3
Functional Description
14.3.1
Initialization
Before enabling Events within the device, the Event Users Multiplexer and Event Channels must be
configured.
Related Links
Event User Multiplexer Setup
Event System Channel
14.3.2
Operation
14.3.2.1 Event User Multiplexer Setup
The Event User multiplexer selects the channel for an Event User. Each Event User has one dedicated
Event User multiplexer. Each multiplexer is connected to the supported Event channel outputs, and can
be configured to select one of these channels.
Event Users which support asynchronous Events also support synchronous Events. There are also Event
Users that support only synchronous Events.
The Event User multiplexers are configured by writing to the corresponding registers:
•
Event Users supporting both synchronous and asynchronous Events are configured by writing to
the respective asynchronous User Channel Input Selection n register (EVSYS.ASYNCUSERn).
•
The users of synchronous-only Events are configured by writing to the respective Synchronous
User Channel Input Selection n register (EVSYS.SYNCUSERn).
Default setup of all user multiplexers is Off.
14.3.2.2 Event System Channel
An Event channel can be connected to one of the Event generators. Event channels either support
asynchronous generators or synchronous generators.
The source for each asynchronous Event channel is configured by writing to the respective Asynchronous
Channel n Input Selection register (EVSYS.ASYNCCHn).
The source for each synchronous Event channel is configured by writing to the respective Synchronous
Channel n Input Selection register (EVSYS.SYNCCHn).
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
14.3.2.3 Event Generators
Each Event channel can receive the Events from several Event generators. For details on Event
generation, refer to the documentation of the corresponding peripheral.
For each Event channel, there are several possible Event generators, only one of which can be selected
at a time. The Event generator trigger is selected for each channel by writing to the respective channel
registers (EVSYS.ASYNCCHn, EVSYS.SYNCCHn). By default, the channels are not connected to any
Event generator.
14.3.2.4 Software Event
In a Software Event, the CPU will “strobe” an Event channel by inverting the current value for one system
clock cycle.
A Software Event is triggered on a channel by writing a '1' to the respective Strobe bit in the appropriate
Channel Strobe register:
•
Software Events on asynchronous channel l are initiated by writing a '1' to the ASYNCSTROBE[l]
bit in the Asynchronous Channel Strobe register (EVSYS.ASYNCSTROBE).
•
Software Events on synchronous channel k are initiated by writing a '1' to the SYNCSTROBE[k] bit
in the Synchronous Channel Strobe register (EVSYS.SYNCSTROBE).
Software Events are no different to those produced by Event generator peripherals with respect to Event
users: when the bit is written to '1', an Event will be generated on the respective channel, and received
and processed by the Event User.
14.3.3
Interrupts
Not applicable.
14.3.4
Sleep Mode Operation
When configured, the Event System will work in all sleep modes. One exception are software Events
which require a system clock.
14.3.5
Debug Operation
This peripheral is unaffected by entering debug mode.
Related Links
UPDI - Unified Program and Debug Interface
14.3.6
Synchronization
Asynchronous Events are synchronized and handled by the compatible Event users. Event User
peripherals not compatible with asynchronous Events can only be configured to listen to synchronous
Event channels.
14.3.7
Configuration Change Protection
Not applicable.
Related Links
Sequence for Write Operation to Configuration Change Protected I/O Registers
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
14.4
Register Summary - EVSYS
Offset
Name
Bit Pos.
0x00
ASYNCSTROBE
7:0
ASYNCSTROBE[7:0]
0x01
SYNCSTROBE
7:0
SYNCSTROBE[7:0]
0x02
ASYNCCH0
7:0
ASYNCCH[7:0]
0x03
ASYNCCH1
7:0
ASYNCCH[7:0]
0x04
ASYNCCH2
7:0
ASYNCCH[7:0]
0x05
ASYNCCH3
7:0
ASYNCCH[7:0]
0x06
...
Reserved
0x09
0x0A
SYNCCH0
7:0
SYNCCH[7:0]
0x0B
SYNCCH1
7:0
SYNCCH[7:0]
0x0C
...
Reserved
0x11
0x12
ASYNCUSER0
7:0
ASYNCUSER[7:0]
0x13
ASYNCUSER1
7:0
ASYNCUSER[7:0]
0x14
ASYNCUSER2
7:0
ASYNCUSER[7:0]
0x15
ASYNCUSER3
7:0
ASYNCUSER[7:0]
0x16
ASYNCUSER4
7:0
ASYNCUSER[7:0]
0x17
ASYNCUSER5
7:0
ASYNCUSER[7:0]
0x18
ASYNCUSER6
7:0
ASYNCUSER[7:0]
0x19
ASYNCUSER7
7:0
ASYNCUSER[7:0]
0x1A
ASYNCUSER8
7:0
ASYNCUSER[7:0]
0x1B
ASYNCUSER9
7:0
ASYNCUSER[7:0]
0x1C
ASYNCUSER10
7:0
ASYNCUSER[7:0]
0x1D
...
Reserved
0x21
0x22
SYNCUSER0
7:0
SYNCUSER[7:0]
0x23
SYNCUSER1
7:0
SYNCUSER[7:0]
14.5
Register Description
14.5.1
Asynchronous Channel Strobe
Name: ASYNCSTROBE
Offset: 0x00
Reset: 0x00
Property:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
ASYNCSTROBE[7:0]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Reset
Bits 7:0 – ASYNCSTROBE[7:0]: Asynchronous Channel Strobe
If the strobe register location is written, each Event channel will be inverted for one system clock cycle,
i.e. a single Event is generated.
14.5.2
Synchronous Channel Strobe
Name: SYNCSTROBE
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
SYNCSTROBE[7:0]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Reset
Bits 7:0 – SYNCSTROBE[7:0]: Synchronous Channel Strobe
If the strobe register location is written, each Event channel will be inverted for one system clock cycle,
i.e. a single event is generated.
14.5.3
Asynchronous Channel n Generator Selection
Name: ASYNCCH0, ASYNCCH1, ASYNCCH2, ASYNCCH3
Offset: 0x02 + n*0x01 [n=0..3]
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
ASYNCCH[7:0]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Reset
Bits 7:0 – ASYNCCH[7:0]: Asynchronous Channel Generator Selection
ASYNCCH0
Value
Description
0x00
OFF
0x01
CCL_LUT0
0x02
CCL_LUT1
0x03
AC0_OUT
0x04
TCD0_CMPBCLR
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ASYNCCH0
Value
Description
0x05
TCD0_CMPASET
0x06
TCD0_CMPBSET
0x07
TCD0_PROGEV
0x08
RTC_OVF
0x09
RTC_CMP
0x0A
PORTA0
0x0B
PORTA1
0x0C
PORTA2
0x0D
PORTA3
0x0E
PORTA4
0x0F
PORTA5
0x10
PORTA6
0x11
PORTA7
0x12
UPDI
0x13
AC1_OUT
0x14
AC2_OUT
Other
Reserved
ASYNCCH1
Value
Description
0x00
OFF
0x01
CCL_LUT0
0x02
CCL_LUT1
0x03
AC0_OUT
0x04
TCD0_CMPBCLR
0x05
TCD0_CMPASET
0x06
TCD0_CMPBSET
0x07
TCD0_PROGEV
0x08
RTC_OVF
0x09
RTC_CMP
0x0A
PORTB0
0x0B
PORTB1
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ASYNCCH0
Value
Description
0x0C
PORTB2
0x0D
PORTB3
0x0E
PORTB4
0x0F
PORTB5
0x10
PORTB6
0x11
PORTB7
0x12
AC1_OUT
0x13
AC2_OUT
Other
Reserved
ASYNCCH2
Value
Description
0x00
OFF
0x01
CCL_LUT0
0x02
CCL_LUT1
0x03
AC0_OUT
0x04
TCD0_CMPBCLR
0x05
TCD0_CMPASET
0x06
TCD0_CMPBSET
0x07
TCD0_PROGEV
0x08
RTC_OVF
0x09
RTC_CMP
0x0A
PORTC0
0x0B
PORTC1
0x0C
PORTC2
0x0D
PORTC3
0x0E
PORTC4
0x0F
PORTC5
0x10
AC1_OUT
0x11
AC2_OUT
Other
Reserved
ASYNCCH3
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Datasheet Preliminary
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8-bit AVR Microcontroller
ASYNCCH0
14.5.4
Value
Description
Value
Description
0x00
OFF
0x01
CCL_LUT0
0x02
CCL_LUT1
0x03
AC0_OUT
0x04
TCD0_CMPBCLR
0x05
TCD0_CMPASET
0x06
TCD0_CMPBSET
0x07
TCD0_PROGEV
0x08
RTC_OVF
0x09
RTC_CMP
0x0A
PIT_DIV8192
0x0B
PIT_DIV4096
0x0C
PIT_DIV2048
0x0D
PIT_DIV1024
0x0E
PIT_DIV512
0x0F
PIT_DIV256
0x10
PIT_DIV128
0x11
PIT_DIV64
0x12
AC1_OUT
0x13
AC2_OUT
Other
Reserved
Synchronous Channel n Generator Selection
Name: SYNCCH0, SYNCCH1
Offset: 0x0A + n*0x01 [n=0..1]
Reset: 0x00
Property:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
SYNCCH[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – SYNCCH[7:0]: Synchronous Channel Generator Selection
Table 14-2. Synchronous Channel Generator selection
Value
14.5.5
SYNCCH0
SYNCCH1
0x00
OFF
0x01
TCB0
0x02
TCA0_OVF_LUNF
0x03
TCA0_HUNF
0x04
TCA0_CMP0
0x05
TCA0_CMP1
0x06
TCA0_CMP2
0x07
PORTC_PIN0
-
0x08
PORTC_PIN1
PORTB_PIN0
0x09
PORTC_PIN2
PORTB_PIN1
0x0A
PORTC_PIN3
PORTB_PIN2
0x0B
PORTC_PIN4
PORTB_PIN3
0x0C
PORTC_PIN5
PORTB_PIN4
0x0D
PORTA_PIN0
PORTB_PIN5
0x0E
PORTA_PIN1
PORTB_PIN6
0x0F
PORTA_PIN2
PORTB_PIN7
0x10
PORTA_PIN3
TCB1
0x11
PORTA_PIN4
-
0x12
PORTA_PIN5
-
0x13
PORTA_PIN6
-
0x14
PORTA_PIN7
-
0x15
TCB1
-
Other
-
-
Asynchronous User Channel n Input Selection
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Datasheet Preliminary
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8-bit AVR Microcontroller
Name:
ASYNCUSER0, ASYNCUSER1, ASYNCUSER2, ASYNCUSER3, ASYNCUSER4,
ASYNCUSER5, ASYNCUSER6, ASYNCUSER7, ASYNCUSER8, ASYNCUSER9,
ASYNCUSER10
Offset: 0x12 + n*0x01 [n=0..10]
Reset: 0x00
Property:
Bit
7
6
5
4
R/W
R/W
R/W
R/W
0
0
0
0
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
0
ASYNCUSER[7:0]
Access
Reset
Bits 7:0 – ASYNCUSER[7:0]: Asynchronous User Channel Selection
Table 14-3. User Multiplexer Numbers
USERn
User Multiplexer
Description
n=0
TCB0
Timer/Counter B 0
n=1
ADC0
ADC 0
n=2
CCL_LUT0EV0
CCL LUT0 Event 0
n=3
CCL_LUT1EV0
CCL LUT1 Event 0
n=4
CCL_LUT0EV1
CCL LUT0 Event 1
n=5
CCL_LUT1EV1
CCL LUT1 Event 1
n=6
TCD0_EV0
Timer Counter D 0 Event 0
n=7
TCD0_EV1
Timer Counter D 0 Event 1
n=8
EVOUT0
Event OUT 0
n=9
EVOUT1
Event OUT 1
n=10
EVOUT2
Event OUT 2
n=11
TCB1
Timer/Counter B 1
n=12
ADC1
ADC 1
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
14.5.6
Description
OFF
SYNCCH0
SYNCCH1
ASYNCCH0
ASYNCCH1
ASYNCCH2
ASYNCCH3
Synchronous User Channel n Input Selection
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Datasheet Preliminary
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8-bit AVR Microcontroller
Name: SYNCUSER0, SYNCUSER1
Offset: 0x22 + n*0x01 [n=0..1]
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
SYNCUSER[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – SYNCUSER[7:0]: Synchronous User Channel Selection
Table 14-4. User Multiplexer Numbers
USERn
User Multiplexer
Description
n=0
TCA0
Timer/Counter A
n=1
USART0
USART
Value
0x0
0x1
0x2
Name
OFF
SYNCCH0
SYNCCH1
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8-bit AVR Microcontroller
15.
PORTMUX - Port Multiplexer
15.1
Overview
The Port Multiplexer (PORTMUX) can either enable or disable functionality of pins, or change between
default and alternative pin positions. This depends on the actual pin and property, and is described in
detail in the PORTMUX register map.
For available pins and functionalities, refer to the Multiplexed Signals table.
Related Links
I/O Multiplexing and Considerations
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
15.2
Register Summary - PORTMUX
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
CTRLC
7:0
0x03
CTRLD
7:0
LUT1
LUT0
TCA05
TCA04
EVOUT2
TWI0
15.3
Register Description
15.3.1
Control A
EVOUT1
SPI0
TCA03
EVOUT0
USART0
TCA02
TCA01
TCA00
TCB1
TCB0
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
7
6
Access
Reset
5
4
2
1
0
LUT1
LUT0
3
EVOUT2
EVOUT1
EVOUT0
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 5 – LUT1: CCL LUT 1 output
Write this bit to '1' to select alternative pin location for CCL LUT 1.
Bit 4 – LUT0: CCL LUT 0 output
Write this bit to '1' to select alternative pin location for CCL LUT 0.
Bit 2 – EVOUT2: Event Output 2
Write this bit to '1' to enable event output 2.
Bit 1 – EVOUT1: Event Output 1
Write this bit to '1' to enable event output 1.
Bit 0 – EVOUT0: Event Output 0
Write this bit to '1' to enable event output 0.
15.3.2
Control B
Name: CTRLB
Offset: 0x01
Reset: 0x00
Property:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
7
6
5
Access
Reset
4
3
2
1
0
TWI0
SPI0
USART0
R/W
R/W
R/W
0
0
0
Bit 4 – TWI0: TWI 0 communication
Write this bit to '1' to select alternative communication pins for TWI 0.
Bit 2 – SPI0: SPI 0 communication
Write this bit to '1' to select alternative communication pins for SPI 0.
Bit 0 – USART0: USART 0 communication
Write this bit to '1' to select alternative communication pins for USART 0.
15.3.3
Control C
Name: CTRLC
Offset: 0x02
Reset: 0x00
Property:
Bit
7
6
Access
Reset
5
4
3
2
1
0
TCA05
TCA04
TCA03
TCA02
TCA01
TCA00
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit 5 – TCA05: TCA0 Waveform output 5
Write this bit to '1' to select alternative output pin for TCA0 waveform output 5 in split mode.
Not applicable when TCA in normal mode.
Bit 4 – TCA04: TCA0 Waveform output 4
Write this bit to '1' to select alternative output pin for TCA0 waveform output 4 in split mode.
Not applicable when TCA in normal mode.
Bit 3 – TCA03: TCA0 Waveform output 3
Write this bit to '1' to select alternative output pin for TCA0 waveform output 3 in split mode.
Not applicable when TCA in normal mode.
Bit 2 – TCA02: TCA0 Waveform output 2
Write this bit to '1' to select alternative output pin for TCA0 waveform output 2.
In Split Mode, this bit controls output from low-byte compare channel 2.
Bit 1 – TCA01: TCA0 Waveform output 1
Write this bit to '1' to select alternative output pin for TCA0 waveform output 1.
In Split Mode, this bit controls output from low-byte compare channel 1.
Bit 0 – TCA00: TCA0 Waveform output 0
Write this bit to '1' to select alternative output pin for TCA0 waveform output 0.
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
In Split Mode, this bit controls output from low-byte compare channel 0.
15.3.4
Control D
Name: CTRLD
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
Access
Reset
1
0
TCB1
TCB0
R/W
R/W
0
0
Bit 1 – TCB1: TCB1 output
Write this bit to '1' to select alternative output pin for 16-bit timer/counter B 1.
Bit 0 – TCB0: TCB0 output
Write this bit to '1' to select alternative output pin for 16-bit timer/counter B 0.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
16.
PORT - I/O Pin Configuration
16.1
Features
•
•
•
•
•
16.2
General purpose input and output pins with individual configuration
Output driver with configurable inverted I/O and pullup.
Input with interrupts and events:
– Sense both edges
– Sense rising edges
– Sense falling edges
– Sense low level
Asynchronous pin change sensing that can wake the device from all sleep modes
Efficient and safe access to PORT pins
– Hardware read-modify-write through dedicated toggle/clear/set registers
– Mapping of often-used PORT registers into bit-accessible I/O memory space (Virtual Ports)
Overview
The I/O pins of the device are controlled by instances of the PORT peripheral registers. This device has
up to three instances of the I/O Pin Configuration (PORT) called PORTA, PORTB, and PORTC. Each
instance controls a pin group of up to eight pins, called PA[7:0], PB[7:0], and PC[7:0].
Refer to the I/O Multiplexing table to see which pins are controlled by what instance of PORT. The offsets
of the PORT instances and of the corresponding Virtual PORT instances are listed in the Peripherals and
Architecture section.
Each of the port pins has a corresponding bit in the Data Direction (PORT.DIR) and Data Output Value
(PORT.OUT) registers to enable that pin as an output and to define the output state. For example, pin
PB3 is controlled by DIR[3] and OUT[3] of the PORTB instance.
The Data Input Value (PORT.IN) is set as the input value of a PORT pin with resynchronization to the
Main Clock. To reduce power consumption, these input synchronizers are not clocked if the Input Sense
Configuration bit field (ISC) in PORT.PINnCTRL is INPUT_DISABLE. The value of the pin can always be
read, whether the pin is configured as input or output.
The PORT also supports synchronous and asynchronous input sensing with interrupts for selectable pin
change conditions. Asynchronous pin-change sensing means that a pin change can wake the device
from all sleep modes, including the modes where no clocks are running.
All pin functions are configurable individually per pin. The pins have hardware read-modify-write (RMW)
functionality for safe and correct change of drive value and/or pull resistor configuration. The direction of
one port pin can be changed without unintentionally changing the direction of any other pin.
The PORT pin configuration also controls input and output selection of other device functions.
Related Links
I/O Multiplexing and Considerations
Peripherals and Architecture
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
16.2.1
Block Diagram
Figure 16-1. PORT Block Diagram
Pullup enable
Invert Enable
OUTn
Q
D
Pxn
OUT Override
R
DIRn
Q
D
DIR
Override
R
Input Disable
Input
Disable
Override
Synchronizer
INn
Synchronized
input
Q
D Q
R
D
R
Digital Input /
Asynchronous event
Analog input/output
16.2.2
Signal Description
Signal
Type
Description
EXTINT
Digital input
External interrupt - available on all I/O pins
Related Links
I/O Multiplexing and Considerations
16.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
© 2017 Microchip Technology Inc.
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Table 16-1. PORT System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
No
-
Related Links
Events
Clocks
Interrupts
16.2.3.1 Clocks
This peripheral depends on the peripheral clock.
16.2.3.2 I/O Lines and Connections
Not applicable.
16.2.3.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
Related Links
CPUINT - CPU Interrupt Controller
Interrupts
SREG
16.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
EVSYS - Event System
16.2.3.5 Debug Operation
This peripheral is unaffected by entering debug mode.
16.3
Functional Description
16.3.1
Initialization
After Reset, all standard function device I/O pads are connected to the PORT with outputs tri-stated and
input buffers enabled, even if there is no clock running.
For best power consumption, disable the input of unused pins and pins that are used as analog inputs or
outputs.
Specific pins, such as those used for connecting a debugger, may be configured differently, as required
by their special function.
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8-bit AVR Microcontroller
16.3.2
Operation
16.3.2.1 Basic Functions
Each I/O pin Pxn can be controlled by the registers in PORT x. Each pin group x has its own set of PORT
registers, the base address of the register set for pin n is at the byte address PORT + 0x10 + � . The
index within that register set is n.
To use pin number n as an output only, write bit n of the PORT.DIR register to '1'. This can also be done
by writing bit n in the PORT.DIRSET register to '1' - this will avoid disturbing the configuration of other
pins in that group. The nth bit in the PORT.OUT register must be written to the desired output value.
Similarly, writing a PORT.OUTSET bit to '1' will set the corresponding bit in the PORT.OUT register to '1'.
Writing a bit in PORT.OUTCLR to '1' will clear that bit in PORT.OUT to zero. Writing a bit in
PORT.OUTTGL or PORT.IN to '1' will toggle that bit in PORT.OUT.
To use pin n as an input, bit n in the PORT.DIR register must be written to '0' to disable the output driver.
This can also be done by writing bit n in the PORT.DIRCLR register to '1' - this will avoid disturbing the
configuration of other pins in that group. The input value can be read from bit n in register PORT.IN as
long as the ISC bit is not set to INPUT_DISABLE.
Writing a bit to '1' in PORT.DIRTGL will toggle that bit in PORT.DIR, and toggle the direction of the
corresponding pin.
16.3.2.2 Virtual Ports
The Virtual Port registers map the most frequently used regular Port registers into the bit-accessible I/O
space. Writing to the Virtual Port registers has the same effect as writing to the regular registers, but
allows for memory-specific instructions, such as bit-manipulation instructions, which are not valid for the
extended I/O memory space where the regular Port registers reside.
Table 16-2. Virtual Port Mapping
Regular Port Register
Mapped to Virtual Port Register
PORT.DIR
VPORT.DIR
PORT.OUT
VPORT.OUT
PORT.IN
VPORT.IN
PORT.INTFLAG
VPORT.INTFLAG
Related Links
I/O Multiplexing and Considerations
Peripherals and Architecture
16.3.2.3 Pin Configuration
The Pin n Configuration register (PORT.PINnCTRL) is used to configure inverted I/O, pullup, and input
sensing of a pin.
All input and output on the respective pin n can be inverted by writing a '1' to the Inverted I/O Enable bit
(INVEN) in PORT.PINnCTRL.
Toggling the INVEN bit causes an edge on the pin, which can be detected by all peripherals using this
pin, and is seen by interrupts or Events if enabled.
Pullup of pin n is enabled by writing a '1' to the Pullup Enable bit (PULLUPEN) in PORT.PINnCTRL.
Changes of the signal on a pin can trigger an interrupt. The exact conditions are defined by writing to the
Input/Sense bit field (ISC) in PORT.PINnCTRL.
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8-bit AVR Microcontroller
When setting or changing interrupt settings, take these points into account:
•
If an INVEN bit is toggled in the same cycle as the interrupt setting, the edge caused by the
inversion toggling may not cause an interrupt request.
•
If an input is disabled while synchronizing an interrupt, that interrupt may be requested on reenabling the input, even if it is re-enabled with a different interrupt setting.
•
If the interrupt setting is changed while synchronizing an interrupt, that interrupt may not be
accepted.
•
Only few pins support full asynchronous interrupt detection, see I/O Multiplexing and
Considerations. These limitations apply for waking the system from sleep:
Interrupt Type
Fully Asynchronous Pins
Other Pins
BOTHEDGES
will wake system
will wake system
RISING
will wake system
will not wake system
FALLING
will wake system
will not wake system
LEVEL
will wake system
will wake system
Related Links
I/O Multiplexing and Considerations
16.3.3
Interrupts
Table 16-3. Available Interrupt Vectors and Sources
Offset Name
0x00
Vector Description
Conditions
PORTx PORT A, B, C interrupt INTn in PORT.INTFLAGS is raised as configured by ISC bit in
PORT.PINnCTRL.
Each PORT pin n can be configured as an interrupt source. Each interrupt can be individually enabled or
disabled by writing to ISC in PORT.PINCTRL.
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Interrupt Flags register
of the peripheral (peripheral.INTFLAGS).
An interrupt request is generated when the corresponding interrupt is enabled and the Interrupt Flag is
set. The interrupt request remains active until the Interrupt Flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear Interrupt Flags.
Asynchronous Sensing Pin Properties
Table 16-4. Behavior Comparison of Fully/Partly Asynchronous Sense Pin
Property
Synchronous or Partly Asynchronous Sense
Support
Minimum pulse width Minimum one system clock cycle
to trigger interrupt
Waking the device
from sleep
Full Asynchronous Sense
Support
Less than a system clock
cycle
From all interrupt sense configurations from sleep From all interrupt sense
modes with Main Clock running. Only from
configurations from all sleep
BOTHEDGES or LEVEL interrupt sense
modes
configuration from sleep modes with Main Clock
stopped.
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Datasheet Preliminary
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Property
Synchronous or Partly Asynchronous Sense
Support
Full Asynchronous Sense
Support
Interrupt "dead time" No new interrupt for three cycles after the
previous
No limitation
Minimum Wakeup
pulse length
No limitation
Value on pad must be kept until the system clock
has restarted
Related Links
AVR CPU
SREG
16.3.4
Sleep Mode Operation
With the exception of interrupts and input synchronization, all pin configurations are independent of sleep
mode. Peripherals connected to the Ports can be affected by sleep modes, described in the respective
peripherals' documentation.
The PORT peripheral will always use the Main Clock. Input synchronization will halt when this clock
stops.
16.3.5
Synchronization
Not applicable.
16.3.6
Configuration Change Protection
Not applicable.
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Datasheet Preliminary
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8-bit AVR Microcontroller
16.4
Register Summary - PORT
Offset
Name
Bit Pos.
0x00
DIR
7:0
0x01
DIRSET
7:0
DIRSET[7:0]
0x02
DIRCLR
7:0
DIRCLR[7:0]
0x03
DIRTGL
7:0
DIRTGL[7:0]
0x04
OUT
7:0
OUT[7:0]
0x05
OUTSET
7:0
OUTSET[7:0]
0x06
OUTCLR
7:0
OUTCLR[7:0]
0x07
OUTTGL
7:0
OUTTGL[7:0]
0x08
IN
7:0
IN[7:0]
0x09
INTFLAGS
7:0
INT[7:0]
DIR[7:0]
0x0A
...
Reserved
0x0F
0x10
PIN0CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x11
PIN1CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x12
PIN2CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x13
PIN3CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x14
PIN4CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x15
PIN5CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x16
PIN6CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x17
PIN7CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
16.5
Register Description - Ports
16.5.1
Data Direction
Name: DIR
Offset: 0x00
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
DIR[7:0]
Access
Reset
Bits 7:0 – DIR[7:0]: Data Direction
This bit field selects the data direction for the individual pins n of the Port.
Writing a '1' to PORT.DIR[n] configures and enables pin n as output pin.
Writing a '0' to PORT.DIR[n] configures pin n as input pin. It can be configured by writing to the ISC bit in
PORT.PINnCTRL.
16.5.2
Data Direction Set
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Name: DIRSET
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DIRSET[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DIRSET[7:0]: Data Direction Set
This bit field can be used instead of a read-modify-write to set individual pins as output.
Writing a '1' to DIRSET[n] will set the corresponding PORT.DIR[n] bit.
Reading this bit field will always return the value of PORT.DIR.
16.5.3
Data Direction Clear
Name: DIRCLR
Offset: 0x02
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
DIRCLR[7:0]
Access
Reset
Bits 7:0 – DIRCLR[7:0]: Data Direction Clear
This register can be used instead of a read-modify-write to configure individual pins as input.
Writing a '1' to DIRCLR[n] will clear the corresponding bit in PORT.DIR.
Reading this bit field will always return the value of PORT.DIR.
16.5.4
Data Direction Toggle
Name: DIRTGL
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
DIRTGL[7:0]
Access
Reset
Bits 7:0 – DIRTGL[7:0]: Data Direction Toggle
This bit field can be used instead of a read-modify-write to toggle the direction of individual pins.
Writing a '1' to DIRTGL[n] will toggle the corresponding bit in PORT.DIR.
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
Reading this bit field will always return the value of PORT.DIR.
16.5.5
Output Value
Name: OUT
Offset: 0x04
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
OUT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – OUT[7:0]: Output Value
This bit field defines the data output value for the individual pins n of the port.
If OUT[n] is written to '1', pin n is driven high.
If OUT[n] is written to '0', pin n is driven low.
In order to have any effect, the pin direction must be configured as output.
16.5.6
Output Value Set
Name: OUTSET
Offset: 0x05
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
OUTSET[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – OUTSET[7:0]: Output Value Set
This bit field can be used instead of a read-modify-write to set the output value of individual pins to '1'.
Writing a '1' to OUTSET[n] will set the corresponding bit in PORT.OUT.
Reading this bit field will always return the value of PORT.OUT.
16.5.7
Output Value Clear
Name: OUTCLR
Offset: 0x06
Reset: 0x00
Property:
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Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
OUTCLR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – OUTCLR[7:0]: Output Value Clear
This register can be used instead of a read-modify-write to clear the output value of individual pins to '0'.
Writing a '1' to OUTCLR[n] will clear the corresponding bit in PORT.OUT.
Reading this bit field will always return the value of PORT.OUT.
16.5.8
Output Value Toggle
Name: OUTTGL
Offset: 0x07
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
OUTTGL[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – OUTTGL[7:0]: Output Value Toggle
This register can be used instead of a read-modify-write to toggle the output value of individual pins.
Writing a '1' to OUTTGL[n] will toggle the corresponding bit in PORT.OUT.
Reading this bit field will always return the value of PORT.OUT.
16.5.9
Input Value
Name: IN
Offset: 0x08
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
IN[7:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 7:0 – IN[7:0]: Input Value
This register shows the value present on the pins if the digital input driver is enabled. IN[n] shows the
value of pin n of the Port. The input is not sampled and cannot be read if the digital input buffers are
disabled.
16.5.10 Interrupt Flags
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8-bit AVR Microcontroller
Name: INTFLAGS
Offset: 0x09
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
INT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – INT[7:0]: Interrupt Pin Flag
The INT Flag is set when a pin change/state matches the pin's input sense configuration.
Writing a '1' to a flag's bit location will clear the flag.
For enabling and executing the interrupt, refer to ISC bit description in PORT.PINnCTRL.
16.5.11 Pin n Control
Name:
PIN0CTRL, PIN1CTRL, PIN2CTRL, PIN3CTRL, PIN4CTRL, PIN5CTRL, PIN6CTRL,
PIN7CTRL
Offset: 0x10 + n*0x01 [n=0..7]
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
3
2
1
0
INVEN
PULLUPEN
ISC[2:0]
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 7 – INVEN: Inverted I/O Enable
Value
0
1
Description
I/O on pin n not inverted
I/O on pin n inverted
Bit 3 – PULLUPEN: Pullup Enable
Value
0
1
Description
Pullup disabled for pin n
Pullup enabled for pin n
Bits 2:0 – ISC[2:0]: Input/Sense Configuration
These bits configure the input and sense configuration of pin n. The sense configuration determines how
a port interrupt can be triggered. If the input buffer is disabled, the input cannot be read in the IN register.
Value
0x0
0x1
0x2
0x3
Name
INTDISABLE
BOTHEDGES
RISING
FALLING
© 2017 Microchip Technology Inc.
Description
Interrupt disabled but input buffer enabled
Sense both edges
Sense rising edge
Sense falling edge
Datasheet Preliminary
DS40001893B-page 121
8-bit AVR Microcontroller
Value
0x4
0x5
other
Name
INPUT_DISABLE
LEVEL
-
© 2017 Microchip Technology Inc.
Description
Digital input buffer disabled
Sense low level
Reserved
Datasheet Preliminary
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8-bit AVR Microcontroller
16.6
Register Summary - VPORT
Offset
Name
Bit Pos.
0x00
DIR
7:0
DIR[7:0]
0x01
OUT
7:0
OUT[7:0]
0x02
IN
7:0
IN[7:0]
0x03
INTFLAGS
7:0
INT[7:0]
16.7
Register Description - Virtual Ports
16.7.1
Data Direction
Name: DIR
Offset: 0x00
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
3
2
1
0
DIR[7:0]
Access
Reset
Bits 7:0 – DIR[7:0]: Data Direction
This bit field selects the data direction for the individual pins in the Port.
16.7.2
Output Value
Name: OUT
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
OUT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – OUT[7:0]: Output Value
This bit field selects the data output value for the individual pins in the Port.
16.7.3
Input Value
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8-bit AVR Microcontroller
Name: IN
Offset: 0x02
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
IN[7:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 7:0 – IN[7:0]: Input Value
This bit field holds the value present on the pins if the digital input buffer is enabled.
16.7.4
Interrupt Flag
Name: INTFLAGS
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
Access
R
R
R
R
Reset
0
0
0
R
R
R
R
0
0
0
0
0
INT[7:0]
Bits 7:0 – INT[7:0]: Interrupt Pin Flag
The INT flag is set when a pin change/state matches the pin's input sense configuration, and the pin is
configured as source for port interrupt.
Writing a '1' to this flag's bit location will clear the flag.
For enabling and executing the interrupt, refer to PORT_PINnCTRL.ISC.
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8-bit AVR Microcontroller
17.
BOD - Brownout Detector
17.1
Features
•
•
•
•
•
17.2
Brownout detection - monitors the power supply to avoid operation below a programmable level
Three modes:
– Enabled
– Sampled
– Disabled
Separate selection of mode for Active mode and sleep modes
Voltage level monitor (VLM) with interrupt
Programmable VLM level relative to the BOD level
Overview
The Brownout Detector (BOD) monitors the power supply and compares the voltage with two
programmable brownout threshold levels: the brownout threshold level defines when to generate a Reset.
A voltage level monitor (VLM) monitors the power supply, too, but compares it to a threshold higher than
the BOD threshold. The VLM can then generate an interrupt request as an "early warning" when the
supply voltage is about to drop below the VLM threshold. The BOD threshold level is expressed in
percent above the BOD threshold level.
The BOD is mainly controlled by fuses. The mode used in Standby sleep mode and Power Down sleep
mode can be altered in normal program execution. The VLM part of the BOD is controlled by I/O registers
as well.
When activated, The BOD can operate in Enabled mode, where the BOD is continuously active, and in
Sampled mode, where the BOD is activated briefly at a given period to check the supply voltage level.
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
17.2.1
Block Diagram
Figure 17-1. BOD Block Diagram
VDD
BOD level
and
calibration
+
Bandgap
Brownout
detection
-
BOD interrupt level
+
Bandgap
17.2.2
-
Low voltage
interrupt detection
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 17-1. BOD System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
Interrupts
Events
17.2.2.1 Clocks
The BOD uses the 32KHz oscillator (OSCULP32K) as clock source for CLK_BOD.
17.2.2.2 I/O Lines and Connections
Not applicable.
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8-bit AVR Microcontroller
17.2.2.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
Related Links
CPUINT - CPU Interrupt Controller
SREG
Interrupts
17.2.2.4 Events
Not applicable.
17.2.2.5 Debug Operation
This peripheral is unaffected by entering debug mode.
The VLM interrupt will not be executed if the CPU is halted in debug mode.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
17.3
Functional Description
17.3.1
Initialization
The BOD settings are loaded from fuses during reset. The BOD level and operating mode in Active and
Idle sleep mode are set by fuses and cannot be changed by the CPU. The operating mode in Standby
and Power Down sleep mode is loaded from fuses, too, and can be changed by software.
The Voltage Level Monitor function can be enabled by writing a '1' to the VLM Interrupt Enable bit
(VLMIE) in the Interrupt Control register (BOD.INTCTRL). The VLM interrupt is configured by writing the
VLM Configuration bits (VLMCFG) in BOD.INTCTRL. An interrupt is requested when the supply voltage
crosses the VLM threshold either from above, from below, or from any direction.
The VLM functionality will follow the BOD mode. If the BOD is turned off, the VLM will not be enabled,
even if the VLMIE is '1'. If the BOD is using sampled mode, the VLM will also be sampled.
The VLM threshold is defined by writing the VLM Level bits (VLMLVL) in the Control A register
(BOD.VLMCTRLA).
If the BOD/VLM is enabled in sampled mode, only VLMCFG=0x1 (crossing threshold from above) in
BOD.INTCTRL will trigger an interrupt.
17.3.2
Interrupts
Table 17-2. Available Interrupt Vectors and Sources
Offset Name Vector Description
0x00
VLM
Conditions
Voltage Level Monitor Supply voltage crossing the VLM threshold as configured by
VLMCFG in BOD.INTCTRL
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Interrupt Flags register
of the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
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8-bit AVR Microcontroller
An interrupt request is generated when the corresponding interrupt source is enabled and the Interrupt
Flag is set. The interrupt request remains active until the Interrupt Flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear Interrupt Flags.
Related Links
AVR CPU
SREG
17.3.3
Sleep Mode Operation
There are two separate fuses defining the BOD configuration in different sleep modes: One fuse defines
the mode used in Active mode and Idle sleep mode (ACTIVE in FUSE.BODCFG), and is written to the
ACTIVE bits in the Control A register (BOD.CTRLA). The second fuse (SLEEP in FUSE.BODCFG)
selects the mode used in Standby sleep mode and Power Down sleep mode, and is loaded into the
SLEEP bits in the Control A register (BOD.CTRLA).
The operating mode in Active mode and Idle sleep mode (i.e. ACTIVE in BOD.CTRLA) cannot be altered
by software. The operating mode in Standby sleep mode and Power Down sleep mode can be altered by
writing to the SLEEP bits in the Control A register (BOD.CTRLA).
When the device is going into Standby sleep mode or Power Down sleep mode, the BOD will change
operation mode as defined by SLEEP in BOD.CTRLA. When the device is waking up from Standby or
Power Down sleep mode, the BOD will operate in the mode defined by the ACTIVE bit field in
BOD.CTRLA.
17.3.4
Synchronization
When the BOD changes mode from Enabled to Sampled mode it needs to re-synchronize to the sampled
clock. This is done automatically.
When the sampling rate for the BOD is 1KHz and the BOD is switching from Enabled to Sampled mode,
the first sample is delayed up to 1/2 cycle due to synchronization. This only happens on the first sample
after changing to Sampled mode.
17.3.5
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
Table 17-3. Registers under Configuration Change Protection
Register
Key
SLEEP in BOD.CTRLA
IOREG
Related Links
Sequence for Write Operation to Configuration Change Protected I/O Registers
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
17.4
Register Summary - BOD
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
SAMPFREQ
ACTIVE[1:0]
SLEEP[1:0]
LVL[2:0]
0x02
...
Reserved
0x07
0x08
VLMCTRLA
7:0
0x09
INTCTRL
7:0
VLMLVL[1:0]
0x0A
INTFLAGS
7:0
VLMIF
0x0B
STATUS
7:0
VLMS
VLMCFG[1:0]
17.5
Register Description
17.5.1
Control A
VLMIE
Name: CTRLA
Offset: 0x00
Reset: Loaded from fuse
Property: Configuration Change Protection
Bit
7
6
5
4
Access
R
R
R
R
Reset
0
0
0
x
3
2
1
R
R
R/W
R/W
x
x
x
x
SAMPFREQ
ACTIVE[1:0]
0
SLEEP[1:0]
Bit 4 – SAMPFREQ: Sample Frequency
This bit selects the BOD sample frequency.
The Reset value is loaded from the SAMPFREQ bit in FUSE.BODCFG.This bit is under Configuration
Change Protection (CCP).
Value
0x0
0x1
Description
Sample frequency is 1kHz
Sample frequency is 125Hz
Bits 3:2 – ACTIVE[1:0]: Active
These bits selects the BOD operation mode when the device is in active or idle mode.
The Reset value is loaded from the ACTIVE bits in FUSE.BODCFG.These bits are not under
Configuration Change Protection (CCP).
Value
0x0
0x1
0x2
0x3
Description
Disabled
Enabled
Sampled
Enabled with wake-up halted until BOD is ready
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Bits 1:0 – SLEEP[1:0]: Sleep
These bits select the BOD operation mode when the device is in standby or power-down sleep mode.
These bits are under Configuration Change Protection (CCP).
The Reset value is loaded from the SLEEP bits in FUSE.BODCFG.
Value
0x0
0x1
0x2
0x3
17.5.2
Description
Disabled
Enabled
Sampled
Reserved
Control B
Name: CTRLB
Offset: 0x01
Reset: Loaded from fuse
Property:
Bit
7
6
5
4
3
2
1
0
LVL[2:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
x
x
x
Bits 2:0 – LVL[2:0]: BOD Level
These bits selects the BOD threshold level.
The Reset value is loaded from the BOD Level bits (LVL) in the BOD Configuration fuse
(FUSE.BODCFG).
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
17.5.3
Name
BODLEVEL0
BODLEVEL1
BODLEVEL2
BODLEVEL3
BODLEVEL4
BODLEVEL5
BODLEVEL6
BODLEVEL7
Description
1.8V
2.15V
2.60V
2.95V
3.30V
3.70V
4.00V
4.30V
VLM Control A
Name: VLMCTRLA
Offset: 0x08
Reset: 0x00
Property:
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Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
VLMLVL[1:0]
Access
R
R
R
R
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 1:0 – VLMLVL[1:0]: VLM Level
These bit select the Voltage Level Monitor threshold relative to the BOD threshold (LVL in BOD.CTRLB).
Value
0x0
0x1
0x2
other
17.5.4
Description
VLM threshold 5% above BOD threshold
VLM threshold 15% above BOD threshold
VLM threshold 25% above BOD threshold
Reserved
Interrupt Control
Name: INTCTRL
Offset: 0x09
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
VLMCFG[1:0]
0
VLMIE
Access
R
R
R
R
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 2:1 – VLMCFG[1:0]: VLM Configuration
These bits select which incidents will trigger a VLM interrupt.
Value
0x0
0x1
0x2
Other
Description
Voltage crosses VLM threshold from above
Voltage crosses VLM threshold from below
Either direction is triggering an interrupt request
Reserved
Bit 0 – VLMIE: VLM Interrupt Enable
Writing a '1' to this bit enables the Voltage Level Monitor (VLM) interrupt.
17.5.5
VLM Interrupt Flags
Name: INTFLAGS
Offset: 0x0A
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
VLMIF
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
Bit 0 – VLMIF: VLM Interrupt Flag
This flag is set when a trigger from the VLM is given, as configured by the VLMCFG bit in the
BOD.INTCTRL register. The flag remains set only as long as the BOD is enabled.
17.5.6
VLM Status
Name: STATUS
Offset: 0x0B
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
VLMS
Bit 0 – VLMS: VLM Status
Value
0
1
Description
The voltage is above the VLM threshold level
The voltage is below the VLM threshold level
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8-bit AVR Microcontroller
18.
VREF - Voltage Reference
18.1
Features
•
•
18.2
Five programmable voltage reference sources
– One for each ADC peripheral
– One for each AC and DAC peripheral
Each reference source supports five different voltages:
– 0.55V
– 1.1V
– 1.5V
– 2.5V
– 4.3V
Overview
The Voltage Reference peripheral (VREF) provides control registers for the voltage reference sources
used by several peripherals. The user can select the reference voltages for the ADC0 by writing to the
ADC0 Reference Select bit field (ADC0REFSEL) in the Control A register (VREF.CTRLA), and for both
AC0 and DAC0 by writing to the DAC0 and AC0 Reference Select bit field DAC0REFSEL in
VREF.CTRLA.
A voltage reference source is enabled automatically when requested by a peripheral. The user can
enable the reference voltage sources (and thus, override the automatic disabling of unused sources) by
writing to the respective Force Enable bit (ADC0REFEN, DAC0REFEN) in the Control B register
(VREF.CTRLB). This may be desirable to decrease start-up time, at the cost of increased power
consumption.
18.2.1
Block Diagram
Figure 18-1. Block Diagram VREF
Reference reque st
Reference enable
Reference se lect
Bandgap
Reference
Gen erator
Ban dgap
ena ble
0.55V
1.1V
1.5V
2.5V
4.3V
BUF
Inte rnal
Reference
18.3
Functional Description
18.3.1
Initialization
The default configuration will enable the respective source when the ADC0, AC0 or DAC0 is requesting a
reference voltage. The default reference voltages are 0.55V, but can be configured by writing to the
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8-bit AVR Microcontroller
respective Reference Select bit field (ADC0REFSEL, DAC0REFSEL) in the Control A register
(VREF.CTRLA).
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8-bit AVR Microcontroller
18.4
Register Summary - VREF
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
CTRLC
7:0
0x03
CTRLD
7:0
ADC0REFSEL[2:0]
DAC0REFSEL[2:0]
DAC2REFEN ADC1REFEN DAC1REFEN
ADC1REFSEL[2:0]
ADC0REFEN DAC0REFEN
DAC1REFSEL[2:0]
DAC2REFSEL[2:0]
18.5
Register Description
18.5.1
Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
ADC0REFSEL[2:0]
Access
Reset
1
0
DAC0REFSEL[2:0]
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bits 6:4 – ADC0REFSEL[2:0]: ADC0 Reference Select
These bits select the reference voltage for the ADC0.
Value
0x0
0x1
0x2
0x3
0x4
other
Description
0.55V
1.1V
2.5V
4.3V
1.5V
Reserved
Bits 2:0 – DAC0REFSEL[2:0]: DAC0 and AC0 Reference Select
These bits select reference voltage for the DAC0 and AC0.
Value
0x0
0x1
0x2
0x3
0x4
other
18.5.2
Description
0.55V
1.1V
2.5V
4.3V
1.5V
Reserved
Control B
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8-bit AVR Microcontroller
Name: CTRLB
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
Access
Reset
5
4
3
1
0
DAC2REFEN
ADC1REFEN
DAC1REFEN
2
ADC0REFEN
DAC0REFEN
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 5 – DAC2REFEN: DAC2 and AC2 Reference Force Enable
Writing a '1' to this bit forces the voltage reference for the DAC2 and AC2 to be running, even if it not
requested.
Writing a '0' to this bit allows to automatic enable/disable of the reference source when not requested.
Bit 4 – ADC1REFEN: ADC1 Reference Force Enable
Writing a '1' to this bit forces the voltage reference for the ADC1 to be running, even if it not requested.
Writing a '0' to this bit allows to automatic enable/disable of the reference source when not requested.
Bit 3 – DAC1REFEN: DAC1 and AC1 Reference Force Enable
Writing a '1' to this bit forces the voltage reference for the DAC1 and AC1 to be running, even if it not
requested.
Writing a '0' to this bit allows to automatic enable/disable of the reference source when not requested.
Bit 1 – ADC0REFEN: ADC0 Reference Force Enable
Writing a '1' to this bit forces the voltage reference for the ADC0 to be running, even if it not requested.
Writing a '0' to this bit allows to automatic enable/disable of the reference source by the peripheral.
Bit 0 – DAC0REFEN: DAC0 and AC0 Reference Force Enable
Writing a '1' to this bit forces the voltage reference for the DAC0 and AC0 to be running, even if it not
requested.
Writing a '0' to this bit allows to automatic enable/disable of the reference source by the peripheral.
18.5.3
Control C
Name: CTRLC
Offset: 0x02
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
ADC1REFSEL[2:0]
Access
Reset
1
0
DAC1REFSEL[2:0]
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bits 6:4 – ADC1REFSEL[2:0]: ADC1 Reference Select
These bits select the reference voltage for the ADC1.
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8-bit AVR Microcontroller
Value
0x0
0x1
0x2
0x3
0x4
other
Description
0.55V
1.1V
2.5V
4.3V
1.5V
Reserved
Bits 2:0 – DAC1REFSEL[2:0]: DAC1 and AC1 Reference Select
These bits select reference voltage for the DAC1 and AC1.
Value
0x0
0x1
0x2
0x3
0x4
other
18.5.4
Description
0.55V
1.1V
2.5V
4.3V
1.5V
Reserved
Control D
Name: CTRLD
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DAC2REFSEL[2:0]
Access
Reset
R/W
R/W
R/W
0
0
0
Bits 2:0 – DAC2REFSEL[2:0]: DAC2 and AC2 Reference Select
These bits select reference voltage for the DAC2 and AC2.
Value
0x0
0x1
0x2
0x3
0x4
other
Description
0.55V
1.1V
2.5V
4.3V
1.5V
Reserved
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8-bit AVR Microcontroller
19.
WDT - Watchdog Timer
19.1
Features
•
•
•
•
•
•
•
19.2
Issues a System Reset if the Watchdog Timer is not cleared before its timeout period
Operating asynchronously from system clock using an independent oscillator
Using the 1KHz output of the 32KHz Ultra Low Power oscillator (OSCULP32K)
11 selectable timeout periods, from 8ms to 8s
Two operation modes:
– Normal Mode
– Window Mode
Configuration lock to prevent unwanted changes
Closed period timer activation after first WDT instruction for easy setup
Overview
The Watchdog Timer (WDT) is a system function for monitoring correct program operation. It allows to
recover from situations such as runaway or deadlocked code, by issuing a Reset. When enabled, the
WDT is a constantly running timer configured to a predefined timeout period. If the WDT is not reset
within the timeout period, it will issue a System Reset. The WDT is reset by executing the WDR (Watchdog
Timer Reset) instruction from software.
The WDT has two modes of operation, Normal mode and Window mode. The settings in the Control A
register (WDT.CTRLA) determine the mode of operation.
A window mode allows to define a time slot or "window" inside the timeout period during which the WDT
must be reset. If the WDT is reset outside this window, either too early or too late, a System Reset will be
issued. Compared to the normal mode, the window mode can also catch situations where a code error
causes constant WDR execution.
When enabled, the WDT will run in active mode and all sleep modes. It is asynchronous, i.e. running from
a CPU-independent clock source. For this reason it will continue to operate and be able to issue a
System Reset even if the main clock fails.
The Configuration Change Protection mechanism ensures that the WDT settings cannot be changed by
accident. For increased safety, a configuration for locking the WDT settings is also available.
Related Links
CCP - Configuration Change Protection
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
19.2.1
Block Diagram
Figure 19-1. WDT Block Diagram
"Inside closed window"
CTRLA
WINDOW
CLK_WDT
"Enable
open window
and clear count"
=
COUNT
=
PERIOD
System
Reset
CTRLA
WDR
(instruction)
19.2.2
Signal Description
Not applicable.
19.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 19-1. WDT System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
No
-
Events
No
-
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
19.2.3.1 Clocks
A 1KHz oscillator clock (CLK_WDT_OSC) is sourced from the internal ultra-low-power oscillator,
OSCULP32K. Due to the ultra-low-power design, the oscillator is not very accurate, and so the exact
time-out period may vary from device to device. This variation must be kept in mind when designing
software that uses the WDT to ensure that the time-out periods used are valid for all devices.
The counter clock CLK_WDT_OSC is asynchronous to the system clock. Due to this asynchronicity,
writing to WDT control register will require synchronization between the clock domains.
19.2.3.2 I/O Lines and Connections
Not applicable.
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8-bit AVR Microcontroller
19.2.3.3 Interrupts
Not applicable.
19.2.3.4 Events
Not applicable.
19.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in debugging
mode will halt normal operation of the peripheral.
When halting the CPU in debug mode, the WDT counter is reset.
when starting the CPU again and the WDT was operating in window mode, the first closed window
timeout period will be disabled, and a normal mode timeout period is executed.
Related Links
Window Mode
19.3
Functional Description
19.3.1
Initialization
•
•
The WDT is enabled when a non-zero value is written to the Period bits (PERIOD) in the Control A
register (WDT.CTRLA).
Optional: Write a non-zero value to the Window bits (WINDOW) in WDT.CTRLA to enable window
mode operation.
All bits in the Control A register and the Lock bit (LOCK) in the Status register (WDT.STATUS) are write
protected by the Configuration Change Protection mechanism.
The Reset value of WDT.CTRLA is defined by a fuse (FUSE.WDTCFG), so the WDT can be enabled at
boot time. If this is the case, the LOCK bit in WDT.STATUS is set at boot time, too.
Related Links
Register Summary - WDT
19.3.2
Operation
19.3.2.1 Normal Mode
In normal mode operation, a single timeout period is set for the WDT. If the WDT is not reset from
software using the WDR any time before the timeout occurs, the WDT will issue a System Reset.
A new WDT timeout period will be started each time the WDT is reset by WDR.
There are 11 possible WDT timeout periods (TOWDT), selectable from 8ms to 8s by writing to the Period
bit field (PERIOD) in the Control A register (WDT.CTRLA).
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8-bit AVR Microcontroller
Figure 19-2. Normal Mode Operation
WDT Count
Timely WDT Reset (WDR)
WDT Timeout
System Reset
Here:
TO WDT = 16ms
5
10
15
20
25
30
TOWDT
35
t [ms]
Normal mode is enabled as long as the WINDOW bit field in the Control A register (WDT.CTRLA) is 0x0.
Related Links
Register Summary - WDT
19.3.2.2 Window Mode
In window mode operation, the WDT uses two different timeout periods, a "closed" window timeout period
(TOWDTW) and the normal timeout period (TOWDT):
The closed window timeout period defines a duration from 8ms to 8s where the WDT cannot be reset. If
the WDT is reset during this period, the WDT will issue a System Reset.
The normal WDT timeout period, which is also 8ms to 8s, defines the duration of the "open" period during
which the WDT can (and should) be reset. The open period will always follow the closed period, so the
total duration of the timeout period is the sum of the closed window and the open window timeout periods.
When enabling window mode or when going out of debug mode, the first closed period is activated after
the first WDR instruction.
Figure 19-3. Window Mode Operation
WDT Count
Open
Timely WDT Reset (WDR)
Closed
WDR too early:
System Reset
Here:
TOWDTW =TOWDT = 8ms
5
10
15
20
TOWDTW
25
30
TOWDT
35
t [ms]
The window mode is enabled by writing a non-zero value to the WINDOW bit field in the Control A
register (WDT.CTRLA), and disabled by writing WINDOW=0x0.
19.3.2.3 Configuration Protection and Lock
The WDT provides two security mechanisms to avoid unintentional changes to the WDT settings:
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8-bit AVR Microcontroller
The first mechanism is the Configuration Change Protection mechanism, employing a timed write
procedure for changing the WDT control registers.
The second mechanism locks the configuration by writing a '1' to the LOCK bit in the Status register
(WDT.STATUS). When this bit is '1', the Control A register (WDT.CTRLA) cannot be changed.
Consequently, the WDT cannot be disabled from software.
LOCK in WDT.STATUS can only be written to '1'. It can only be cleared in debug mode.
If the WDT configuration is loaded from fuses, LOCK is automatically set in WDT.STATUS.
Related Links
CCP - Configuration Change Protection
19.3.3
Events
Not applicable.
19.3.4
Interrupts
Not applicable.
19.3.5
Sleep Mode Operation
The WDT will continue to operate in any sleep mode where the source clock is active.
19.3.6
Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domain, the Control A
register (WDT.CTRLA) is synchronized when written. The Synchronization Busy flag (SYNCBUSY) in the
Status register (WDT.STATUS) indicates if there is an ongoing synchronization.
Writing to WDT.CTRLA while SYNCBUSY=1 is not allowed.
The following registers are synchronized when written:
•
PERIOD bits in Control A register (WDT.CTRLA)
•
Window Period bits (WINDOW) in WDT.CTRLA.
The WDR instruction will need 2 to 3 cycles of the WDT clock in order to be synchronized. Issuing a new
WDR instruction while a WDR instruction is being synchronized will be ignored
19.3.7
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
Table 19-2. WDT - Registers under Configuration Change Protection
Register
Key
WDT.CTRLA
IOREG
LOCK bit in WDT.STATUS
IOREG
List of bits/registers protected by CCP.
•
Period bits in Control A register (CTRLA.PERIOD)
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8-bit AVR Microcontroller
•
•
Window Period bits in Control A register (CTRLA.WINDOW)
Lock bit in Status register (STATUS.LOCK)
Related Links
CCP - Configuration Change Protection
Sequence for Write Operation to Configuration Change Protected I/O Registers
CCP
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8-bit AVR Microcontroller
19.4
Register Summary - WDT
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
STATUS
7:0
WINDOW[3:0]
PERIOD[3:0]
LOCK
19.5
Register Description
19.5.1
Control A
SYNCBUSY
Name: CTRLA
Offset: 0x00
Reset: From FUSE.WDTCFG
Property: Configuration Change Protection
Bit
7
6
5
4
3
2
R/W
x
1
0
R/W
R/W
R/W
R/W
R/W
x
x
x
x
R/W
R/W
x
x
x
WINDOW[3:0]
Access
Reset
PERIOD[3:0]
Bits 7:4 – WINDOW[3:0]: Window
Writing a non-zero value to these bits enables the window mode, and selects the according duration of
the closed period.
The bits are optionally lock protected:
•
•
If LOCK bit in WDT.STATUS is '1', all bits are change protected (Access = R)
If LOCK bit in WDT.STATUS is '0', all bits can be changed (Access = R/W)
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
other
Name
OFF
8CLK
16CLK
32CLK
64CLK
128CLK
256CLK
512CLK
1KCLK
2KCLK
4KCLK
8KCLK
-
Description
0.008s
0.016s
0.032s
0.064s
0.128s
0.256s
0.512s
1.0s
2.0s
4.1s
8.2s
Reserved
Bits 3:0 – PERIOD[3:0]: Period
Writing a non-zero value to this bit enables the WDT, and selects the according timeout period in normal
mode. In window mode, these bits select the duration of the open window.
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The bits are optionally lock protected:
•
•
If LOCK in WDT.STATUS is '1', all bits are change protected (Access = R)
If LOCK in WDT.STATUS is '0', all bits can be changed (Access = R/W)
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
other
19.5.2
Name
OFF
8CLK
16CLK
32CLK
64CLK
128CLK
256CLK
512CLK
1KCLK
2KCLK
4KCLK
8KCLK
-
Description
0.008s
0.016s
0.032s
0.064s
0.128s
0.256s
0.512s
1.0s
2.0s
4.1s
8.2s
Reserved
Status
Name: STATUS
Offset: 0x01
Reset: 0x00
Property: Configuration Change Protection
Bit
Access
Reset
7
6
5
4
3
2
1
0
LOCK
SYNCBUSY
R/W
R
0
0
Bit 7 – LOCK: Lock
Writing this bit to '1' write protects the WDT.CTRLA register.
It is only possible to write this bit to '1'. This bit can only be cleared in debug.
If the PERIOD bits in WDT.CTRLA are different from zero after boot code, Lock will automatically be set.
This bit is under Configuration Change Protection (CCP).
Bit 0 – SYNCBUSY: Synchronization Busy
This bit is set after writing to the WDT.CTRLA register while the data is being synchronized from the
system clock domain to the WDT clock domain.
This bit is cleared by system after the synchronization is finished.
This bit is not under Configuration Change Protection (CCP).
Related Links
Synchronization
Configuration Change Protection
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8-bit AVR Microcontroller
20.
TCA - 16-bit Timer/Counter Type A
20.1
Features
•
•
•
•
•
•
•
•
•
20.2
16-bit timer/counter
Three compare channels
Double buffered timer period setting
Double buffered compare channels
Waveform generation:
– Frequency generation
– Single-slope PWM (pulse width modulation)
– Dual-slope PWM
Count on event
Timer overflow interrupts/events
One compare match per compare channel
Two 8-bit timer/counters in Split Mode
Overview
The flexible 16-bit PWM Timer/Counter type A (TCA) provides accurate program execution timing,
frequency and waveform generation, and command execution.
A TCA consists of a base counter and a set of compare channels. The base counter can be used to count
clock cycles or events, or let events control how it counts clock cycles. It has direction control and period
setting that can be used for timing. The compare channels can be used together with the base counter to
do compare match control, frequency generation, and pulse width waveform modulation.
Depending on the mode of operation, the counter is cleared, reloaded, incremented, or decremented at
each timer/counter clock or event input.
A timer/counter can be clocked and timed from the peripheral clock with optional prescaling or from the
event system. The event system can also be used for direction control or to synchronize operations.
By default, the TCA is a 16-bit timer/counter. The timer/Counter has a Split mode feature that splits it into
two 8-bit timer/counters with three compare channels each.
A block diagram of the 16-bit timer/counter with closely related peripheral modules (in grey) is shown
below.
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Figure 20-1. 16-bit Timer/counter and Closely Related Peripherals
Timer/Counter
Base Counter
Counter
Control Logic
Compare Channel 0
Compare Channel 1
Compare Channel 2
Comparator
Buffer
Waveform
Generation
CLK_PER
Event
System
PORTS
Timer Period
Prescaler
This device provides one instance of the TCA peripheral, TCA0.
20.2.1
Block Diagram
The below figure shows a detailed block diagram of the timer/counter.
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8-bit AVR Microcontroller
Figure 20-2. Timer/Counter Block Diagram
Base Coun ter
PERB
CTRLA
PER
EVCTRL
Clock Select
Event
Select
"count"
"clear"
"load"
"direction"
Counter
CNT
=
=0
TOP
BOTTOM
OVF/UNF
(INT Req.)
Control Logi c
"ev"
UPDATE
BV
Compare
(Unit x = {A,B,C})
BV
CMPnBUF
Control Logi c
CMPn
=
Wav efo rm
Generation
"match"
WOn Out
CMPn
(INT Req.)
The counter register (CNT), period registers with buffer (PER and PERBUF), and compare registers with
buffers (CMPx and CMPBUFx) are 16-bit registers. All buffer registers have a buffer valid (BV) flag that
indicates when the buffer contains a new value.
During normal operation, the counter value is continuously compared to zero and the period (PER) value
to determine whether the counter has reached TOP or BOTTOM.
The counter value is also compared to the CMPx registers. These comparisons can be used to generate
interrupt requests. The waveform generator modes use these comparisons to set the waveform period or
pulse width.
A prescaled peripheral clock and events from the event system can be used to control the counter.
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8-bit AVR Microcontroller
Figure 20-3. Timer/Counter Clock Logic
CLK_PER
Prescaler
Event System
event
CKSEL
EVACT
(Encoding)
CLK_TCA
CNT
CNTEI
20.2.2
20.2.3
Signal Description
Signal
Description
Type
WO[2:0]
Digital output
Waveform output
WO[5:3]
Digital output
Waveform output - Split Mode only
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 20-1. TCA System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
WO[5:0]
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
Interrupts
Events
20.2.3.1 Clocks
This peripheral uses the system clock CLK_PER, and has its own prescaler.
Related Links
CLKCTRL - Clock Controller
20.2.3.2 I/O Lines and Connections
Using the I/O lines of the peripheral requires configuration of the I/O pins.
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Related Links
I/O Multiplexing and Considerations
PORT - I/O Pin Configuration
I/O Multiplexing and Considerations
PORT - I/O Pin Configuration
20.2.3.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
Related Links
CPUINT - CPU Interrupt Controller
SREG
Interrupts
CPUINT - CPU Interrupt Controller
SREG
Interrupts
20.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
EVSYS - Event System
20.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in debugging
mode will halt normal operation of the peripheral.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
Related Links
UPDI - Unified Program and Debug Interface
20.3
Functional Description
20.3.1
Definitions
The following definitions are used throughout the documentation:
Table 20-2. Timer/Counter Definitions
Name
Description
BOTTOM The counter reaches BOTTOM when it becomes zero.
MAX
The counter reaches MAXimum when it becomes all ones.
TOP
The counter reaches TOP when it becomes equal to the highest value in the count
sequence.
UPDATE The update condition is met when the timer/counter reaches BOTTOM or TOP, depending on
the waveform generator mode.
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Name
Description
CNT
Counter register value
CMP
Compare register value
In general, the term “timer” is used when the timer/counter is counting periodic clock ticks. The term
“counter” is used when the input signal has sporadic or irregular ticks.
20.3.2
Initialization
To start using the timer/counter in a basic mode, follow these steps:
•
Write a TOP value to the Period register (TCA.PER)
•
Enable the peripheral by writing a '1' to the ENABLE bit in the Control A register (TCA.CTRLA).
The counter will start counting clock ticks according to the prescaler setting in the Clock Select bit
field (CLKSEL) in TCA.CTRLA.
•
Optional: By writing a '1' to the Enable Count on Event Input bit (CNTEI) in the Event Control
register (TCA.EVCTRL), Event inputs are counted instead of clock ticks.
•
The counter value can be read from the Counter bit field (CNT) in the Counter register (TCA.CNT).
20.3.3
Operation
20.3.3.1 Normal Operation
In normal operation, the counter is counting clock ticks in the direction selected by the Direction bit (DIR)
in the Control E register (TCA.CTRLE), until it reaches TOP or BOTTOM. The clock ticks are from the
peripheral clock CLK_PER, optionally prescaled, depending on the Clock Select bit field (CLKSEL) in the
Control A register (TCA.CTRLA).
When up-counting and TOP is reached, the counter will wrap to zero at the next clock tick. When downcounting, the counter is reloaded with the Period register value (TCA.PER) when BOTTOM is reached.
Figure 20-4. Normal Operation
CNT written
MAX
"update"
CNT
TOP
BOTTOM
DIR
It is possible to change the Counter value in the Counter register (TCA.CNT) when the counter is running.
The write access to TCA.CNT has higher priority than count, clear, or reload, and will be immediate. The
direction of the counter can also be changed during normal operation by writing to DIR in TCA.CTRLE.
20.3.3.2 Double Buffering
The Period register value (TCA.PER) and the Compare n register values (TCA.CMPn) are all double
buffered (TCA.PERBUF and TCA.CMPnBUF).
Each buffer register has a Buffer Valid flag (PERBV, CMPnBV) in the Control F register (TCA.CTRLF),
which indicates that the buffer register contains a valid, i.e. new, value that can be copied into the
corresponding Period or Compare register. When the Period register and Compare n registers are used
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for a Compare operation, the BV flag is set when data is written to the buffer register, and cleared on an
UPDATE condition. This is shown for a Compare register in below.
Figure 20-5. Period and Compare Double Buffering
"write enable"
"data write"
EN
CMPnBUF
BV
EN
UPDATE
CMPn
CNT
=
"match"
Both the TCA.CMPn and TCA.CMPnBUF registers are available as I/O registers. This allows initialization
and bypassing of the buffer register and the double buffering function.
20.3.3.3 Changing the Period
The Counter period is changed by writing a new TOP value to the Period register (TCA.PER).
No Buffering: If double buffering is not used, any period update is immediate.
Figure 20-6. Changing the Period without Buffering
Counter wraparound
MAX
"update"
"write"
CNT
BOTTOM
New TOP written to
PER that is higher
than current CNT.
New TOP written to
PER that is lower
than current CNT.
A counter wraparound can occur in any mode of operation when up-counting without buffering. This is
due to the fact that the registers TCA.CNT and TCA.PER are continuously compared: if a new TOP value
is written to TCA.PER that is lower than current TCA.CNT, the counter will wrap first before a compare
match happened.
Figure 20-7. Unbuffered Dual-slope Operation
Counter wraparound
MAX
"update"
"write"
CNT
BOTTOM
New TOP written to
PER that is higher
than current CNT.
© 2017 Microchip Technology Inc.
New TOP written to
PER that is lower
than current CNT.
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With Buffering: When double buffering is used, the buffer can be written at any time and still maintain
correct operation. The TCA.PER is always updated on the UPDATE condition, as shown for dual-slope
operation in the figure below. This prevents wraparound and the generation of odd waveforms.
Figure 20-8. Changing the Period Using Buffering
MAX
"update"
"write"
CNT
BOTTOM
New Period written to
PERB that is higher
than current CNT.
New Period written to
PERB that is lower
than current CNT.
New PER is updated
with PERB value.
20.3.3.4 Compare Channel
Each Compare Channel n continuously compares the counter value (TCA.CNT) with the Compare n
register (TCA.CMPn). If TCA.CNT equals TCA.CMPn, the comparator n signals a match. The match will
set the Compare Channel's interrupt flag at the next timer clock cycle, and the optional interrupt is
generated.
The Compare n Buffer register (TCA.CMPnBUF) provides double buffer capability equivalent to that for
the period buffer. The double buffering synchronizes the update of the TCA.CMPn register with the buffer
value to either the TOP or BOTTOM of the counting sequence, according to the UPDATE condition. The
synchronization prevents the occurrence of odd-length, non-symmetrical pulses for glitch-free output.
Waveform Generation
The compare channels can be used for waveform generation on the corresponding port pins. To make
the waveform visible on the connected port pin, the following requirements must be fulfilled:
1.
2.
3.
4.
5.
A waveform generation mode must be selected by writing the WGMODE bit field in TCA.CTRLB.
The TCA is counting clock tick, not Events (CNTEI=0 in TCA.EVCTRL)
The compare channels used must be enabled (CMPnEN=1 in TCA.CTRLB). This will override the
corresponding PORT pin output register. An alternative pin can be selected by writing to the
respective TCA Waveform Output n bit (TCA0n) in the Control C register of the Port Multiplexer
(PORTMUX.CTRLC).
The direction for the associated Port pin n must be configured as output (PORT.DIR[n]=1).
Optional: Enable inverted waveform output for the associated Port pin n (INVEN=1 in PORT.PINn).
Frequency (FRQ) Waveform Generation
For frequency generation, the period time (T) is controlled by a TCA.CMPn register instead of the Period
register (TCA.PER). The waveform generation output WG is toggled on each compare match between
the TCA.CNT and TCA.CMPn registers.
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8-bit AVR Microcontroller
Figure 20-9. Frequency Waveform Generation
Period (T)
Direction change
CNT written
MAX
"update"
CNT
TOP
BOTTOM
WG Output
The waveform frequency (fFRQ) is defined by the following equation:
�FRQ =
f CLK_PER
2� CMPn+1
where N represents the prescaler divider used (CLKSEL in TCA.CTRLA), and fCLK_PER is the system
clock for the peripherals.
The maximum frequency of the waveform generated is half of the peripheral clock frequency (fCLK_PER/2)
when TCA.CMPn is written to zero (0x0000) and no prescaling is used (N=1, CLKSEL=0x0 in
TCA.CTRLA).
Single-Slope PWM Generation
For single-slope Pulse Width Modulation (PWM) generation, the period (T) is controlled by TCA.PER,
while the values of TCA.CMPn control the duty cycle of the WG output. The figure below shows how the
counter counts from BOTTOM to TOP and then restarts from BOTTOM. The waveform generator (WO)
output is set at TOP, and cleared on the compare match between the TCA.CNT and TCA.CMPn registers.
Figure 20-10. Single-Slope Pulse Width Modulation
Period (T)
CMPn=BOTTOM
CMPn=TOP
MAX
TOP
"update"
"match"
CNT
CMPn
BOTTOM
Output WOn
The TCA.PER register defines the PWM resolution. The minimum resolution is 2 bits
(TCA.PER=0x0003), and the maximum resolution is 16 bits (TCA.PER=MAX).
The following equation calculates the exact resolution for single-slope PWM (RPWM_SS):
�PWM_SS =
log PER+1
log 2
�PWM_SS =
�CLK_PER
� PER+1
The single-slope PWM frequency (fPWM_SS) depends on the period setting (TCA_PER), the system's
peripheral clock frequency fCLK_PER, the TCA prescaler (CLKSEL in TCA.CTRLA). It is calculated by the
following equation:
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8-bit AVR Microcontroller
where N represents the prescaler divider used.
Dual-slope PWM
For dual-slope PWM generation, the period (T) is controlled by TCA.PER, while the values of TCA.CMPn
control the duty cycle of the WG output.
The figure below shows how for dual-slope PWM the counter counts repeatedly from BOTTOM to TOP
and then from TOP to BOTTOM. The waveform generator output is set on BOTTOM, cleared on compare
match when up-counting, and set on compare match when down-counting.
Figure 20-11. Dual-slope Pulse Width Modulation
Period (T)
CMPn=BOTTOM
CMPn=TOP
"update"
"match"
MAX
CMPn
TOP
CNT
BOTTOM
Waveform Output WOn
Using dual-slope PWM results in a lower maximum operation frequency compared to the single-slope
PWM operation.
The period register (TCA.PER) defines the PWM resolution. The minimum resolution is 2 bits
(TCA.PER=0x0003), and the maximum resolution is 16 bits (TCA.PER=MAX).
The following equation calculate the exact resolution for dual-slope PWM (RPWM_DS):
�PWM_DS =
log PER+1
log 2
�PWM_DS =
�CLK_PER
2� ⋅ PER
The PWM frequency depends on the period setting (TCA.PER), the peripheral clock frequency (fCLK_PER),
and the prescaler divider used (CLKSEL in TCA.CTRLA). It is calculated by the following equation:
N represents the prescaler divider used.
Port Override for Waveform Generation
To make the waveform generation available on the Port pins, the corresponding Port pin direction must
be set as output (PORT.DIR[n]=1). The TCA will override the port pin values when the compare channel
is enabled (CMPnEN=1 in TCA.CTRLB) and a waveform generation mode is selected.
The figure below shows the port override for TCA. The timer/counter compare channel will override the
port pin output value (OUT) on the corresponding port pin. Enabling inverted I/O on the port pin
(INVEN=1 in PORT.PINn) inverts the corresponding WG output.
Figure 20-12. Port Override for Timer/Counter Type A
OUT
WOn
Waveform
CMPnEN
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20.3.3.5 Timer/Counter Commands
A set of commands can be issued by software to immediately change the state of the peripheral. These
commands give direct control of the UPDATE, RESTART, and RESET signals. A command is issued by
writing the respective value to the Command bit field (CMD) in the Control E register (TCA.CTRLESET).
An UPDATE command has the same effect as when an update condition occurs, except that the UPDATE
command is not affected by the state of the Lock Update bit (LUPD) in the Control E register
(TCA.CTRLE).
The software can force a restart of the current waveform period by issuing a RESTART command. In this
case the counter, direction, and all compare outputs are set to zero.
A RESET command will set all timer/counter registers to their initial values. A RESET can be issued only
when the timer/counter is not running (ENABLE=0 in TCA.CTRLA).
20.3.3.6 Split Mode - Two 8-Bit Timer/Counters
Split Mode Overview
To double the number of timers and PWM channels in the TCA, a Split Mode is provided. In this Split
Mode, the 16-bit timer/counter acts as two separate 8-bit timers, which each have three compare
channels for PWM generation. The split mode will only work with single slope down count. Split Mode
does not support Event action controlled operation.
Split Mode Differences to Normal Mode
•
Count
– Down-count only
– Timer/Counter counter high and low byte are independent (TCA.LCNT, TCA.HCNT)
•
Waveform generation
– Single Slope PWM only (WGMODE=SINGLESLOPE in TCA.CTRLB)
•
Interrupt
– No change for low byte Timer/Counter (TCA.LCNT)
– Underflow interrupt for high byte Timer/Counter (TCA.HCNT)
– No compare interrupt or flag for High-byte Compare n registers (TCA.HCMPn)
•
Event actions: Not compatible
•
Buffer registers and Buffer Valid flags: Unused
•
Register access: Byte access to all registers.
•
Temp register: Unused, 16-bit register of the Normal Mode are accessed as 8-bit 'TCA_H' and
'TCA_L', respectively.
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8-bit AVR Microcontroller
Block Diagram
Figure 20-13. Timer/Counter Block Diagram Split Mode
Base Counter
HPER
LPER
"count high"
"load high"
"count low"
"load low"
Counter
HCNT
Clock Select
CTRLA
LCNT
HUNF
Control Logic
(INT Req.)
LUNF
(INT Req.)
=0
BOTTOML
BOTTOMH
=0
Compare
(Unit n = {0,1,2})
LCMPn
Waveform
Generation
"match"
=
WOn Out
LCMPn
(INT Req.)
Compare
(Unit n = {0,1,2})
HCMPn
=
Waveform
Generation
WO[n+3] Out
"match"
Split Mode Initialization
When shifting between Normal Mode and Split Mode, the functionality of some registers and bits change,
but their values do not. For this reason, disabling the peripheral (ENABLE=0 in TCA.CTRLA) and doing a
Hard Reset (CMD=RESET in TCA.CTRLESET) is recommended when changing the mode to avoid
unexpected behavior.
To start using the timer/counter in basic Split Mode after a Hard Reset, follow these steps:
•
Enable Split Mode by writing a '1' to the Split Mode Enable bit in the Control D register (SPLITM in
TCA.CTRLD).
•
Write a TOP value to the Period registers (TCA.PER)
•
Enable the peripheral by writing a '1' to the ENABLE bit in the Control A register (TCA.CTRLA).
The counter will start counting clock ticks according to the prescaler setting in the Clock Select bit
field (CLKSEL) in TCA.CTRLA.
•
The counter values can be read from the Counter bit field in the Counter registers (TCA.CNT).
Activating Split Mode results in changes to the functionality of some registers and register bits. The
modifications are described in a separate register map. See Register Summary - Split Mode.
20.3.4
Events
The peripheral can take the following actions on an input Event:
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8-bit AVR Microcontroller
•
•
•
•
The counter counts positive edges of the Event signal.
The counter counts both positive and negative edges of the Event signal.
The counter counts prescaled clock cycles as long as the Event signal is high.
The counter counts prescaled clock cycles. Event signal controls the direction of counting. Upcount when Event signal is low, down-count when Event signal is high.
The specific action is selected by writing to the Event Action bits (EVACT) in the Event Control register
(TCA.EVCTRL). Events as input are enabled by writing a '1' to the Enable Count on Event Input bit
(CNTEI in TCA.EVCTRL).
Event controlled operation is not available in Split Mode.
20.3.5
Interrupts
Table 20-3. Available Interrupt Vectors and Sources in Normal Mode
Offset Name Vector Description
Conditions
0x00
OVF
The counter has reached its top value and wrapped to
zero.
0x04
CMP0 Compare channel 0 interrupt
Match between the counter value and the Compare 0
register.
0x06
CMP1 Compare channel 1 interrupt
Match between the counter value and the Compare 1
register.
0x08
CMP2 Compare channel 2 interrupt
Match between the counter value and the Compare 2
register.
Overflow and Compare match
interrupt
Table 20-4. Available Interrupt Vectors and Sources in Split Mode
Offset Name
Vector Description
Conditions
0x00
LUNF
Low-byte Underflow interrupt Low-byte timer reaches BOTTOM.
0x02
HUNF
High-byte Underflow interrupt High-byte timer reaches BOTTOM.
0x04
LCMP0 Compare channel 0 interrupt Match between the counter value and the low-byte of
Compare 0 register.
0x06
LCMP1 Compare channel 1 interrupt Match between the counter value and the low-byte of
Compare 1 register.
0x08
LCMP2 Compare channel 2 interrupt Match between the counter value and the low-byte of
the Compare 2 register.
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Interrupt Flags register
of the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the Interrupt
Flag is set. The interrupt request remains active until the Interrupt Flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear Interrupt Flags.
Related Links
AVR CPU
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8-bit AVR Microcontroller
SREG
20.3.6
Sleep Mode Operation
The timer/counter will halt operation in all sleep modes.
20.3.7
Configuration Change Protection
Not applicable.
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8-bit AVR Microcontroller
20.4
Register Summary - TCA in Normal Mode (CTRLD.SPLITM=0)
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
CLKSEL[2:0]
CMPnEN2
CMPnEN1
CMPnEN0
ALUPD
ENABLE
0x01
CTRLB
7:0
0x02
CTRLC
7:0
WGMODE[2:0]
0x03
CTRLD
7:0
0x04
CTRLECLR
7:0
CMD[1:0]
LUPD
0x05
CTRLESET
7:0
CMD[1:0]
LUPD
DIR
0x06
CTRLFCLR
7:0
CMP2BV
CMP1BV
CMP0BV
PERBV
0x07
CTRLFSET
7:0
CMP2BV
CMP1BV
CMP0BV
PERBV
0x08
Reserved
CMP2OV
CMP1OV
CMP0OV
SPLITM
EVACT[1:0]
DIR
0x09
EVCTRL
7:0
0x0A
INTCTRL
7:0
CMP2
CMP1
CMP0
CNTEI
OVF
0x0B
INTFLAGS
7:0
CMP2
CMP1
CMP0
OVF
0x0C
...
Reserved
0x0D
0x0E
DBGCTRL
7:0
0x0F
TEMP
7:0
TEMP[7:0]
DBGRUN
7:0
CNT[7:0]
15:8
CNT[15:8]
0x10
...
Reserved
0x1F
0x20
0x21
CNT
0x22
...
Reserved
0x25
0x26
0x27
0x28
0x29
0x2A
0x2B
0x2C
0x2D
PER
CMP0
CMP1
CMP2
7:0
PER[7:0]
15:8
PER[15:8]
7:0
CMP[7:0]
15:8
CMP[15:8]
7:0
CMP[7:0]
15:8
CMP[15:8]
7:0
CMP[7:0]
15:8
CMP[15:8]
0x2E
...
Reserved
0x35
0x36
0x37
0x38
0x39
0x3A
0x3B
0x3C
0x3D
PERBUF
CMP0BUF
CMP1BUF
CMP2BUF
7:0
PERBUF[7:0]
15:8
PERBUF[15:8]
7:0
CMPBUF[7:0]
15:8
CMPBUF[15:8]
7:0
CMPBUF[7:0]
15:8
CMPBUF[15:8]
7:0
CMPBUF[7:0]
15:8
CMPBUF[15:8]
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8-bit AVR Microcontroller
20.5
Register Description - Normal Mode
20.5.1
Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
CLKSEL[2:0]
Access
0
ENABLE
R/W
R/W
R/W
R/W
0
0
0
0
1
0
Reset
Bits 3:1 – CLKSEL[2:0]: Clock Select
These bits select the clock frequency for the timer/counter.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
DIV1
DIV2
DIV4
DIV8
DIV16
DIV64
DIV256
DIV1024
Description
fTCA = fCLK_PER/1
fTCA = fCLK_PER/2
fTCA = fCLK_PER/4
fTCA = fCLK_PER/8
fTCA = fCLK_PER/16
fTCA = fCLK_PER/64
fTCA = fCLK_PER/256
fTCA = fCLK_PER/1024
Bit 0 – ENABLE: Enable
Value
0
1
20.5.2
Description
The peripheral is disabled
The peripheral is enabled
Control B - Normal Mode
Name: CTRLB
Offset: 0x01
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
3
CMPnEN2
CMPnEN1
CMPnEN0
ALUPD
2
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
WGMODE[2:0]
Bits 4, 5, 6 – CMPnEN: Compare n Enable
In the FRQ or PWM waveform generation mode, these bits will override the PORT output register for the
corresponding pin.
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8-bit AVR Microcontroller
Value
0
1
Description
PORT output settings for the pin with WOn output respected.
PORT output settings for pin with WOn output overridden in FRQ or PWM waveform
generation mode.
Bit 3 – ALUPD: Auto Lock Update
The Auto Lock Update feature controls the Lock Update (LUPD) bit in the TCA.CTRLE register. When
ALUPD is written to ‘1’, LUPD will be set to ‘1’ until the Buffer Valid (CMPnBV) bits of all enabled compare
channels are ‘1’. This condition will clear LUPD.
It will remain cleared until the next UPDATE condition, where the buffer values will be transferred to the
CMPn registers and LUPD will be set to ‘1’ again. This makes sure that CMPnBUF register values are not
transferred to the CMPn registers until all enabled compare buffers are written.
Value
0
1
Description
LUPD in TCA.CTRLE not altered by system.
LUPD in TCA.CTRLE set and cleared automatically.
Bits 2:0 – WGMODE[2:0]: Waveform Generation Mode
These bits select the waveform generation mode, and control the counting sequence of the counter, TOP
value, UPDATE condition, interrupt condition, and type of waveform that is generated.
No waveform generation is performed in the normal mode of operation. For all other modes, the result
from the waveform generator will only be directed to the PORT pins if the corresponding CMPnEN bit has
been set to enable this. The port pin direction must be set as output.
Table 20-5. Timer Waveform Generation Mode
WGMODE[2:0]
Value
0x0
0x1
0x3
0x5
0x6
0x7
Other
20.5.3
Group Configuration Mode of Operation
Top
Update
OVF
Normal
PER
TOP
TOP
000
NORMAL
001
FRQ
Frequency
CMP0 TOP
TOP
010
-
Reserved
-
-
-
011
SINGLESLOPE
Single-slope PWM
PER
BOTTOM BOTTOM
100
-
Reserved
-
-
101
DSTOP
Dual-slope PWM
PER
BOTTOM TOP
110
DSBOTH
Dual-slope PWM
PER
BOTTOM TOP and BOTTOM
111
DSBOTTOM
Dual-slope PWM
PER
BOTTOM BOTTOM
Name
NORMAL
FRQ
SINGLESLOPE
DSTOP
DSBOTH
DSBOTTOM
-
-
Description
Normal operation mode
Frequency mode
Single-slope PWM mode
Dual-slope PWM mode
Dual-slope PWM mode
Dual-slope PWM mode
Reserved
Control C - Normal Mode
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8-bit AVR Microcontroller
Name: CTRLC
Offset: 0x02
Reset: 0x00
Property:
Bit
7
6
5
4
3
Access
Reset
2
1
0
CMP2OV
CMP1OV
CMP0OV
R/W
R/W
R/W
0
0
0
Bit 2 – CMP2OV: Compare Output Value 2
See CMP0OV.
Bit 1 – CMP1OV: Compare Output Value 1
See CMP0OV.
Bit 0 – CMP0OV: Compare Output Value 0
The CMPnOV bits allow direct access to the waveform generator's output compare value when the timer/
counter is not enabled. This is used to set or clear the WG output value when the timer/counter is not
running.
20.5.4
Control D
Name: CTRLD
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
SPLITM
Access
R/W
Reset
0
Bit 0 – SPLITM: Enable Split Mode
This bit sets the timer/counter in split mode operation. It will then work as two 8-bit timer/counters. The
register map will change compared to normal 16-bit mode.
20.5.5
Control Register E Clear - Normal Mode
The individual status bit can be cleared by writing a one to its bit location. This allows each bit to be
cleared without use of a read-modify-write operation on a single register.
Each Status bit can be read out either by reading TCA.CTRLESET or TCA.CTRLECLR.
Name: CTRLECLR
Offset: 0x04
Reset: 0x00
Property:
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Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
CMD[1:0]
Access
1
0
LUPD
DIR
R/W
R/W
R/W
R/W
0
0
0
0
Reset
Bits 3:2 – CMD[1:0]: Command
These bits are used for software control of update, restart, and reset of the timer/counter. The command
bits are always read as zero.
Value
0x0
0x1
0x2
0x3
Name
NONE
UPDATE
RESTART
RESET
Description
No command
Force update
Force restart
Force hard Reset (ignored if TC is enabled)
Bit 1 – LUPD: Lock Update
Lock update can be used to ensure that all buffers are valid before an update is performed.
Value
0
1
Description
The buffered registers are updated as soon as an UPDATE condition has occurred.
No update of the buffered registers is performed, even though an UPDATE condition has
occurred.
Bit 0 – DIR: Counter Direction
Normally this bit is controlled in hardware by the waveform generation mode or by event actions, but this
bit can also be changed from software.
Value
0
1
20.5.6
Description
The counter is counting up (incrementing).
The counter is counting down (decrementing).
Control Register E Set - Normal Mode
The individual status bit can be set by writing a '1' to its bit location. This allows each bit to be set without
use of a read-modify-write operation on a single register.
Each Status bit can be read out either by reading TCA.CTRLESET or TCA.CTRLECLR.
Name: CTRLESET
Offset: 0x05
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
CMD[1:0]
Access
Reset
1
0
LUPD
DIR
R/W
R/W
R/W
R/W
0
0
0
0
Bits 3:2 – CMD[1:0]: Command
These bits are used for software control of update, restart, and reset of the timer/counter. The command
bits are always read as zero.
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Value
0x0
0x1
0x2
0x3
Name
NONE
UPDATE
RESTART
RESET
Description
No command
Force update
Force restart
Force hard Reset (ignored if TC is enabled)
Bit 1 – LUPD: Lock Update
Locking the update ensures that all buffers are valid before an update is performed.
Value
0
1
Description
The buffered registers are updated as soon as an UPDATE condition has occurred.
No update of the buffered registers is performed, even though an UPDATE condition has
occurred.
Bit 0 – DIR: Counter Direction
Normally this bit is controlled in hardware by the waveform generation mode or by event actions, but this
bit can also be changed from software.
Value
0
1
20.5.7
Description
The counter is counting up (incrementing).
The counter is counting down (decrementing).
Control Register F Clear
The individual status bit can be cleared by writing a one to its bit location. This allows each bit to be
cleared without use of a read-modify-write operation on a single register.
Name: CTRLFCLR
Offset: 0x06
Reset: 0x00
Property:
Bit
7
6
5
Access
Reset
4
3
2
1
0
CMP2BV
CMP1BV
CMP0BV
PERBV
R/W
R/W
R/W
R/W
0
0
0
0
Bit 3 – CMP2BV: Compare 2 Buffer Valid
See CMP0BV.
Bit 2 – CMP1BV: Compare 1 Buffer Valid
See CMP0BV.
Bit 1 – CMP0BV: Compare 0 Buffer Valid
The CMPnBV bits are set when a new value is written to the corresponding CMPnBUF register. These
bits are automatically cleared on an UPDATE condition.
Bit 0 – PERBV: Period Buffer Valid
This bit is set when a new value is written to the PERB register. This bit is automatically cleared on an
UPDATE condition.
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8-bit AVR Microcontroller
20.5.8
Control Register F Set
The individual status bit can be set by writing a one to its bit location. This allows each bit to be set
without use of a read-modify-write operation on a single register.
Name: CTRLFSET
Offset: 0x07
Reset: 0x00
Property:
Bit
7
6
5
4
Access
Reset
3
2
1
0
CMP2BV
CMP1BV
CMP0BV
PERBV
R/W
R/W
R/W
R/W
0
0
0
0
Bit 3 – CMP2BV: Compare 2 Buffer Valid
See CMP0BV.
Bit 2 – CMP1BV: Compare 1 Buffer Valid
See CMP0BV.
Bit 1 – CMP0BV: Compare 0 Buffer Valid
The CMPnBV bits are set when a new value is written to the corresponding CMPnBUF register. These
bits are automatically cleared on an UPDATE condition.
Bit 0 – PERBV: Period Buffer Valid
This bit is set when a new value is written to the PERB register. This bit is automatically cleared on an
UPDATE condition.
20.5.9
Event Control
Name: EVCTRL
Offset: 0x09
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
EVACT[1:0]
Access
Reset
0
CNTEI
R/W
R/W
R/W
0
0
0
Bits 2:1 – EVACT[1:0]: Event Action
These bits define on what type of event action the counter will increment or decrement.
Value
0x0
0x1
0x2
0x3
Name
EVACT_POSEDGE
EVACT_ANYEDGE
EVACT_HIGHLVL
EVACT_UPDOWN
© 2017 Microchip Technology Inc.
Description
Count on positive edge event
Count on any edge event
Count on prescaled clock while event line is 1.
Count on prescaled clock. Event controls count direction. Up-count
when event line is 0, down-count when event line is 1.
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8-bit AVR Microcontroller
Bit 0 – CNTEI: Enable Count on Event Input
Value
0
1
Description
Counting on Event input is disabled.
Counting on Event input is enabled according to EVACT bit field.
20.5.10 Interrupt Control Register - Normal Mode
Name: INTCTRL
Offset: 0x0A
Reset: 0x00
Property:
Bit
7
Access
Reset
6
5
4
3
2
1
0
CMP2
CMP1
CMP0
OVF
R/W
R/W
R/W
R/W
0
0
0
0
Bit 6 – CMP2: Compare Channel 2 Interrupt Enable
See CMP0.
Bit 5 – CMP1: Compare Channel 1 Interrupt Enable
See CMP0.
Bit 4 – CMP0: Compare Channel 0 Interrupt Enable
Writing CMPn bit to '1' enables compare interrupt from channel n.
Bit 0 – OVF: Timer Overflow/Underflow Interrupt Enable
Writing OVF bit to '1' enables overflow interrupt.
20.5.11 Interrupt Flag Register - Normal Mode
The individual status bit can be cleared by writing a '1'e to its bit location. This allows each bit to be set
without use of a read-modify-write operation on a single register.
Name: INTFLAGS
Offset: 0x0B
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
CMP2
CMP1
CMP0
3
2
1
OVF
0
R/W
R/W
R/W
R/W
0
0
0
0
Bit 6 – CMP2: Compare Channel 2 Interrupt Flag
See CMP0 flag description.
Bit 5 – CMP1: Compare Channel 1 Interrupt Flag
See CMP0 flag description.
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8-bit AVR Microcontroller
Bit 4 – CMP0: Compare Channel 0 Interrupt Flag
The compare interrupt flag (CMPn) is set on a compare match on the corresponding compare channel.
For all modes of operation, the CMPn flag will be set when a compare match occurs between the count
register (CNT) and the corresponding compare register (CMPn). The CMPn flag will not be cleared
automatically and has to be cleared by software. This is done by writing a one to its bit location.
Bit 0 – OVF: Overflow/Underflow Interrupt Flag
This flag is set either on a TOP (overflow) or BOTTOM (underflow) condition, depending on the
WGMODE setting. OVF is not automatically cleared and needs to be cleared by software. This is done by
writing a one to its bit location.
20.5.12 Debug Control Register
Name: DBGCTRL
Offset: 0x0E
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN: Run in Debug
Value
0
1
Description
The peripheral is halted in break debug mode and ignores events.
The peripheral will continue to run in break debug mode when the CPU is halted.
20.5.13 Temporary bits for 16-bit Access
The Temporary register is used by the CPU for single-cycle, 16-bit access to the 16-bit registers of this
peripheral. It can also be read and written by software. See also Accessing 16-bit Registers. There is one
common Temporary register for all the 16-bit registers of this peripheral.
Name: TEMP
Offset: 0x0F
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
TEMP[7:0]
Access
Reset
Bits 7:0 – TEMP[7:0]: Temporary Bits for 16-bit Access
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8-bit AVR Microcontroller
20.5.14 Counter Register - Normal Mode
The TCA.CNTL and TCA.CNTH register pair represents the 16-bit value, TCA.CNT. The low byte [7:0]
(suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset +
0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
CPU and UPDI write access has priority over internal updates of the register.
Name: CNT
Offset: 0x20
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
CNT[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
CNT[7:0]
Access
Reset
Bits 15:8 – CNT[15:8]: Counter high byte
These bits hold the MSB of the 16-bit counter register.
Bits 7:0 – CNT[7:0]: Counter low byte
These bits hold the LSB of the 16-bit counter register.
20.5.15 Period Register - Normal Mode
TCA.PER contains the 16-bit TOP value in the timer/counter.
The TCA.PERL and TCA.PERH register pair represents the 16-bit value, TCA.PER. The low byte [7:0]
(suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset +
0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
Name: PER
Offset: 0x26
Reset: 0xFFFF
Property:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
15
14
13
12
11
10
9
8
PER[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
1
1
1
1
1
1
1
1
Bit
7
6
5
4
3
2
1
0
PER[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
1
1
1
1
1
1
1
Bits 15:8 – PER[15:8]: Periodic high byte
These bits hold the MSB of the 16-bit period register.
Bits 7:0 – PER[7:0]: Periodic low byte
These bits hold the LSB of the 16-bit period register.
20.5.16 Compare n Register - Normal Mode
This register is continuously compared to the counter value. Normally, the outputs from the comparators
are then used for generating waveforms.
TCA.CMPn registers are updated with the buffer value from their corresponding CMPnBUF register when
an UPDATE condition occurs.
The TCA.CMPnL and TCA.CMPnH register pair represents the 16-bit value, TCA.CMPn. The low byte
[7:0] (suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset
+ 0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
Name: CMP0, CMP1, CMP2
Offset: 0x28 + n*0x02 [n=0..2]
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
CMP[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
CMP[7:0]
Access
Reset
Bits 15:8 – CMP[15:8]: Compare high byte
These bits hold the MSB of the 16-bit compare register.
Bits 7:0 – CMP[7:0]: Compare low byte
These bits hold the LSB of the 16-bit compare register.
20.5.17 Period Buffer Register
This register serves as the buffer for the period register (TCA.PER). Accessing this register using the
CPU or UPDI will affect the PERBV flag.
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The TCA.PERBUFL and TCA.PERBUFH register pair represents the 16-bit value, TCA.PERBUF. The low
byte [7:0] (suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at
offset + 0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
Name: PERBUF
Offset: 0x36
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
PERBUF[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
1
1
1
1
1
1
1
1
Bit
7
6
5
4
3
2
1
0
PERBUF[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
1
1
1
1
1
1
1
Bits 15:8 – PERBUF[15:8]: Period Buffer high byte
These bits hold the MSB of the 16-bit period buffer register.
Bits 7:0 – PERBUF[7:0]: Period Buffer low byte
These bits hold the LSB of the 16-bit period buffer register.
20.5.18 Compare n Buffer Register
This register serves as the buffer for the associated compare registers (TCA.CMPn). Accessing any of
these registers using the CPU or UPDI will affect the corresponding CMPnBV status bit.
The TCA.CMPnBUFL and TCA.CMPnBUFH register pair represents the 16-bit value, TCA.CMPnBUF.
The low byte [7:0] (suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be
accessed at offset + 0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16bit Registers.
Name: CMP0BUF, CMP1BUF, CMP2BUF
Offset: 0x38 + n*0x02 [n=0..2]
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
15
14
13
12
11
10
9
8
CMPBUF[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
CMPBUF[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:8 – CMPBUF[15:8]: Compare high byte
These bits hold the MSB of the 16-bit compare buffer register.
Bits 7:0 – CMPBUF[7:0]: Compare low byte
These bits hold the LSB of the 16-bit compare buffer register.
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20.6
Register Summary - TCA in Split Mode (CTRLD.SPLITM=1)
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
HCMP2EN
HCMP1EN
HCMP0EN
LCMP2EN
LCMP1EN
LCMP0EN
0x02
CTRLC
7:0
HCMP2OV
HCMP1OV
HCMP0OV
LCMP2OV
LCMP1OV
LCMP0OV
0x03
CTRLD
7:0
0x04
CTRLECLR
7:0
CMD[1:0]
0x05
CTRLESET
7:0
CMD[1:0]
CLKSEL[2:0]
ENABLE
SPLITM
0x06
...
Reserved
0x09
0x0A
INTCTRL
7:0
LCMP2
LCMP1
LCMP0
HUNF
LUNF
0x0B
INTFLAGS
7:0
LCMP2
LCMP1
LCMP0
HUNF
LUNF
0x0C
...
Reserved
0x0D
0x0E
DBGCTRL
7:0
DBGRUN
0x0F
...
Reserved
0x1F
0x20
LCNT
7:0
LCNT[7:0]
0x21
HCNT
7:0
HCNT[7:0]
0x22
...
Reserved
0x25
0x26
LPER
7:0
LPER[7:0]
0x27
HPER
7:0
HPER[7:0]
0x28
LCMP0
7:0
LCMP[7:0]
0x29
HCMP0
7:0
HCMP[7:0]
0x2A
LCMP1
7:0
LCMP[7:0]
HCMP[7:0]
0x2B
HCMP1
7:0
0x2C
LCMP2
7:0
LCMP[7:0]
0x2D
HCMP2
7:0
HCMP[7:0]
20.7
Register Description - Split Mode
20.7.1
Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
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Bit
7
6
5
4
3
2
1
CLKSEL[2:0]
Access
0
ENABLE
R/W
R/W
R/W
R/W
0
0
0
0
Reset
Bits 3:1 – CLKSEL[2:0]: Clock Select
These bits select the clock frequency for the timer/counter.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
DIV1
DIV2
DIV4
DIV8
DIV16
DIV64
DIV256
DIV1024
Description
fTCA = fCLK_PER/1
fTCA = fCLK_PER/2
fTCA = fCLK_PER/4
fTCA = fCLK_PER/8
fTCA = fCLK_PER/16
fTCA = fCLK_PER/64
fTCA = fCLK_PER/256
fTCA = fCLK_PER/1024
Bit 0 – ENABLE: Enable
Value
0
1
20.7.2
Description
The peripheral is disabled
The peripheral is enabled
Control B - Split Mode
Name: CTRLB
Offset: 0x01
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
2
1
0
HCMP2EN
HCMP1EN
HCMP0EN
3
LCMP2EN
LCMP1EN
LCMP0EN
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit 6 – HCMP2EN: High-byte Compare 2 Enable
See LCMP0EN.
Bit 5 – HCMP1EN: High-byte Compare 1 Enable
See LCMP0EN.
Bit 4 – HCMP0EN: High-byte Compare 0 Enable
See LCMP0EN.
Bit 2 – LCMP2EN: Low-byte Compare 2 Enable
See LCMP0EN.
Bit 1 – LCMP1EN: Low-byte Compare 1 Enable
See LCMP0EN.
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Bit 0 – LCMP0EN: Low-byte Compare 0 Enable
Setting the LCMPnEN/HCMPnEN bits in the FRQ or PWM waveform generation mode of operation will
override the port output register for the corresponding WOn pin.
20.7.3
Control C - Split Mode
Name: CTRLC
Offset: 0x02
Reset: 0x00
Property:
Bit
7
Access
6
5
4
2
1
0
HCMP2OV
HCMP1OV
HCMP0OV
LCMP2OV
LCMP1OV
LCMP0OV
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Reset
3
Bit 6 – HCMP2OV: High-byte Compare 2 Output Value
See LCMP0OV.
Bit 5 – HCMP1OV: High-byte Compare 1 Output Value
See LCMP0OV.
Bit 4 – HCMP0OV: High-byte Compare 0 Output Value
See LCMP0OV.
Bit 2 – LCMP2OV: Low-byte Compare 2 Output Value
See LCMP0OV.
Bit 1 – LCMP1OV: Low-byte Compare 1 Output Value
See LCMP0OV.
Bit 0 – LCMP0OV: Low-byte Compare 0 Output Value
The LCMPnOV/HCMPn bits allow direct access to the waveform generator's output compare value when
the timer/counter is not enabled. This is used to set or clear the WOn output value when the timer/counter
is not running.
20.7.4
Control D
Name: CTRLD
Offset: 0x03
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
SPLITM
Access
R/W
Reset
0
Bit 0 – SPLITM: Enable Split Mode
This bit sets the timer/counter in split mode operation. It will then work as two 8-bit timer/counters. The
register map will change compared to normal 16-bit mode.
20.7.5
Control Register E Clear - Split Mode
The individual status bit can be cleared by writing a '1' to its bit location. This allows each bit to be cleared
without use of a read-modify-write operation on a single register.
Each Status bit can be read out either by reading TCA.CTRLESET or TCA.CTRLECLR.
Name: CTRLECLR
Offset: 0x04
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
CMD[1:0]
Access
Reset
R/W
R/W
0
0
Bits 3:2 – CMD[1:0]: Command
These bits are used for software control of update, restart, and reset of the timer/counter. The command
bits are always read as zero.
Value
0x0
0x1
0x2
0x3
20.7.6
Name
NONE
UPDATE
RESTART
RESET
Description
No command
Force update
Force restart
Force hard Reset (ignored if TC is enabled)
Control Register E Set - Split Mode
The individual status bit can be set by writing a '1' to its bit location. This allows each bit to be set without
use of a read-modify-write operation on a single register.
Each Status bit can be read out either by reading TCA.CTRLESET or TCA.CTRLECLR.
Name: CTRLESET
Offset: 0x05
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
CMD[1:0]
Access
Reset
R/W
R/W
0
0
Bits 3:2 – CMD[1:0]: Command
These bits are used for software control of update, restart, and reset of the timer/counter. The command
bits are always read as zero.
Value
0x0
0x1
0x2
0x3
20.7.7
Name
NONE
UPDATE
RESTART
RESET
Description
No command
Force update
Force restart
Force hard Reset (ignored if TC is enabled)
Interrupt Control Register - Split Mode
Name: INTCTRL
Offset: 0x0A
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
1
0
LCMP2
LCMP1
LCMP0
3
2
HUNF
LUNF
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 6 – LCMP2: Low-byte Compare Channel 0 Interrupt Enable
See LCMP0.
Bit 5 – LCMP1: Low-byte Compare Channel 1 Interrupt Enable
See LCMP0.
Bit 4 – LCMP0: Low-byte Compare Channel 0 Interrupt Enable
Writing LCMPn bit to '1' enables low-byte compare interrupt from channel n.
Bit 1 – HUNF: High-byte Underflow Interrupt Enable
Writing HUNF bit to '1' enables high-byte underflow interrupt.
Bit 0 – LUNF: Low-byte Underflow Interrupt Enable
Writing HUNF bit to '1' enables low-byte underflow interrupt.
20.7.8
Interrupt Flag Register - Split Mode
The individual status bit can be cleared by writing a ‘1’ to its bit location. This allows each bit to be set
without use of a read-modify-write operation on a single register.
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Name: INTFLAGS
Offset: 0x0B
Reset: 0x00
Property:
Bit
7
Access
Reset
6
5
4
1
0
LCMP2
LCMP1
LCMP0
3
2
HUNF
LUNF
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 6 – LCMP2: Low-byte Compare Channel 0 Interrupt Flag
See LCMP0 flag description.
Bit 5 – LCMP1: Low-byte Compare Channel 0 Interrupt Flag
See LCMP0 flag description.
Bit 4 – LCMP0: Low-byte Compare Channel 0 Interrupt Flag
The compare interrupt flag (LCMPn) is set on a compare match on the corresponding compare channel.
For all modes of operation, the LCMPn flag will be set when a compare match occurs between the Lowbyte count register (LCNT) and the corresponding compare register (LCMPn). The LCMPn flag will not be
cleared automatically and has to be cleared by software. This is done by writing a ‘1’ to its bit location.
Bit 1 – HUNF: High-byte Underflow Interrupt Flag
This flag is set on a high-byte timer BOTTOM (underflow) condition. HUNF is not automatically cleared
and needs to be cleared by software. This is done by writing a ‘1’ to its bit location.
Bit 0 – LUNF: Low-byte Underflow Interrupt Flag
This flag is set on a low-byte timer BOTTOM (underflow) condition. LUNF is not automatically cleared and
needs to be cleared by software. This is done by writing a ‘1’ to its bit location.
20.7.9
Debug Control Register
Name: DBGCTRL
Offset: 0x0E
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN: Run in Debug
Value
0
1
Description
The peripheral is halted in break debug mode and ignores events.
The peripheral will continue to run in break debug mode when the CPU is halted.
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20.7.10 Low-byte Timer Counter Register - Split Mode
TCA.LCNT contains the counter value in low-byte timer. CPU and UPDI write access has priority over
count, clear, or reload of the counter.
Name: LCNT
Offset: 0x20
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
LCNT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – LCNT[7:0]: Counter value for low-byte timer
These bits define the counter value of the low-byte timer.
20.7.11 High-byte Timer Counter Register - Split Mode
TCA.HCNT contains the counter value in high-byte timer. CPU and UPDI write access has priority over
count, clear, or reload of the counter.
Name: HCNT
Offset: 0x21
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
HCNT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – HCNT[7:0]: Counter value for high-byte timer
These bits define the counter value in high-byte timer.
20.7.12 Low-byte Timer Period Register - Split Mode
The TCA.LPER register contains the TOP value of low-byte timer.
Name: LPER
Offset: 0x26
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
LPER[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
1
1
1
1
1
1
1
3
2
1
0
Bits 7:0 – LPER[7:0]: Period value low-byte timer
These bits hold the TOP value of low-byte timer.
20.7.13 High-byte Period Register - Split Mode
The TCA.HPER register contains the TOP value of high-byte timer.
Name: HPER
Offset: 0x27
Reset: 0x00
Property:
Bit
7
6
5
4
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
1
1
1
1
1
1
1
HPER[7:0]
Access
Reset
Bits 7:0 – HPER[7:0]: Period value high-byte timer
These bits hold the TOP value of high-byte timer.
20.7.14 Compare Register n for low-byte Timer - Split Mode
The TCA.LCMPn register represents the compare value of compare channel n for low-byte Timer. This
register is continuously compared to the counter value of low-byte timer, LCNT. Normally, the outputs
from the comparators are then used for generating waveforms.
Name: LCMP
Offset: 0x28 + n*0x02 [n=0..2]
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
LCMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – LCMP[7:0]: Compare value of channel n
These bits hold the compare value of channel n that is compared to LCNT.
20.7.15 High-byte Compare Register n - Split Mode
The TCA.HCMPn register represents the compare value of compare channel n for high-byte Timer. This
register is continuously compared to the counter value of high-byte timer, HCNT. Normally, the outputs
from the comparators are then used for generating waveforms.
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8-bit AVR Microcontroller
Name: HCMP0, HCMP1, HCMP2
Offset: 0x29 + n*0x02 [n=0..2]
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
HCMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – HCMP[7:0]: Compare value of channel n
These bits hold the compare value of channel n that is compared to HCNT.
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8-bit AVR Microcontroller
21.
TCB - 16-bit Timer/Counter Type B
21.1
Features
•
•
•
21.2
16-bit counter operation modes:
– Periodic interrupt
– Timeout check
– Input capture
• On event
• Frequency measurement
• Pulse width measurement
• Frequency and pulse width measurement
– Single shot
– 8-bit Pulse Width Modulation (PWM)
Noise canceler on event input
Optional: Operation synchronous with TCA0
Overview
The capabilities of the 16-bit Timer/Counter type B (TCB) include frequency and waveform generation,
and input capture on Event with time and frequency measurement of digital signals. The TCB consists of
a base counter and control logic which can be set in one of eight different modes, each mode providing
unique functionality. The base counter is clocked by the peripheral clock with optional prescaling.
This device has two instances of the TCB peripheral: TCB0 and TCB1.
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21.2.1
Block Diagram
Figure 21-1. Timer/Counter Type B Block Diagram
TCB
ClockSelect
CTRLA
Mode
CTRLB
EVCTRL
Edge Select
CCMP
DIV2
Counter
"count"
"clear"
CNT
CLK_PER
Control
Logic
CLK_TCA
Event System
IF
(INT Req.)
=
TOP
BOTTOM
=0
Mode, Output enable, initial value
Synchronous
output
Output control
and
Asynchronous logic
Asynchronous
output
21.2.1.1 Noise Canceler
The noise canceler improves noise immunity by using a simple digital filter scheme. When the noise filter
is enabled the peripheral monitors the event channel and keeps a record of the last four observed
samples. If four consecutive samples are equal, the input is considered to be stable and the signal is fed
to the edge detector.
When enabled, the noise canceler introduces an additional delay of four system clock cycles between a
change applied to the input and the update of the input compare register.
The noise canceler uses the system clock and is therefore not affected by the prescaler.
21.2.2
Signal Description
Signal
Description
Type
WO
Digital asynchronous output
Waveform Output
Related Links
I/O Multiplexing and Considerations
21.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 21-1. TCB System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
WO
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Dependency
Applicable
Peripheral
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
Interrupts
Events
21.2.3.1 Clocks
This peripheral uses the system's peripheral clock CLK_PER. The peripheral has its own local prescaler,
or can be configured to run off the prescaled clock signal of the Timer Counter type A (TCA).
Related Links
CLKCTRL - Clock Controller
21.2.3.2 I/O Lines and Connections
Using the I/O lines of the peripheral requires configuration of the I/O pins.
21.2.3.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
21.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
EVSYS - Event System
21.2.3.5 Debug Operation
When the CPU is halted in debug mode, this peripheral will halt normal operation. This peripheral can be
forced to continue operation during debugging.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
Related Links
UPDI - Unified Program and Debug Interface
21.3
Functional Description
21.3.1
Definitions
The following definitions are used throughout the documentation:
Table 21-2. Timer/Counter Definitions
Name
Description
BOTTOM The counter reaches BOTTOM when it becomes zero.
MAX
The counter reaches MAXimum when it becomes all ones.
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Name
Description
TOP
The counter reaches TOP when it becomes equal to the highest value in the count
sequence.
UPDATE The update condition is met when the timer/counter reaches BOTTOM or TOP, depending on
the waveform generator mode.
CNT
Counter register value
CCMP
Capture/Compare register value
In general, the term “timer” is used when the timer/counter is counting periodic clock ticks. The term
“counter” is used when the input signal has sporadic or irregular ticks.
21.3.2
Initialization
By default the TCB is in Periodic Interrupt mode. Follow these steps to start using it:
•
Write a TOP value to the Compare/Capture register (TCB.CCMP).
•
Enable the counter by writing a '1' to the ENABLE bit in the Control A register (TCB.CTRLA).
The counter will start counting clock ticks according to the prescaler setting in the Clock Select bit
field (CLKSEL in TCB.CTRLA).
•
The counter value can be read from the Count register (TCB.CNT). The peripheral will generate an
interrupt when the CNT value reaches TOP.
21.3.3
Operation
21.3.3.1 Modes
The timer can be configured to run in one of the eight different modes listed below. The event pulse
needs to be longer than one system clock cycle in order to guarantee edge detection.
Periodic Interrupt Mode
In the periodic interrupt mode the counter counts to the capture value and restarts from zero. Interrupt is
generated when counter is equal to TOP. If TOP is updated to a value lower than count, the counter will
continue until MAX and wrap around without generating an interrupt.
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8-bit AVR Microcontroller
Figure 21-2. Periodic Interrupt Mode
TOP changed to a value
lower than CNT
Counter wraps around
MAX
"Interrupt"
TOP
CNT
BOTTOM
Timeout Check Mode
In this mode, the counter counts to MAX and wraps around. On the first edge the counter is restarted and
on the second edge the counter is stopped. If the count register (TCB.CNT) reaches TOP before the
second edge, an interrupt will be generated. In freeze state, the counter will restart on a new edge.
Reading count (TCB.CNT) or compare/capture (TCB.CCMP) register, or writing run bit (RUN in
TCB.STATUS) in freeze state will have no effect.
Figure 21-3. Timeout Check Mode
Event Input
TOP changed to a value
lower than CNT
Edge detector
Counter wraps
around
MAX
“ Inter rupt”
CNT
TOP
BOTTOM
Input Capture on Event Mode
The counter will count from BOTTOM to MAX continuously. When an event is detected the counter value
will be transferred to the Compare/Capture register (TCB.CCMP) and interrupt is generated. The module
has an edge detector which can be configured to trigger count capture on either rising or falling edges.
The figure below shows the input capture unit configured to capture on falling edge on the event input
signal. The interrupt flag is automatically cleared after the high byte of the capture register has been read.
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Figure 21-4. Input Capture on Event
" Interrupt"
Event Input
Edge detector
MAX
CNT
BOTTOM
Co py CN T to CCMP
an d in ter rup t
W rap aro un d
Co py CN T to CCMP
an d in ter rup t
It is recommended to write zero to the TCB.CNT register when entering this mode from any other mode.
Input Capture Frequency Measurement Mode
In this mode, the TCB captures the counter value and restarts on either a positive or negative edge of the
event input signal.
The interrupt flag is automatically cleared after the high byte of the Compare/Capture register
(TCB.CCMP) has been read, and an interrupt request is generated.
The figure below illustrates this mode when configured to act on rising edge.
Figure 21-5. Input Capture Frequency Measurement
" Interrupt "
Event Input
Edge detector
MAX
CNT
BOTTOM
Copy CNT to CCMP,
interrupt and restart
© 2017 Microchip Technology Inc.
Copy CNT to CCMP,
interrupt and restart
Datasheet Preliminary
Copy CNT to CCMP,
interrupt and restart
DS40001893B-page 187
8-bit AVR Microcontroller
Input Capture Pulse Width Measurement Mode
The input capture pulse width measurement will restart the counter on a positive edge and capture on the
next falling edge before an interrupt request is generated. The interrupt flag is automatically cleared when
the high byte of the capture register is read. The timer will automatically switch between rising and falling
edge detection, but a minimum edge separation of two clock cycles is required for correct behavior.
Figure 21-6. Input Capture Pulse Width Measurement
" Interrupt "
Event Input
Edge detector
MAX
CNT
BOTTOM
Re sta rt
co unter
Co py CN T to CCMP
an d in ter rup t
Re sta rt
co unter
Co py CN T to CCMP
an d g ive inte rru pt
Re sta rt
co unter
Input Capture Frequency and Pulse Width Measurement Mode
In this mode, the timer will start counting when a positive edge is detected on the even input signal. On
the following falling edge, the count value is captured. The counter stops when the second rising edge of
the event input signal is detected. This will also set the interrupt flag.
Reading the capture will clear the interrupt flag. When the capture register is read or the interrupt flag is
cleared the TC is ready for a new capture sequence. The counter register should therefor be read before
the capture register as this is reset to zero at the next positive edge.
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8-bit AVR Microcontroller
Figure 21-7. Input Capture Frequency and Pulse Width Measurement
Ignore till
Capture is read
Trigger next
capture sequence
Event Input
Edge detector
MAX
" Interrupt"
CNT
BOTTOM
Start
counter
Copy CNT to
CCMP
Stop counter and
interrupt
CPU reads the
CCMP register
Single Shot Mode
This mode can be used to generate a pulse with a duration that is defined by the Compare register
(TCB.CCMP), every time a rising or falling edge is observed on a connected event channel.
When the counter is stopped, the output pin is driven to low. If an event is detected on the connected
event channel, the timer will reset and start counting from zero to TOP while driving its output high. The
RUN bit in the Status register can be read to see if the counter is counting or not. When the counter
register reaches the CCMP register value, counter will stop and the output pin will go low for at least one
prescaler cycle. If a new event arrives during this time, that event will be ignored. The following figure
shows an example waveform. There is a two clock cycle delay from when the event is received until the
output is set high. If the ASYNC bit in TCB.CTRLB is written to '1', an asynchronous edge detector is
used for input events to give immediate action. When the EDGE bit of the TCB.EVCTRL register is written
to '1', any edge can trigger the start of counter. If the EDGE bit is '0', only positive edges will trigger the
start.
The counter will start as soon as the module is enabled, even without triggering event. This is prevented
by writing TOP to the counter register.
Similar behavior is seen if the EDGE bit in the TCB.EVCTRL register is '1' while the module is enabled.
Writing TOP to the Counter register prevents this as well.
It is not recommended to change configuration while the module is enabled.
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8-bit AVR Microcontroller
Figure 21-8. Single-Shot Mode
Ignored
Ignored
Edge detector
TOP
CNT
" Interrupt"
BOTTOM
Output
Counter reaches
TOP value
Event starts
counter
Event starts
counter
Counter reaches
TOP value
If the ASYNC bit in TCB.CTRLB is '0', the event pulse needs to be longer than one system clock cycle in
order to guarantee edge detection.
8-bit PWM Mode
This timer can also be configured to run in 8-bit PWM mode where each of the register pairs in the 16-bit
compare/capture register (TCB.CCMPH and TCB.CCMPL) are used as individual compare registers. The
counter will continuously count from zero to CCMPL and the output will be set at BOTTOM and cleared
when the counter reaches CCMPH.
When this peripheral is enabled and in PWM mode, changing the value of the compare/capture register
will change the output, but the transition may output invalid values. It is hence recommended to
1. Disable the peripheral
2. Write compare/capture register to {CCMPH, CCMPL}
3. Write 0x0000 to count register
4. Re-enable the module.
CCMPH is the number of cycles for which the output will be driven high, CCMPL+1 is the period of the
output pulse.
Output of the module for different capture register values are explained below.
•
CCMPL = 0
•
CCMPL = 0xFF
•
CCMPH = 0
•
•
Output = 0
Output = 0
0 < CCMPH ≤ 0xFF
Output = 1 for CCMPH cycles, low for the rest of the period
For 0 < CCMPL < 0xFF
•
CCMPH = 0
Output = 0
•
If 0 < CCMPH ≤ CCL
•
CCMPH = CCMPL + 1
© 2017 Microchip Technology Inc.
Output = 1 for CCMPH cycles, low for the rest
Output = 1
Datasheet Preliminary
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8-bit AVR Microcontroller
Figure 21-9. 8-bit PWM Mode
" Interrupt "
CCMPL
CNT
CCMPH
BOTTOM
Output
(CNT == CCMPL) and
output goes high
(CNT == CCMPH) and
output goes low
21.3.3.2 Output
If ASYNC in TCB.CTRLB is written to '0' ('1'), the output pin is driven synchronously (asynchronously) to
the TCB clock. The bits CCMPINIT, CCMPEN, and CNTMODE in TCB.CTRLB control how the
synchronous output is driven. The bits CCMPINIT, CCMPEN, and CNTMODE in TCB.CTRLB control how
the synchronous output is driven. The different configurations and their impact on the output is listen in
the table below.
Table 21-3. Synchronous Output
CNTMODE
Output, CTRLB=’0’,
CCMPEN=1
Output, CTRLB=’1’,
CCMPEN=1
Single shot mode
Output high when counter starts
and output low when counter
stops
Output high when event arrives
and output low when counter
stops
8-bit PWM mode
PWM mode output
PWM mode output
Modes except single shot and
PWM
Bit CCMPINIT in TCB.CTRLB
Bit CCMPINIT in TCB.CTRLB
21.3.3.3 Noise Canceler
The noise canceler improves noise immunity by using a simple digital filter scheme. When the noise filter
is enabled the peripheral monitors the event channel and keeps a record of the last four observed
samples. If four consecutive samples are equal, the input is considered to be stable and the signal is fed
to the edge detector.
When enabled, the noise canceler introduces an additional delay of four system clock cycles between a
change applied to the input and the update of the input compare register.
The noise canceler uses the system clock and is therefore not affected by the prescaler.
21.3.3.4 Synchronized with TCA0
The TCB can be configured to use the clock (CLK_TCA) of the Timer/Counter type A (TCA0) by writing
0x2 to the Clock Select bit field (CLKSEL) in the Control A register (TCB.CTRLA). In this setting the TCB
will count either on the prescaled clock signal from TCA0 which is configured by CLKSEL in TCA.CTRLA,
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or event clocking for TCA configured by EVACT in TCA.EVCTRL. Event clocking from TCA0 is only used
if enable count on event (CNTEI) is set to '1' in TCA.EVCTRL.
When the Synchronize Update bit (SYNCUPD) in the Control A register (TCB.CTRLA) is written to '1', the
TCB counter will restart when the TCA0 counter restarts.
Related Links
Block Diagram
21.3.4
Events
If TCB is connected to the Event System as an event generator, the TCB will generate a strobe on the
connected event channel when the configured event condition is met.
The peripheral accepts one event input. If the Capture Event Input Enable bit (CAPTEI) in the Event
Control register (TCB.EVCTRL) is written to '1', incoming events will result in an event action as defined
by the Event Edge bit (EDGE) in TCB.EVCTRL. A change on event line needs to be held for at least on
system clock cycle to guarantee action on event except single shot mode.
Related Links
EVCTRL
EVSYS - Event System
21.3.5
Interrupts
Table 21-4. Available Interrupt Vectors and Sources
Offset Name Vector Description Conditions
0x00
CAPT TCB interrupt
Depending on operating mode. See description of CAPT in
TCB.INTFLAG.
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Interrupt Flags register
of the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the Interrupt
Flag is set. The interrupt request remains active until the Interrupt Flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear Interrupt Flags.
Related Links
CPUINT - CPU Interrupt Controller
INTFLAGS
21.3.6
Sleep Mode Operation
TCB will halt operation in the Power Down Sleep mode. Standby sleep operation is dependent on the
Run in Standby bit (RUNSTDBY) in the Control A register (TCB.CTRLA).
21.3.7
Synchronization
Not applicable.
21.3.8
Configuration Change Protection
Not applicable.
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21.4
Register Summary - TCB
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
RUNSTDBY
0x01
CTRLB
7:0
ASYNC
FILTER
SYNCUPD
CCMPINIT
CLKSEL[1:0]
CCMPEN
ENABLE
CNTMODE[2:0]
0x02
...
Reserved
0x03
0x04
EVCTRL
7:0
0x05
INTCTRL
7:0
CAPT
0x06
INTFLAGS
7:0
CAPT
0x07
STATUS
7:0
RUN
0x08
DBGCTRL
7:0
DBGRUN
0x09
TEMP
7:0
0x0A
CNT
0x0B
0x0C
CCMP
0x0D
EDGE
CAPTEI
TEMP[7:0]
7:0
CNT[7:0]
15:8
CNT[15:8]
7:0
CCMP[7:0]
15:8
CCMP[15:8]
21.5
Register Description
21.5.1
Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
7
Access
Reset
6
5
4
3
2
1
CLKSEL[1:0]
0
RUNSTDBY
SYNCUPD
ENABLE
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 6 – RUNSTDBY: Run Standby
Writing a '1' to this bit will enable the peripheral to run in Standby sleep mode. Not applicable when
CLKSEL is set to 0x2 (CLK_TCA).
Bit 4 – SYNCUPD: Synchronize Update
When this bit is written to '1', the TCB will restart whenever the TCA0 is restarted.
Bits 2:1 – CLKSEL[1:0]: Clock Select
Writing these bits selects the clock source for this peripheral.
Value
0x0
0x1
Description
CLK_PER
CLK_PER / 2
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Value
0x2
0x3
Description
Use CLK_TCA from TCA0
Reserved
Bit 0 – ENABLE: Enable
Writing this bit to '1' enables the Timer/Counter type B peripheral.
21.5.2
Control B
Name: CTRLB
Offset: 0x01
Reset: 0x00
Property:
Bit
7
Access
Reset
6
5
4
ASYNC
CCMPINIT
CCMPEN
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
CNTMODE[2:0]
Bit 6 – ASYNC: Asynchronous Enable
Writing this bit to '1' will allow asynchronous updates of the TCB output signal in single shot mode
Value
0
1
Description
The output will go HIGH when the counter actually starts
The output will go HIGH when an Event arrives
Bit 5 – CCMPINIT: Compare/Capture Pin Initial Value
This bit is used to set the initial output value of the pin when a pin output is used.
Value
0
1
Description
Initial pin state is LOW
Initial pin state is HIGH
Bit 4 – CCMPEN: Compare/Capture Output Enable
This bit is used to set the output value of the Compare/Capture Output.
Value
0
1
Description
Compare/Capture Output is zero
Compare/Capture Output has a valid value
Bits 2:0 – CNTMODE[2:0]: Timer Mode
Writing these bits selects the timer mode.
Value
0x0
0x1
0x2
0x3
0x4
0x5
Description
Periodic interrupt mode
Timeout check mode
Input capture on event mode
Input capture frequency measurement mode
Input capture pulse width measurement mode
Input capture frequency and pulse width measurement mode
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Value
0x6
0x7
21.5.3
Description
Single shot mode
8-bit PWM mode
Event Control
Name: EVCTRL
Offset: 0x04
Reset: 0x00
Property:
Bit
7
Access
Reset
6
5
4
3
2
1
0
FILTER
EDGE
CAPTEI
R/W
R/W
R/W
0
0
0
Bit 6 – FILTER: Input Capture Noise Cancellation Filter
Writing this bit to '1' enables the input capture noise cancellation unit.
Bit 4 – EDGE: Event Edge
This bit is used to select the Event edge. The effect of this bit is dependent on the selected Count Mode
(CNTMODE) in TCB.CTRLB.
Count Mode
EDGE Positive Edge
Negative Edge
Periodic Interrupt Mode
0
Not Applicable
Not Applicable
1
Not Applicable
Not Applicable
0
Start counter
Stop counter
1
Stop counter
Start counter
0
Input capture frequency and
Not Applicable
pulse width measurement mode
1
Not Applicable
Capture = count
0
Capture = count, initialize,
interrupt
Not Applicable
1
Not Applicable
Capture = count, initialize,
interrupt
Input Capture Pulse Width
Measurement Mode
0
Initialize
Capture = count, interrupt
1
Capture = count, interrupt
Initialize
Input Capture Frequency and
Pulse Width Measurement Mode
0
On 1st Positive: initialize
Timeout Check Mode
Input Capture on Event Mode
Input Capture Frequency
Measurement Mode
On following Negative: capture
2nd Positive: stop, interrupt
1
On 1st Negative: initialize
On following Positive: capture
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8-bit AVR Microcontroller
Count Mode
EDGE Positive Edge
Negative Edge
2nd Negative: stop, interrupt
Single Shot Mode
8-bit PWM Mode
0
Start counter
Not Applicable
1
Start counter
Start counter
0
Not Applicable
Not Applicable
1
Not Applicable
Not Applicable
Bit 0 – CAPTEI: Capture Event Input Enable
Writing this bit to '1' enables the event input capture.
21.5.4
Interrupt Control
Name: INTCTRL
Offset: 0x05
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
CAPT
Access
R/W
Reset
0
Bit 0 – CAPT: Capture Interrupt Enable
Writing this bit to '1' enables the Capture interrupt.
21.5.5
Interrupt Flags
Name: INTFLAGS
Offset: 0x06
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
CAPT
Access
R/W
Reset
0
Bit 0 – CAPT: Interrupt Flag
This bit is set when an interrupt occurs. The interrupt conditions are dependent on the Counter mode
(CNTMODE) in TCB.CTRLB.
This bit is cleared by writing a '1' to it or when the Capture register is read in capture mode.
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21.5.6
Counter Mode
Interrupt Set Condition
Periodic Interrupt Mode
Set when the counter reaches TOP
Timeout Check Mode
Set when the counter reaches TOP
Input Capture on Event Mode
Set when an event occurs and the capture register is loaded, Flag
clears when capture is read
Input Capture Frequency
Measurement Mode
Set on edge when the capture register is loaded and count
initialized, Flag clears when capture is read
Input Capture Pulse Width
Measurement Mode
Set on a edge when the capture register is loaded, previous edge
initialized the count, Flag clears when capture is read
Input Capture Frequency and Pulse
Width Measurement Mode
Set on second (positive or negative) edge when the counter is
stopped, Flag clears when capture is read
Single Shot Mode
Set when counter reaches TOP
8-bit PWM Mode
Set when the counter reaches CCH
Status
Name: STATUS
Offset: 0x07
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
RUN
Access
R
Reset
0
Bit 0 – RUN: Run
When the counter is running, this bit is set to '1'. When the counter is stopped, this bit is cleared '0'.
The bit it is read only and cannot be set by UPDI.
21.5.7
Debug Control
Name: DBGCTRL
Offset: 0x08
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN: Debug Run
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8-bit AVR Microcontroller
Value
0
1
21.5.8
Description
The peripheral is halted in break debug mode and ignores events.
The peripheral will continue to run in break debug mode when the CPU is halted.
Temporary Value
The Temporary register is used by the CPU for single-cycle, 16-bit access to the 16-bit registers of this
peripheral. It can also be read and written by software. See also Accessing 16-bit Registers. There is one
common Temporary register for all the 16-bit registers of this peripheral.
Name: TEMP
Offset: 0x09
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
TEMP[7:0]
Access
Reset
Bits 7:0 – TEMP[7:0]: Temporary Value
21.5.9
Count
The TCB.CNTL and TCB.CNTH register pair represents the 16-bit value TCB.CNT. The low byte [7:0]
(suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset +
0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
CPU and UPDI write access has priority over internal updates of the register.
Name: CNT
Offset: 0x0A
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
CNT[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
CNT[7:0]
Access
Reset
Bits 15:8 – CNT[15:8]: Count Value high
These bits hold the MSB of the 16-bit counter register.
Bits 7:0 – CNT[7:0]: Count Value low
These bits hold the LSB of the 16-bit counter register.
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8-bit AVR Microcontroller
21.5.10 Capture/Compare
The TCB.CCMPL and TCB.CCMPH register pair represents the 16-bit value TCB.CCMP. The low byte
[7:0] (suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset
+ 0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
This register has different functions depending on the mode of operation:
•
For capture operation, these registers contain the captured value of the counter at the time the
capture occurs
•
In periodic interrupt/timeout and single shot mode this register acts as the TOP value.
•
In 8-bit PWM mode, TCB.CCMPL and TCB.CCMPH act as two independent registers.
Name: CCMP
Offset: 0x0C
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
CCMP[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
CCMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:8 – CCMP[15:8]: Capture/Compare Value high byte
These bits hold the MSB of the 16-bit compare, capture and top value
Bits 7:0 – CCMP[7:0]: Capture/Compare Value low byte
These bits hold the LSB of the 16-bit compare, capture and top value
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8-bit AVR Microcontroller
22.
TCD - 12-bit Timer/Counter Type D
22.1
Features
•
•
•
•
•
•
•
•
22.2
12-bit timer/counter
Programmable prescaler
Double buffered compare registers
Waveform generation
– One ramp mode
– Two ramp mode
– Four ramp mode
– Dual-slope mode
Two separate input capture, double buffered
Connection to event system
– Programmable filter
Conditional waveform on external events
– Fault handling
– Input blanking
– Overload protection function
– Fast emergency stop by hardware
Supports both half bridge and full bridge output
Overview
The Timer/Counter type D (TCD) is a high performance waveform controller that consists of an
asynchronous counter, a prescaler, compare logic, capture logic, and control logic. The purpose of the
TCD is to control power applications like LED, motor control, H-bridge and power converters.
The TCD contains an counter that can run on a clock which is asynchronous from the system clock. It
contains compare logic that can generate two independent outputs with optional dead time. It is
connected to the event system for capture and deterministic fault control. The timer/counter can generate
interrupts and events on compare match and overflow.
This device provides one instance of the TCD peripheral, TCD0.
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22.2.1
Block Diagram
Figure 22-1. Timer/Counter Block Diagram
System
Clock
domain
TCD clock
domain
Counter and
Fractional
Accumulator
CMPASET
CMPASET_
BUF
=
CMPACLR
SET A
CMPACLR_
BUF
Event Input A
WOA
Event Input
Logic A
CAPTUREA
CAPTUREA_
BUF
CMPBSET
CMPBSET_
BUF
=
WOC
Compare/Capture
Unit B
WOD
SET B
CMPBCLR_
BUF
Waveform
generator B
WOB
CLR B
=
Event Input
Logic B
Event Input B
CAPTUREB
Waveform
generator A
CLR A
=
CMPBCLR
Compare/Capture
Unit A
CAPTUREB_
BUF
The TCD core is asynchronous to the system clock. The timer/counter consist of two compare/capture
units, each with a separate waveform output. In addition there are two extra waveform outputs which can
be equal to the output from one of the units. The compare registers CMPxSET, CMPxCLR are stored in
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the respective registers (TCD.CMPxSET, TCD.CMPxCLR), which consist of both a low and a high byte.
The registers are synchronized to the TCD domain after writing to the registers.
During normal operation, the counter value is continuously compared to the compare registers. This is
used to generate both interrupts and events.
The TCD can use the input events in ten different input modes, selected separately for the two input
events. The input mode defines how the input event will affect the outputs, and where in the TCD cycle
the counter should go when an event occurs.
22.2.2
22.2.3
Signal Description
Signal
Description
Type
WOA
TCD waveform output A
Digital output
WOB
TCD waveform output B
Digital output
WOC
TCD waveform output C
Digital output
WOD
TCD waveform output D
Digital output
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 22-1. TCD System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
WOA/B/C/D
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
Interrupts
Events
22.2.3.1 Clocks
The TCD can be connected directly to the internal 16/20MHz RC Oscillator (OSC20M), to an external
clock, or to the System clock. This is configured by the Clock Select bit field (CLKSEL) in the Control A
register (TCD.CTRLA).
Related Links
CLKCTRL - Clock Controller
22.2.3.2 I/O Lines and Connections
Using the I/O lines of the peripheral requires configuration of the I/O pins.
Related Links
I/O Multiplexing and Considerations
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8-bit AVR Microcontroller
PORT - I/O Pin Configuration
22.2.3.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
Related Links
CPUINT - CPU Interrupt Controller
SREG
Interrupts
22.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
EVSYS - Event System
22.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in debugging
mode will halt normal operation of the peripheral.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
When the Fault Detection bit (FAULTDET in TCD.DBGCTRL) is written to '1' and the CPU is halted in
debug mode, an event/fault is created on both input event channels. These events/faults will last as long
as the break, and can serve as safeguard in Debug mode, e.g. by forcing external components off.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
UPDI - Unified Program and Debug Interface
22.2.4
Definitions
The following definitions are used throughout the documentation:
Table 22-2. Timer/Counter definitions
Name
Description
TCD cycle
The sequence of four states that the counter need
to go through before it has returned to the same
position.
Input Blanking
Functionality to ignore event input for a
programmable time in a selectable part of the TCD
cycle.
Asynchronous output control
Allows the Event to override the output instantly
when the Event occurs. It is used for handling nonrecoverable faults.
One ramp
Counter is reset to zero once during a TCD cycle.
Two ramp
Counter is reset to zero two times during a TCD
cycle.
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Name
Description
Four ramp
Counter is reset to zero four times during a TCD
cycle.
Dual ramp
Counter count both up and down between zero
and selected top value.
22.3
Functional Description
22.3.1
Initialization and Disabling
To initialize the TCD:
1. Configure the static registers to the desired functionality.
2. Write desired initial values to the double-buffered registers.
3. Ensure that the Enable Ready bit (ENRDY) in the Status register (TCD.STATUS) is set to '1'.
4. Enable the TCD by writing a '1' to the ENABLE bit in the Control A register (TCD.CTRLA).
It is possible to disable the TCD in two different ways:
1. By writing a '0' to ENABLE in TCD.CTRLA. This disables the TCD instantly when synchronized to
the TCD core domain.
2. By writing a '1' to the Disable at End of Cycle Strobe bit (DISEOC) in the Control E register
(TCD.CTRLE). This disables the TCD at the end of the TCD cycle.
The bit fields in the TCD.CTRLA register are enable-protected, with exception of the ENABLE bit. They
can only be written when ENABLE is written to '0' first.
Related Links
Register Synchronization Categories
22.3.2
Operation
22.3.2.1 Register Synchronization Categories
Most of the IO registers need to be synchronized to the asynchronous TCD core clock domain. This is
done in different ways for different register categories:
•
•
•
•
Command and Enable Control registers
Doubled-buffered registers
Static registers
Normal IO and STATUS registers
See Table 22-3 for categorized registers.
Command and Enable Registers
Because of synchronization between the clock domains it is only possible to change the Enable bits while
the Enable Ready bit (ENRDY) in the Status register (TCD.STATUS) is '1'.
The Control E register commands (TCD.CTRLE) are automatically synchronized to the TCD core domain
when the TCD is enabled and as long as there not a synchronization ongoing already. Check in the
Status register if the Command Ready bit (CCMDRDY) is '1' (TCD.STATUS) to ensure that it is possible
to write a new command. TCD.CTRLE is a strobe register that will clear itself when the command is done.
The Control E register commands are:
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•
•
•
•
•
Synchronize at end of TCD cycle: synchronizes all doubled buffered registers to TCD clock domain
at the end of the TCD cycle
Synchronize: synchronized all doubled buffered registers to TCD clock domain when the command
is synchronized to TCD clock domain
Restart: Restarts the TCD counter
Software Capture A: Capture TCD counter value to TCD.CAPTUREA
Software Capture B: Capture TCD counter value to TCD.CAPTUREB
Double-Buffered Registers
The doubled-buffered registers can be updated in normal IO writes while the TCD is enabled and no
synchronization between the two clock domains is ongoing. Check that the CMDRDY bit in TCD.STATUS
is '1' to ensure that it is possible to update the doubled buffered IO registers. The values will be
synchronized to the TCD core domain when a synchronization command is sent or when the TCD is
enabled.
Static Registers
The static registers are kept static whenever the TCD is enabled. That means that these registers must
be configured before enabling the TCD. It is not possible to write to these registers as long as the TCD is
enabled. To see if the TCD is enabled, check if ENABLE in TCD.CTRLA is reading '1'.
Normal IO and Status Registers
The read-only registers inform about synchronization status and values synchronized from the core
domain. The reset of these registers and normal IO registers are not constrained by any synchronization
between the domains.
Table 22-3. Categorization of Registers
Enable and
Command
registers
Doubled-buffered
registers
Static registers
Read-only
registers
Normal IO
registers
TCD.CTRLA
(ENABLE bit)
TCD.DLYCTRL
TCD.CTRLA (All bits
Except ENABLE bit)
TCD.STATUS
TCD.INTCTRL
TCD.CTRLE
TCD.DLYVAL
TCD.CTRLB
TCD.CAPTUREA
TCD.INTFLAGS
TCD.DITCTRL
TCD.CTRLC
TCD.CAPTUREB
TCD.DITVAL
TCD.CTRLD
TCD.DBGCTRL
TCD.EVCTRLA
TCD.CMPASET
TCD.EVCTRLB
TCD.CMPACLR
TCD.INPUTCTRLA
TCD.CMPBSET
TCD.INPUTCTRLB
TCD.CMPBCLR
TCD.FAULTCTRL
22.3.2.2 Clock Selection and Prescalers
The TCD can select between 3 different clock sources that can be prescaled. There are three different
prescalers with separate controls as shown below.
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Figure 22-2. Clock Selection and Prescalers Overview
CLKSEL
Counter
prescaler
OSC20M
EXTCLK
CLK_PER
CLK_TCD
Synchronization
prescaler
Counter clock
(CLK_TCD_CNT)
Synchronizer clock
(CLK_TCD_SYNC)
Delay
prescaler (1)
Delay clock
(CLK_TCD_DLY)
1. Used by input blanking/delay event out
The TCD synchronizer clock is separate from the other module clocks enabling faster synchronization
between the TCD domain and the IO domain. The total prescalingfor the counter is:
SYNCPRESC_division_factor × CNTPRESC_division_factor
The Delay prescaler is used to prescale the clock used for the input blanking/ delayed event output
functionality. The prescaler can be configured independently allowing separate range and accuracy
settings from the counter functionality.
22.3.2.3 Waveform Generation Modes
The TCD provides four different waveform generation modes. The waveform generation modes
determine how the counter is counting during a TCD cycle, and when the compare values are matching.
A TCD cycle is split into these states:
•
•
•
•
Dead time WOA (DTA)
On time WOA (OTA)
Dead time WOB (DTB)
On time WOB (OTB)
In a standard configuration all states are present in the order they are listed and they are nonoverlapping. The compare values Compare A Set (TCD.CMPASET), Compare A Clear (TCD.CMPACLR),
Compare B Set (TCD.CMPBSET) and Compare B Clear (TCD.CMPBCLR) defines when each of the
states are ending and the next is beginning. There are four different ways to go through a TCD cycle. The
different ways are called Waveform Generation Modes. They are controlled by the Waveform Generation
Mode bits (WGMODE) in the Control A register (TCD.CTRLA). The waveform generation modes are:
•
•
•
•
One Ramp mode
Two Ramp mode
Four Ramp mode
Dual Slope mode
The name indicates how the counter is operating during one TCDcycle.
One Ramp Mode
In One Ramp Mode, TCD counter counts up until it reaches the CMPBCLR value. Then the TCD cycle is
done and the counter restarts from 0x000, beginning a new TCD cycle. The TCD cycle period is
�TCD_cycle =
CMPBCLR + 1
�CLK_TCD_CNT
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Figure 22-3. One Ramp Mode
TCD cycle
Dead time A
compare
values
On time A
Dead time B
On time B
counter
value
CMPBCLR
CMPBSET
CMPACLR
CMPASET
WOA
WOB
In the figure above, CMPASET < CMPACLR < CMPBSET < CMPBCLR. This is required in One Ramp
Mode to avoid overlapping outputs. The figure below is an example where CMPBSET < CMPASET <
CMPACLR < CMPBCLR, resulting in an overlap of the outputs.
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Figure 22-4. One Ramp Mode with CMPBSET < CMPASET
TCD cycle
Dead time A
On time A
On time B
Compare
values
Counter
value
CMPBCLR
CMPACLR
CMPASET
CMPBSET
WOA
WOB
If any of the other compare values are bigger than CMPBCLR it will never be triggered when running in
One ramp mode. And if The CMPACLR is smaller than the CMPASET value, the clear value will not have
any effect.
Two Ramp Mode
In Two Ramp Mode the TCD counter counts up until it reaches the CMPACLR value, then it resets and
counts up until it reaches the CMPBCLR value. Then, the TCD cycle is done and the counter restarts
from 0x000, beginning a new TCD cycle. The TCD cycle period is give by:
�TCD_cycle =
CMPACLR + 1 + CMPBCLR + 1
�CLK_TCD_CNT
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Figure 22-5. Two Ramp Mode
TCD cycle
Dead time A
On time A
Dead time B
On time B
counter
value
CMPBCLR
CMPACLR
CMPBSET
CMPASET
WOA
WOB
In the figure above, CMPASET < CMPACLR and CMPBSET < CMPBCLR. This causes the outputs to go
high. There are no restrictions on the CMPASET/CLR compared to the CMPBSET/CLR values.
In two ramp mode it is not possible to get overlapping outputs.
Four Ramp Mode
In Four Ramp Mode the TCD cycle is following this pattern:
1. A TCD cycle begins with the TCD counter counting up from zero until it reaches the CMPASET
value, and resets to zero.
2. The Counter counts up from zero until it reaches the CMPACLR value, and resets to zero.
3. The Counter counts up from zero until it reaches the CMPBSET value, and resets to zero.
4. The Counter counts up from zero until it reaches the CMPBCLR value, and ends the TCD cycle by
resetting to zero.
The TCD cycle period is given by
�TCD_cycle =
CMPASET + 1 + CMPACLR + 1 + CMPBSET + 1 + CMPBCLR + 1
�CLK_TCD_CNT
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Figure 22-6. Four Ramp Mode
TCD cycle
Dead time A
On time A
Dead time B
On time B
counter
value
CMPBCLR
CMPACLR
CMPBSET
CMPASET
WOA
WOB
There are no restrictions on the compare values compared to each others.
In Four Ramp Mode it is not possible to get overlapping outputs.
Dual Slope Mode
In Dual Slope mode, a TCD cycle consists of the TCD counter counting down from CMPBCLR value to
zero, and up again to the CMPBCLR value. This gives a TCD cycle period:
�TCD_cycle =
2 × CMPBCLR + 1
�CLK_TCD_CNT
The WOA output is set when the TCD counter counts up and matches the CMPASET value. WOA is
cleared when the TCD counter counts down and matches the CMPASET value.
The WOB output is set when the TCD counter counts down and matches the CMPBSET value. WOB is
cleared when the TCD counter counts up and matches the CMPBSET value.
Figure 22-7. Dual Slope Mode
TCD cycle
On time B
CMPBCLR
Dead
time A
On time A
Dead
time B
On time B
counter
value
CMPASET
CMPBSET
WOA
WOB
The outputs will be overlapping if CMPBSET > CMPASET.
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CMPACLR is not used in Dual Slope Mode. Writing a value to CMPACLR has no effect.
When starting the TCD in Dual Slope Mode, the TCD counter starts at the CMPBCLR value and counts
down. The WOA will not be set before the end of the first TCD cycle.
Figure 22-8. Dual Slope Mode Starting and Stopping
TCD cycle
CMPBCLR
counter
value
CMPASET
CMPBSET
WOA
WOB
Stop
Start-up
22.3.2.4 TCD Inputs
The TCD has two inputs that are connected to the Event System, Input A and Input B. Each input has
functionality that are connected to corresponding output (WOA and WOB). That functionality is controlled
by the Event Control x registers (TCD.EVCTRLA and TCD.EVCTRLB) and the Input Control x registers
(TCD.INPUTACTRL and TCD.INPUTBCTRL).
To enable the input Events, write a '1' to the Trigger Event Input Enable bit (TRIGEI) in the Event Control
register (TCD.EVCTRLx). The inputs will be used as a fault detect and/or capture trigger. To enable
capture trigger, write a '1' to the ACTION bit in Event Control register (TCD.EVCTRLx).
There are ten different input modes for the fault detection. The two inputs have the same functionality,
except for input blanking which is only supported by input A. Input blanking is configured by the Delay
Control and Delay Value registers (TCD.DLYCTRL and TCD.DLYVAL).
The inputs are connected to the Event System. The connections between the Event source and the TCD
input must be configured in the Event System.
An overview of the input system is shown below.
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Figure 22-9. TCD Input Overview
EVCTRLA.EDGE
Asynchonous overrride
EVCTRLA.ASYNC
Input Event A
Input processing logic
(Input mode logic A)
Digital
Filter
INPUT
BLANKING
EVCTRLA.FILTER
DLYPRESC
Change flow
INPUT
MODE
DLYTRIG
Synchronized
override
TC Core
(Timer/Counter,
compare values,
waveform generator)
DLYSEL
Output state
Output
control
INPUT
MODE
EVCTRLB.FILTER
Digital
Filter
Input Event B
EVCTRLB.EDGE
Change flow
Synchronized
override
Input processing logic
(Input mode logic B)
EVCTRLB.ASYNC
Asynchonous overrride
There is a delay of 2-3 clock cycles on the TCD synchronizer clock between receiving the input Event and
processing it and overriding the outputs. If using the asynchronous Event detection, the outputs will
override instantly outside the input processing.
Input Blanking
Input blanking functionality are masking out the input Events for a programmable time in a selectable part
of the TCD cycle. Input blanking can be used to mask out "false" input Events that are triggered right after
changes on the outputs.
To enable input blanking, write 0x1 to the Delay Select bit field in the Delay Control register (DLYSEL in
TCD.DLYCTRL). The trigger source is selected by the Delay Trigger bit field (DLYTRIG in
TCD.DLYCTRL).
Input blanking uses the Delay clock: after a trigger, a counter is counting up until the Delay Value
(DLYVAL in TCD.DLYVAL) is reached before input blanking is turned off. The TCD delay clock is a
prescaled version of the Synchronization clock. The division factor is set by the Delay Prescaler bit field in
the Delay Control register (DLYPRESC in TCD.DLYCTRL). The duration of the input blanking is given by
�BLANK =
DLYPRESC_division_factor × DLYVAL
�CLK_TCD_SYNC
Input blanking is using the same logic as the programmable output Event. For this reason it is not
possible to use both at the same time.
Digital Filter
The digital filter for Event input x is enabled by writing a '1' to the FILTER bit in the Event Control x
register (TCD.EVCTRLx). When the digital filter is enabled, any pulse lasting less than 4 Counter clock
cycles will be filtered out. Any change on incoming event will therefore take 4 Counter clock cycles before
it will affect the input processing logic.
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Asynchronous Event Detection
To enable asynchronous Event detection on an input Event, write a '1' to the Asynchronous Event Control
bit (ASYNC) in the Event Control register (TCD.EVCTRLx).
The Asynchronous Event Detection makes it possible to asynchronously override the output when the
input Event occurs. What the Input event will do is depending on Input Mode for the event input. The
outputs have direct override while the counter flow will be changed when the event is synchronized to the
Synchronization clock.
It is not possible to use both asynchronous Event detection and digital filtering at the same time.
Input Modes
The user can select between 10 input modes. The selection is done by writing the Input Mode bit field
(INPUTMODE) in the Input control x register (TCD.INPUTCTRLx).
Table 22-4. Input mode description
INPUTMODE
Description
0x0
Input has no action
0x1
Stop output, jump to opposite compare cycle and wait
0x2
Stop output, execute opposite compare cycle and wait
0x3
Stop output, execute opposite compare cycle while fault active
0x4
Stop all outputs, maintain frequency
0x5
Stop all outputs, execute dead time while fault active
0x6
Stop all outputs, jump to next compare cycle and wait
0x7
Stop all outputs, wait for software action
0x8
Stop output on edge, jump to next compare cycle
0x9
Stop output on edge, maintain frequency
0xA
Stop output at level, maintain frequency
other
Reserved
Not all input modes works in all waveform generation modes. Below is a table that shows what waveform
generation modes the different input modes are valid in.
Table 22-5. Ramp mode the different input modes are vaild in
INPUTMODE
One Ramp mode
Two ramp mode
Four ramp mode
Dual slope mode
0x1
Valid
Valid
Valid
Do not use
0x2
Do not use
Valid
Valid
Do not use
0x3
Do not use
Valid
Valid
Do not use
0x4
Valid
Valid
Valid
Valid
0x5
Do not use
Valid
Valid
Do not use
0x6
Do not use
Valid
Valid
Do not use
0x7
Valid
Valid
Valid
Valid
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INPUTMODE
One Ramp mode
Two ramp mode
Four ramp mode
Dual slope mode
0x8
Valid
Valid
Valid
Do not use
0x9
Valid
Valid
Valid
Do not use
0xA
Valid
Valid
Valid
Do not use
In the following sections the different input modes are presented in detail.
Input Mode 1: Stop Output, Jump to Opposite Compare Cycle and Wait
An input Event in Input mode 1 will stop the output signal, jump to the opposite dead-time, and wait until
the input event goes low before the TCD counter continues.
If Input mode 1 is used on input A, an Event will only have an effect if the TCD is in Dead time A or Ontime A, and it will only effect the output WOA. When the Event is done, the TCD counter starts at Dead
time B.
Figure 22-10. Input Mode 1 on Input A
DTA
OTA
DTB
OTB
DTA
OTA
Wait
DTB
OTB
DTA
OTA
WOA
WOB
INPUT A
INPUT B
If Input mode 1 is used on input B, an Event will only have an effect if the TCD is in Dead time B or Ontime B, and it will only effect the output WOB. When the event is done, the TCD counter starts at Dead
time A.
Figure 22-11. Input Mode 1 on Input B
DTA
OTA
DTB
OTB
Wait
DTA
OTA
DTB
OTB
DTA
OTA
WOA
WOB
INPUT A
INPUT B
Input Mode 2: Stop Output, Execute Opposite Compare Cycle and Wait
An input Event in Input mode 2 will stop the output signal, execute to the opposite dead-time and on-time,
then wait until the input Event goes low before the TCD counter continues. If the input is done before the
opposite dead-time and on-time have finished, there will be no waiting, but the opposite dead-time and
on-time will continue.
If Input mode 2 is used on input A, an Event will only have an effect if the TCD is in Dead time A or Ontime A, and it will only effect the output WOA.
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Figure 22-12. Input Mode 2 on Input A
DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
Wait
DTA
OTA
WOA
WOB
INPUT A
INPUT B
If Input mode 2 is used on input B, an Event will only have an effect if the TCD is in Dead time B or Ontime B, and it will only effect the output WOB.
Figure 22-13. Input Mode 2 on Input B
DTA
OTA
DTB
OTB
DTA
OTA
Wait
DTB
OTB
DTA
OTA
WOA
WOB
INPUT A
INPUT B
Input Mode 3: Stop Output, Execute Opposite Compare Cycle while Fault Active
An input Event in Input mode 3 will stop the output signal and start executing the opposite dead-time and
on-time, as long as the fault/input is active. When the input is released, the ongoing dead time and/or ontime will finish and then, normal flow will start.
If Input mode 3 is used on input A, an Event will only have an effect if the TCD is in Dead time A or Ontime A.
Figure 22-14. Input Mode 3 on Input A
DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
DTB
OTB
DTA
OTA
WOA
WOB
INPUT A
INPUT B
If Input mode 3 is used on input B, an Event will only have an effect if the TCD is in Dead time B or Ontime B.
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Figure 22-15. Input Mode 3 on Input B
DTA
OTA
DTB
OTB
DTA
OTA
DTA
OTA
DTB
OTB
DTA
OTA
WOA
WOB
INPUT A
INPUT B
Input Mode 4: Stop all Outputs, Maintain Frequency
When input mode 4 is used, both input A and input B will give the same functionality.
An input Event will deactivate the outputs as long as the Event is active. TheTCD counter will not be
affected by Events in this input mode.
Figure 22-16. Input Mode 4
DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
WOA
WOB
INPUT A/B
Input Mode 5: Stop all Outputs, Execute Dead Time while Fault Active
When input mode 5 is used, both input A and input B give the same functionality:
The input Event stops the outputs and starts on the opposite dead time if it occurs during an on-time. If
the Event occurs during a dead time, it will continue until the next on-time should start, but instead it will
jump to the next dead time. As long as the input Event is active, alternating dead times will occur. When
the input Event stops, the ongoing dead time will finish and the next on-time will continue in the normal
flow.
Figure 22-17. Input Mode 5
DTA
OTA
DTB
OTB
DTA
OTA
DTB
DTA
DTB
DTA
DTB
OTB
WOA
WOB
INPUT A/B
Input Mode 6: Stop all Outputs, Jump to next Compare Cycle and Wait
When input mode 6 is used both input A and input B will give the same functionality. The input Event
stops the outputs and jumps to the opposite dead time if it occurs during a on time. If the Event occurs
during a dead time, it will continue until the next on-time should start, but instead, it will jump to the next
dead time. As long as the input Event is active, the TCD counter will wait. When the input Events stops,
the next dead time will start and normal flow will continue.
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Figure 22-18. Input Mode 6
DTA
OTA
DTB
Wait
DTA
OTA
Wait
DTB
OTB
DTA
OTA
WOA
WOB
INPUT A/B
Input Mode 7: Stop all Outputs, Wait for Software Action
When input mode 7 is used, both input A and input B will give the same functionality. The input Events
stops the outputs and TCD counter. It will be stopped until a Restart command is given. If the input Event
still is high when the Restart command is given, it will just stop again. When the TCD counter restarts, it
will always start on Dead time A.
Figure 22-19. Input Mode 7
DTA
OTA
DTB
OTB
DTA
OTA
Wait
DTA
OTA
WOA
WOB
INPUT A/B
Software Restart
command
Input Mode 8: Stop Output on Edge, Jump to Next Compare Cycle
In Input mode 8, a positive edge on the input Event while the corresponding output is on will cause the
output to stop and the TCD counter jump to the opposite Dead time.
If Input mode 8 is used on input A and an positive input event occurs while in On time A, the TCD counter
jumps to Dead time B.
Figure 22-20. Input Mode 8 on Input A
DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
WOA
WOB
INPUT A
OR
INPUT A
If Input mode 8 is used on input B and an positive input event occurs while in On time B, the TCD counter
jumps to Dead time A.
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Figure 22-21. Input Mode 8 on Input B
DTA
OTA
DTB
OTB DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
WOA
WOB
INPUT B
OR
INPUT B
Input Mode 9: Stop Output at Level, Maintain Frequency
In Input mode 9 a positive edge on the input Event while the corresponding output is on will cause the
output to stop during the rest of the on-time. The TCD counter will not be affected by the Event, only the
output.
If Input mode 9 is used on input A and an positive input Event occurs while in On time A, the output will
be off for the rest of the on-time.
Figure 22-22. Input Mode 9 on Input A
DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
DTA
OTA
WOA
WOB
INPUT A
INPUT B
If Input mode 9 is used on input B and an positive input event occurs while in On time B, the output will be
off for the rest of the on-time.
Figure 22-23. Input Mode 9 on Input B
DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
DTA
OTA
WOA
WOB
INPUT A
INPUT B
Input Mode 10: Stop Output on Edge, Maintain Frequency
In Input mode 10 the input Event will cause the corresponding output to stop as long as the input is
active. If the input goes low while there should have been an on-time on the corresponding output, the
output will be deactivated for the rest of the on-time, too. The TCD counter is not affected by the Event,
only the output.
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If Input mode 10 is used on input A and an input event occurs, the WOA will be off as long as the event
lasts. If released during an on-time, it will be off for the rest of the on-time, too.
Figure 22-24. Input Mode 10 on Input A
DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
DTA
OTA
WOA
WOB
INPUT A
INPUT B
If Input mode 10 is used on input B and an input Event occurs, the WOB will be off as long as the Event
lasts. If released during an on-time, it will be off for the rest of the on-time, too.
Figure 22-25. Input Mode 10 on Input B
DTA
OTA
DTB
OTB
DTA
OTA
DTB
OTB
DTA
OTA
WOA
WOB
INPUT A
INPUT B
Input Mode Summary
The table below summarizes the conditions as illustrated in the timing diagrams of the preceding
sections.
Table 22-6. Input mode summary
INPUTMODE
Trigger → Output affected
Fault On/Active
Fault Release/Inactive
0x00
-
No action
No action
0x01
Input A→WOA
End current on-time and Start with dead-time for
wait
other compare
Input B→WOB
0x02
0x03
0x04
Input A→WOA
End current on-time.
Input B→WOB
Execute other compare
cycle and wait
Input A→WOA
End current on-time.
Input B→WOB
Execute other compare
cycle
Input A→{WOA, WOB}
Deactivate outputs
Start with dead-time for
current compare
Re-enable current
compare cycle
Input B→{WOA, WOB}
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INPUTMODE
Trigger → Output affected
Fault On/Active
0x05
Input A→{WOA, WOB}
Execute dead-time only
Fault Release/Inactive
Input B→{WOA, WOB}
0x06
Input A→{WOA, WOB}
End on-time and wait
Start with dead-time for
other compare
End on-time and wait
for software action
Start with dead-time for
current compare
Input B→{WOA, WOB}
0x07
Input A→{WOA, WOB}
Input B→{WOA, WOB}
0x08
Input A→WOA
Input B→WOB
0x09
Input A→WOA
Input B→WOB
0x0A
Input A→WOA
Input B→WOB
other
-
End current on-time and
continue with other offtime
Block current on-time
and continue sequence
Deactivate on-time until
end of sequence while
trigger is active
-
-
22.3.2.5 Dithering
If it is not possible to achieve the desired frequency because of pre-scaler/period selection limitations,
Dithering can be used to approximate the desired frequency and reduce waveform drift.
Dither accumulates the fractional error of the counter clock for each cycle. When the fractional error
overflows, an additional cycle is added to the selected part of the cycle.
Example
If the timer clock frequency is 10MHz, it will give the timer a resolution of 100ns. Then,
the output frequency should be 75 kHz. Here 75 kHz means a period of 13333ns, and
that is not possible to achieve with a constant period with a 100ns resolution because it
equals 133.33 cycles. The output period can be set to either 133 cycles (75.188kHz) or
134 cycles (74.626 kHz).
It is possible to change the period between the two frequencies manually in the firmware
to get an average output frequency of 75 kHz. (change the every 3rd period to 134
cycles) The dither can do this automatically by accumulating the error (0.33 cycles). The
accumulator calculate when the accumulated error is larger than one clock cycle and
when that happens it adds an additional cycle to the timer period.
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Figure 22-26. Dither Logic
Overflow
Dither value
ACCUMULATOR REGISTER
The user can select where in the TCD cycle the dither will be added by writing to the Dither Selection bits
in the Dither Control register (DITHERSEL in TCD.DITCTRL):
•
On-time B
•
On-time A and B
•
Dead-time B
•
Dead-time A and B
How much the dithering will affect the TCD cycle time depends on what Waveform Generation Mode is
used, see table below.
Dithering is not supported in Dual Slope Mode.
Table 22-7. Mode-Dependent Dithering Additions to TCD Cycle
WAVEGEN
DITHERSEL in TCD.DITCTRL
Additional TCD clock cycles to TCD cycle
One Ramp Mode
On-time B
1
On-time A and B
1
Dead-time B
0
Dead-time A and B
0
On-time B
1
On-time A and B
2
Dead-time B
0
Dead-time A and B
0
On-time B
1
On-time A and B
2
Dead-time B
1
Dead-time A and B
2
On-time B
0 (not supported)
On-time A and B
0 (not supported)
Two Ramp Mode
Four Ramp Mode
Dual Slope Mode
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8-bit AVR Microcontroller
WAVEGEN
DITHERSEL in TCD.DITCTRL
Additional TCD clock cycles to TCD cycle
Dead-time B
0 (not supported)
Dead-time A and B
0 (not supported)
The differences in the number of TCD clock cycles added to the TCD cycle is caused by the different
number of compare values used by the TCD cycle. For example in One Ramp Mode, only CMPBCLR
affects the TCD cycle time.
For DITHERSEL configurations where no extra cycles are added to the TCD cycles, compensation is
reached by shortening the following output state.
Example:
In One Ramp Mode with DITHERSEL selecting Dead-time B, the Dead-time B will be
increased by one cycle when dither overflow occurs. This reduces On-time B by one
cycle.
22.3.2.6 TCD Counter Capture
Because the TCD counter is asynchronous to the system clock it is not possible to read out the counter
value directly. It is possible to capture the TCD counter value, synchronized to the IO clock domain in two
different ways.
•
Capture value on input Events
•
Software capture
The capture logic contains two separate capture blocks, CAPTUREA and CAPTUREB, that can capture
and synchronize the TCD counter value to the IO clock domain. CAPTUREA/B can be triggered by input
Event A/B or by software.
The capture values can be read by reading first TCD.CAPTURExL and then TCD.CAPTURExH registers.
Captures Triggered by Input Events
To enable capture on input Event, write a '1' to the ACTION bit in the respective Event Control x register
(TCD.EVCTRL) when configuring an Event input.
When a capture has occurred, the TRIGA/B flag is raised in the Interrupt Flags register (TCD.INTFLAGS).
The according TRIGA/B interrupt is executed if enabled by writing a '1' to the respective Trigger Interrupt
x Enable bit (TRIGx) in the Interrupt Control register (TCD.INTCTRL). By polling TRIGx in
TCD.INTFLAGS, the user knows that a CAPTUREx value is available, and can read out the value by
reading first the TCD.CAPTURExL and then TCD.CAPTURxH registers.
Example
In order to do PWM capture both event A and B should be connected to the same
asynchronous event channel that contains the PWM signal. To get information on the
PWM signal one event input should be configured to capture the rising edge of the signal.
The other event input should be configured to capture the falling edge of the signal.
Capture Triggered by Software
Software can capture the TCD value by writing a '1' to respective Software Capture A/B Strobe bit
(SCAPTUREx) in the Control E register (TCD.CTRLE). When this command is executed and the
Command Ready bit (CMDRDY) in the Status register (TCD.STATUS) reads '1' again, the CAPTUREA/B
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value is available. It can now be read by reading first the TCD.CAPTURExL and then the
TCD.CAPTURxH registers.
Using Capture together with input modes
The capture functionality can be used together with input modes. The same event will then both capture
the counter value and trigger a change in the counter flow depending on the input mode selected.
Example
If the user what to reset the counter when running in One Ramp mode whenever the
input event capture the counter value this can be done by using input event B and setting
INPUTCTRLB register to 0x08.
Related Links
Initialization and Disabling
22.3.2.7 Output Control
The outputs are configured by writing to the Fault Control register (TCD.FAULTCTRL). TCD.FAULTCTRL
is only reset to zero after a POR reset. During the reset sequence after any Reset, TCD.FAULTCTRL will
get its values from the TCD Fuse (FUSE.TCDCFG).
The Compare x Enable bits (CMPxEN in TCD.FAULTCTRL) enable the different outputs. The CMPx bits
in TCD.FAULTCTRL set the value the registers should have after Reset or when a fault is triggered.
The TCD itself generates two different outputs, WOA and WOB. The two additional outputs WOC and
WOD can be configured by software to be connected to either WOA or WOB by writing the Compare C/D
Output Select bits (CMPCSEL and CMPDSEL) in the Control C register (TCD.CTRLC).
The user can also override the outputs based on the TCD counter state by writing a '1' to the Compare
Output Value Override bit in the Control C register (CMPOVR in TCD.CTRLC). The user can then select
the output values in the different dead- and on times by writing to the Compare x Value bit fields in the
Control D register (CMPAVAL and CMPBVAL in TCD.CTRLD).
When used in One Ramp mode, WOA will only use the setup for Dead Time A (DTA) and On Time A
(OTA) to set the output. WOB will only use Dead-Time B (DTB) and On Time B (OTB) values to set the
output.
When using the override feature together with faults detection (input modes) the CMPA (and CMPC/D if
WOC/D equals WOA) bit in TCD.FAULTCTRL should be equal to CMPAVAL[0] and [2] in TCD.CTRLD. if
not the first cycle after a fault is detected can have the wrong polarity on the outputs. The same applies to
CMPB in TCD.FAULTCTRL (and CMPC/D if WOC/D equals WOB) bit, which should be equal to
CMPBVAL[0] and [2] in TCD_CTRLD.
Due to the asynchronous nature of the TCD, that input events immediately can affect the output signal,
there is a risk of nano-second spikes occurring on the output when there is no load on the pin. The case
occurs in any input mode different from 0 and when an input event is triggering. The spike value will
always be in direction of the CMPx value given by the FAULTCTRL register.
Related Links
TCD0CFG
22.3.3
Events
The TCD can generate the following output events:
•
TCD counter matches CMPBCLR
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8-bit AVR Microcontroller
•
•
•
TCD counter matches CMPASET
TCD counter matches CMPBSET
Programmable TCD output event. The user can select trigger, and all the different compare
matches. In addition it is possible to delay the output Event from 0 to 256 TCD delay cycles.
The three events based on the counter match directly generate event strobes that last one clock cycle on
the TCD counter clock. The programmable output event generates a event strobe that last one clock
cycle on the TCD synchronizer clock.
The TCD has the possibility to receive these input Events:
•
•
Input A
Input B
Related Links
TCD Inputs
EVSYS - Event System
22.3.3.1 Programmable output events
Programmable output event uses the same logic as the Input blanking for trigger selection and delay. It is
therefore not possible to configure the functionalities independently. If the input blanking functionality is
used, the output event cannot be delayed and the trigger used for input blanking will also be used for the
output event.
The programmable output events are controlled by the DLYCTRL and DLYVAL registers. It is possible to
delay the output event by 0 to 256 TCD delay clock cycles if the DLYTRIG bits in DLYCTRL is set to 0x2.
The delayed output event functionality uses the TCD delay clock and counts until the DLYVAL value is
reached before the trigger is sent out as a event. The TCD delay clock is a prescaled version of the TCD
synchronization clock and the division factor is set by the DLYPRESC bits in the DLYCTRL register. The
output event will be delayed by TCD clock period x DLYPRESC division factor x DLYVAL.
22.3.4
Interrupts
Table 22-8. Available Interrupt Vectors and Sources
Offset
Name
Vector Description
Conditions
0x00
OVF
Overflow interrupt
The TCD is done with one TCD cycle.
0x02
TRIG
Trigger interrupt
•
•
TRIGA: Counter is entering On-Time A
TRIGB: Counter is entering On-Time B
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Interrupt Flags register
of the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the Interrupt
Flag is set. The interrupt request remains active until the Interrupt Flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear Interrupt Flags.
When several interrupt request conditions are supported by an interrupt vector, the interrupt requests are
ORed together into one combined interrupt request to the Interrupt Controller. The user must read the
peripheral's INTFLAGS register to determine which of the interrupt conditions are present.
Related Links
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Datasheet Preliminary
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8-bit AVR Microcontroller
CPUINT - CPU Interrupt Controller
SREG
22.3.5
Sleep Mode Operation
The TCD operates in Idle sleep, and is stopped when entering Standby and Power Down sleep modes.
22.3.6
Synchronization
The TCD has two different clock domains and needs to synchronize the communication between the
domains. See Initialization section for detail on how the synchronization of values from the IO clock
domain to the TCD clock domain is done. See the Capture section for details on how the synchronization
of values from the TCD clock domain to the IO clock domain is done.
Related Links
Initialization and Disabling
TCD Counter Capture
22.3.7
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
Table 22-9. TCD - Registers under Configuration Change Protection
Register
Key
TCD.FAULTCTRL
IOREG
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8-bit AVR Microcontroller
22.4
Register Summary - TCD
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
CTRLC
7:0
0x03
CTRLD
7:0
0x04
CTRLE
7:0
CLKSEL[1:0]
CNTPRES[1:0]
SYNCPRES[1:0]
ENABLE
WGMODE[1:0]
CMPDSEL
CMPCSEL
FIFTY
AUPDATE
CMPBVAL[3:0]
DISEOC
CMPOVR
CMPAVAL[3:0]
SCAPTUREB SCAPTUREA
RESTART
SYNC
SYNCEOC
0x05
...
Reserved
0x07
0x08
EVCTRLA
7:0
CFG[1:0]
EDGE
ACTION
TRIGEI
0x09
EVCTRLB
7:0
CFG[1:0]
EDGE
ACTION
TRIGEI
OVF
0x0A
...
Reserved
0x0B
0x0C
INTCTRL
7:0
TRIGB
TRIGA
0x0D
INTFLAGS
7:0
TRIGB
TRIGA
0x0E
STATUS
7:0
PWMACTB
PWMACTA
OVF
CMDRDY
0x0F
Reserved
0x10
INPUTCTRLA
7:0
INPUTMODE[3:0]
0x11
INPUTCTRLB
7:0
INPUTMODE[3:0]
0x12
FAULTCTRL
7:0
0x13
Reserved
0x14
DLYCTRL
7:0
0x15
DLYVAL
7:0
CMPDEN
CMPCEN
CMPBEN
CMPAEN
CMPD
DLYPRESC[1:0]
CMPC
CMPB
DLYTRIG[1:0]
ENRDY
CMPA
DLYSEL[1:0]
DLYVAL[7:0]
0x16
...
Reserved
0x17
0x18
DITCTRL
7:0
0x19
DITVAL
7:0
DITHERSEL[1:0]
DITHER[3:0]
0x1A
...
Reserved
0x1D
0x1E
DBGCTRL
7:0
FAULTDET
DBGRUN
0x1F
...
Reserved
0x21
0x22
0x23
0x24
0x25
CAPTUREA
CAPTUREB
7:0
CAPTURE[7:0]
15:8
7:0
CAPTURE[11:8]
CAPTURE[7:0]
15:8
CAPTURE[11:8]
0x26
...
Reserved
0x27
0x28
0x29
0x2A
CMPASET
CMPACLR
7:0
CMPSET[7:0]
15:8
7:0
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CMPSET[11:8]
CMPCLR[7:0]
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8-bit AVR Microcontroller
Offset
Name
0x2B
Bit Pos.
15:8
0x2C
CMPBSET
0x2D
0x2E
CMPBCLR
0x2F
CMPCLR[11:8]
7:0
CMPSET[7:0]
15:8
CMPSET[11:8]
7:0
CMPCLR[7:0]
15:8
CMPCLR[11:8]
22.5
Register Description
22.5.1
Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property: Enable-protected
Bit
7
6
5
4
CLKSEL[1:0]
Access
Reset
3
CNTPRES[1:0]
2
1
SYNCPRES[1:0]
0
ENABLE
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
Bits 6:5 – CLKSEL[1:0]: Clock Select
The clock select bits select the clock source of the TCD clock.
Value
0x0
0x1
0x2
0x3
Description
OSC20M
Reserved
External clock
System clock
Bits 4:3 – CNTPRES[1:0]: Counter Prescaler
The Counter Prescaler bits select the division factor of the TCD counter clock.
Value
0x0
0x1
0x2
0x3
Description
Division factor 1
Division factor 4
Division factor 32
Reserved
Bits 2:1 – SYNCPRES[1:0]: Synchronization Prescaler
The synchronization prescaler bits select the division factor of the TCD clock.
Value
0x0
0x1
0x2
0x3
Description
Division factor 1
Division factor 2
Division factor 4
Division factor 8
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8-bit AVR Microcontroller
Bit 0 – ENABLE: Enable
When this bit is written to, it will automatically be synchronized to the TCD clock domain.
This bit can be changed as long as synchronization of this bit is not ongoing, see Enable Ready bit
(ENRDY) in Status register (STATUS).
This bit is not enable-protected.
Value
0
1
22.5.2
Description
The TCD is disabled.
The TCD is enabled and running.
Control B
Name: CTRLB
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
WGMODE[1:0]
Access
Reset
R/W
R/W
0
0
Bits 1:0 – WGMODE[1:0]: Waveform Generation Mode
These bits select the waveform generation
Value
0x0
0x1
0x2
0x3
22.5.3
Name
ONERAMP
TWORAMP
FOURRAMP
DS
Description
One ramp mode
Two ramp mode
Four ramp mode
Dual-slope mode
Control C
Name: CTRLC
Offset: 0x02
Reset: 0x00
Property:
Bit
Access
Reset
7
6
1
0
CMPDSEL
CMPCSEL
5
4
FIFTY
3
2
AUPDATE
CMPOVR
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 7 – CMPDSEL: Compare D Output Select
Value
0
1
Name
PWMA
PWMB
© 2017 Microchip Technology Inc.
Description
Waveform A
Waveform B
Datasheet Preliminary
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8-bit AVR Microcontroller
Bit 6 – CMPCSEL: Compare C Output Select
Value
0
1
Name
PWMA
PWMB
Description
Waveform A
Waveform B
Bit 3 – FIFTY: Fifty Percent Waveform
If the two waveforms have identical characteristics, this bit can be written to '1'. This will cause any values
written to register CMPBSET/CLR also to be written to the register CMPASET/CLR.
Bit 1 – AUPDATE: Automatically Update
If this bit is set a synchronization at the end of the TCD cycle is automatically requested after the
Compare B Clear High register (CMPBCLRH) is written.
If the Fifty Percent Waveform is enabled by setting the FIFTY bit in this register, writing the Compare A
Clear High register will also request a synchronization at the end of the TCD cycle if the AUPDATE bit is
set.
Bit 0 – CMPOVR: Compare Output Value Override
When this bit is written, default values of the Waveform Outputs A and B are overridden by the values
written in the Compare x Value in active state bit fields in the Control D register (CTRLD.CMPnxVAL).
See the Control D register description for more details.
22.5.4
Control D
Name: CTRLD
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
R/W
0
1
0
R/W
R/W
R/W
R/W
R/W
0
0
0
0
R/W
R/W
0
0
0
CMPBVAL[3:0]
Access
Reset
CMPAVAL[3:0]
Bits 0:3, 4:7 – CMPAVAL, CMPBVAL: Compare x Value (in active state)
These bits sets the active state for the different ramps for compare x.
These settings are only valid if the Compare Output Value Override bit in the Control C register
(CTRLC.CMPOVR) is written to '1'.
CMPxVAL
A_off
A_on
B_off
B_on
PWMA
CMPAVAL[0]
CMPAVAL[1]
CMPAVAL[2]
CMPAVAL[3]
PWMB
CMPBVAL[0]
CMPBVAL[1]
CMPBVAL[2]
CMPBVAL[3]
In One Ramp mode, PWMA will only use A_off and A_on values and PWMB will only use B_off and B_on
values. This is due to possible overlap between the values A_off, A_on, B_off and B_on.
22.5.5
Control E
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8-bit AVR Microcontroller
Name: CTRLE
Offset: 0x04
Reset: 0x00
Property:
Bit
Access
Reset
4
3
2
1
0
DISEOC
7
6
5
SCAPTUREB
SCAPTUREA
RESTART
SYNC
SYNCEOC
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit 7 – DISEOC: Disable at End of TCD Cycle Strobe
When this bit is written, the TCD will automatically disable at the end of the TCD cycle.
When this bit is written to '1', the ENRDY in TCD.STATUS will keep low until the TCD is disabled.
Writing to this bit only has effect if there is no ongoing synchronization of Enable. See also ENRDY bit in
TCD.STATUS.
Bit 4 – SCAPTUREB: Software Capture B Strobe
When this bit is written to '1', a software capture to Capture register B (TCD.CAPTUREBL/H) is done as
soon as the strobe is synchronized to the TCD domain.
Writing to this bit only has effect if there is no ongoing synchronization of a command. See also CMDRDY
bit in TCD.STATUS.
Bit 3 – SCAPTUREA: Software Capture A Strobe
When this bit is written to '1', a software capture to Capture register A (TCD.CAPTUREAL/H) is done as
soon as the strobe is synchronized to the TCD domain.
Writing to this bit only has effect if there is no ongoing synchronization of a command. See also CMDRDY
bit in TCD.STATUS.
Bit 2 – RESTART: Restart Strobe
When this bit is written a Restart of the TCD counter is executed as soon as this bit is synchronized to the
TCD domain.
Writing to this bit only has effect if there is no ongoing synchronization of a command. See also CMDRDY
bit in TCD.STATUS.
Bit 1 – SYNC: Synchronize Strobe
When this bit is written to '1' the doubled buffered registers will be loaded to the TCD domain as soon as
this bit is synchronized to the TCD domain.
Writing to this bit only has effect if there is no ongoing synchronization of a command. See also CMDRDY
bit in TCD.STATUS.
Bit 0 – SYNCEOC: Synchronize End of TCD Cycle Strobe
When this bit is written to '1' the doubled buffered registers will be loaded to the TCD domain at the end of
the next TCD cycle.
Writing to this bit only has effect if there is no ongoing synchronization of a command. See also CMDRDY
bit in TCD.STATUS.
22.5.6
Event Control x
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8-bit AVR Microcontroller
Name: EVCTRLA, EVCTRLB
Offset: 0x08 + n*0x01 [n=0..1]
Reset: 0x00
Property:
Bit
7
6
CFG[1:0]
Access
Reset
5
4
3
2
1
0
EDGE
ACTION
TRIGEI
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bits 7:6 – CFG[1:0]: Event Configuration
When the Input Capture Noise canceler is activated (FILTERON), the Event input is filtered. The filter
function requires four successive equal valued samples of the Retrigger pin for changing its output. The
Input Capture is therefore delayed by four clock cycles when the noise canceler is enabled.
When the Asynchronous Event is enabled (ASYNCON), the Event input will qualify the output directly.
Value
0x0
0x1
0x2
other
Name
NEITHER
FILTERON
ASYNCON
-
Description
Neither Filter nor Asynchronous Event is enabled.
Input Capture Noise Cancellation Filter enabled.
Asynchronous Event output qualification enabled.
Reserved.
Bit 4 – EDGE: Edge Selection
This bit is used to select the active edge or level for the event input.
Value
0
1
Name
Description
FALL_LOW The falling edge or low level of the Event input generates Retrigger or Fault
action.
RISE_HIGH The rising edge or high level of the Event input generates Retrigger or Fault
action.
Bit 2 – ACTION: Event Action
This bit enables Capture on Event input. By default, the input will trigger a Fault, depending on the Input x
register input mode (TCD.INPUTx). It is also possible to trigger a Capture on the Event input.
Value
0
1
Name
FAULT
CAPTURE
Description
Event triggers a Fault.
Event triggers a Fault and Capture.
Bit 0 – TRIGEI: Trigger Event Input Enable
Writing this bit to '1' enables Event as trigger for input A.
22.5.7
Interrupt Control
Name: INTCTRL
Offset: 0x0C
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
7
6
5
4
Access
Reset
3
2
TRIGB
TRIGA
1
OVF
0
R/W
R/W
R/W
0
0
0
Bits 2, 3 – TRIGA, TRIGB: Trigger x Interrupt Enable
Writing this bit to '1' enables executing an interrupt when trigger input x is received.
Bit 0 – OVF: Counter Overflow
Writing this bit to '1' enables executing an interrupt at Restart of the sequence or Overflow of the counter.
22.5.8
Interrupt Flags
Name: INTFLAGS
Offset: 0x0D
Reset: 0x00
Property:
Bit
7
6
5
4
Access
Reset
3
2
TRIGB
TRIGA
1
OVF
0
R/W
R/W
R/W
0
0
0
Bits 2, 3 – TRIGA, TRIGB: Trigger x Interrupt Flag
When a capture has occurred, the TRIGA/B is raised. This bit is cleared by writing a '1' to it.
Bit 0 – OVF: Overflow Interrupt Flag
When a capture is overflow, this flag is raised. This bit is cleared by writing a '1' to it.
22.5.9
Status
Name: STATUS
Offset: 0x0E
Reset: 0x00
Property:
Bit
Access
Reset
7
6
1
0
PWMACTB
PWMACTA
5
4
3
2
CMDRDY
ENRDY
R/W
R/W
R
R
0
0
0
0
Bits 6, 7 – PWMACTA, PWMACTB: PWM Activity on x
This bit is set by hardware each time the output WO1 toggles from 0 to 1 or from 1 to 0.
This status bit must be cleared by software by writing a '1' to it before new PWM activity can be detected.
Bit 1 – CMDRDY: Command Ready
This status bit tells when a command is synced to the TCD domain and the system is ready to receive
new commands.
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8-bit AVR Microcontroller
The following clears the CMDRDY bit:
1. TCD.CTRLE SYNCEOC strobe
2. TCD.CTRLE SYNC strobe
3. TCD.CTRLE RESTART strobe
4. TCD.CTRLE SCAPTUREA Capture A strobe
5. TCD.CTRLE SCAPTUREB Capture B strobe
6. TCD.CTRLC AUPDATE written to '1' and writing to TCD.CMPBCLRH register
Bit 0 – ENRDY: Enable Ready
This status bit tells when the ENABLE value in TCD.CTRLA is synced to the TCD domain, and is ready to
be written to again.
The following clears the ENRDY bit:
1. Writing to the ENABLE bit in (TCD.CTRLA
2.
3.
TCD.CTRLE DISEOC strobe
Going to break in an On-Chip Debugging (OCD) session with and the Debug Run bit (DBGCTRL)
in TCD.DBGCTRL is not '1'
22.5.10 Input Control x
Name: INPUTCTRLA, INPUTCTRLB
Offset: 0x10 + n*0x01 [n=0..1]
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
INPUTMODE[3:0]
Access
Reset
R/W
R/W
R/W
R/W
0
0
0
0
Bits 3:0 – INPUTMODE[3:0]: Input Mode
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
Name
NONE
JMPWAIT
EXECWAIT
EXECFAULT
FREQ
EXECDT
WAIT
WAITSW
EDGETRIG
EDGETRIGFREQ
LVLTRIGFREQ
Description
Input has no action
Stop output, jump to opposite compare cycle and wait
Stop output, execute opposite compare cycle and wait
Stop output, execute opposite compare cycle while fault active
Stop all outputs, maintain frequency
Stop all outputs, execute dead time while fault active
Stop all outputs, jump to next compare cycle and wait
Stop all outputs, wait for software action
Stop output on edge, jump to next compare cycle
Stop output on edge, maintain frequency
Stop output at level, maintain frequency
22.5.11 Fault Control
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8-bit AVR Microcontroller
Name: FAULTCTRL
Offset: 0x12
Reset: Loaded from fuse
Property: Configuration Change Protection
Bit
Access
Reset
7
6
5
4
3
2
1
0
CMPDEN
CMPCEN
CMPBEN
CMPAEN
CMPD
CMPC
CMPB
CMPA
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
x
x
x
x
x
x
x
x
Bits 4, 5, 6, 7 – CMPAEN, CMPBEN, CMPCEN, CMPDEN: Compare x Enable
These bits enable Compare as output on pin. At reset the content is kept and during the reset sequence
loaded from the TCD Configuration Fuse (FUSE.TCDFG).
Bits 0, 1, 2, 3 – CMPA, CMPB, CMPC, CMPD: Compare Value x
These bits set the default state from Reset, or when a input Event triggers a Fault causing changes to the
output. At reset the content is kept and during the reset sequence loaded from the TCD Configuration
Fuse (FUSE.TCDFG).
22.5.12 Delay Control
Name: DLYCTRL
Offset: 0x14
Reset: 0x00
Property:
Bit
7
6
5
4
3
DLYPRESC[1:0]
Access
Reset
2
1
DLYTRIG[1:0]
0
DLYSEL[1:0]
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bits 5:4 – DLYPRESC[1:0]: Delay Prescaler
These bits control the prescaler settings for the blanking or output event delay.
Value
0x0
0x1
0x2
0x3
Description
Prescaler division factor 1
Prescaler division factor 2
Prescaler division factor 4
Prescaler division factor 8
Bits 3:2 – DLYTRIG[1:0]: Delay Trigger
These bits control what should trigger the blanking or output event delay.
Value
0x0
0x1
0x2
0x3
Name
CMPASET
CMPACLR
CMPBSET
CMPBCLR
© 2017 Microchip Technology Inc.
Description
CMPASET triggers delay
CMPACLR triggers delay
CMPBSET triggers delay
CMPASET triggers delay (end of cycle)
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8-bit AVR Microcontroller
Bits 1:0 – DLYSEL[1:0]: Delay Select
These bits control what function should be used by the delay trigger the blanking or output event delay.
Value
0x0
0x1
0x2
0x3
Description
Delay functionality not used
Input blanking enabled
Event delay enabled
Reserved
22.5.13 Delay Value
Name: DLYVAL
Offset: 0x15
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DLYVAL[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DLYVAL[7:0]: Delay Value
These bits configure the blanking/ output event delay time or event output synchronization delay in
number of prescaled TCD cycles.
22.5.14 Dither Control
Name: DITCTRL
Offset: 0x18
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DITHERSEL[1:0]
Access
Reset
R/W
R/W
0
0
Bits 1:0 – DITHERSEL[1:0]: Dither Select
These bits select which Compare register is using the dither function. See also Dithering.
Value
0x0
0x1
0x2
0x3
Name
ONTIMEB
ONTIMEAB
DEADTIMEB
DEADTIMEAB
Description
On-time ramp B
On-time ramp A and B
Dead-time ramp B
Dead-time ramp A and B
22.5.15 Dither Value
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8-bit AVR Microcontroller
Name: DITVAL
Offset: 0x19
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DITHER[3:0]
Access
Reset
R/W
R/W
R/W
R/W
0
0
0
0
Bits 3:0 – DITHER[3:0]: Dither Value
These bits configure the fractional adjustment of the on-time or off-time according to Dither Selection bits
(DITHERSEL) in the Dither Control register (TCD.DITCTRL). The DITHER value is added to a 4-bit
accumulator at the end of each TCD cycle. When the accumulator overflows the frequency adjustment
will occur.
The DITHER bits are doubled buffered so the new value is copied in at an update condition.
22.5.16 Debug Control
Name: DBGCTRL
Offset: 0x1E
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
FAULTDET
DBGRUN
R/W
R/W
0
0
Access
Reset
Bit 2 – FAULTDET: Fault Detection
This bit defines how the peripheral behaves when stopped in Debug Mode.
Value
0
1
Name Description
NONE No fault is generated if TCD is stopped in debug mode.
FAULT A fault is generated and both trigger flags are set if TCD is halted in debug mode.
Bit 0 – DBGRUN: Debug Run
Value
0
1
Description
The peripheral is halted in break debug mode and ignores events.
The peripheral will continue to run in break debug mode when the CPU is halted.
22.5.17 Capture x
For capture operation, these registers constitute the second buffer level and access point for the CPU.
The TCD.CAPTUREx registers are updated with the buffer value when an UPDATE condition occurs.
CAPTURE A register contains the value from the TCD counter when a Trigger A or a software capture A
occurs. CAPTURE B register contain the value from the TCD counter when Trigger B or software capture
B occurs.
The TCD counter value is synchronized to CAPTUREx by either software or an event.
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The capture register is blocked for update of new capture data until TCDn.CAPTURExH is read.
Name: CAPTUREA, CAPTUREB
Offset: 0x22 + n*0x02 [n=0..1]
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
CAPTURE[11:8]
Access
R
R
R
R
Reset
0
0
0
0
3
2
1
0
Bit
7
6
5
4
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
CAPTURE[7:0]
Bits 11:0 – CAPTURE[11:0]: Capture Byte
22.5.18 Compare Set x
For compare operation, these registers are continuously compared to the counter value. Normally, the
outputs form the comparators are then used for generating waveforms.
Name: CMPASET, CMPBSET
Offset: 0x28 + n*0x04 [n=0..1]
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
CMPSET[11:8]
Access
R/W
R/W
R/W
R/W
0
0
0
0
3
2
1
0
Reset
Bit
7
6
5
4
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
CMPSET[7:0]
Access
Reset
Bits 11:0 – CMPSET[11:0]: Compare Set
These bits hold value of the compare register.
22.5.19 Compare Clear x
For compare operation, these registers are continuously compared to the counter value. Normally, the
outputs form the comparators are then used for generating waveforms.
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8-bit AVR Microcontroller
Name: CMPACLR, CMPBCLR
Offset: 0x2A + n*0x04 [n=0..1]
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
CMPCLR[11:8]
Access
R/W
R/W
R/W
R/W
0
0
0
0
3
2
1
0
Reset
Bit
7
6
5
4
CMPCLR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 11:0 – CMPCLR[11:0]: Compare x Clear
These bits hold the value of the compare register.
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8-bit AVR Microcontroller
23.
RTC - Real Time Counter
23.1
Features
•
•
•
•
•
•
•
•
23.2
16-bit resolution
Selectable clock source
– 32.768kHz external crystal (XOSC32K)
– External clock
– 32KHz internal ULP oscillator (OSCULP32K)
– OSCULP32K divided by 32
Programmable 15-bit clock prescaling
One compare register
One period register
Clear timer on period overflow
Optional interrupt/Event on overflow and compare match
Periodic interrupt and Event
Overview
The RTC peripheral offers two timing functions: the Real-Time Counter (RTC) and a Periodic Interrupt
Timer (PIT).
The PIT functionality can be enabled independent of the RTC functionality.
RTC - Real-Time Counter
The RTC counts (prescaled) clock cycles in a Counter register, and compares the content of the Counter
register to a Period register and a Compare register.
The RTC can generate both interrupts and Events on compare match or overflow. It will generate a
compare interrupt and/or Event at the first count after the counter equals the Compare register value, and
an overflow interrupt and/or Event at the first count after the counter value equals the Period register
value. The overflow will also reset the Counter value to zero.
The RTC peripheral typically runs continuously, including in low-power sleep modes, to keep track of
time. It can wake up the device from sleep modes and/or interrupt the device at regular intervals.
The reference clock is typically the 32.768kHz output from an external crystal. The RTC can also be
clocked from an external clock signal, the 32KHz internal Ultra-Low Power oscillator (OSCULP32K), or
the OSCULP32K divided by 32.
The RTC peripheral includes a 15-bit programmable prescaler that can scale down the reference clock
before it reaches the counter. A wide range of resolutions and time-out periods can be configured for the
RTC. With a 32.768kHz clock source, the maximum resolution is 30.5μs, and time-out periods can be up
to 2 seconds. With a resolution of 1s, the maximum time-out period is more than 18 hours (65536
seconds). The RTC can give a compare interrupt and/or Event when the counter equals the compare
register value, and an overflow interrupt and/or Event when it equals the period register value.
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8-bit AVR Microcontroller
PIT - Periodic Interrupt Timer
Using the same clock source as the RTC function, the PIT can request an interrupt or trigger an output
Event on every n-th clock period. n can be selected from {4, 8, 16,.. 32768}.
The PIT uses the same clock source (CLK_RTC) as the RTC function .
Related Links
RTC Functional Description
PIT Functional Description
23.2.1
Block Diagram
Figure 23-1. Block Diagram
Pxn
32KHz ULP int. Osc.
DIV32
RTC
CLK_RTC
23.2.2
Signal Description
Not applicable.
23.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 23-1. RTC System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
Related Links
Clocks
I/O Lines and Connections
Debug Operation
Interrupts
Events
23.2.3.1 Clocks
System clock (CLK_PER) is required to be at least four times faster than RTC clock (CLK_RTC) for
reading counter value, and this is regardless of the RTC_PRESC setting.
Related Links
CLKCTRL - Clock Controller
23.2.3.2 I/O Lines and Connections
A 32.768kHz crystal can be connected to the TOSC1 or TOSC2 pins, along with any required load
capacitors.
An external clock can be used on the TOSC1 pin.
Related Links
CLKCTRL - Clock Controller
23.2.3.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
Related Links
CPUINT - CPU Interrupt Controller
SREG
Interrupts
23.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
EVSYS - Event System
23.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in debugging
mode will halt normal operation of the peripheral.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
Related Links
UPDI - Unified Program and Debug Interface
23.3
RTC Functional Description
The RTC peripheral offers two timing functions: the Real-Time Counter (RTC) and a Periodic Interrupt
Timer (PIT). This subsection describes the RTC.
Related Links
PIT Functional Description
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23.3.1
Initialization
To operate the RTC, the source clock for the RTC counter must be configured before enabling the RTC
peripheral, and the desired actions (interrupt requests, output Events).
Related Links
CLKCTRL - Clock Controller
PIT Functional Description
23.3.1.1 Configure the clock CLK_RTC
To configure CLK_RTC, follow these steps:
1.
2.
Configure the desired oscillator to operate as required, in the Clock Controller peripheral
(CLKCTRL).
Write the Clock Select bits (CLKSEL) in the Clock Selection register (RTC.CLKSEL) accordingly.
The CLK_RTC clock configuration is used by both RTC and PIT functionality.
23.3.1.2 Configure RTC
To operate the RTC, follow these steps:
1.
2.
3.
4.
23.3.2
Configure the RTC-internal prescaler by writing the PRESCALER bit field in the Control A register
(RTC.CTRLA).
Set the Compare value in the Compare register (RTC.CMP), and/or the Overflow value in the Top
register (RTC.PER).
Enable the desired Interrupts by writing to the respective Interrupt Enable bits (CMP, OVF) in the
Interrupt Control register (RTC.INTCTRL).
Enable the RTC by writing a '1' to the RTC Enable bit (RTCEN) in the Control A register
(RTC.CTRLA).
Operation - RTC
23.3.2.1 Enabling, Disabling, and Resetting
The RTC is enabled by setting the Enable bit in the Control A register (CTRLA.ENABLE=1). The RTC is
disabled by writing CTRLA.ENABLE=0.
23.4
PIT Functional Description
The RTC peripheral offers two timing functions: the Real-Time Counter (RTC) and a Periodic Interrupt
Timer (PIT). This subsection describes the PIT.
Related Links
RTC Functional Description
23.4.1
Initialization
To operate the PIT, follow these steps:
1. Configure the RTC clock CLK_RTC as described in Configure the clock CLK_RTC.
2. Select the period for the interrupt by writing the PERIOD bit field in the PIT Control A register
(RTC.PITCTRLA).
3. Enable the interrupt by writing a '1' to the Periodic Interrupt bit (PI) in the PIT Interrupt Control
register (RTC.PITINTCTRL).
4. Enable the PIT by writing a '1' to the PIT Enable bit (PITENABLE) in the PIT Control A register
(RTC.PITCTRLA).
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Datasheet Preliminary
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8-bit AVR Microcontroller
23.4.2
Operation - PIT
23.4.2.1 Enabling, Disabling, and Resetting
The PIT is enabled by setting the Enable bit in the PIT Control A register (RTC_PITCTRLA.PITEN=1).
The PIT is disabled by writing RTC_PITCTRLA.PITEN=0.
23.5
Events
The RTC, when enabled, will generate the following output Events:
•
•
Overflow (OVF): Generated when the counter has reached its top value and wrapped to zero.
Compare (CMP): Indicates a match between the counter value and the compare register.
The PIT, when enabled, will generate the following output Events:
•
•
•
•
•
•
•
•
Event 0: 8192 RTC clock periods interval.
Event 1: 4096 RTC clock periods interval.
Event 2: 2048 RTC clock periods interval.
Event 3: 1024 RTC clock periods interval.
Event 4: 512 RTC clock periods interval.
Event 5: 256 RTC clock periods interval.
Event 6: 128 RTC clock periods interval.
Event 7: 64 RTC clock periods interval.
The Event users are configured by the Event System (EVSYS).
Related Links
EVSYS - Event System
23.6
Interrupts
Table 23-2. Available Interrupt Vectors and Sources
Offset Name Vector Description
0x00
0x02
RTC
PIT
Real-time counter
overflow and compare
match interrupt
Periodic Interrupt Timer
interrupt
Conditions
•
•
Overflow (OVF): The counter has reached its top
value and wrapped to zero.
Compare (CMP): Match between the counter value
and the compare register.
A time period has passed, as configured in
RTC_PITCTRLA.PERIOD.
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Interrupt Flags register
of the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the Interrupt
Flag is set. The interrupt request remains active until the Interrupt Flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear Interrupt Flags.
Related Links
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8-bit AVR Microcontroller
CPUINT - CPU Interrupt Controller
INTCTRL
PITINTCTRL
23.7
Sleep Mode Operation
The RTC will continue to operate in Idle sleep mode. It will run in Standby sleep mode if
RTC.CTRLA.RUNSTDBY is set.
The PIT will continue to operate in any sleep mode.
Related Links
CTRLA
23.8
Synchronization
Both the RTC and the PIT are asynchronous, operating from a different clock source (CLK_RTC)
independently of the main clock (CLK_PER). For control and count register updates, it will take a number
of RTC clock and/or peripheral clock cycles before an updated register value is available in a register or
until a configuration change has effect on the RTC or PIT, respectively. This synchronization time is
described for each register in the Register Description.
For some RTC registers, a Synchronization Busy flag is available (CMPBUSY, PERBUSY, CNTBUSY,
CTRLABUSY) in the Status register (RTC.STATUS).
For the RTC.PITCTRLA register, a Synchronization Busy flag (SYNCBUSY) is available in the PIT Status
register (RTC.PITSTATUS).
Check for busy should be performed before writing to the mentioned registers.
Related Links
CLKCTRL - Clock Controller
23.9
Configuration Change Protection
Not applicable.
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8-bit AVR Microcontroller
23.10
Register Summary - RTC
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
STATUS
7:0
CNTBUSY
CTRLABUSY
0x02
INTCTRL
7:0
CMP
OVF
0x03
INTFLAGS
7:0
CMP
OVF
0x04
TEMP
7:0
0x05
DBGCTRL
7:0
0x06
Reserved
0x07
CLKSEL
0x08
CNT
0x09
0x0A
PER
0x0B
0x0C
CMP
0x0D
RUNSTDBY
PRESCALER[3:0]
RTCEN
CMPBUSY
PERBUSY
TEMP[7:0]
DBGRUN
7:0
CLKSEL[1:0]
7:0
CNT[7:0]
15:8
CNT[15:8]
7:0
PER[7:0]
15:8
PER[15:8]
7:0
CMP[7:0]
15:8
CMP[15:8]
0x0E
...
Reserved
0x0F
0x10
PITCTRLA
7:0
PERIOD[3:0]
PITEN
0x11
PITSTATUS
7:0
SYNCBUSY
0x12
PITINTCTRL
7:0
PI
0x13
PITINTFLAGS
7:0
PI
7:0
DBGRUN
0x14
Reserved
0x15
PITDBGCTRL
23.11
Register Description
23.11.1 Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
7
6
RUNSTDBY
Access
Reset
5
4
3
2
1
PRESCALER[3:0]
0
RTCEN
R/W
R/W
R/W
R/W
R/W
R
R
R/W
0
0
0
0
0
0
0
0
Bit 7 – RUNSTDBY: Run in Standby
Value
0
1
Description
RTC disabled in Standby sleep mode
RTC enabled in Standby sleep mode
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8-bit AVR Microcontroller
Bits 6:3 – PRESCALER[3:0]: Prescaler
These bits define the prescaling of the CLK_RTC clock signal. Due to synchronization between the RTC
clock and system clock domains, there is a latency of two RTC clock cycles from updating the register
until this has an effect. Application software needs to check that the STATUS.CTRLABUSY flag is cleared
before writing to this register.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC
0xD
0xE
0xF
Name
DIV1
DIV2
DIV4
DIV8
DIV16
DIV32
DIV64
DIV128
DIV256
DIV512
DIV1024
DIV2048
DIV4096
DIV8192
DIV16384
DIV32768
Description
RTC clock / 1 (no prescaling)
RTC clock / 2
RTC clock / 4
RTC clock / 8
RTC clock / 16
RTC clock / 32
RTC clock / 64
RTC clock / 128
RTC clock / 256
RTC clock / 512
RTC clock / 1024
RTC clock / 2048
RTC clock / 4096
RTC clock / 8192
RTC clock / 16384
RTC clock / 32768
Bit 0 – RTCEN: RTC Enable
Value
0
1
Description
RTC disabled
RTC enabled
23.11.2 Status
Name: STATUS
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
Access
R
R
R
R
Reset
0
0
0
0
3
2
1
0
CMPBUSY
PERBUSY
CNTBUSY
CTRLABUSY
R
R
R
R
0
0
0
0
Bit 3 – CMPBUSY: Compare Synchronization Busy
This bit is indicating whether the RTC is busy synchronizing the Compare register (RTC.CMP) in RTC
clock domain.
Bit 2 – PERBUSY: Period Synchronization Busy
This bit is indicating whether the RTC is busy synchronizing the Period register (RTC.PER) in RTC clock
domain.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Bit 1 – CNTBUSY: Counter Synchronization Busy
This bit is indicating whether the RTC is busy synchronizing the Count register (RTC.CNT) in RTC clock
domain.
Bit 0 – CTRLABUSY: Control A Synchronization Busy
This bit is indicating whether the RTC is busy synchronizing the Control A register (RTC.CTRLA) in RTC
clock domain.
23.11.3 Interrupt Control
Name: INTCTRL
Offset: 0x02
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
CMP
OVF
Access
R
R
R
R
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit 1 – CMP: Compare Match Interrupt Enable
Enable interrupt on compare match, i.e. when the Counter value (RTC.CNT) matches the Compare value
(RTC.CMP).
Bit 0 – OVF: Overflow Interrupt Enable
Enable interrupt on counter overflow, i.e. when the Counter value (RTC.CNT) matched the Period value
(RTC.PER) and wraps around to zero.
23.11.4 Interrupt Flag
Name: INTFLAGS
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
CMP
OVF
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bit 1 – CMP: Compare Match Interrupt Flag
This flag is set when the Counter value (RTC.CNT) matches the Compare value (RTC.CMP).
Writing a '1' to this bit clears the flag.
Bit 0 – OVF: Overflow Interrupt Flag
This flag is set when the Counter value (RTC.CNT) has reached the Period value (RTC.PER) and
wrapped to zero.
Writing a '1' to this bit clears the flag.
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8-bit AVR Microcontroller
23.11.5 Temporary
The Temporary register is used by the CPU for single-cycle, 16-bit access to the 16-bit registers of this
peripheral. It can also be read and written by software. See also Accessing 16-bit Registers. There is one
common Temporary register for all the 16-bit registers of this peripheral.
Name: TEMP
Offset: 0x4
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
4
3
2
1
TEMP[7:0]
Access
Reset
Bits 7:0 – TEMP[7:0]: Temporary
23.11.6 Debug Control
Name: DBGCTRL
Offset: 0x05
Reset: 0x00
Property:
Bit
7
6
5
0
DBGRUN
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
Bit 0 – DBGRUN: Debug Run
Value
0
1
Description
The peripheral is halted in break debug mode and ignores events.
The peripheral will continue to run in break debug mode when the CPU is halted.
23.11.7 Clock Selection
Name: CLKSEL
Offset: 0x07
Reset: 0x00
Property:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 248
8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
CLKSEL[1:0]
Access
R
R
R
R
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 1:0 – CLKSEL[1:0]: Clock Select
Writing these bits selects the source for the RTC clock (CLK_RTC).
When configuring the RTC to use either XOSC32K or the external clock on TOSC1, XOSC32K needs to
be enabled and the Source Select bit (SEL) and Run Standby bit (RUNSTDBY) in the XOSC32K Control
A register of the Clock Controller (CLKCTRL.XOSC32KCTRLA) must be configured accordingly.
Value
0x0
0x1
0x2
0x3
Description
32KHz from OSCULP32K
1KHz from OSCULP32K
32.768kHz from XOSC32K
External clock from TOSC1 pin
23.11.8 Count
The RTC.CNTL and RTC.CNTH register pair represents the 16-bit value, RTC.CNT. The low byte [7:0]
(suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset +
0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
Due to synchronization between the RTC clock and system clock domains, there is a latency of two RTC
clock cycles from updating the register until this has an effect. Application software needs to check that
the STATUS.CNTBUSY flag is cleared before writing to this register.
Name: CNT
Offset: 0x08
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
R/W
R/W
R/W
R/W
Reset
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
CNT[15:8]
Access
CNT[7:0]
Access
Reset
Bits 15:8 – CNT[15:8]: Counter high byte
These bits hold the MSB of the 16-bit counter register.
Bits 7:0 – CNT[7:0]: Counter low byte
These bits hold the LSB of the 16-bit counter register.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
23.11.9 Period
The RTC.PERL and RTC.PERH register pair represents the 16-bit value, RTC.PER. The low byte [7:0]
(suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset +
0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
Due to synchronization between the RTC clock and system clock domains, there is a latency of two RTC
clock cycles from updating the register until this has an effect. Application software needs to check that
the STATUS.PERBUSY flag is cleared before writing to this register.
Name: PER
Offset: 0x0A
Reset: 0xFF
Property:
Bit
15
14
13
12
11
10
9
8
PER[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
1
1
1
1
1
1
1
1
Bit
7
6
5
4
3
2
1
0
PER[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
1
1
1
1
1
1
1
Bits 15:8 – PER[15:8]: Period high byte
These bits hold the MSB of the 16-bit period register.
Bits 7:0 – PER[7:0]: Period low byte
These bits hold the LSB of the 16-bit period register.
23.11.10 Compare
The RTC.CMPL and RTC.CMPH register pair represents the 16-bit value, RTC.CMP. The low byte [7:0]
(suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset +
0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
Name: CMP
Offset: 0x0C
Reset: 0x00
Property:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
15
14
13
12
11
10
9
8
CMP[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
CMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
3
2
1
Bits 15:8 – CMP[15:8]: Compare high byte
These bits hold the MSB of the 16-bit compare register.
Bits 7:0 – CMP[7:0]: Compare low byte
These bits hold the LSB of the 16-bit compare register.
23.11.11 Periodic Interrupt Timer Control A
Name: PITCTRLA
Offset: 0x10
Reset: 0x00
Property:
Bit
7
6
5
4
PERIOD[3:0]
0
PITEN
Access
R
R/W
R/W
R/W
R/W
R
R
R/W
Reset
0
0
0
0
0
0
0
0
Bits 6:3 – PERIOD[3:0]: Period
Writing this bit field selects the number of RTC clock cycles between each interrupt.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC
0xD
0xE
0xF
Name
OFF
CYC4
CYC8
CYC16
CYC32
CYC64
CYC128
CYC256
CYC512
CYC1024
CYC2048
CYC4096
CYC8192
CYC16384
CYC32768
-
© 2017 Microchip Technology Inc.
Description
No interrupt
4 cycles
8 cycles
16 cycles
32 cycles
64 cycles
128 cycles
256 cycles
512 cycles
1024 cycles
2048 cycles
4096 cycles
8192 cycles
16384 cycles
32768 cycles
Reserved
Datasheet Preliminary
DS40001893B-page 251
8-bit AVR Microcontroller
Bit 0 – PITEN: Periodic Interrupt Timer Enable
Writing a '1' to this bit enables the Periodic Interrupt Timer.
23.11.12 Periodic Interrupt Timer Status
Name: PITSTATUS
Offset: 0x11
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
SYNCBUSY
Access
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
Bit 0 – SYNCBUSY: Synchronization Busy
This bit indicates whether the RTC is busy synchronizing RTC.PITCTRLA settings in the RTC clock
domain.
23.11.13 PIT Interrupt Control
Name: PITINTCTRL
Offset: 0x12
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
PI
Access
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
Bit 0 – PI: Periodic interrupt
Value
0
1
Description
The periodic interrupt is disabled
The periodic interrupt is enabled
23.11.14 PIT Interrupt Flag
Name: PITINTFLAGS
Offset: 0x13
Reset: 0x00
Property:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 252
8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
PI
Access
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
3
2
1
Bit 0 – PI: Periodic interrupt Flag
This flag is set when a periodic interrupt is issued.
Writing a '1' clears the flag.
23.11.15 Periodic Interrupt Timer Debug Control
Name: PITDBGCTRL
Offset: 0x15
Reset: 0x00
Property:
Bit
7
6
5
4
0
DBGRUN
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
Bit 0 – DBGRUN: Debug Run
Value
0
1
Description
The peripheral is halted in break debug mode and ignores events.
The peripheral will continue to run in break debug mode when the CPU is halted.
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
24.
USART - Universal Synchronous and Asynchronous Receiver and
Transmitter
24.1
Features
•
•
•
•
•
•
•
•
•
•
•
•
24.2
Full-duplex or one-wire half-duplex operation
Asynchronous or synchronous operation
– Synchronous clock rates up to 1/2 of the device clock frequency
– Asynchronous clock rates up to 1/8 of the device clock frequency
Supports serial frames with:
– 5, 6, 7, 8, or 9 data bits
– Optionally even and odd parity bits
– 1 or 2 stop bits
Fractional baud rate generator
– Can generate desired baud rate from any system clock frequency
– No need for external oscillator with certain frequencies
Built-in error detection and correction schemes
– Odd or even parity generation and parity check
– Data overrun and framing error detection
– Noise filtering includes false start bit detection and digital low-pass filter
Separate interrupts for
– Transmit complete
– Transmit Data Register empty
– Receive complete
Multiprocessor communication mode
– Addressing scheme to address a specific devices on a multi-device bus
– Enable unaddressed devices to automatically ignore all frames
Start Frame detection in UART mode
Master SPI mode
– Double buffered operation
– Configurable data order
– Operation up to 1/2 of the peripheral clock frequency
IRCOM module for IrDA compliant pulse modulation/demodulation
LIN slave support
– Auto-baud and Break character detection
RS-485 support
Overview
The Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) peripheral is a
fast and flexible serial communication module. The USART supports full-duplex communication,
asynchronous and synchronous operation and one-wire configurations. The USART can be set in SPI
master mode and used for SPI communication.
The USART uses three communication lines for data transfer:
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
•
•
•
RxD for receiving
TxD for transmitting
XCK for the transmission clock in synchronous operation
Communication is frame based, and the frame format can be customized to support a wide range of
standards. One frame can be directly followed by a new frame, or the communication line can return to
the idle (high) state. A serial frame consists of:
•
1 start bit
•
5, 6, 7, 8, or 9 data bits (MSB or LSB first)
•
Parity bit: Even, odd, or none
•
1 or 2 stop bits.
The USART is buffered in both directions, enabling continued data transmission without any delay
between frames. Separate interrupts for receive and transmit completion allow fully interrupt driven
communication. Frame error and buffer overflow are detected in hardware and indicated with separate
status flags. Even or odd parity generation and parity check can also be enabled.
The main functional blocks are the clock generator, the transmitter, and the receiver:
•
•
•
The clock generator includes a fractional baud rate generator that is able to generate a wide range
of USART baud rates from any system clock frequencies. This removes the need to use an
external crystal oscillator with a specific frequency to achieve a required baud rate. It also supports
external clock input in synchronous slave operation.
The transmitter consists of a single write buffer (DATA), a shift register and a parity generator. The
write buffer allows continuous data transmission without any delay between frames.
The receiver consists of a two-level receive buffer (DATA) and a Shift Register. Data and clock
recovery units ensure robust synchronization and noise filtering during asynchronous data
reception. It includes frame error, buffer overflow, and parity error detection.
When the USART is set in one-wire mode, the transmitter and the receiver share the same RxD I/O pin.
When the USART is set in master SPI mode, all USART-specific logic is disabled, leaving the transmit
and receive buffers, Shift registers, and baud rate generator enabled. Pin control and interrupt generation
are identical in both modes. The registers are used in both modes, but their functionality differs for some
control settings.
An IRCOM module can be enabled for one USART to support IrDA 1.4 physical compliant pulse
modulation and demodulation for baud rates up to 115.2kbps.
The USART can be linked to the Configurable Custom Logic unit (CCL). When used with the CCL, the
TxD/RxD data can be encoded/decoded before the signal is fed into the USART receiver or after the
signal is output from transmitter when the USART is connected to CCL LUT outputs.
Related Links
CCL – Configurable Custom Logic
24.2.1
Signal Description
Signal
Type
Description
RxD
Input/output
Receiving line
TxD
Output
Transmitting line
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 255
8-bit AVR Microcontroller
Signal
Type
Description
XCK
Input/output
Clock for synchronous operation
XDIR
Output
Transmit Enable for RS485
Related Links
I/O Multiplexing and Considerations
24.2.2
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 24-1. USART System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Debug Operation
Clocks
I/O Lines and Connections
Interrupts
Events
24.2.2.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
CLKCTRL - Clock Controller
24.2.2.2 I/O Lines and Connections
Using the I/O lines of the peripheral requires configuration of the I/O pins.
Related Links
PORT - I/O Pin Configuration
Multiplexed Signals
24.2.2.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
Related Links
CPUINT - CPU Interrupt Controller
SREG
Interrupts
24.2.2.4 Events
The events of this peripheral are connected to the Event System.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 256
8-bit AVR Microcontroller
Related Links
EVSYS - Event System
24.2.2.5 Debug Operation
When the CPU is halted in debug mode, this peripheral will continue normal operation. If the peripheral is
configured to require periodical service by the CPU through interrupts or similar, improper operation or
data loss may result during debugging. This peripheral can be forced to halt operation during debugging.
Related Links
UPDI - Unified Program and Debug Interface
24.2.2.6 Block Diagram
Figure 24-1. USART Block Diagram
Clock Generator
BAUD
OSC
Fractional Baud Rate
Generator
Synt Logic
Pin
Control
XCK
Transmitter
TXDATA
Parity
Generator
Transmit Shift Register
TX
Control
XDIR
Pin
Control
TxD
Receiver
Clock
Recovery
RX
Control
Receive Shift Register
Data
Recovery
Pin
Control
RXDATA Buffer
Parity
Checker
RxD
RXDATA
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
24.3
Functional Description
24.3.1
Initialization
For setting the USART in full-duplex mode, the following initialization sequence is recommended:
1.
2.
3.
4.
5.
Set the TxD pin value high, and optionally set the XCK pin low (OUT[n] in PORT.OUT).
Set the TxD and optionally the XCK pin as output (DIR[n] in PORT.DIR).
Set the baud rate (USART.BAUD) and frame format.
Set the mode of operation (enables XCK pin output in synchronous mode).
Enable the transmitter or the receiver, depending on the usage.
For interrupt-driven USART operation, global interrupts should be disabled during the initialization.
Before doing a re-initialization with a changed baud rate or frame format, be sure that there are no
ongoing transmissions while the registers are changed.
For setting the USART in one-wire mode, the following initialization sequence is recommended:
1.
2.
3.
4.
5.
6.
Set the TxD/RxD pin value high, and optionally set the XCK pin low.
Optionally, write the ODME bit in the USART.CTRLB register to '1' for Wired-AND functionality.
Set the TxD/RxD and optionally the XCK pin as output.
Select the baud rate and frame format.
Select the mode of operation (enables XCK pin output in synchronous mode).
Enable the transmitter or the receiver, depending on the usage.
For interrupt-driven USART operation, global interrupts should be disabled during the initialization.
Before doing a re-initialization with a changed baud rate or frame format, be sure that there are no
ongoing transmissions while the registers are changed.
24.3.2
Operation
24.3.2.1 Clock Generation
The clock used for baud rate generation and for shifting and sampling data bits is generated internally by
the fractional baud rate generator or externally from the transfer clock (XCK) pin. Five modes of clock
generation are supported: normal and double-speed asynchronous mode, master and slave synchronous
mode, and master SPI mode.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Figure 24-2. Clock Generation Logic Block Diagram
BAUD
RXMODE
BAUD Rate
Generator
fBAUD
/2
/4
/2
txclk
1
DDR_XCK
PORT_INV
XCK
Pin
0
1
CLK_PER
xcki
0
Sync
Register
Edge
Detector
CMODE[0]
0
1
xcko
1
0
DDR_XCK
rxclk
Internal Clock Generation - The Fractional Baud Rate Generator
The baud rate generator is used for internal clock generation for asynchronous modes, synchronous
master mode, and master SPI mode operation. The output frequency generated (fBAUD) is determined by
the Baud register value (BAUD in USART.BAUD) and the peripheral clock frequency (fCLK_PER). The
following table contains equations for calculating the baud rate (in bits per second) and for calculating the
BAUD value for each mode of operation. It also shows the maximum baud rate versus peripheral clock
frequency. For asynchronous operation, the BAUD register value is 16 bits. The 10 MSBs (BAUD[15:6])
hold the integer part, while the 6 LSBs (BAUD[5:0]) hold the fractional part. In synchronous mode, only
the integer part of the BAUD register determine the baud rate.
Table 24-2. Equations for Calculating Baud Rate Register Setting
Operating Mode Conditions
Asynchronous
Synchronous
����� ≤
����� ≤
Baud Rate (Bits Per Seconds) USART.BAUD Register Value
Calculation
����_���
64 × ����_���
����� =
�
� × ����
����_���
����_���
����� =
2
2 × ���� 15: 6
���� =
64 × ����_���
� × �����
���� 15: 6 =
����_���
2 × �����
S is the number of samples per bit. In Asynchronous operating mode (CMODE[0]=0), it could be set as
16 (NORMAL mode) or 8 (CLK2X mode) by RXMODE in USART.CTRLB. For Synchronous operating
mode (CMODE[0]=1), S equals 2.
External Clock
External clock (XCK) is used in synchronous slave mode operation. The XCK clock input is sampled on
the peripheral clock frequency, and the maximum XCK clock frequency (fXCK) is limited by the following:
����<
����_���
4
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
For each high and low period, XCK clock cycles must be sampled twice by the peripheral clock. If the
XCK clock has jitter, or if the high/low period duty cycle is not 50/50, the maximum XCK clock speed must
be reduced accordingly.
Double Speed Operation
Double speed operation allows for higher baud rates under asynchronous operation with lower peripheral
clock frequencies. This operation mode is enabled by writing the RXMODE bit in the Control B register
(USART.CTRLB) to CLK2X.
When enabled, the baud rate for a given asynchronous baud rate setting shown in Table 24-2 will be
doubled. In this mode, the receiver will use half the number of samples (reduced from 16 to 8) for data
sampling and clock recovery. This requires a more accurate baud rate setting and peripheral clock. See
Asynchronous Data Reception for more details.
Synchronous Clock Operation
When synchronous mode is used, the XCK pin controls whether the transmission clock is input (slave
mode) or output (master mode). The corresponding port pin must be set to output for master mode or to
input for slave mode (PORT.DIR[n]). The normal port operation of the XCK pin will be overridden. The
dependency between the clock edges and data sampling or data change is the same. Data input (on
RxD) is sampled at the XCK clock edge which is opposite the edge where data output (TxD) is changed.
Figure 24-3. Synchronous Mode XCK Timing
INVEN = 1
XCK
RxD / TxD
Sample
INVEN = 0
XCK
RxD / TxD
Sample
The I/O pin can be inverted by writing a '1' to the Inverted I/O Enable bit (INVEN) in the Pin n Control
register of the Port peripheral (PORT.PINnCTRL). Using the inverted I/O setting for the corresponding
XCK port pin, the XCK clock edges used for data sampling and data change can be selected. If inverted
I/O is disabled (INVEN=0), data will be changed at the rising XCK clock edge and sampled at the falling
XCK clock edge. If inverted I/O is enabled (INVEN=1), data will be changed at the falling XCK clock edge
and sampled at the rising XCK clock edge.
Master SPI Mode Clock Generation
For master SPI mode operation, only internal clock generation is supported. This is identical to the
USART synchronous master mode, and the baud rate or BAUD setting is calculated using the same
equations (see Table 24-2).
There are four combinations of the SPI clock (SCK) phase and polarity with respect to the serial data, and
these are determined by the Clock Phase bit (UCPHA) in the Control C register (USART.CTRLC) and the
Inverted I/O Enable bit (INVEN) in the Pin n Control register of the Port peripheral (PORT.PINnCTRL).
The data transfer timing diagrams are shown in Figure 24-4.
Data bits are shifted out and latched in on opposite edges of the XCK signal, ensuring sufficient time for
data signals to stabilize. The settings are summarized in the following Table. Changing the setting of any
of these bits during transmission will corrupt both the receiver and transmitter.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
DS40001893B-page 260
8-bit AVR Microcontroller
Table 24-3. Functionality of INVEN in PORT.PINnCTRL and UCPHA in USART.CTRLC
SPI mode
INVEN
UCPHA
Leading edge
Trailing edge
0
0
0
Rising, sample
Falling, setup
1
0
1
Rising, setup
Falling, sample
2
1
0
Falling, sample
Rising, setup
3
1
1
Falling, setup
Rising, sample
The leading edge is the first clock edge of a clock cycle. The trailing edge is the last clock edge of a clock
cycle.
Figure 24-4. UCPHA and INVEN Data Transfer Timing Diagrams
UCPHA=0
UCPHA=1
INVEN=0
INVEN=1
SPI Mode 1
SPI Mode 3
XCK
Data setup (TXD)
Data sample (RXD)
XCK
Data setup (TXD)
Data sample (RXD)
SPI Mode 0
SPI Mode 2
XCK
Data setup (TXD)
Data sample (RXD)
XCK
Data setup (TXD)
Data sample (RXD)
Related Links
CTRLC
24.3.2.2 Frame Formats
Data transfer is frame based, where a serial frame consists of one character of data bits with
synchronization bits (start and stop bits) and an optional parity bit for error checking. This does not apply
to master SPI operation (See SPI Frame Formats). The USART accepts all combinations of the following
as valid frame formats:
•
•
•
•
1 start bit
5, 6, 7, 8 or 9 data bits
no, even, or odd parity bit
1 or 2 stop bits
Figure 24-5 illustrates the possible combinations of frame formats. Bits inside brackets are optional.
Figure 24-5. Frame Formats
St Start bit, always low.
(n) Data bits (0 to 8).
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
P Parity bit, may be odd or even.
Sp Stop bit, always high.
IDLE No transfer on the communication line (RxD or TxD). The IDLE state is always high.
Parity
Even or odd parity can be selected for error checking by writing the Parity Mode bits (PMODE) in the
Control C register (USART.CTRLC). If even parity is selected, the parity bit is set to '1' if the number of
logical one data bits is odd (making the total number of logical ones even). If odd parity is selected, the
parity bit is set to '1' if the number of logical one data bits is even (making the total number of ones odd).
When enabled, the parity checker calculates the parity of the data bits in incoming frames and compares
the result with the parity bit of the corresponding frame. If a parity error is detected, the parity error flag is
set.
SPI Frame Formats
The serial frame in SPI mode is defined to be one character of eight data bits. The USART in master SPI
mode has two valid frame formats:
•
•
8-bit data, msb first
8-bit data, lsb first
The data order is selected by writing to the Data Order bit (UDORD) in the Control C register
(USART.CTRLC).
After a complete frame is transmitted, a new frame can directly follow it, or the communication line can
return to the idle (high) state.
24.3.2.3 Data Transmission - USART Transmitter
When the transmitter has been enabled, the normal Port operation of the TxD pin is overridden by the
USART and given the function as the transmitter's serial output. The direction of the pin n must be
configured as output by writing the Direction register for the corresponding port (PORT_DIR.DIR[n]). If the
USART is configured for one-wire operation, the USART will automatically override the RxD/TxD pin to
output, when the transmitter is enabled.
Related Links
PORTMUX - Port Multiplexer
PORT - I/O Pin Configuration
Sending Frames
A data transmission is initiated by loading the Transmit buffer (DATA in USART.TXDATA) with the data to
be sent. The data in the transmit buffer are moved to the Shift Register when the Shift Register is empty
and ready to send a new frame. The Shift Register is loaded if it is in idle state (no ongoing transmission)
or immediately after the last stop bit of the previous frame is transmitted. When the Shift Register is
loaded with data, it will transfer one complete frame.
When the entire frame in the Shift Register has been shifted out and there are no new data present in the
transmit buffer, the Transmit Complete Interrupt Flag (TXCIF in USART.STATUS) is set and the optional
interrupt is generated.
TXDATA can only be written when the Data Register Empty Flag (DREIF in USART.STATUS) is set,
indicating that the register is empty and ready for new data.
When using frames with fewer than eight bits, the most-significant bits written to TXDATA are ignored. If
9-bit characters are used, DATA[8] in USART.TXDATAH has to be written before DATA[7:0] in
USART.TXDATAL.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Disabling the Transmitter
A disabling of the transmitter will not become effective until ongoing and pending transmissions are
completed; i.e., when the Transmit Shift Register and Transmit Buffer Register do not contain data to be
transmitted. When the transmitter is disabled, it will no longer override the TxDn pin, and the pin direction
is set as input automatically by hardware, even if it was configured as output by the user.
24.3.2.4 Data Reception - USART Receiver
When the receiver is enabled, the RxD pin functions as the receiver's serial input. The direction of the pin
n must be set as input in the Direction register of the Port (PORT_DIR.DIR[n]=0), which is the default pin
setting.
Receiving Frames
The receiver starts data reception when it detects a valid start bit. Each bit that follows the start bit will be
sampled at the baud rate or XCK clock, and shifted into the Receive Shift Register until the first stop bit of
a frame is received. A second stop bit will be ignored by the receiver. When the first stop bit is received
and a complete serial frame is present in the Receive Shift Register, the contents of the Shift Register will
be moved into the receive buffer. The receive complete interrupt flag (RXCIF in USART.STATUS) is set,
and the optional interrupt is generated.
The receiver buffer can be read by reading RXDATA, comprising of DATA[7:0] in USART.RXDATAL, and
DATA[8] in USART.RXDATAH. RXDATA should not be read unless the Receive Complete Interrupt Flag
(RXCIF in USART.STATUS) is set. When using frames with fewer than eight bits, the unused mostsignificant bits are read as zero. If 9-bit characters are used, the ninth bit (DATA[8] in USART.RXDATAH)
must be read before the low byte (DATA[7.0] in USART.RXDATAL).
Receiver Error Flags
The USART receiver has three error flags in the Receiver Data Register High Byte register
(USART.RXDATAH):
•
Frame Error (FERR)
•
Buffer overflow (BUFOVF)
•
Parity error (PERR)
The error flags are located in the receive FIFO buffer together with their corresponding frame. Due to the
buffering of the error flags, the USART.RXDATAH must be read before the USART.RXDATAL, since
reading the USART.RXDATAL changes the FIFO buffer.
Parity Checker
When enabled, the parity checker calculates the parity of the data bits in incoming frames and compares
the result with the parity bit of the corresponding frame. If a parity error is detected, the Parity Error flag
(PERR in USART.RXDATAH) is set.
If USART LIN mode is enabled (by writing RXMODE to '1' in USART.CTRLB), a parity check is only
performed on the protected identifier field. An parity error is detected if one of the equations below is not
true which sets PERR in USART.RXDATAH.
�0 = ��0 ⊕ ��1 ⊕ ��2 ⊕ ��4
�1 = ¬ ��1 ⊕ ��3 ⊕ ��4 ⊕ ��5
Figure 24-6. Protected identifier field and mapping of identifier and parity bits
St
© 2017 Microchip Technology Inc.
Protected identifier field
ID0 ID1 ID2 ID3 ID4 ID5 P0
Datasheet Preliminary
P1
Sp
DS40001893B-page 263
8-bit AVR Microcontroller
Disabling the Receiver
A disabling of the receiver will be immediate. The receiver buffer will be flushed, and data from ongoing
receptions will be lost.
Flushing the Receive Buffer
If the receive buffer has to be flushed during normal operation, read the DATA location
(USART.RXDATAH and USART.RXDATAL registers) until the Receive Complete Interrupt Flag (RXCIF in
USART.RXDATAH) is cleared.
Asynchronous Data Reception
The USART includes a clock recovery and a data recovery unit for handling asynchronous data reception.
The clock recovery unit is used for synchronizing the incoming asynchronous serial frames at the RxD pin
to the internally generated baud rate clock. It samples and low-pass filters each incoming bit, thereby
improving the noise immunity of the receiver. The asynchronous reception operational range depends on
the accuracy of the internal baud rate clock, the rate of the incoming frames, and the frame size in
number of bits.
Asynchronous Clock Recovery
The clock recovery unit synchronizes the internal clock to the incoming serial frames. Figure 24-7
illustrates the sampling process for the start bit of an incoming frame. The sample rate is 16 times the
baud rate for normal mode, and eight times the baud rate for double speed mode. The horizontal arrows
illustrate the synchronization variation due to the sampling process. The larger time variation when using
the double speed mode of operation. Samples denoted as zero are samples done when the RxD line is
idle; i.e., when there is no communication activity.
Figure 24-7. Start Bit Sampling
RxD
IDLE
START
BIT 0
Sample
(RXMODE = 0x0)
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
2
3
Sample
(RXMODE = 0x1)
0
1
2
3
4
5
6
7
8
1
2
When the clock recovery logic detects a high (idle) to low (start) transition on the RxD line, the start bit
detection sequence is initiated. Sample 1 denotes the first zero-sample, as shown in the figure. The clock
recovery logic then uses samples 8, 9, and 10 for normal mode and samples 4, 5, and 6 for double speed
mode to decide if a valid start bit is received. If two or three samples have a low level, the start bit is
accepted. The clock recovery unit is synchronized, and the data recovery can begin. If two or three
samples have a high level, the start bit is rejected as a noise spike, and the receiver looks for the next
high-to-low transition. The process is repeated for each start bit.
Asynchronous Data Recovery
The data recovery unit uses sixteen samples in normal mode and eight samples in double speed mode
for each bit. The following Figure shows the sampling process of data and parity bits.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Figure 24-8. Sampling of Data and Parity Bits
RxD
BIT n
Sample
(CLK2X = 0)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
Sample
(CLK2X = 1)
1
2
3
4
5
6
7
8
1
As for start bit detection, an identical majority voting technique is used on the three center samples for
deciding of the logic level of the received bit. The process is repeated for each bit until a complete frame
is received. It includes the first stop bit, but excludes additional ones. If the sampled stop bit is a '0' value,
the Frame Error (FERR in USART.RXDATAH) flag will be set. The next Figure shows the sampling of the
stop bit in relation to the earliest possible beginning of the next frame's start bit.
Figure 24-9. Stop Bit and Next Start Bit Sampling
RxD
STOP 1
(A)
(B)
(C)
Sample
(CLK2X = 0)
1
2
3
4
5
6
7
8
9
10
0/1
0/1
0/1
Sample
(CLK2X = 1)
1
2
3
4
5
6
0/1
A new high-to-low transition indicating the start bit of a new frame can come right after the last of the bits
used for majority voting. For normal speed mode, the first low level sample can be at the point marked (A)
in Stop Bit Sampling and Next Start Bit Sampling. For double speed mode, the first low level must be
delayed to point (B). Point (C) marks a stop bit of full length at nominal baud rate. The early start bit
detection influences the operational range of the receiver.
Asynchronous Operational Range
The operational range of the receiver is dependent on the mismatch between the received bit rate and
the internally generated baud rate. If an external transmitter is sending using bit rates that are too fast or
too slow, or if the internally generated baud rate of the receiver does not match the external source’s base
frequency, the receiver will not be able to synchronize the frames to the start bit.
The following equations can be used to calculate the ratio of the incoming data rate and internal receiver
baud rate.
����� =
16 � + 1
16 � + 1 + 6
����� =
D Sum of character size and parity size (D = 5 to 10 bit).
16 � + 2
16 � + 1 + 8
Rslow Is the ratio of the slowest incoming data rate that can be accepted in relation to the receiver baud
rate.
Rfast Is the ratio of the fastest incoming data rate that can be accepted in relation to the receiver baud
rate.
The following tables list the maximum receiver baud rate error that can be tolerated. Normal Speed mode
has higher toleration of baud rate variations.
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8-bit AVR Microcontroller
Table 24-4. Recommended Maximum Receiver Baud Rate Error for Normal Speed Mode (CLK2X =
0)
D #(Data + Parity bit) Rslow [%] Rfast [%] Maximum total error [%] Receiver max. receiver error
[%]
5
93.20
106.67
+6.67/-6.80
±3.0
6
94.12
105.79
+5.79/-5.88
±2.5
7
94.81
105.11
+5.11/-5.19
±2.0
8
95.36
104.58
+4.58/-4.54
±2.0
9
95.81
104.14
+4.14/-4.19
±1.5
10
96.17
103.78
+3.78/-3.83
±1.5
Table 24-5. Recommended Maximum Receiver Baud Rate Error for Double Speed Mode (CLK2X =
1)
D #(Data + Parity bit) Rslow [%] Rfast [%] Maximum total error [%] Receiver max. receiver error
[%]
5
94.12
105.66
+5.66/-5.88
±2.5
6
94.92
104.92
+4.92/-5.08
±2.0
7
95.52
104.35
+4.35/-4.48
±1.5
8
96.00
103.90
+3.90/-4.00
±1.5
9
96.39
103.53
+3.53/-3.61
±1.5
10
96.70
103.23
+3.23/-3.30
±1.0
The recommendations of the maximum receiver baud rate error were made under the assumption that
the receiver and transmitter equally divide the maximum total error.
24.3.2.5 USART in Master SPI mode
Using the USART in master SPI mode requires the transmitter to be enabled. The receiver can optionally
be enabled to serve as the serial input. The XCK pin will be used as the transfer clock.
As for the USART, a data transfer is initiated by writing to the DATA Register. This is the case for both
sending and receiving data, since the transmitter controls the transfer clock. The data written to DATA are
moved from the transmit buffer to the Shift Register when the Shift Register is ready to send a new frame.
The transmitter and receiver interrupt flags and corresponding USART interrupts used in master SPI
mode are identical in function to their use in normal USART operation. The receiver error status flags are
not in use and are always read as zero.
Disabling of the USART transmitter or receiver in master SPI mode is identical to their disabling in normal
USART operation.
Related Links
CTRLC
USART SPI vs. SPI
The USART in master SPI mode is fully compatible with the standalone SPI module in that:
•
Timing diagrams are the same
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8-bit AVR Microcontroller
•
•
UCPHA bit functionality is identical to that of the SPI CPHA bit
UDORD bit functionality is identical to that of the SPI DORD bit
When the USART is set in master SPI mode, configuration and use are in some cases different from
those of the standalone SPI module. In addition, the following difference exists:
•
The USART in master SPI mode does not include the SPI (Write Collision) feature
The USART in master SPI mode does not include the SPI double speed mode feature, but this can be
achieved by configuring the baud rate generator accordingly:
•
•
Interrupt timing is not compatible
Pin control differs due to the master-only operation of the USART in SPI master mode
A comparison of the USART in master SPI mode and the SPI pins is shown in Table 24-6.
Table 24-6. Comparison of USART in master SPI mode and SPI pins.
USART
SPI
Comment
TxD
MOSI
Master out only
RxD
MISO
Master in only
XCK
SCK
Functionally identical
-
SS
Not supported by USART in master SPI mode
Related Links
CTRLC
24.3.2.6 RS485 Mode of Operation
The RS485 feature enables the support of external components to comply with the RS-485 standard.
Either an external line driver is supported as shown in the figure below (RS485=0x1 in USART.CTRLA),
or control of the transmitter driving the TxD pin is provided (RS485=0x2).
While operating in RS485 mode, the Transmit Enable pin (TE) is driven high when the transmitter is
active.
Figure 24-10. RS485 Bus Connection
USART
RXD
TXD
Differential
Bus
TE
The TE pin goes high one baud clock cycle in advance of data being shifted out, to allow some guard
time to enable the external line driver. The TE pin will remain high for the complete frame including stop
bit(s).
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
Figure 24-11. TE Drive Timing
Guard
Time Start
Data
Stop
TxD
TE
Related Links
Signal Description
24.3.2.7 Start Frame Detection
The start frame detection is supported in UART mode only. The UART start frame detector is limited to
Standby sleep mode only and can wake up the system when a start bit is detected.
When a high-to-low transition is detected on RxDn, the oscillator is powered up and the UART clock is
enabled. After start-up, the rest of the data frame can be received, provided that the baud rate is slow
enough in relation to the oscillator start-up time. Start-up time of the oscillators varies with supply voltage
and temperature. For details on oscillator start-up time characteristics, refer to the Electrical
Characteristics.
If a false start bit is detected and if the system has not been waken-up by another source, the clock will
automatically be turned off and the UART waits for the next transition.
The UART start frame detection works in asynchronous mode only. It is enabled by writing the Start
Frame Detection bit (SFDEN) in CTRLB. If the start bit is detected while the device is in Standby sleep
mode, the UART Start Interrupt Flag (RXSIF) bit is set.
In Active, Idle and Power Down sleep modes, the asynchronous detection is automatically disabled.
The UART receive complete flag and UART start interrupt flag share the same interrupt line, but each has
its dedicated interrupt settings. The Table 21-5 shows the USART start frame detection modes,
depending of interrupt setting.
Table 24-7. USART Start Frame Detection Modes
SFDEN RXSIF interrupt RXCIF interrupt Comment
0
x
x
Standard mode
1
Disabled
Disabled
Only the oscillator is powered during the frame reception.
If the interrupts are disabled and buffer overflow is
ignored, all incoming frames will be lost
1 (1)
Disabled
Enabled
System/all clocks waked-up on Receive Complete
interrupt
1 (1)
Enabled
x
System/all clocks waked-up on UART Start Detection
Note:
1. The SLEEP instruction will not shut down the oscillator if there is ongoing communication.
24.3.2.8 Break Character Detection and Auto-baud
When USART receive mode is set to LINAUTO mode (RXMODE in USART.CTRLB), it follows the LIN
format. All LIN Frames start with a Break Field followed by a Sync Field. The USART uses a break
detection threshold of greater than 11 nominal bit times at the configured baud rate. At any time, if more
than 11 consecutive dominant bits are detected on the bus, the USART detects a Break Field. When a
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Break Field has been detected, the USART expects the Sync Field character to be 0x55. This field is
used to update the actual baud rate in order to stay synchronized. If the received Sync character is not
0x55, then the Inconsistent Sync Field error flag (ISFIF in USART.STATUS) is set and the baud rate is
unchanged.
Figure 24-12. LIN Break and Sync Fields
Break Field
Sync Field
Tbit
8 Tbit
After a break field is detected and the start bit of the Sync Field is detected, a counter is started. The
counter is then incremented for the next 8 Tbit of the Sync Field. At the end of these 8 bit times, the
counter is stopped. At this moment, the 10 most significant bits of the counter (value divided by 64) gives
the new clock divider and the 6 least significant bits of this value (the remainder) gives the new fractional
part. When the Sync Field has been received and all bits found valid, the clock divider and the fractional
part are updated in the Baud Rate Generator register (USART.BAUD). After the Break and Sync Fields, n
characters of data can be received.
When the USART receive mode is set to GENAUTO mode, a generic auto-baud mode is enabled. In this
mode there no check of Sync character to equal 0x55. After detection of a Break Field the USART
expects the next character to be a Sync field, counting 8 low and high bit times. If the measured Sync
field result in a valid BAUD value (0x0064-0xffff), the BAUD register is updated. Setting the Wait for Break
bit (WFB in USART.STATUS) before receiving the next Break character, the next negative plus positive
edge of RxD line is detected as a Break. This makes it possible to set an arbitrary new Baud Rate without
knowing the current Baud Rate.
24.3.2.9 One-wire Mode
In this mode the TxD pin is connected to the RxD pin internally. If the receiver is enabled when
transmitting it will receive what the transmitter is sending. This can be used to check that no one else is
trying to transmit since received data will not be the same as the transmitted data.
24.3.2.10 Multiprocessor Communication Mode
The multiprocessor communication mode (MCPM) effectively reduces the number of incoming frames
that have to be handled by the receiver in a system with multiple microcontrollers communicating via the
same serial bus. This mode is enabled by writing a '1' to the MCPM bit in the Control B register
(USART.CTRLB). In this mode, a dedicated bit in the frames is used to indicate whether the frame is an
address or data frame type.
If the receiver is set up to receive frames that contain five to eight data bits, the first stop bit is used to
indicate the frame type. If the receiver is set up for frames with nine data bits, the ninth bit is used to
indicate frame type. When the frame type bit is one, the frame contains an address. When the frame type
bit is zero, the frame is a data frame. If 5-bit to 8-bit character frames are used, the transmitter must be
set to use two stop bits, since the first stop bit is used for indicating the frame type.
If a particular slave MCU has been addressed, it will receive the following data frames as usual, while the
other slave MCUs will ignore the frames until another address frame is received.
Using Multiprocessor Communication Mode
The following procedure should be used to exchange data in multiprocessor communication mode
(MPCM):
1.
2.
All slave MCUs are in multiprocessor communication mode.
The master MCU sends an address frame, and all slaves receive and read this frame.
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
3.
4.
5.
Each slave MCU determines if it has been selected.
The addressed MCU will disable MPCM and receive all data frames. The other slave MCUs will
ignore the data frames.
When the addressed MCU has received the last data frame, it must enable MPCM again and wait
for a new address frame from the master.
The process then repeats from step 2.
Using any of the 5- to 8-bit character frame formats is impractical, as the receiver must change between
using n and n+1 character frame formats. This makes full-duplex operation difficult, since the transmitter
and receiver must use the same character size setting.
24.3.2.11 IRCOM Mode of Operation
The IRCOM mode enables IrDA 1.4 compliant modulation and demodulation for baud rates up to
115.2kbps. When IRCOM mode is enabled, double speed mode cannot be used for the USART.
Overview
The device contains one infrared communication module (IRCOM) that is IrDA compatible for baud rates
up to 115.2kbps.
The IRCOM is automatically enabled when the USART is set in IRCOM mode (by writing 0x2 to
CTRLC.CMODE). The signals between the USART and the RX/TX pins are then routed through the
module. The data on the TX/RX pins are the inverted value of the transmitted/received infrared pulse. It is
also possible to select an event channel from the event system as input for the IRCOM receiver. This will
disable the RX input from the USART pin.
For transmission, three pulse modulation schemes are available:
•
•
•
3/16 of the baud rate period
Fixed programmable pulse time based on the peripheral clock frequency
Pulse modulation disabled
For reception, a fixed programmable minimum high-level pulse width for the pulse to be decoded as a
logical '0' is used. Shorter pulses will then be discarded, and the bit will be decoded to logical '1' as if no
pulse was received.
Block Diagram
Figure 24-13. Block Diagram
IRCOM
Event System
Events
Encoded RXD
Pulse
Decoding
Decoded RXD
USART
TXD
Decoded RXD
Pulse
Encoding
© 2017 Microchip Technology Inc.
RXD
Encoded RXD
Datasheet Preliminary
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8-bit AVR Microcontroller
IRCOM and Event System
The event system can be used as the receiver input. This enables the IRCOM or USART input from the
I/O pins or sources other than the corresponding RX pin. If event system input is enabled, input from the
USART's RX pin is automatically disabled.
Related Links
EVSYS - Event System
24.3.3
Events
The USART can accept the following input Events:
•
IREI - IrDA Event Input
The Event is enabled by writing a '1' to the IrDA Event Input bit (IREI) in the Event Control register
(USART.EVCTRL).
Related Links
EVSYS - Event System
EVCTRL
24.3.4
Interrupts
Table 24-8. Available Interrupt Vectors and Sources
Offset Name Vector Description
Conditions
0x00
RXC
Receive Complete
interrupt
•
•
•
There are unread data in the receive buffer (RXCIE)
Receive of Start-of-Frame detected (RXSIE)
Auto-Baud Error/ISFIF flag set (ABEIE)
0x02
DRE
Data Register Empty
interrupt
The transmit buffer is empty/ready to receive new data
(DREIE).
0x04
TXC
Transmit Complete
interrupt
The entire frame in the Transmit Shift Register has been
shifted out and there are no new data in the transmit buffer
(TXCIE).
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Status register
(USART.STATUS).
An interrupt source is enabled or disabled by writing to the corresponding bit in the Control A register
(USART.CTRLA).
An interrupt request is generated when the corresponding interrupt source is enabled and the Interrupt
Flag is set. The interrupt request remains active until the Interrupt Flag is cleared. See the
USART.STATUS register for details on how to clear Interrupt Flags.
Related Links
CPUINT - CPU Interrupt Controller
STATUS
CTRLA
24.3.5
Configuration Change Protection
Not applicable.
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Datasheet Preliminary
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8-bit AVR Microcontroller
24.4
Register Summary - USART
Offset
Name
Bit Pos.
0x00
RXDATAL
7:0
0x01
RXDATAH
7:0
0x02
TXDATAL
7:0
0x03
TXDATAH
7:0
0x04
STATUS
7:0
RXCIF
TXCIF
DREIF
RXSIF
ISFIF
0x05
CTRLA
7:0
RXCIE
TXCIE
DREIE
RXSIE
LBME
0x06
CTRLB
7:0
RXEN
TXEN
SFDEN
ODME
0x07
CTRLC
7:0
0x08
BAUD
0x09
DATA[7:0]
RXCIF
BUFOVF
FERR
CMODE[1:0]
PMODE[1:0]
15:8
BAUD[15:8]
0x0B
DBGCTRL
7:0
0x0C
EVCTRL
7:0
0x0D
TXPLCTRL
7:0
0x0E
RXPLCTRL
7:0
BDF
ABEIE
WFB
RS485[1:0]
RXMODE[1:0]
SBMODE
BAUD[7:0]
Reserved
DATA[8]
DATA[8]
7:0
0x0A
PERR
DATA[7:0]
MPCM
CHSIZE[2:0]
DBGRUN
IREI
TXPL[7:0]
RXPL[6:0]
24.5
Register Description
24.5.1
Receiver Data Register Low Byte
Reading the RXDATAL Register location will return the contents of the Receive Data Buffer Register
(RXB).
The receive buffer consists of a two level FIFO. The FIFO and the corresponding flags in the high byte of
RXDATA will change state whenever the receive buffer is accessed (read). If CHSIZE in USART.CTRLC
is set to 9BIT Low byte first, read USART.RXDATAL before USART.RXDATAH, otherwise always read
USART.RXDATAH before USART.RXDATAL in order to get the correct flags.
Name: RXDATAL
Offset: 0x00
Reset: 0x00
Property: R
Bit
7
6
5
4
3
2
1
0
DATA[7:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 7:0 – DATA[7:0]: Receiver Data Register
24.5.2
Receiver Data Register High Byte
Reading the RXDATAH Register location will return the contents of the ninth DATA bit plus status bits.
The receive buffer consists of a two level FIFO. The FIFO and the corresponding flags in the high byte of
USART.RXDATAH will change state whenever the receive buffer is accessed (read). If CHSIZE in
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
USART.CTRLC is set to 9BIT Low byte first, read USART.RXDATAL before USART.RXDATAH, otherwise
always read USART.RXDATAH before USART.RXDATAL in order to get the correct flags.
Name: RXDATAH
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
RXCIF
BUFOVF
FERR
PERR
DATA[8]
Access
R
R
R
R
R
Reset
0
0
0
0
0
Bit 7 – RXCIF: USART Receive Complete Interrupt Flag
This flag is set when there are unread data in the receive buffer and cleared when the receive buffer is
empty (i.e., does not contain any unread data). When the Receiver is disabled, the receive buffer will be
flushed and consequently the RXCIF will become zero.
Bit 6 – BUFOVF: Buffer Overflow
The BUFOVF flag indicates data loss due to a receiver buffer full condition. This flag is set if a Buffer
Overflow condition is detected. A Buffer Overflow occurs when the receive buffer is full (two characters), it
is a new character waiting in the Receive Shift Register, and a new start bit is detected. This flag is valid
until the receive buffer (USART.RXDATAL) is read.
This flag is not used in Master SPI mode of operation.
Bit 2 – FERR: Frame Error
The FERR flag indicates the state of the first stop bit of the next readable frame stored in the receive
buffer. The bit is set if the received character had a Frame Error, i.e. when the first stop bit was zero, and
cleared when the stop bit of the received data is '1'. This bit is valid until the receive buffer
(USART.RXDATAL) is read. The FERR is not affected by the SBMODE bit in USART.CTRLC since the
Receiver ignores all, except for the first stop bit.
This flag is not used in Master SPI mode of operation.
Bit 1 – PERR: Parity Error
If parity checking is enabled and the next character in the receive buffer has a Parity Error this flag is set.
If Parity Check is not enabled the PERR will always be read as zero. This bit is valid until the receive
buffer (USART.RXDATAL) is read. For details on parity calculation refer to Parity . If USART is set to
LINAUTO mode, this bit will be a Parity Check of the Protected identifier field and will be valid when
DATA[8] in USART.RXDATAH reads low.
This flag is not used in Master SPI mode of operation.
Bit 0 – DATA[8]: Receiver Data Register
When USART receiver is set to LINAUTO mode, this bit indicates if the received data is within the
response space of a LIN frame. If the received data is the Protected identifier field, this bit will be read as
zero. Otherwise the bit will be read as one. For receiver mode other than LINAUTO mode, DATA[8] holds
the ninth data bit in the received character when operating with serial frames with nine data bits.
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8-bit AVR Microcontroller
24.5.3
Transmit Data Register Low Byte
The Transmit Data Buffer Register (TXB) will be the destination for data written to the USART.TXDATAL
Register location.
For 5-, 6-, or 7-bit characters the upper unused bits will be ignored by the Transmitter and set to zero by
the Receiver.
The transmit buffer can only be written when the DREIF Flag in the USART.STATUS Register is set. Data
written to DATA when the DREIF Flag is not set, will be ignored by the USART Transmitter. When data is
written to the transmit buffer, and the Transmitter is enabled, the Transmitter will load the data into the
Transmit Shift Register when the Shift Register is empty. The data is then transmitted on the TxD pin.
Name: TXDATAL
Offset: 0x02
Reset: 0x00
Property: R/W
Bit
7
6
5
4
3
2
1
0
DATA[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DATA[7:0]: Transmit Data Register
24.5.4
Transmit Data Register High Byte
USART.TXDATAH holds the ninth data bit in the character to be transmitted when operating with serial
frames with nine data bits. When used this bit must be written before writing to USART.TXDATAL except if
CHSIZE in USART.CTRLC is set to 9BIT Low byte first where USART.TXDATAL should be written first.
This bit is unused in Master SPI mode of operation.
Name: TXDATAH
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DATA[8]
Access
W
Reset
0
Bit 0 – DATA[8]: Transmit Data Register
This bit is used when CHSIZE=9BIT in USART.CTRLC.
24.5.5
USART Status Register
Name: STATUS
Offset: 0x04
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
1
0
RXCIF
TXCIF
DREIF
RXSIF
ISFIF
2
BDF
WFB
Access
R
R/W
R
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
Bit 7 – RXCIF: USART Receive Complete Interrupt Flag
This flag is set to '1' when there are unread data in the receive buffer and cleared when the receive buffer
is empty (i.e., does not contain any unread data). When the Receiver is disabled, the receive buffer will
be flushed and consequently the RXCIF will become zero.
When interrupt-driven data reception is used, the receive complete interrupt routine must read the
received data from RXDATA in order to clear the RXCIF. If not, a new interrupt will occur directly after the
return from the current interrupt.
Bit 6 – TXCIF: USART Transmit Complete Interrupt Flag
This flag is set when the entire frame in the Transmit Shift Register has been shifted out and there are no
new data in the transmit buffer (TXDATA).
This flag is automatically cleared when the transmit complete interrupt vector is executed. The flag can
also be cleared by writing a '1' to its bit location.
Bit 5 – DREIF: USART Data Register Empty Flag
The DREIF indicates if the transmit buffer (TXDATA) is ready to receive new data. The flag is set to '1'
when the transmit buffer is empty, and is '0' when the transmit buffer contains data to be transmitted that
has not yet been moved into the Shift Register. DREIF is set after a reset to indicate that the Transmitter
is ready. Always write this bit to '0' when writing the STATUS register.
DREIF is cleared to '0' by writing TXDATAL. When interrupt-driven data transmission is used, the Data
Register Empty interrupt routine must either write new data to TXDATA in order to clear DREIF or disable
the Data Register Empty interrupt. If not, a new interrupt will occur directly after the return from the
current interrupt.
Bit 4 – RXSIF: USART Receive Start Interrupt Flag
The RXSIF flag indicates a valid start condition on RxD line. The flag is set when the system is in standby
modes and a high (IDLE) to low (START) valid transition is detected on the RxD line. If the start detection
is not enabled, the RXSIF will always be read as zero. This flag can only be cleared by writing a '1' to its
bit location. This flag is not used in master SPI mode operation.
Bit 3 – ISFIF: Inconsistent Sync Field Interrupt Flag
This bit is set when the auto-baud is enabled and the sync field bit time are too fast or too slow to give a
valid baud setting. It will also be set when USART is set to LINAUTO mode and the SYNC character differ
from data value 0x55.
Writing a '1' to this bit will clear the flag and bring the USART back to idle state.
Bit 1 – BDF: Break Detected Flag
This bit is intended for USART configured to LINAUTO receive mode, see CTRLB. The break detector
has a fixed threshold of 11 bits low for a BREAK to be detected. The BDF bit is set after a valid BREAK
and SYNC character is detected. The bit is automatically cleared when next data is received. The bit will
behave identically when USART is set to GENAUTO mode. In NORMAL or CLK2X receive mode, the
BDF bit is unused.
This bit is cleared by writing a '1' to it.
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8-bit AVR Microcontroller
Bit 0 – WFB: Wait For Break
Writing this bit to '1' will register the next low and high transition on RxD line as a break character. This
can be used to wait for a BREAK character of arbitrary width. Combined with USART set to GENAUTO
mode, this allow the user to set any BAUD rate trough BREAK and SYNC as long as it falls within valid
range of the USART.BAUD register. This bit will always read '0'.
24.5.6
Control A
Name: CTRLA
Offset: 0x05
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
RXCIE
TXCIE
DREIE
RXSIE
LBME
ABEIE
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Access
Reset
1
0
RS485[1:0]
Bit 7 – RXCIE: Receive Complete Interrupt Enable
The bit enables the Receive Complete Interrupt (interrupt vector RXC). The enabled interrupt will be
triggered when RXCIF in the USART.STATUS register is set.
Bit 6 – TXCIE: Transmit Complete Interrupt Enable
This bit enables the Transmit Complete Interrupt (interrupt vector TXC). The enabled interrupt will be
triggered when the TXCIF in the USART.STATUS register is set.
Bit 5 – DREIE: Data Register Empty Interrupt Enable
This bit enables the Data Register Empty Interrupt (interrupt vector DRE). The enabled interrupt will be
triggered when the DREIF in the USART.STATUS register is set.
Bit 4 – RXSIE: Receiver Start Frame Interrupt Enable
Writing a '1' to this bit enables the Start Frame Detector to generate an interrupt on interrupt vector RXC
when a start of frame condition is detected.
Bit 3 – LBME: Loop-back Mode Enable
Writing this bit to '1' enables an internal connection between TxD and RxD pin.
Bit 2 – ABEIE: Auto-baud Error Interrupt Enable
Writing this bit to '1' enables the auto-baud error interrupt on interrupt vector RXC. The enabled interrupt
will trigger for conditions where ISFIF flag is set.
Bits 1:0 – RS485[1:0]: RS485 Mode
These bits enable the RS485 and select the operation mode.
Value
0x0
0x1
0x2
0x3
Name Description
OFF Disabled.
EXT Enables RS485 mode with control of an external line driver through a dedicated
Transmit Enable (TE) pin.
INT
Enables RS485 mode with control of the internal USART transmitter.
Reserved.
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8-bit AVR Microcontroller
24.5.7
Control B
Name: CTRLB
Offset: 0x06
Reset: 0x00
Property:
Bit
Access
Reset
7
6
4
3
RXEN
TXEN
5
SFDEN
ODME
2
1
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
RXMODE[1:0]
0
MPCM
Bit 7 – RXEN: Receiver Enable
Writing this bit to '1' enables the USART Receiver. The Receiver will override normal port operation for
the RxD pin when enabled. Disabling the Receiver will flush the receive buffer invalidating the FERR,
BUFOVF, and PERR flags. In GENAUTO and LINAUTO mode, disabling the receiver will reset the autobaud detection logic.
Bit 6 – TXEN: Transmitter Enable
Writing this bit to '1' enables the USART Transmitter. The Transmitter will override normal port operation
for the TxD pin when enabled. Disabling the Transmitter (writing TXEN to zero) will not become effective
until ongoing and pending transmissions are completed, i.e., when the Transmit Shift Register and
Transmit Buffer Register do not contain data to be transmitted. When disabled, the Transmitter will no
longer override the TxD port.
Bit 4 – SFDEN: Start Frame Detection Enable
Writing this bit to '1' enables the USART Start Frame Detection mode. The start frame detector is able to
wake up the system from idle or standby sleep modes when a high (IDLE) to low (START) transition is
detected on the RxD line.
Bit 3 – ODME: Open Drain Mode Enable
Writing this bit to '1' will make the TxD pin to have open-drain functionality. A pull-up resistor is needed to
prevent the line from floating when a logic one is output to TxD pin.
Bits 2:1 – RXMODE[1:0]: Receiver Mode
In CLK2X mode, the divisor of the baud rate divider will be reduced from 16 to 8 effectively doubling the
transfer rate for asynchronous communication modes. For synchronous operation the CLK2X mode has
no effect and RXMODE should always be written to zero. RXMODE must be zero when the USART
Communication Mode is configured to IRCOM. Setting RXMODE to GENAUTO enables generic autobaud where the SYNC character is valid when eight low and high bits has been registered. In this mode
any SYNC character that gives a valid BAUD rate will be accepted. In LINAUTO mode the SYNC
character is constrained and found valid if each bits falls within 16 +/- 3 baud samples of the internal baud
rate and match data value 0x55. Both GENAUTO and LINAUTO mode is only supported for USART
operated in asynchronous slave mode.
Value
0x0
0x1
0x2
0x3
Name
NORMAL
CLK2X
GENAUTO
LINAUTO
© 2017 Microchip Technology Inc.
Description
Normal USART Mode, Standard Transmission Speed
Normal USART Mode, Double Transmission Speed
Generic Auto-baud Mode
LIN Constrained Auto-baud Mode
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8-bit AVR Microcontroller
Bit 0 – MPCM: Multi-Processor Communication Mode
Writing a '1' to this bit enables the Multi-Processor Communication mode: the USART Receiver ignores
all the incoming frames that do not contain address information. The Transmitter is unaffected by the
MPCM setting. For more detailed information see Multiprocessor Communication Mode.
24.5.8
Control C - Async Mode
This register description is valid for all modes except Master SPI mode. When the USART
Communication Mode bits (CMODE) in this register are written to 'MSPI', see Control C - Master SPI
Mode for the correct description.
Name: CTRLC
Offset: 0x07
Reset: 0x00
Property:
Bit
7
6
5
CMODE[1:0]
Access
Reset
4
PMODE[1:0]
3
2
SBMODE
1
0
CHSIZE[2:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
1
1
Bits 7:6 – CMODE[1:0]: USART Communication Mode
Writing these bits selects the communication mode of the USART.
Writing a 0x3 to these bits alters the available bit fields in this register, see Control C - Master SPI ModeMaster SPI Mode .
Value
0x0
0x1
0x2
0x3
Name
ASYNCHRONOUS
SYNCHRONOUS
IRCOM
MSPI
Description
Asynchronous USART
Synchronous USART
Infrared Communication
Master SPI
Bits 5:4 – PMODE[1:0]: Parity Mode
Writing these bits enables and selects the type of parity generation.
When enabled, the Transmitter will automatically generate and send the parity of the transmitted data bits
within each frame. The Receiver will generate a parity value for the incoming data, compare it to the
PMODE setting, and set the Parity Error flag (PERR) in the Status register (USART.STATUS) if a
mismatch is detected.
Value
0x0
0x1
0x2
0x3
Name
DISABLED
EVEN
ODD
Description
Disabled
Reserved
Enabled, Even Parity
Enabled, Odd Parity
Bit 3 – SBMODE: Stop Bit Mode
Writing this bit selects the number of stop bits to be inserted by the Transmitter.
The Receiver ignores this setting.
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8-bit AVR Microcontroller
Value
0
1
Description
1 stop bit
2 stop bits
Bits 2:0 – CHSIZE[2:0]: Character Size
Writing these bits select the number of data bits in a frame. The Receiver and Transmitter use the same
setting. For 9BIT character size, the order of which byte to read or write first, low or high byte of RXDATA
or TXDATA is selectable.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
24.5.9
Name
5BIT
6BIT
7BIT
8BIT
9BIT
9BIT
Description
5-bit
6-bit
7-bit
8-bit
Reserved
Reserved
9-bit (Low byte first)
9-bit (High byte first)
Control C - Master SPI Mode
This register description is only valid when the USART is in Master SPI mode (CMODE written to MSPI).
For other CMODE values, see Control C - Async Mode the correct description.
See USART in Master SPI mode for full description of the Master SPI Mode operation.
Name: CTRLC
Offset: 0x07
Reset: 0x00
Property:
Bit
7
6
5
4
3
CMODE[1:0]
Access
Reset
2
1
UDORD
UCPHA
R/W
R/W
R/W
R/W
0
0
0
0
0
Bits 7:6 – CMODE[1:0]: USART Communication Mode
Writing these bits selects the communication mode of the USART.
Writing a value different than 0x3 to these bits alters the available bit fields in this register, see Control C Async Mode.
Value
0x0
0x1
0x2
0x3
Name
ASYNCHRONOUS
SYNCHRONOUS
IRCOM
MSPI
Description
Asynchronous USART
Synchronous USART
Infrared Communication
Master SPI
Bit 2 – UDORD: Data Order
Writing this bit selects the frame format.
The Receiver and Transmitter use the same setting. Changing the setting of UDORD will corrupt all
ongoing communication for both receiver and transmitter.
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8-bit AVR Microcontroller
Value
0
1
Description
MSB of the data word is transmitted first
LSB of the data word is transmitted first
Bit 1 – UCPHA: Clock Phase
The UCPHA bit setting determine if data is sampled on the leading (first) edge or tailing (last) edge of
XCKn. Refer to the Master SPI Mode Clock Generation for details.
24.5.10 Baud Register
The USART.BAUDL and USART.BAUDH register pair represents the 16-bit value, USART.BAUD. The low
byte [7:0] (suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at
offset + 0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
Ongoing transmissions of the Transmitter and Receiver will be corrupted if the baud rate is changed.
Writing this register will trigger an immediate update of the baud rate prescaler. For more information of
how to set the baud rate, see Table 24-2
Name: BAUD
Offset: 0x08
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
BAUD[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
BAUD[7:0]
Access
Reset
Bits 15:8 – BAUD[15:8]: USART Baud Rate high byte
These bits hold the MSB of the 16-bit Baud register.
Bits 7:0 – BAUD[7:0]: USART Baud Rate low byte
These bits hold the LSB of the 16-bit Baud register.
24.5.11 Debug Control Register
Name: DBGCTRL
Offset: 0x0B
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN: Debug Run
Value
0
1
Description
The peripheral is halted in break debug mode and ignores events.
The peripheral will continue to run in break debug mode when the CPU is halted.
24.5.12 IrDA Control Register
Name: EVCTRL
Offset: 0x0C
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
IREI
Access
R/W
Reset
0
Bit 0 – IREI: IrDA Event Input Enable
This bit enables the event source for the IRCOM Receiver. If event input is selected for the IRCOM
Receiver, the input from the USART’s RX pin is automatically disabled.
24.5.13 IRCOM Transmitter Pulse Length Control Register
Name: TXPLCTRL
Offset: 0x0D
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
TXPL[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – TXPL[7:0]: Transmitter Pulse Length
The 8-bit value sets the pulse modulation scheme for the transmitter. Setting this register will only have
effect if IRCOM mode is selected by a USART. By leaving this register value to zero, 3/16 of baud rate
period pulse modulation is used. Setting this value from 1 to 254 will give a fixed pulse length coding. The
8-bit value sets the number of system clock periods for the pulse. The start of the pulse will be
synchronized with the rising edge of the baud rate clock. Setting the value to 255 (0xFF) will disable pulse
coding, letting the RX and TX signals pass through the IRCOM Module unaltered. This enables other
features through the IRCOM Module, such as half-duplex USART, Loop-back testing and USART RX
input from an Event Channel.
TXPL must be configured before USART transmitter is enabled (TXEN).
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24.5.14 IRCOM Receiver Pulse Length Control Register
Name: RXPLCTRL
Offset: 0x0E
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
RXPL[6:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
Bits 6:0 – RXPL[6:0]: Receiver Pulse Length
The 8-bit value sets the filter coefficient for the IRCOM transceiver. Setting this register will only have
effect if IRCOM mode is selected by a USART.
By leaving this register value to zero, filtering is disabled. Setting this value between 0x01 and 0xFF will
enable filtering, where x+1 equal samples are required for the pulse to be accepted.
RXPL must be configured before USART receiver is enabled (RXEN).
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8-bit AVR Microcontroller
25.
SPI - Serial Peripheral Interface
25.1
Features
•
•
•
•
•
•
•
•
25.2
Full-duplex, Three-wire Synchronous Data Transfer
Master or Slave Operation
LSB First or MSB First Data Transfer
Seven Programmable Bit Rates
End of Transmission Interrupt Flag
Write Collision Flag Protection
Wake-up from Idle Mode
Double Speed (CK/2) Master SPI Mode
Overview
The Serial Peripheral Interface (SPI) is a high-speed synchronous data transfer interface using three or
four pins. It allows fast communication between an AVR device and peripheral devices or between
several microcontrollers. The SPI supports full-duplex communication.
The SPI peripheral can be configured as either Master, controlling all data transactions by pulling a
Slave's Select (SS) signal low, or Slave, controlled by an SPI Master.
A device connected to the bus must act as a master or slave. The master initiates and controls all data
transactions. The interconnection between master and slave devices with SPI is shown in the block
diagram. The system consists of two shift registers and a master clock generator. The SPI master initiates
the communication cycle by pulling the slave select (SS) signal low for the desired slave. Master and
slave prepare the data to be sent in their respective shift registers, and the master generates the required
clock pulses on the SCK line to exchange data. Data is always shifted from master to slave on the master
output, slave input (MOSI) line, and from slave to master on the master input, slave output (MISO) line.
After each data packet, the master can synchronize the slave by pulling the SS line high.
In SPI slave mode, the control logic will sample the incoming signal on the SCK pin. To ensure correct
sampling of this clock signal, the minimum low and high periods must each be longer than two CPU clock
cycles.
This device provides one instance of the SPI peripheral, SPI0.
Related Links
Block Diagram
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Datasheet Preliminary
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8-bit AVR Microcontroller
25.2.1
Block Diagram
Figure 25-1. SPI Block Diagram
MASTER
SLAVE
Transmit Data Register
(DATA)
msb
Transmit Data Register
(DATA)
lsb
MISO
MISO
MOSI
MOSI
8-bit Shift Register
lsb
msb
8-bit Shift Register
SPI CLOCK
GENERATOR
SCK
SCK
SS
SS
Receive Buffer Register
Receive Buffer Register
Receive Data Register
(DATA)
Receive Data Register
(DATA)
25.2.2
Signal Description
Table 25-1. Signals in Master and Slave Mode
Signal
Description
Type
Master Mode
Slave Mode
MOSI
Master Out Slave In
User defined output
Input
MISO
Master In Slave Out
Input
User defined output
SCK
Slave clock (generated
by master)
User defined output
Input
SS
Slave select (generated
by master)
User defined output
Input
Related Links
I/O Multiplexing and Considerations
25.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 25-2. SPI System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
No
-
Debug
Yes
UPDI
Related Links
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
I/O Lines and Connections
Debug Operation
Interrupts
Clocks
25.2.3.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
CLKCTRL - Clock Controller
25.2.3.2 I/O Lines and Connections
The SPI signals (MOSI, MISO, SCK, SS) are either input or outputs, depending on whether the SPI is in
Master or Slave Mode, as described in the Signal Description.
Using the I/O lines requires configuration of the I/O pins.
Related Links
I/O Multiplexing and Considerations
PORT - I/O Pin Configuration
Signal Description
PORT - I/O Pin Configuration
Multiplexed Signals
25.2.3.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
Related Links
CPUINT - CPU Interrupt Controller
SREG
Interrupts
CPUINT - CPU Interrupt Controller
SREG
Interrupts
25.2.3.4 Events
Not applicable.
25.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in debugging
mode will halt normal operation of the peripheral.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
UPDI - Unified Program and Debug Interface
25.3
Functional Description
25.3.1
Initialization
Initialize the SPI to a basic functional state by following these steps:
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8-bit AVR Microcontroller
1.
2.
3.
4.
5.
6.
7.
8.
Configure the SS pin in the Port peripheral.
Select SPI Master / Slave operation by writing the Master/Slave Select bit (MASTER) in the Control
A register (SPI.CTRLA).
In Master mode, select the clock speed by writing the Prescaler bits (PRESC) and the Clock
Double bit (CLK2X) in SPI.CTRLA.
Optional: Select the data transfer mode by writing to the MODE bits in the Control B register
(SPI.CTRLB).
Optional: Write the Data Order bit (DORD) in SPI.CTRLA.
Optional: Setup buffer mode by writing BUFEN and BUFWR bits in the Control B register
(SPI.CTRLB).
Optional: To disable the multimaster support in Master mode, write '1' to the Slave Select Disable
bit (SSD) in SPI.CTRLB.
Enable the SPI by writing a '1' to the ENABLE bit in SPI.CTRLA.
Related Links
I/O Multiplexing and Considerations
PORT - I/O Pin Configuration
Signal Description
25.3.2
Operation
25.3.2.1 Master Mode Operation
In master mode, the SPI interface has no automatic control of the SS line. If the SS pin is used, it must be
configured as output and controlled by user software. If the bus consists of several SPI slaves and/or
masters, a SPI master can use general purpose I/O pins to control the SS line to each of the slaves on
the bus.
Writing a byte to the DATA register starts the SPI clock generator and the hardware shifts the eight bits
into the selected slave. After shifting one byte and when there is no pending data, the Data Register
Empty Interrupt flag (DREIF) in SPI.INTFLAGS is set, the SPI clock generator stops, and the Transfer
Complete interrupt flag (TXCIF) in SPI.INTFLAGS is set.
If there is pending data, the flag DREIF is cleared; the master will continue to shift out the next bytes.
After each byte is shifted out, the new data is copied to the shift register and the DREIF flag is set. Only
when a shift is completed and there is no more pending data, the TXCIF flag is set. An end-of-transfer
can also be signaled by pulling the SS line high. The last incoming byte will be kept in the shift register.
If the SS pin is not used it can be disabled by writing the Slave Select Disable bit (SSD) in the Control B
register (SPI.CTRLB). If not disabled and configured as input, the pin must be held high to ensure master
operation.
If the SS pin is set as input and is being driven low, the SPI peripheral will interpret this as another master
trying to take control of the bus. To avoid bus contention, the master will take the following action:
1.
2.
The master enters slave mode.
The Slave Select Interrupt Flag (SSIF) in SPI.INTFLAGS is set.
25.3.2.2 Slave Mode
In slave mode, the SPI peripheral will remain idle with the MISO line tri-stated as long as the SS pin is
driven high. In this state, software may update the contents of the DATA register, but the data will not be
shifted out by incoming clock pulses on the SCK pin until the SS pin is driven low. If SS is driven low, the
slave will start to shift out data on the first SCK clock pulse. When one byte has been completely shifted,
the SPI Interrupt flag (IF) in SPI.INTFLAGS is set. The slave may continue placing new data to be sent
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8-bit AVR Microcontroller
into the SPI.DATA register before reading the incoming data. The last incoming byte will be kept in the
register.
When SS is driven high, the SPI logic is halted, and the SPI slave will not receive any new data. Any
partially received packet in the shift register will be lost.
As the SS pin is used to signal the start and end of a transfer, it is useful for achieving packet/byte
synchronization, and keeping the slave bit counter synchronized with the master clock generator.
To avoid write collisions, the SPI peripheral can be configured in buffered mode by writing a '1' to the
Buffer Mode Enable bit (BUFEN) in the Control B register (SPI.CTRLB). Then, data is copied from the
Transmit Register to the Shift Register only when a receive has been completed. This means that, after
data is written to the Transmit Buffer, one SPI transfer must be completed before the data is copied into
the shift register.
25.3.2.3 Buffer Modes
There are three buffer modes:
•
Unbuffered mode:
The default mode is unbuffered in the transmit direction and single buffered in the receive direction.
This means that bytes to be transmitted cannot be written to the SPI.DATA register before the entire
shift cycle is completed. When receiving data, a received character must be read from the
SPI.DATA register before the next character has been completely shifted in. Otherwise, the first
byte will be lost.
•
Buffered mode with dummy transfer:
The SPI peripheral is single buffered in the transmit direction and double buffered in the receive
direction. A byte written to the transmit register will be copied to the shift register when a full
character has been received. When receiving data, a received character must be read from the
SPI.DATA register before the third character has been completely shifted in to avoid losing data.
•
Buffered mode without dummy transfer:
The SPI peripheral is single buffered in the transmit direction and double buffered in the receive
direction. A byte written to the transmit register will be copied to the shift register when the SPI is
enabled and SS is high.
25.3.2.4 Data Modes
There are four combinations of SCK phase and polarity with respect to serial data. The desired
combination is selected by writing to the MODE bits in the Control B register (SPI.CTRLB).
The SPI data transfer formats are shown below. Data bits are shifted out and latched in on opposite
edges of the SCK signal, ensuring sufficient time for data signals to stabilize.
The leading edge is the first clock edge of a clock cycle. The trailing edge is the last clock edge of a clock
cycle.
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8-bit AVR Microcontroller
Figure 25-2. SPI Data Transfer Modes
SPI Mode 0
Cycle #
4
3
SS
SCK
sampling
MISO
4
MOSI
4
SPI Mode 1
Cycle #
4
SS
SCK
sampling
MISO
4
MOSI
4
SPI Mode 2
Cycle #
4
SS
SCK
sampling
MISO
4
MOSI
4
SPI Mode 3
Cycle #
4
SS
SCK
sampling
MISO
MOSI
25.3.3
Interrupts
Table 25-3. Available Interrupt Vectors and Sources
Offset
Name
Vector Description
0x00
SPI
SPI interrupt
© 2017 Microchip Technology Inc.
Conditions
•
•
•
•
SSI: Slave Select Trigger Interrupt
DRE: Data Register Empty Interrupt
TXC: Transfer Complete Interrupt
RXC: Receive Complete Interrupt
Datasheet Preliminary
DS40001893B-page 288
8-bit AVR Microcontroller
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Interrupt Flags register
of the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the Interrupt
Flag is set. The interrupt request remains active until the Interrupt Flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear Interrupt Flags.
Related Links
SREG
CPUINT - CPU Interrupt Controller
25.3.4
Sleep Mode Operation
The SPI will continue working in Idle sleep mode. When entering any deeper sleep mode, an active
transaction will be stopped.
Related Links
SLPCTRL - Sleep Controller
25.3.5
Configuration Change Protection
Not applicable.
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8-bit AVR Microcontroller
25.4
Register Summary - SPI
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
BUFEN
BUFWR
0x02
INTCTRL
7:0
RXCIE
TXCIE
0x03
INTFLAGS
7:0
0x04
DATA
7:0
DORD
TXCIF/
RXCIF/IF
WRCOL
MASTER
CLK2X
PRESC[1:0]
DREIE
SSIE
IE
DREIF
SSIF
BUFOVF
SSD
ENABLE
MODE[1:0]
DATA[7:0]
25.5
Register Description
25.5.1
Control A
Name: CTRLA
Offset: 0x00 [ID-000004d0]
Reset: 0x00
Property:
Bit
7
Access
Reset
6
5
4
DORD
MASTER
CLK2X
3
2
1
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
PRESC[1:0]
0
ENABLE
Bit 6 – DORD: Data Order
Value
0
1
Description
The MSB of the data word is transmitted first.
The LSB of the data word is transmitted first.
Bit 5 – MASTER: Master/Slave Select
If SS is configured as input and driven low while this bit is '1', this bit is cleared, and the IF flag in
SPI.INTFLAGS is set. The user has to write MASTER=1 again to re-enable SPI Master mode.
This behavior is controlled by the Slave Select Disable bit (SSD) in SPI.CTRLB.
Value
0
1
Description
SPI Slave mode selected
SPI Master mode selected
Bit 4 – CLK2X: Clock Double
When this bit is written to '1' the SPI speed (SCK frequency, after internal prescaler) is doubled in Master
mode.
Value
0
1
Description
SPI speed (SCK frequency) is not doubled.
SPI speed (SCK frequency) is doubled in Master mode
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8-bit AVR Microcontroller
Bits 2:1 – PRESC[1:0]: Prescaler
This bit field controls the SPI clock rate configured in master mode. These bits have no effect in slave
mode. The relationship between SCK and the peripheral clock frequency (fCLK_PER) is shown below.
The output of the SPI prescaler can be doubled by writing the CLK2X bit to '1'.
Value
0x0
0x1
0x2
0x3
Name
DIV4
DIV16
DIV64
DIV128
Description
CLK_PER/4
CLK_PER/16
CLK_PER/64
CLK_PER/128
Bit 0 – ENABLE: SPI Enable
Value
0
1
25.5.2
Description
SPI is disabled.
SPI is enabled.
Control B
Name: CTRLB
Offset: 0x01 [ID-000004d0]
Reset: 0x00
Property:
Bit
Access
Reset
7
6
BUFEN
BUFWR
5
4
3
SSD
2
1
0
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
MODE[1:0]
Bit 7 – BUFEN: Buffer Mode Enable
Writing this bit to '1' enables Buffer Mode, meaning two buffers in receive direction, one buffer in transmit
direction, and separate interrupt flags for both transmit complete and receive complete.
Bit 6 – BUFWR: Buffer Mode Wait for Receive
When writing this bit to '0' the first data transferred will be a dummy sample.
Value
0
1
Description
One SPI transfer must be completed before the data is copied into the shift register.
When writing to the data register when the SPI is enabled and SS is high, the first write will
go directly to the shift register.
Bit 2 – SSD: Slave Select Disable
When this bit is set and when operating as SPI Master (MASTER=1 in SPI.CTRLA), SS does not disable
Master Mode.
Value
0
1
Description
Enable the Slave Select line when operating as SPI Master.
Disable the Slave Select line when operating as SPI Master.
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8-bit AVR Microcontroller
Bits 1:0 – MODE[1:0]: Mode
These bits select the transfer mode. The four combinations of SCK phase and polarity with respect to the
serial data are shown in the table below. These bits decide whether the first edge of a clock cycle (leading
edge) is rising or falling, and whether data setup and sample occur on the leading or trailing edge. When
the leading edge is rising, the SCK signal is low when idle, and when the leading edge is falling, the SCK
signal is high when idle.
Value
0x0
Name
0
0x1
1
0x2
2
0x3
3
Description
Leading edge: Rising, sample
Trailing edge: Falling, setup
Leading edge: Rising, setup
Trailing edge: Falling, sample
Leading edge: Falling, sample
Trailing edge: Rising, setup
Leading edge: Falling, setup
Trailing edge: Rising, sample
Related Links
Data Modes
25.5.3
Interrupt Control
Name: INTCTRL
Offset: 0x02 [ID-000004d0]
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
3
2
1
0
RXCIE
TXCIE
DREIE
SSIE
IE
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 7 – RXCIE: Receive Complete Interrupt Enable
In buffer mode this bit enables the receive complete interrupt. The enabled interrupt will be triggered
when the RXCIF flag in the INTFLAG register is set. In non-buffer mode this bit is zero.
Bit 6 – TXCIE: Transfer Complete Interrupt Enable
In buffer mode this bit enables the transfer complete interrupt. The enabled interrupt will be triggered
when the TXCIF flag in the INTFLAG register is set. In non-buffer mode this bit is zero.
Bit 5 – DREIE: Data Register Empty Interrupt Enable
In buffer mode this bit enables the data register empty interrupt. The enabled interrupt will be triggered
when the DREIF flag in the INTFLAG register is set. In non-buffer mode this bit is zero.
Bit 4 – SSIE: Slave Select Trigger Interrupt Enable
In buffer mode this bit enables the Slave Select interrupt. The enabled interrupt will be triggered when the
SSIF flag in the INTFLAG register is set. In non-buffer mode this bit is zero.
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8-bit AVR Microcontroller
Bit 0 – IE: Interrupt Enable
This bit enables the SPI interrupt when the SPI is not in buffer mode. The enabled interrupt will be
triggered when RXCIF/IF is set in the INTFLAG register.
25.5.4
Interrupt Flags
Name: INTFLAGS
Offset: 0x03 [ID-000004d0]
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
RXCIF/IF
TXCIF/WRCOL
DREIF
SSIF
3
2
1
BUFOVF
0
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 7 – RXCIF/IF: Receive Complete Interrupt Flag/Interrupt Flag
RXCIF: In buffer mode this flag is set when there is unread data in the receive buffer and cleared when
the receive buffer is empty (i.e., does not contain any unread data). In non-buffer mode this bit does not
have any effect.
When interrupt-driven data reception is used, the receive complete interrupt routine must read the
received data from DATA in order to clear RXCIF. If not, a new interrupt will occur directly after the return
from the current interrupt. This flag can also be cleared by writing a one to its bit location.
IF: This flag is set when a serial transfer is complete and one byte is completely shifted in/out of the DATA
register. If SS is configured as input and is driven low when the SPI is in master mode, this will also set
this flag. IF is cleared by hardware when executing the corresponding interrupt vector. Alternatively, the IF
flag can be cleared by first reading the SPI.INTFLAGS register when IF is set, and then accessing the
DATA register.
Bit 6 – TXCIF/WRCOL: Transfer Complete Interrupt Flag/Write Collision Flag
TXCIF: In buffer mode this flag is set when all the data in the transmit shift register has been shifted out
and there are no new data in the transmit buffer (DATA). The flag is cleared by writing a one to its bit
location. In non-buffer mode this bit does not have any effect.
WRCOL: The WRCOL flag is set if the DATA register is written to before a complete byte has been
shifted out. This flag is cleared by first reading the SPI.INTFLAGS register when WRCOL is set, and then
accessing the DATA register.
Bit 5 – DREIF: Data Register Empty Interrupt Flag
In buffer mode this flag indicates whether the transmit buffer (DATA) is ready to receive new data. The
flag is one when the transmit buffer is empty and zero when the transmit buffer contains data to be
transmitted that has not yet been moved into the shift register. DREIF is set to '0' after a reset to indicate
that the transmitter is ready. In non-buffer mode this bit is always zero.
DREIF is cleared by writing DATA. When interrupt-driven data transmission is used, the data register
empty interrupt routine must either write new data to DATA in order to clear DREIF or disable the data
register empty interrupt. If not, a new interrupt will occur directly after the return from the current interrupt.
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8-bit AVR Microcontroller
Bit 4 – SSIF: Slave Select Trigger Interrupt Flag
In buffer mode this flag indicates that the SPI has been in master mode and the SS line has been pulled
low externally so the SPI is now working in slave mode. The flag will only be set if the Slave Select
Disable bit (SSD) is not '1'. The flag is cleared by writing a one to its bit location. In non-buffer mode this
bit is always zero.
Bit 0 – BUFOVF: Buffer Overflow
This flash is only used in buffer mode. This flag indicates data loss due to a receiver buffer full condition.
This flag is set if a buffer overflow condition is detected. A buffer overflow occurs when the receive buffer
is full (two characters) and a third byte has been received in the shift register. If there is no transmit data
the buffer overflow will not be set before the start of a new serial transfer. This flag is valid until the
receive buffer (DATA) is read. Always write this bit location to zero when writing the SPI.INTFLAGS
register. In non-buffer mode this bit is always zero
25.5.5
Data
Name: DATA
Offset: 0x04 [ID-000004d0]
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
DATA[7:0]
Access
Reset
Bits 7:0 – DATA[7:0]: SPI Data
The DATA register is used for sending and receiving data. Writing to the register initiates the data
transmission, and the byte written to the register will be shifted out on the SPI output line.
Reading the register causes the first byte in the buffer FIFO to be read, and the following received bytes
will move forward in the FIFO.
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8-bit AVR Microcontroller
26.
TWI - Two Wire Interface
26.1
Features
•
Bidirectional, two-wire communication interface
– Philips I2C compatible
– System Management Bus (SMBus) compatible
•
Bus master and slave operation supported
– Slave operation
– Single bus master operation
– Bus master in multi-master bus environment
– Multi-master arbitration
Flexible slave address match functions
– 7-bit and general call address recognition in hardware
– 10-bit addressing supported
– Address mask register for dual address match or address range masking
– Optional software address recognition for unlimited number of addresses
Slave can operate in all sleep modes, including power-down
Slave address match can wake device from all sleep modes
Up to 1MHz bus frequency support
Slew-rate limited output drivers
Input filter for bus noise and spike suppression
Support arbitration between start/repeated start and data bit (SMBus)
Slave arbitration allows support for address resolve protocol (ARP) (SMBus)
Supports SMBus Layer 1 timeouts
Configurable timeout values
•
•
•
•
•
•
•
•
•
•
26.2
Overview
The Two-Wire Interface (TWI) peripheral is a bidirectional, two-wire communication interface. It is I2C and
System Management Bus (SMBus) compatible. The only external hardware needed to implement the bus
is one pull-up resistor on each bus line.
Any device connected to the bus must act as a master or a slave. The master initiates a data transaction
by addressing a slave on the bus and telling whether it wants to transmit or receive data. One bus can
have many slaves and one or several masters that can take control of the bus. An arbitration process
handles priority if more than one master tries to transmit data at the same time. Mechanisms for resolving
bus contention are inherent in the protocol.
The TWI peripheral supports master and slave functionality. The master and slave functionality are
separated from each other, and can be enabled and configured separately. The master module supports
multi-master bus operation and arbitration. It contains the baud rate generator. All 100kHz, 400kHz, and
1MHz bus frequencies are supported. Quick command and smart mode can be enabled to auto-trigger
operations and reduce software complexity.
The slave module implements 7-bit address match and general address call recognition in hardware. 10bit addressing is also supported. A dedicated address mask register can act as a second address match
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
register or as a register for address range masking. The slave continues to operate in all sleep modes,
including power-down mode. This enables the slave to wake up the device from all sleep modes on TWI
address match. It is possible to disable the address matching to let this be handled in software instead.
The TWI peripheral will detect START and STOP conditions, bus collisions, and bus errors. Arbitration
lost, errors, collision, and clock hold on the bus are also detected and indicated in separate status flags
available in both master and slave modes.
This device provides one instance of the TWI peripheral, TWI0.
26.2.1
Block Diagram
Figure 26-1. TWI Block Diagram
Master
BAUD
TxDATA
SCL
0
baud rate generator
Slave
TxDATA
SCL hold low
0
SCL hold low
shift register
shift register
SDA
0
0
RxDATA
26.2.2
ADDR/ADDRMASK
RxDATA
==
Signal Description
Signal
Description
Type
SCL
Serial clock line
Digital I/O
SDA
Serial data line
Digital I/O
Related Links
I/O Multiplexing and Considerations
26.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 26-1. TWI System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
No
-
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
I/O Lines and Connections
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
Interrupts
26.2.3.1 Clocks
This peripheral requires the system clock (CLK_PER). The relationship between CLK_PER and the TWI
bus clock (SCL) is explained in the TWI.MBAUD register.
Related Links
CLKCTRL - Clock Controller
MBAUD
26.2.3.2 I/O Lines and Connections
Using the I/O lines of the peripheral requires configuration of the I/O pins.
26.2.3.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
26.2.3.4 Events
Not applicable.
26.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in debugging
mode will halt normal operation of the peripheral.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
When the CPU is halted in debug mode and DBGRUN=1, that reading/writing the DATA register will
neither trigger a bus operation nor cause transmit and clear flags.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
UPDI - Unified Program and Debug Interface
26.3
Functional Description
26.3.1
Initialization
To start the TWI as Master, write a '1' to the ENABLE bit in the Master Control A register (TWI.MCTRLA),
followed by writing the slave address to the Master Address (TWI.MADDR) register. The TWI.MADDR
register also has a R/W bit which indicates whether the Master is transmitting or receiving. The Master
DATA register (TWI.MDATA) is written in case master is transmitting data.
To enable the TWI as Slave, write the Slave Address (ADDR) in TWI.SADDR, and write a '1' to the
ENABLE bit in the Slave Control A register (TWI.SCTRLA). The TWI peripheral will wait to receive a byte
addressed to it.
26.3.2
General TWI Bus Concepts
The TWI provides a simple, bidirectional, two-wire communication bus consisting of a serial clock line
(SCL) and a serial data line (SDA). The two lines are open-collector lines (wired-AND), and pull-up
resistors (Rp) are the only external components needed to drive the bus. The pull-up resistors provide a
high level on the lines when none of the connected devices are driving the bus.
The TWI bus is a simple and efficient method of interconnecting multiple devices on a serial bus. A device
connected to the bus can be a master or slave, where the master controls the bus and all communication.
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Figure 26-2 illustrates the TWI bus topology.
VCC
RP
RP
TWI
DEVICE #1
TWI
DEVICE #2
TWI
DEVICE #N
RS
RS
RS
RS
RS
RS
SDA
SCL
Note: RS is optional
Figure 26-2. TWI Bus Topology
An unique address is assigned to all slave devices connected to the bus, and the master will use this to
address a slave and initiate a data transaction.
Several masters can be connected to the same bus, called a multi-master environment. An arbitration
mechanism is provided for resolving bus ownership among masters, since only one master device may
own the bus at any given time.
A device can contain both master and slave logic, and can emulate multiple slave devices by responding
to more than one address.
A master indicates the start of a transaction by issuing a START condition (S) on the bus. An address
packet with a slave address (ADDRESS) and an indication whether the master wishes to read or write
data (R/W) are then sent. After all data packets (DATA) are transferred, the master issues a STOP
condition (P) on the bus to end the transaction. The receiver must acknowledge (A) or not-acknowledge
(A) each byte received.
Figure 26-3 shows a TWI transaction.
Figure 26-3. Basic TWI Transaction Diagram Topology for a 7-bit Address Bus
SDA
SCL
6 ... 0
S
ADDRESS
S
ADDRESS
7 ... 0
R/W
R/W
ACK
DATA
DATA
A
7 ... 0
ACK
A
DATA
P
ACK/NACK
A/A
DATA
P
Direction
Address Packet
Data Packet #0
Data Packet #1
Transaction
The master provides data on the bus
The master or slave can provide data on the bus
The slave provides data on the bus
The master provides the clock signal for the transaction, but a device connected to the bus is allowed to
stretch the low-level period of the clock to decrease the clock speed.
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26.3.2.1 START and STOP Conditions
Two unique bus conditions are used for marking the beginning (START) and end (STOP) of a transaction.
The master issues a START condition (S) by indicating a high-to-low transition on the SDA line while the
SCL line is kept high. The master completes the transaction by issuing a STOP condition (P), indicated by
a low-to-high transition on the SDA line while SCL line is kept high.
Figure 26-4. START and STOP Conditions
SDA
SCL
S
P
START
Condition
STOP
Condition
Multiple START conditions can be issued during a single transaction. A START condition that is not
directly following a STOP condition is called a repeated START condition (Sr).
26.3.2.2 Bit Transfer
As illustrated by Figure 26-5, a bit transferred on the SDA line must be stable for the entire high period of
the SCL line. Consequently the SDA value can only be changed during the low period of the clock. This is
ensured in hardware by the TWI module.
Figure 26-5. Data Validity
SDA
SCL
DATA
Valid
Change
Allowed
Combining bit transfers results in the formation of address and data packets. These packets consist of
eight data bits (one byte) with the most-significant bit transferred first, plus a single-bit not-acknowledge
(NACK) or acknowledge (ACK) response. The addressed device signals ACK by pulling the SCL line low
during the ninth clock cycle, and signals NACK by leaving the line SCL high.
26.3.2.3 Address Packet
After the START condition, a 7-bit address followed by a read/write (R/W) bit is sent. This is always
transmitted by the master. A slave recognizing its address will ACK the address by pulling the data line
low for the next SCL cycle, while all other slaves should keep the TWI lines released and wait for the next
START and address. The address, R/W bit, and acknowledge bit combined is the address packet. Only
one address packet for each START condition is allowed, also when 10-bit addressing is used.
The R/W bit specifies the direction of the transaction. If the R/W bit is low, it indicates a master write
transaction, and the master will transmit its data after the slave has acknowledged its address. If the R/W
bit is high, it indicates a master read transaction, and the slave will transmit its data after acknowledging
its address.
26.3.2.4 Data Packet
An address packet is followed by one or more data packets. All data packets are nine bits long, consisting
of one data byte and an acknowledge bit. The direction bit in the previous address packet determines the
direction in which the data are transferred.
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26.3.2.5 Transaction
A transaction is the complete transfer from a START to a STOP condition, including any repeated START
conditions in between. The TWI standard defines three fundamental transaction modes: Master write,
master read, and a combined transaction.
Figure 26-6 illustrates the master write transaction. The master initiates the transaction by issuing a
START condition (S) followed by an address packet with the direction bit set to zero (ADDRESS+W).
Figure 26-6. Master Write Transaction
Transaction
Data Packet
Address Packet
S
ADDRESS
W
A
DATA
A
DATA
A/A
P
N data packets
Assuming the slave acknowledges the address, the master can start transmitting data (DATA) and the
slave will ACK or NACK (A/A) each byte. If no data packets are to be transmitted, the master terminates
the transaction by issuing a STOP condition (P) directly after the address packet. There are no limitations
to the number of data packets that can be transferred. If the slave signals a NACK to the data, the master
must assume that the slave cannot receive any more data and terminate the transaction.
Figure 26-7 illustrates the master read transaction. The master initiates the transaction by issuing a
START condition followed by an address packet with the direction bit set to one (ADDRESS+R). The
addressed slave must acknowledge the address for the master to be allowed to continue the transaction.
Figure 26-7. Master Read Transaction
Transaction
Data Packet
Address Packet
S
ADDRESS
R
A
DATA
A
DATA
A
P
N data packets
Assuming the slave acknowledges the address, the master can start receiving data from the slave. There
are no limitations to the number of data packets that can be transferred. The slave transmits the data
while the master signals ACK or NACK after each data byte. The master terminates the transfer with a
NACK before issuing a STOP condition.
Figure 26-8 illustrates a combined transaction. A combined transaction consists of several read and write
transactions separated by repeated START conditions (Sr).
Figure 26-8. Combined Transaction
Transaction
Address Packet #1
S
ADDRESS
R/W
Address Packet #2
N Data Packets
A
DATA
A/A Sr
ADDRESS
R/W
M Data Packets
A
DATA
A/A
P
Direction
Direction
26.3.2.6 Clock and Clock Stretching
All devices connected to the bus are allowed to stretch the low period of the clock to slow down the
overall clock frequency or to insert wait states while processing data. A device that needs to stretch the
clock can do this by holding/forcing the SCL line low after it detects a low level on the line.
Three types of clock stretching can be defined, as shown in Figure 26-9.
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Figure 26-9. Clock Stretching (1)
SDA
bit 7
bit 6
bit 0
ACK/NACK
SCL
S
Wakeup clock
stretching
Periodic clock
stretching
Random clock
stretching
Note: Clock stretching is not supported by all I2C slaves and masters.
If a slave device is in sleep mode and a START condition is detected, the clock stretching normally works
during the wake-up period. For AVR devices, the clock stretching will be either directly before or after the
ACK/NACK bit, as AVR devices do not need to wake up for transactions that are not addressed to it.
A slave device can slow down the bus frequency by stretching the clock periodically on a bit level. This
allows the slave to run at a lower system clock frequency. However, the overall performance of the bus
will be reduced accordingly. Both the master and slave device can randomly stretch the clock on a byte
level basis before and after the ACK/NACK bit. This provides time to process incoming or prepare
outgoing data, or perform other time-critical tasks.
In the case where the slave is stretching the clock, the master will be forced into a wait state until the
slave is ready, and vice versa.
26.3.2.7 Arbitration
A master can start a bus transaction only if it has detected that the bus is idle. As the TWI bus is a multimaster bus, it is possible that two devices may initiate a transaction at the same time. This results in
multiple masters owning the bus simultaneously. This is solved using an arbitration scheme where the
master loses control of the bus if it is not able to transmit a high level on the SDA line. The masters who
lose arbitration must then wait until the bus becomes idle (i.e., wait for a STOP condition) before
attempting to reacquire bus ownership. Slave devices are not involved in the arbitration procedure.
Figure 26-10. TWI Arbitration
DEVICE1 Loses arbitration
DEVICE1_SDA
DEVICE2_SDA
SDA
(wired-AND)
bit 7
bit 6
bit 5
bit 4
SCL
S
Figure 26-10 shows an example where two TWI masters are contending for bus ownership. Both devices
are able to issue a START condition, but DEVICE1 loses arbitration when attempting to transmit a high
level (bit 5) while DEVICE2 is transmitting a low level.
Arbitration between a repeated START condition and a data bit, a STOP condition and a data bit, or a
repeated START condition and a STOP condition are not allowed and will require special handling by
software.
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26.3.2.8 Synchronization
A clock synchronization algorithm is necessary for solving situations where more than one master is
trying to control the SCL line at the same time. The algorithm is based on the same principles used for
the clock stretching previously described. Figure 26-11shows an example where two masters are
competing for control over the bus clock. The SCL line is the wired-AND result of the two masters clock
outputs.
Figure 26-11. Clock Synchronization
Low Period
Count
Wait
State
High Period
Count
DEVICE1_SCL
DEVICE2_SCL
SCL
(wired-AND)
A high-to-low transition on the SCL line will force the line low for all masters on the bus, and they will start
timing their low clock period. The timing length of the low clock period can vary among the masters.
When a master (DEVICE1 in this case) has completed its low period, it releases the SCL line. However,
the SCL line will not go high until all masters have released it. Consequently, the SCL line will be held low
by the device with the longest low period (DEVICE2). Devices with shorter low periods must insert a wait
state until the clock is released. All masters start their high period when the SCL line is released by all
devices and has gone high. The device which first completes its high period (DEVICE1) forces the clock
line low, and the procedure is then repeated. The result is that the device with the shortest clock period
determines the high period, while the low period of the clock is determined by the device with the longest
clock period.
26.3.3
TWI Bus State Logic
The bus state logic continuously monitors the activity on the TWI bus lines when the master is enabled. It
continues to operate in all sleep modes, including power-down.
The bus state logic includes START and STOP condition detectors, collision detection, inactive bus
timeout detection, and a bit counter. These are used to determine the bus state. Software can get the
current bus state by reading the bus state bits in the master status register. The bus state can be
unknown, idle, busy, or owner, and is determined according to the state diagram shown in Figure 26-12.
The values of the bus state bits according to state are shown in binary in the figure.
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RESET
UNKNOWN
(0b00)
P + Timeout
S
IDLE
BUSY
P + Timeout
(0b01)
Sr
(0b11)
Command P
Write ADDRESS
(S)
OWNER
Arbitration
Lost
(0b10)
Write
ADDRESS(Sr)
Figure 26-12. Bus State, State Diagram
After a system reset and/or TWI master enable, the bus state is unknown. The bus state machine can be
forced to enter idle by writing to the bus state bits accordingly. If no state is set by the application
software, the bus state will become idle when the first STOP condition is detected. If the master inactive
bus timeout is enabled, the bus state will change to idle on the occurrence of a timeout. After a known
bus state is established, only a system reset or disabling of the TWI master will set the state to unknown.
When the bus is idle, it is ready for a new transaction. If a START condition generated externally is
detected, the bus becomes busy until a STOP condition is detected. The STOP condition will change the
bus state to idle. If the master inactive bus timeout is enabled, the bus state will change from busy to idle
on the occurrence of a timeout.
If a START condition is generated internally while in idle state, the owner state is entered. If the complete
transaction was performed without interference, i.e., no collisions are detected, the master will issue a
STOP condition and the bus state will change back to idle. If a collision is detected, the arbitration is
assumed lost and the bus state becomes busy until a STOP condition is detected. A repeated START
condition will only change the bus state if arbitration is lost during the issuing of the repeated START.
Arbitration during repeated START can be lost only if the arbitration has been ongoing since the first
START condition. This happens if two masters send the exact same ADDRESS+DATA before one of the
masters issues a repeated START (Sr).
26.3.4
Operation
26.3.4.1 Electrical Characteristics
The TWI module in AVR devices follows the electrical specifications and timing of I2C bus and SMBus.
These specifications are not 100% compliant, and so to ensure correct behavior, the inactive bus timeout
period should be set in TWI master mode. Refer to TWI Master Operation for more details.
26.3.4.2 TWI Master Operation
The TWI master is byte-oriented, with an optional interrupt after each byte. There are separate interrupt
flags for master write and master read. Interrupt flags can also be used for polled operation. There are
dedicated status flags for indicating ACK/NACK received, bus error, arbitration lost, clock hold, and bus
state.
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When an interrupt flag is set, the SCL line is forced low. This will give the master time to respond or
handle any data, and will in most cases require software interaction. Figure 26-13 shows the TWI master
operation. The diamond shaped symbols (SW) indicate where software interaction is required. Clearing
the interrupt flags releases the SCL line.
Figure 26-13. TWI Master Operation
APPLICATION
MASTER WRITE INTERRUPT + HOLD
M1
M3
M2
BUSY
P
IDLE
S
Wait for
IDLE
SW
M4
ADDRESS
R/W BUSY
SW
R/W
A
SW
P
W
A
SW
Sr
M2
IDLE
M3
BUSY
M4
A/A
DATA
SW
SW
M1
BUSY
Driver software
MASTER READ INTERRUPT + HOLD
The master provides data
on the bus
SW
Slave provides data on
the bus
A
A/A
BUSY
P
Bus state
Mn
A/A Sr
Diagram connections
IDLE
M4
M2
M3
A/A
R
A
DATA
The number of interrupts generated is kept to a minimum by automatic handling of most conditions.
Clock Generation
The BAUD must be set to a value that results in a TWI bus clock frequency (fSCL) equal or less than
100kHz/400kHz/1MHz, dependent on the mode used by the application (Standard mode Sm/Fast mode
Fm/Fast mode plus Fm+).
The low (TLOW) and high (THIGH) times are determined by the Baud Rate register (BAUD), while the rise
(TRISE) and fall (TFALL) times are determined by the bus topology. Because of the wired-AND logic of the
bus, TFALL will be considered as part of TLOW. Likewise, TRISE will be in a state between TLOW and THIGH
until a high state has been detected.
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Figure 26-14. SCL Timing
RISE
•
•
•
•
•
•
•
•
TLOW – Low period of SCL clock
TSU;STO – Set-up time for stop condition
TBUF – Bus free time between stop and start conditions
THD;STA – Hold time (repeated) start condition
TSU;STA – Set-up time for repeated start condition
THIGH is timed using the SCL high time count from TWI.MBAUD
TRISE is determined by the bus impedance; for internal pull-ups. Refer to Electrical Characteristics.
TFALL is determined by the open-drain current limit and bus impedance; can typically be regarded
as zero. Refer to Electrical Characteristics for details.
The SCL frequency is given by:
�SCL =
1
�LOW + �HIGH + �RISE
�SCL =
�CLK_PER
10 + 2���� +�CLK_PER ⋅ �RISE
The TWI.MBAUD value is used to time both SCL high and SCL low which gives the following formula of
SCL frequency:
Transmitting Address Packets
After issuing a START condition, the master starts performing a bus transaction when the master address
register is written with the 7-bit slave address and direction bit. If the bus is busy, the TWI master will wait
until the bus becomes idle before issuing the START condition.
Depending on arbitration and the R/W direction bit, one of four distinct cases (M1 to M4) arises following
the address packet. The different cases must be handled in software.
Case M1: Arbitration Lost or Bus Error during Address Packet
If arbitration is lost during the sending of the address packet, the Master Write Interrupt Flag (WIF in
TWI.MSTATUS) and Arbitration Lost Flag (ARBLOST in TWI.MSTATUS) are both set. Serial data output
to the SDA line is disabled, and the SCL line is released. The master is no longer allowed to perform any
operation on the bus until the bus state has changed back to idle.
A bus error will behave in the same way as an arbitration lost condition, but the Bus Error Flag (BUSERR
in TWI.MSTATUS) is set in addition to the write interrupt and arbitration lost flags.
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Case M2: Address Packet Transmit Complete - Address not Acknowledged by Slave
If no slave device responds to the address, the Master Write Interrupt Flag (WIF in TWI.MSTATUS) and
the Master Received Acknowledge Flag (RXACK in TWI.MSTATUS) are set. The RXACK flag reflects the
physical state of the ACK bit, i.e. no slave did pull the ACK bit low. The clock hold is active at this point,
preventing further activity on the bus.
Case M3: Address Packet Transmit Complete - Direction Bit Cleared
If the master receives an ACK from the slave, the Master Write Interrupt Flag (WIF in TWI.MSTATUS) is
set and the Master Received Acknowledge Flag (RXACK in TWI_MSTATUS) is cleared. The clock hold is
active at this point, preventing further activity on the bus.
Case M4: Address Packet Transmit Complete - Direction Bit Set
If the master receives an ACK from the slave, the master proceeds to receive the next byte of data from
the slave. When the first data byte is received, the Master Read Interrupt Flag (RIF in TWI.MSTATUS) is
set and the Master Received Acknowledge Flag (RXACK in TWI.MSTATUS) is cleared. The clock hold is
active at this point, preventing further activity on the bus.
Transmitting Data Packets
The slave will know when an address packet with R/W direction bit set has been successfully received. It
can then start sending data by writing to the slave data register. When a data packet transmission is
completed, the data interrupt flag is set. If the master indicates NACK, the slave must stop transmitting
data and expect a STOP or repeated START condition.
Receiving Data Packets
The slave will know when an address packet with R/W direction bit cleared has been successfully
received. After acknowledging this, the slave must be ready to receive data. When a data packet is
received, the data interrupt flag is set and the slave must indicate ACK or NACK. After indicating a NACK,
the slave must expect a STOP or repeated START condition.
Quick Command Mode
With Quick Command enabled (QCEN in MCTRLA), the R/W# bit of the slave address denotes the
command. This is a SMBus specific command where the R/W# bit may be used to simply turn a device
function on or off, or enable/disable a low power standby mode. There is no data sent or received.
After the master receives an acknowledge from the slave, either RIF or WIF flag in MSTATUS will be set
depending on polarity of R/W#. When either RIF or WIF flag is set after issuing a Quick Command, the
TWI will accept a stop command through writing the CMD bits in MCTRLB.
Figure 26-15. Quick Command Frame Format
S
Address
R/W#
A
P
26.3.4.3 TWI Slave Operation
The TWI slave is byte-oriented with optional interrupts after each byte. There are separate slave data and
address/stop interrupt flags. Interrupt flags can also be used for polled operation. There are dedicated
status flags for indicating ACK/NACK received, clock hold, collision, bus error, and read/write direction.
When an interrupt flag is set, the SCL line is forced low. This will give the slave time to respond or handle
data, and will in most cases require software interaction. Figure 26-16. shows the TWI slave operation.
The diamond shapes symbols (SW) indicate where software interaction is required.
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Figure 26-16. TWI Slave Operation
SLAVE ADDRESS INTERRUPT
S1
S3
S2
S
A
ADDRESS
R
SW
P
S2
Sr
S3
DATA
SW
S1
P
S2
Sr
S3
A/A
Driversoftware
The master provides data
on the bus
Slave provides data on
the bus
Sn
S1
A
A
SW
SLAVE DATA INTERRUPT
W
SW
Interrupton STOP
ConditionEnabled
SW
A/A
DATA
SW
A/A
Diagramconnections
The number of interrupts generated is kept to a minimum by automatic handling of most conditions. Quick
command can be enabled to auto-trigger operations and reduce software complexity.
Address Recognition Mode can be enabled to allow the slave to respond to all received addresses.
Receiving Address Packets
When the TWI slave is properly configured, it will wait for a START condition to be detected. When this
happens, the successive address byte will be received and checked by the address match logic, and the
slave will ACK a correct address and store the address in the DATA register. If the received address is not
a match, the slave will not acknowledge and store address, and will wait for a new START condition.
The slave address/stop interrupt flag is set when a START condition succeeded by a valid address byte is
detected. A general call address will also set the interrupt flag.
A START condition immediately followed by a STOP condition is an illegal operation, and the bus error
flag is set.
The R/W direction flag reflects the direction bit received with the address. This can be read by software to
determine the type of operation currently in progress.
Depending on the R/W direction bit and bus condition, one of four distinct cases (S1 to S4) arises
following the address packet. The different cases must be handled in software.
Case S1: Address Packet Accepted - Direction Bit Set
If the R/W direction flag is set, this indicates a master read operation. The SCL line is forced low by the
slave, stretching the bus clock. If ACK is sent by the slave, the slave hardware will set the data interrupt
flag indicating data is needed for transmit. Data, repeated START, or STOP can be received after this. If
NACK is sent by the slave, the slave will wait for a new START condition and address match.
Case S2: Address Packet Accepted - Direction Bit Cleared
If the R/W direction flag is cleared, this indicates a master write operation. The SCL line is forced low,
stretching the bus clock. If ACK is sent by the slave, the slave will wait for data to be received. Data,
repeated START, or STOP can be received after this. If NACK is sent, the slave will wait for a new START
condition and address match.
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Case S3: Collision
If the slave is not able to send a high level or NACK, the collision flag is set, and it will disable the data
and acknowledge output from the slave logic. The clock hold is released. A START or repeated START
condition will be accepted.
Case S4: STOP Condition Received
When the STOP condition is received, the slave address/stop flag will be set, indicating that a STOP
condition, and not an address match, occurred.
Receiving Data Packets
The slave will know when an address packet with R/W direction bit cleared has been successfully
received. After acknowledging this, the slave must be ready to receive data. When a data packet is
received, the data interrupt flag is set and the slave must indicate ACK or NACK. After indicating a NACK,
the slave must expect a STOP or repeated START condition.
Transmitting Data Packets
The slave will know when an address packet with R/W direction bit set has been successfully received. It
can then start sending data by writing to the slave data register. When a data packet transmission is
completed, the data interrupt flag is set. If the master indicates NACK, the slave must stop transmitting
data and expect a STOP or repeated START condition.
26.3.4.4 Smart Mode
The TWI interface has a smart mode that simplifies application code and minimizes the user interaction
needed to adhere to the I2C protocol. For TWI Master, smart mode accomplishes this by automatically
sending an ACK as soon as data register TWI.MDATA is read. This feature is only active when the
ACKACT bit in TWI.MCTRLA register is set to ACK. If ACKACT is set to NACK, the TWI Master will not
generate a NACK bit followed by reading the data register.
With smart mode enabled for TWI Slave (SMEN bit in TWI.SCTRLA), DIF (Data Interrupt Flag) will
automatically be cleared if data register (TWI.SDATA) is read or written.
26.3.5
Events
Not applicable.
26.3.6
Interrupts
Table 26-2. Available Interrupt Vectors and Sources
Offset Name
Vector Description
0x00
Slave
TWI Slave interrupt
0x02
Master TWI Master interrupt
Conditions
•
•
DIF: Data Interrupt Flag in SSTATUS set
APIF: Address or Stop Interrupt Flag in SSTATUS set
•
•
RIF: Read Interrupt Flag in MSTATUS set
WIF: Write Interrupt Flag in MSTATUS set
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Master register
(TWI.MSTATUS) or Slave Status register (TWI.SSTATUS).
When several interrupt request conditions are supported by an interrupt vector, the interrupt requests are
ORed together into one combined interrupt request to the Interrupt Controller. The user must read the
peripheral's INTFLAGS register to determine which of the interrupt conditions are present.
Related Links
CPUINT - CPU Interrupt Controller
SREG
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26.3.7
Sleep Mode Operation
The bus state logic and Slave continue to operate in all sleep modes, including Power Down sleep mode.
If a Slave device is in sleep mode and a START condition is detected, clock stretching is active during the
wake-up period until the system clock is available. Master will stop operation in all sleep modes.
26.3.8
Synchronization
Not applicable.
26.3.9
Configuration Change Protection
Not applicable.
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26.4
Register Summary - TWI
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
SDASETUP
SDAHOLD[1:0]
FMPEN
QCEN
TIMEOUT[1:0]
SMEN
0x01
Reserved
0x02
DBGCTRL
7:0
0x03
MCTRLA
7:0
0x04
MCTRLB
7:0
0x05
MSTATUS
7:0
0x06
MBAUD
7:0
BAUD[7:0]
0x07
MADDR
7:0
ADDR[7:0]
0x08
MDATA
7:0
DATA[7:0]
0x09
SCTRLA
7:0
0x0A
SCTRLB
7:0
0x0B
SSTATUS
7:0
0x0C
SADDR
7:0
0x0D
SDATA
7:0
0x0E
SADDRMASK
7:0
DBGRUN
RIEN
WIEN
RIF
WIF
DIEN
CLKHOLD
APIEN
RXACK
FLUSH
ACKACT
CMD[1:0]
ARBLOST
BUSERR
BUSSTATE[1:0]
PIEN
PMEN
SMEN
ACKACT
DIF
APIF
CLKHOLD
RXACK
ENABLE
COLL
ENABLE
CMD[1:0]
BUSERR
DIR
AP
ADDR[7:0]
DATA[7:0]
ADDRMASK[6:0]
26.5
Register Description
26.5.1
Control A
ADDREN
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
7
6
5
4
SDASETUP
Access
3
2
SDAHOLD[1:0]
1
FMPEN
R/W
R/W
R/W
R/W
0
0
0
0
Reset
0
Bit 4 – SDASETUP: SDA Setup Time
By default, there are 4 clock cycles of setup time on SDA out signal while reading from slave part of the
TWI module. Writing this bit to '1' will change the setup time to 8 clocks.
Value
0
1
Name
4CYC
8CYC
Description
SDA setup time is 4 clock cycles
SDA setup time is 8 clock cycle
Bits 3:2 – SDAHOLD[1:0]: SDA Hold Time
Writing these bits selects the SDA hold time.
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Table 26-3. SDA Hold Time
SDAHOLD[1:0] Nominal Hold
Time
Hold Time Range across
All Corners (ns)
Description
0x0
OFF
0
Hold time off.
0x1
50ns
36 - 131
Backward compatible setting.
0x2
300ns
180 - 630
Meets SMBus specification under
typical conditions.
0x3
500ns
300 - 1050
Meets SMBus specification across
all corners.
Bit 1 – FMPEN: FM Plus Enable
Writing these bits selects the 1MHz bus speed (Fast mode plus, Fm+) for the TWI in default configuration.
Value
0
1
26.5.2
Description
Fm+ disabled
Fm+ enabled
Debug Control
Name: DBGCTRL
Offset: 0x02
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN: Debug Run
Value
0
1
26.5.3
Description
The peripheral is halted in break debug mode and ignores events.
The peripheral will continue to run in break debug mode when the CPU is halted.
Master Control A
Name: MCTRLA
Offset: 0x03
Reset: 0x00
Property:
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Bit
Access
Reset
7
6
RIEN
WIEN
5
QCEN
4
3
2
R/W
R/W
R/W
R/W
0
0
0
0
1
0
SMEN
ENABLE
R/W
R/W
R/W
0
0
0
TIMEOUT[1:0]
Bit 7 – RIEN: Read Interrupt Enable
Writing this bit to '1' enables interrupt on the Master Read Interrupt Flag (RIF) in the Master Status
register (TWI.MSTATUS). A TWI Master read interrupt would be generated only if this bit, the RIF, and the
Global Interrupt Flag (I) in CPU.SREG are all '1'.
Bit 6 – WIEN: Write Interrupt Enable
Writing this bit to '1' enables interrupt on the Master Write Interrupt Flag (WIF) in the Master Status
register (TWI.MSTATUS). A TWI Master write interrupt will be generated only if this bit, the WIF, and the
Global Interrupt Flag (I) in CPU.SREG are all '1'.
Bit 4 – QCEN: Quick Command Enable
Writing this bit to '1' enables Quick Command. When Quick Command is enabled, the corresponding
interrupt flag is set immediately after the slave acknowledges the address. At this point the software can
either issue a Stop command or a repeated Start by writing either the Command bits (CMD) in the Master
Control B register (TWI.MCTRLB) or the Master Address register (TWI.MADDR).
Bits 3:2 – TIMEOUT[1:0]: Inactive Bus Timeout
Value
0x0
0x1
0x2
0x3
Name
DISABLED
50US
100US
200US
Description
Bus timeout disabled. I2C.
50µs - SMBus (assume baud is set to 100kHz)
100µs (assume baud is set to 100kHz)
200µs (assume baud is set to 100kHz)
Bit 1 – SMEN: Smart Mode Enable
Writing this bit to '1' enables the Master smart mode. When smart mode is enabled, the acknowledge
action is sent immediately after reading the Master Data (TWI.MDATA) register.
Bit 0 – ENABLE: Enable TWI Master
Writing this bit to '1' enables the TWI as Master.
26.5.4
Master Control B
Name: MCTRLB
Offset: 0x04
Reset: 0x00
Property:
Bit
7
6
Access
Reset
5
4
3
2
FLUSH
ACKACT
1
0
R/W
R/W
R/W
R/W
0
0
0
0
CMD[1:0]
Bit 3 – FLUSH: Flush
Writing a '1' to this bit generates a strobe for one clock cycle disabling and then enabling the master.
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Writing '0' has no effect.
The purpose is to clear the internal state of master: For TWI master to transmit successfully, it is
recommended to write the Master Address register (TWI.MADDR) first and then the Master Data register
(TWI.MDATA).
The peripheral will transmit invalid data if TWI.MDATA is written before TWI.MADDR. To avoid this invalid
transmission, write '1' to this bit to clear both registers.
Bit 2 – ACKACT: Acknowledge Action
This bit defines the master’s behavior under certain conditions defined by the bus protocol state and
software interaction. The acknowledge action is performed when DATA is read, or when an execute
command is written to the CMD bits.
The ACKACT bit is not a flag or strobe, but an ordinary read/write accessible register bit. The default
ACKACT for master read interrupt is “Send ACK” (0). For master write, the code will know that no
acknowledge should be sent since it is itself sending data.
Value
0
1
Description
Send ACK
Send NACK
Bits 1:0 – CMD[1:0]: Command
The master command bits are strobes. These bits are always read as zero.
Writing to these bits triggers a master operation as defined by the table below.
Table 26-4. Command Settings
CMD[1:0] DIR Description
0x0
X
NOACT
0x1
X
REPSTART - Execute Acknowledge Action succeeded by repeated Start.
0x2
0
RECVTRANS - Execute Acknowledge Action succeeded by a byte read operation.
1
Execute Acknowledge Action (no action) succeeded by a byte send operation.(1)
X
STOP - Execute Acknowledge Action succeeded by issuing a STOP condition.
0x3
Note:
1. For a master being a sender, it will normally wait for new data written to the Master Data Register
(TWI.MDATA).
The acknowledge action bits and command bits can be written at the same time.
26.5.5
Master Status
Normal TWI operation dictates that this register is regarded purely as a read-only register. Clearing any of
the status flags is done indirectly by accessing the Master transmits address (TWI.MADDR), Master Data
register (TWI.MDATA), or the Command bits (CMD) in the Master Control B register (TWI.MCTRLB).
Name: MSTATUS
Offset: 0x05
Reset: 0x00
Property:
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Bit
Access
Reset
7
6
5
4
3
2
RIF
WIF
CLKHOLD
RXACK
ARBLOST
BUSERR
1
0
R/W
R/W
R/W
R
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
BUSSTATE[1:0]
Bit 7 – RIF: Read Interrupt Flag
This bit is set to '1' when the master byte read operation is successfully completed, i.e. no arbitration lost
or bus error occurred during the operation. The read operation is triggered by software reading DATA or
writing to ADDR registers with bit ADDR[0] written to '1'. A slave device must have responded with an
ACK to the address and direction byte transmitted by the master for this flag to be set.
Writing a '1' to this bit will clear the RIF. However, normal use of the TWI does not require the flag to be
cleared by this method.
Clearing the RIF bit will follow the same software interaction as the CLKHOLD flag.
The RIF flag can generate a master read interrupt (see description of the RIEN control bit in the
TWI.MCTRLA register).
Bit 6 – WIF: Write Interrupt Flag
This bit is set when a master transmit address or byte write is completed, regardless of the occurrence of
a bus error or an arbitration lost condition.
Writing a '1' to this bit will clear the WIF. However, normal use of the TWI does not require the flag to be
cleared by this method.
Clearing the WIF bit will follow the same software interaction as the CLKHOLD flag.
The WIF flag can generate a master write interrupt (see description of the WIEN control bit in the
TWI.MCTRLA register).
Bit 5 – CLKHOLD: Clock Hold
If read as '1', this bit indicates that the master is currently holding the TWI clock (SCL) low, stretching the
TWI clock period.
Writing a '1' to this bit will clear the CLKHOLD flag. However, normal use of the TWI does not require the
CLKHOLD flag to be cleared by this method, since the flag is automatically cleared when accessing
several other TWI registers. The CLKHOLD flag can be cleared by:
1.
2.
3.
4.
5.
Writing a '1' to it.
Writing to the TWI.MADDR register.
Writing to the TWI.MDATA register.
Reading the TWI.DATA register while the ACKACT control bits in TWI.MCTRLB are set to either
send ACK or NACK.
Writing a valid command to the TWI.MCTRLB register.
Bit 4 – RXACK: Received Acknowledge
This bit is read-only and contains to the most recently received acknowledge bit from slave.
Bit 3 – ARBLOST: Arbitration Lost
If read as '1' this bit indicates that the master has lost arbitration while transmitting a high data or NACK
bit, or while issuing a start or repeated start condition (S/Sr) on the bus.
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Writing a '1' to it will clear the ARBLOST flag. However, normal use of the TWI does not require the flag to
be cleared by this method. However, as for the CLKHOLD flag, clearing the ARBLOST flag is not required
during normal use of the TWI.
Clearing the ARBLOST bit will follow the same software interaction as the CLKHOLD flag.
Given the condition where the bus ownership is lost to another master, the software must either abort
operation or resend the data packet. Either way, the next required software interaction is in both cases to
write to the TWI.MADDR register. A write access to the TWI.MADDR register will then clear the
ARBLOST flag.
Bit 2 – BUSERR: Bus Error
The BUSERR flag indicates that an illegal bus condition has occurred. An illegal bus condition is detected
if a protocol violating start (S), repeated start (Sr), or stop (P) is detected on the TWI bus lines. A start
condition directly followed by a stop condition is one example of protocol violation.
Writing a '1' to this bit will clear the BUSERR. However, normal use of the TWI does not require the
BUSERR to be cleared by this method.
A robust TWI driver software design will treat the bus error flag similarly to the ARBLOST flag, assuming
the bus ownership is lost when the bus error flag is set. As for the ARBLOST flag, the next software
operation of writing the TWI.MADDR register will consequently clear the BUSERR flag. For bus error to
be detected, the bus state logic must be enabled and the system frequency must be 4x the SCL
frequency.
Bits 1:0 – BUSSTATE[1:0]: Bus State
These bits indicate the current TWI bus state as defined in the table below. After a System Reset or reenabling, the TWI master bus state will be unknown. The change of bus state is dependent on bus
activity.
Writing 0x1 to the BUSSTATE bits forces the bus state logic into its 'idle' state. However, the bus state
logic cannot be forced into any other state. When the master is disabled, the bus-state is 'unknown'.
Value
0x0
0x1
0x2
0x3
26.5.6
Name
UNKNOWN
IDLE
OWNER
BUSY
Description
Unknown bus state
Bus is idle
This TWI controls the bus
The bus is busy
Master Baud Rate
Name: MBAUD
Offset: 0x06
Reset: 0x00
Property:
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Bit
7
6
5
4
3
2
1
0
BAUD[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – BAUD[7:0]: Baud Rate
This bit field is used to derive the SCL high and low time and should be written while the master is
disabled (ENABLE bit in TWI.MCTRLA is '0').
For more information on how to calculate the frequency, see Clock Generation.
26.5.7
Master Address
Name: MADDR
Offset: 0x07
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
ADDR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – ADDR[7:0]: Address
When this bit field is written, a START condition and slave address protocol sequence is initiated
dependent on the bus state.
If the bus state is unknown the Master Write Interrupt Flag (WIF) and bus error flag (BUSERR) in the
Master Status register (TWI.MSTATUS) are set and the operation is terminated.
If the bus is busy the master awaits further operation until the bus becomes idle. When the bus is or
becomes idle, the master generates a START condition on the bus, copies the ADDR value into the data
shift register (TWI.MDATA) and performs a byte transmit operation by sending the contents of the data
register onto the bus. The master then receives the response i.e. the acknowledge bit from the slave.
After completing the operation the bus clock (SCL) is forced and held low only if arbitration was not lost.
The CLKHOLD bit in the Master Setup register (TWI.MSETUP) is set accordingly. Completing the
operation sets the WIF in the Master Status register (TWI.MSTATUS).
If the bus is already owned, a repeated start (Sr) sequence is performed. In two ways the repeated start
(Sr) sequence deviates from the start sequence. Firstly, since the bus is already owned by the master, no
wait for idle bus state is necessary. Secondly, if the previous transaction was a read, the acknowledge
action is sent before the repeated start bus condition is issued on the bus.
The master receives one data byte from the slave before the master sets the Master Read Interrupt Flag
(RIF) in the Master Status register (TWI.MSTATUS). All TWI Master flags are cleared automatically when
this bit field is written. This includes bus error, arbitration lost, and both master interrupt flags.
This register can be read at any time without interfering with ongoing bus activity, since a read access
does not trigger the master logic to perform any bus protocol related operations.
The master control logic uses bit 0 of the TWI.MADDR register as the bus protocol’s read/write flag
(R/W).
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26.5.8
Master DATA
Name: MDATA
Offset: 0x08
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DATA[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DATA[7:0]: Data
The bit field gives direct access to the masters physical shift register which is used both to shift data out
onto the bus (write) and to shift in data received from the bus (read).
The direct access implies that the data register cannot be accessed during byte transmissions. Build-in
logic prevents any write access to this register during the shift operations. Reading valid data or writing
data to be transmitted can only be successfully done when the bus clock (SCL) is held low by the master,
i.e. when the CLKHOLD bit in the Master Status register (TWI.MSTATUS) is set. However, it is not
necessary to check the CLKHOLD bit in software before accessing this register if the software keeps
track of the present protocol state by using interrupts or observing the interrupt flags.
Accessing this register assumes that the master clock hold is active, auto-triggers bus operations
dependent of the state of the acknowledge action command bit (ACKACT) in TWI.MSTATUS and type of
register access (read or write).
A write access to this register will, independent of ACKACT in TWI.MSTATUS, command the master to
perform a byte transmit operation on the bus directly followed by receiving the acknowledge bit from the
slave. When the acknowledge bit is received, the Master Write Interrupt Flag (WIF) in TWI.MSTATUS is
set regardless of any bus errors or arbitration. If operating in a multi-master environment, the interrupt
handler or application software must check the Arbitration Lost Status Flag (ARBLOST) in TWI.MSTATUS
before continuing from this point. If the arbitration was lost, the application software must decide to either
abort or to resend the packet by rewriting this register. The entire operation is performed (i.e. all bits are
clocked), regardless of winning or losing arbitration before the write interrupt flag is set. When arbitration
is lost, only '1's are transmitted for the remainder of the operation, followed by a write interrupt with
ARBLOST flag set.
Both TWI master interrupt flags are cleared automatically when this register is written. However, the
Master Arbitration Lost and Bus Error flags are left unchanged.
Reading this register triggers a bus operation, dependent on the setting of the acknowledge action
command bit (ACKACT) in TWI.MSTATUS. Normally the ACKACT bit is preset to either ACK or NACK
before the register read operation. If ACK or NACK action is selected, the transmission of the
acknowledge bit precedes the release of the clock hold. The clock is released for one byte, allowing the
slave to put one byte of data on the bus. The Master Read Interrupt flag RIF in TWI.MSTATUS is then set
if the procedure was successfully executed. However, if arbitration was lost when sending NACK, or a
bus error occurred during the time of operation, the Master Write Interrupt flag (WIF) is set instead.
Observe that the two master interrupt flags are mutual exclusive, i.e. both flags will not be set
simultaneously.
Both TWI master interrupt flags are cleared automatically if this register is read while ACKACT is set to
either ACK or NACK. However, arbitration lost and bus error flags are left unchanged.
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26.5.9
Slave Control A
Name: SCTRLA
Offset: 0x09
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
2
1
0
DIEN
APIEN
PIEN
4
3
PMEN
SMEN
ENABLE
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit 7 – DIEN: Data Interrupt Enable
Writing this bit to '1' enables interrupt on the Slave Data Interrupt Flag (DIF) in the Slave Status register
(TWI.SSTATUS). A TWI slave data interrupt will be generated only if this bit, the DIF, and the Global
Interrupt Flag (I) in CPU.SREG are all '1'.
Bit 6 – APIEN: Address or Stop Interrupt Enable
Writing this bit to '1' enables interrupt on the Slave Address or Stop Interrupt Flag (APIF) in the Slave
Status register (TWI.SSTATUS). A TWI slave address or stop interrupt will be generated only if the this
bit, APIF, PIEN in this register, and the Global Interrupt Flag (I) in CPU.SREG are all '1'.
The slave stop interrupt shares the interrupt vector with slave address interrupt. The AP bit determines
which caused the interrupt.
Bit 5 – PIEN: Stop Interrupt Enable
Writing this bit to '1' enables APIF to be set when a STOP condition occurs. To use this feature the
system frequency must be 4x the SCL frequency.
Bit 2 – PMEN: Address Recognition Mode
If this bit is written to '1', the slave address match logic responds to all received addresses.
If this bit is written to '0', the address match logic uses the slave address register (TWI.SADDR) to
determine which address to recognize as the slaves own address.
Bit 1 – SMEN: Smart Mode Enable
Writing this bit to '1' enables the slave smart mode. When smart mode is enabled, issuing a command
with CMD or reading/writing DATA resets the interrupt and operation continues. If smart mode is disabled,
the slave always waits for a CMD command before continuing.
Bit 0 – ENABLE: Enable TWI Slave
Writing this bit to '1' enables the TWI slave.
26.5.10 Slave Control B
Name: SCTRLB
Offset: 0x0A
Reset: 0x00
Property:
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Bit
7
6
5
4
3
2
1
ACKACT
Access
0
CMD[1:0]
R/W
R/W
R/W
0
0
0
Reset
Bit 2 – ACKACT: Acknowledge Action
This bit defines the slave’s behavior under certain conditions defined by the bus protocol state and
software interaction. The table below lists the acknowledge procedure performed by the slave if action is
initiated by software. The acknowledge action is performed when TWI.SDATA is read or written, or when
an execute command is written to the CMD bits in this register.
The ACKACT bit is not a flag or strobe, but an ordinary read/write accessible register bit.
Value
0
1
Name
ACK
NACK
Description
Send ACK
Send NACK
Bits 1:0 – CMD[1:0]: Command
Unlike the acknowledge action bits, the slave command bits are strobes. These bits always read as zero.
Writing to these bits trigger a slave operation as defined in the table below.
Table 26-5. Command Settings
CMD[1:0]
DIR Description
0x0 - NOACT
X
No action
0x1
X
Reserved
0x2 - COMPTRANS Used to complete a transaction.
0x3 - RESPONSE
0
Execute Acknowledge Action succeeded by waiting for any START (S/Sr)
condition.
1
Wait for any START (S/Sr) condition.
Used in response to an address interrupt (APIF).
0
Execute Acknowledge Action succeeded by reception of next byte.
1
Execute Acknowledge Action succeeded by slave data interrupt.
Used in response to a data interrupt (DIF).
0
Execute Acknowledge Action succeeded by reception of next byte.
1
Execute a byte read operation followed by Acknowledge Action.
The acknowledge action bits and command bits can be written at the same time.
26.5.11 Slave Status
Normal TWI operation dictates that the slave status register should be regarded purely as a read-only
register. Clearing any of the status flags will indirectly be done when accessing the slave data
(TWI.SDATA) register or the CMD bits in the Slave Control B register (TWI.SCTRLB).
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Name: SSTATUS
Offset: 0x0B
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
3
2
1
0
DIF
APIF
CLKHOLD
RXACK
COLL
BUSERR
DIR
AP
R/W
R/W
R
R
R/W
R/W
R
R
0
0
0
0
0
0
0
0
Bit 7 – DIF: Data Interrupt Flag
This flag is set when a slave byte transmit or byte receive operation is successfully completed without any
bus error. The flag can be set with an unsuccessful transaction in case of collision detection (see
description of the COLL status bit). Writing a '1' to its bit location will clear the DIF. However, normal use
of the TWI does not require the DIF flag to be cleared by using this method, since the flag is automatically
cleared when:
1.
2.
3.
Writing to the slave DATA register.
Reading the slave DATA register.
Writing a valid command to the CTRLB register.
The DIF flag can be used to generate a slave data interrupt (see description of the DIEN control bit in
TWI.CTRLA).
Bit 6 – APIF: Address or Stop Interrupt Flag
This flag is set when the slave address match logic detects that a valid address has been received or by
a stop condition. Writing a '1' to its bit location will clear the APIF. However, normal use of the TWI does
not require the flag to be cleared by this method since the flag is cleared using same software
interactions as described for the DIF flag.
The APIF flag can be used to generate a slave address or stop interrupt (see description of the AIEN
control bit in TWI.CTRLA). Take special note of that the slave stop interrupt shares the interrupt vector
with slave address interrupt.
Bit 5 – CLKHOLD: Clock Hold
If read as '1', the slave clock hold flag indicates that the slave is currently holding the TWI clock (SCL)
low, stretching the TWI clock period. This is a read only bit that is set when an address or data interrupt is
set. Resetting the corresponding interrupt will indirectly reset this flag.
Bit 4 – RXACK: Received Acknowledge
This bit is read only and contains to the most recently received acknowledge bit from the master.
Bit 3 – COLL: Collision
If read as '1', the transmit collision flag indicates that the slave has not been able to transmit a high data
or NACK bit. If a slave transmit collision is detected, the slave will commence its operation as normal,
except no low values will be shifted out onto the SDA line (i.e., when the COLL flag is set to '1' it disables
the data and acknowledge output from the slave logic). DIF flag will be set to '1' at the end as a result of
internal completion of unsuccessful transaction. Similarly when collision occurs because slave is not been
able to transmit NACK bit, it means address match already happened and APIF flag is set as a result.
APIF/DIF flags can only generate interrupt whose handlers can be used to check for the collision. Writing
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a '1' to its bit location will clear the COLL flag. However, the flag is automatically cleared if any START
condition (S/Sr) is detected.
This flag is intended for systems where address resolution protocol (ARP) is employed. However, a
detected collision in non-ARP situations indicates that there has been a protocol violation and should be
treated as a bus error.
Bit 2 – BUSERR: Bus Error
The BUSERR flag indicates that an illegal bus condition has occurred. An illegal bus condition is detected
if a protocol violating start (S), repeated start (Sr), or stop (P) is detected on the TWI bus lines. A start
condition directly followed by a stop condition is one example of protocol violation. Writing a '1' to its bit
location will clear the BUSERR flag. However, normal use of the TWI does not require the BUSERR to be
cleared by this method. A robust TWI driver software design will assume that the entire packet of data
has been corrupted and restart by waiting for a new START condition (S). For bus errors to be detected,
the master must be enabled (ENABLE bit in TWI.MCTRLA is '1'), and the system clock frequency must
be at least four times the SCL frequency.
Bit 1 – DIR: Read/Write Direction
This bit is read only and indicates the current bus direction state. The DIR bit reflects the direction bit
value from the last address packet received from a master TWI device. If this bit is read as '1', a master
read operation is in progress. Consequently a '0' indicates that a master write operation is in progress.
Bit 0 – AP: Address or Stop
When the TWI slave address or stop interrupt flag (APIF) is set, this bit determines whether the interrupt
is due to address detection or a stop condition.
Value
0
1
Name
STOP
ADR
Description
A stop condition generated the interrupt on APIF.
Address detection generated the interrupt on APIF.
26.5.12 Slave Address
Name: SADDR
Offset: 0x0C
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
ADDR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – ADDR[7:0]: Address
The slave address register in combination with the slave address mask register (TWI.SADDRMASK) is
used by the slave address match logic to determine if a master TWI device has addressed the TWI slave.
The slave address interrupt flag (APIF) is set to one if the received address is recognized. The slave
address match logic supports recognition of 7- and 10-bits addresses, and general call address.
When using 7-bit or 10-bit address recognition mode, the upper 7-bits of the address register (ADDR[7:1])
represents the slave address and the least significant bit (ADDR[0]) is used for general call address
recognition. Setting the ADDR[0] bit in this case enables the general call address recognition logic. The
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TWI slave address match logic only support recognition of the first byte of a 10-bit address i.e. by setting
ADDRA[7:1] = “0b11110aa” where “aa” represents bit 9 and 8 or the slave address. The second 10-bit
address byte must be handled by software.
26.5.13 Slave Data
Name: SDATA
Offset: 0x0D
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
DATA[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DATA[7:0]: Data
The slave data register I/O location (DATA) provides direct access to the slave's physical shift register,
which is used both to shift data out onto the bus (transmit) and to shift in data received from the bus
(receive). The direct access implies that the data register cannot be accessed during byte transmissions.
Built-in logic prevents any write accesses to the data register during the shift operations. Reading valid
data or writing data to be transmitted can only be successfully done when the bus clock (SCL) is held low
by the slave, i.e. when the slave CLKHOLD bit is set. However, it is not necessary to check the
CLKHOLD bit in software before accessing the slave DATA register if the software keeps track of the
present protocol state by using interrupts or observing the interrupt flags. Accessing the slave DATA
register, assumed that clock hold is active, auto-trigger bus operations dependent of the state of the slave
acknowledge action command bits (ACKACT) and type of register access (read or write).
26.5.14 Slave Address Mask
Name: SADDRMASK
Offset: 0x0E
Reset: 0x00
Property:
Bit
7
6
5
R/W
R/W
R/W
0
0
0
4
3
2
1
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
ADDRMASK[6:0]
Access
Reset
0
ADDREN
Bits 7:1 – ADDRMASK[6:0]: Address Mask
The ADDRMASK register acts as a second address match register, or an address mask register
depending on the ADDREN setting.
If ADDREN is written to '0', ADDRMASK can be loaded with a 7-bit Slave Address mask. Each of the bits
in ADDRMASK register can mask (disable) the corresponding address bits in the TWI slave Address
Register (ADDR). If the mask bit is written to '1' then the address match logic ignores the compare
between the incoming address bit and the corresponding bit in slave ADDR register. In other words,
masked bits will always match.
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If ADDREN is written to '1', the slave ADDRMASK can be loaded with a second slave address in addition
to the ADDR register. In this mode, the slave will match on 2 unique addresses, one in ADDR and the
other in ADDRMASK.
Bit 0 – ADDREN: Address Mask Enable
If this bit is written to '1', the slave address match logic responds to the 2 unique addresses in slave
ADDR and ADDRMASK.
If this bit is '0', the ADDRMASK register acts as a mask to the slave ADDR register.
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27.
CRCSCAN - Cyclic Redundancy Check Memory Scan
27.1
Features
•
•
•
•
•
•
27.2
CRC-16-CCITT
Can check full Flash, application code and/or boot section
Single/continuous background or priority check selectable
Selectable NMI trigger on failure
User configurable check during internal reset initialization
Paused in all CPU sleep modes
Overview
A Cyclic Redundancy Check (CRC) takes a data stream of bytes from the NVM (either entire Flash, only
Boot section, or both application code and Boot section) and generates a checksum. The CRC peripheral
(CRCSCAN) can be used to detect errors in program memory:
The last location in the section to check has to contain the correct pre-calculated 16-bit checksum for
comparison. If the checksum calculated by the CRCSCAN and the pre-calculated checksums match, a
status bit in the CRCSCAN is set. If they do not match, the status register will indicate that it failed. The
user can choose to let the CRCSCAN generate a non-maskable interrupt (NMI) if the checksums do not
match.
An n-bit CRC, applied to a data block of arbitrary length, will detect any single alteration (error burst) up to
n bits in length. For longer error bursts, a fraction 1-2-n will be detected.
The CRC-generator supports CRC-16-CCITT.
Polynomial:
•
CRC-16-CCITT: x16 + x12 + x5 + 1
The CRC reads in byte by byte of the content of the section(s) it is set up to check, starting with byte 0,
and generates a new checksum per byte. The byte is sent through an implementation corresponding to
Figure 27-1, starting with the most significant bit. If the last two bytes in the section contain the correct 16bit checksum, the CRC will pass. See Checksum for how to place the checksum. The initial value of the
checksum register is 0xFFFF.
Figure 27-1. CRC Implementation Description
data
15
x14
x13
x12
x11
x10
x9
x8
x7
x6
x5
x4
x3
x2
x1
x0
Q D
Q D
Q D
Q D
Q D
Q D
Q D
Q D
Q D
Q D
Q D
Q D
Q D
Q D
Q D
Q D
x
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8-bit AVR Microcontroller
27.2.1
Block Diagram
Figure 27-2. Cyclic Redundancy Check Block Diagram
CTRLA
Enable, Reset
CTRLB
Mode, Source
BUSY
Memory
(Boot, App., Flash)
CRC-16-CCIT
CHECKSUM
STATUS
CRC OK
Non-Maskable
Interrupt
27.2.2
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 27-1. System Product Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
Yes
CPUINT
Events
No
-
Debug
Yes
UPDI
Related Links
Clocks
Interrupts
27.2.2.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
CLKCTRL - Clock Controller
27.2.2.2 I/O Lines and Connections
Not applicable.
27.2.2.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
Related Links
CPUINT - CPU Interrupt Controller
SREG
Interrupts
27.2.2.4 Events
Not applicable.
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27.2.2.5 Debug Operation
Whenever the debugger accesses the device, for instance reading or writing a peripheral or memory
location, the CRCSCAN peripheral will be disabled.
If the CRCSCAN is busy when the debugger accesses the device, the CRCSCAN will restart the ongoing
operation when the debugger accesses an internal register or when the debugger disconnects.
The BUSY bit in the Status register (CRCSCAN.STATUS) will read '1' if the CRCSCAN was busy when
the debugger caused it to disable, but it will not actively check any section as long as the debugger keeps
it disabled. There are synchronized CRC status bits in the debugger's internal register space, which can
be read by the debugger without disabling the CRCSCAN. Reading the debugger's internal CRC status
bits will make sure that the CRCSCAN is enabled.
It is possible to write the CRCSCAN.STATUS register directly from the debugger:
•
BUSY bit in CRCSCAN.STATUS:
– Writing the BUSY bit to '0' will stop the ongoing CRC operation (so that the CRCSCAN does
not restart its operation when the debugger allows it).
– Writing the BUSY bit to '1' will make the CRC start a single check with the settings in the
Control B register (CRCSCAN.CTRLB), but not until the debugger allows it.
•
As long as the BUSY bit in CRCSCAN.STATUS is '1', CRCSCAN.CRCTRLB and the NonMaskable Interrupt Enable bit (NMIEN) in the Control A register (CRCSCAN.CTRLA) cannot be
altered.
OK bit in CRCSCAN.STATUS:
– Writing the OK bit to '0' can trigger a non-maskable interrupt (NMI) if the NMIEN bit in
CRCSCAN.CTRLA is '1'. If an NMI has been triggered, no writes to the CRCSCAN are
allowed.
– Writing the OK bit to '1' will make the OK bit read as '1' when the BUSY bit in
CRCSCAN.STATUS is '0'.
Writes to CRCSCAN.CTRLA and CRCSCAN.CTRLB from the debugger are treated in the same way as
writes from the CPU.
Related Links
UPDI - Unified Program and Debug Interface
CTRLA
CTRLB
27.3
Functional Description
27.3.1
Initialization
To enable a CRC in software (or via the debugger):
1. Write the MODE and Source (SRC) bit fields of the Control B register (CRCSCAN.CTRLB) to select
the desired mode and source settings.
2. Enable the CRCSCAN by writing a '1' to the ENABLE bit in the Control A register
(CRCSCAN.CTRLA).
The CRCSCAN can be enabled during the internal reset initialization to ensure the Flash is OK before
letting the CPU execute code. If the CRCSCAN fails during the internal reset initialization, the CPU is not
allowed to start normal code execution. The full source settings are available during the internal reset
initialization. See the Fuse description for more information.
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If the CRCSCAN was enabled during the internal reset initialization, the CRC Control A and B registers
will reflect this when normal code execution is started:
•
The ENABLE bit in CRCSCAN.CTRLA will be '1'
•
The MODE bit field in CRCSCAN.CTRLB will be BACKGROUND
•
The SRC bit field in CRCSCAN.CTRLB will reflect the checked section(s).
Related Links
CTRLA
CTRLB
FUSES - Configuration and User Fuses
Reset time
27.3.2
Operation
The CRC can run in these modes:
•
Continuous mode in the background: the CRC restarts checking from the beginning of the selected
section. The CPU can continue executing code and the CRC fetches data when it can.
•
Single mode in the background: A single CRC is executed. The CPU can continue executing code
and the CRC fetches data when it can.
•
Priority mode: the CRC peripheral has priority access to the Flash and will stall the CPU until
completed.
Although the CPU has priority under the continuous mode and single mode in the background, there can
still be a "collision". Therefore, the CPU will have to wait one additional cycle when this condition occurs.
It is important that it should not run continuous background checks during executing or running safety
critical code. Otherwise, it is hard to get test coverage.
The CRC fetches a new word (16-bit) on every third main clock cycle when in priority mode, or when the
CRC module is set to do a scan from startup. In background mode, scan time can not be guaranteed.
27.3.2.1 Checksum
The pre-calculated checksum must be present in the last location of the section to be checked. If the
BOOT section should be checked, the 16-bit checksum must be saved in the last two bytes of the BOOT
section, and similarly for APPLICATION and entire Flash. Table 27-2 shows explicitly how the checksum
should be stored for the different sections. Also see CTRLB for how to configure which section to check
and the device fuse description for how to configure the BOOTEND and APPEND fuses.
Table 27-2. How to place the pre-calculated 16-bit checksum in Flash
27.3.3
Section to Check
CHECKSUM[15:8]
CHECKSUM[7:0]
BOOT
FUSE_BOOTEND*256-2
FUSE_BOOTEND*256-1
BOOT and APPLICATION
FUSE_APPEND*256-2
FUSE_APPEND*256-1
Full Flash
FLASHEND-1
FLASHEND
Interrupts
Table 27-3. Available Interrupt Vectors and Sources
Offset
Name
Vector Description
Conditions
0x00
NMI
Non-Maskable Interrupt
Generated on CRC failure
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When the interrupt condition occurs, the OK flag in the Status register (CRCSCAN.STATUS) is cleared to
'0'.
An interrupt is enabled by writing a '1' to the respective Enable bit (NMIEN) in the Control A register
(CRCSCAN.CTRLA), but can only be disabled with a system Reset. An NMI is generated when the OK
flag in CRCSCAN.STATUS is cleared and the NMIEN bit is '1'. The NMI request remains active until a
system Reset, and can not be disabled.
A non-maskable interrupt can be triggered even if interrupts are not globally enabled.
Related Links
CTRLA
STATUS
CPUINT - CPU Interrupt Controller
27.3.4
Sleep Mode Operation
In all CPU sleep modes, the CRCSCAN peripheral is halted, and will resume operation when the CPU
wakes up.
It is possible to enter sleep mode after setting up the CRCSCAN to start a PRIORITY check (see CTRLB
for more information), but before the actual check is started. If the CPU is able enter sleep mode before
the check starts and a Priority check was configured, the check will start and complete (halting the CPU)
immediately after waking up, and before entering any interrupt handler.
27.3.5
Configuration Change Protection
Not applicable.
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27.4
Register Summary - CRCSCAN
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
STATUS
7:0
RESET
NMIEN
MODE[1:0]
SRC[1:0]
OK
27.5
Register Description
27.5.1
Control A
ENABLE
BUSY
If an NMI has been triggered, this register is not writable.
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
3
2
1
0
RESET
NMIEN
ENABLE
R/W
R/W
R/W
0
0
0
Bit 7 – RESET: Reset CRCSCAN
Writing this bit to '1' resets the CRCSCAN peripheral: The CRCSCAN Control registers and Status
register (CTRLA, CTRLB, STATUS) will be cleared one clock cycle after the RESET bit was written to '1'.
If NMIEN is '0', this bit is writable both when the CRCSCAN is busy (BUSY bit in CRCSCAN.STATUS is
'1') and not busy (BUSY bit is '0'), and will take effect immediately.
If NMIEN is '1', this bit is only writable when the CRCSCAN is not busy (BUSY bit in CRCSCAN.STATUS
is '0').
The RESET bit is a strobe bit.
Bit 1 – NMIEN: Enable NMI Trigger
When this bit is written to '1', any CRC failure will trigger an NMI.
This can only be cleared by a system Reset - it is not cleared by a write to the RESET bit.
This bit can only be written to '1' when the CRCSCAN is not busy (BUSY bit in CRCSCAN.STATUS is '0').
Bit 0 – ENABLE: Enable CRCSCAN
Writing this bit to '1' enables the CRCSCAN peripheral with the current settings. It will stay '1' even after a
CRC check has completed, but writing it to 1 again will start a new check.
Writing the bit to '0' will disable the CRCSCAN after the ongoing check is completed (after reaching the
end of the section it is set up to check). This is the preferred way to stop a continuous background check.
A failure in the ongoing check will still be detected and can cause an NMI if the NMIEN bit is '1'.
The CRCSCAN can be enabled during the internal reset initialization to verify Flash sections before
letting the CPU start normal code execution (see device datasheet fuse description). If the CRCSCAN is
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enabled during the internal reset initialization, the ENABLE bit will read as '1' when normal code
execution starts.
To see whether the CRCSCAN peripheral is busy with an ongoing check, poll the Busy bit (BUSY) in the
Status register (CRCSCAN.STATUS).
Related Links
FUSES - Configuration and User Fuses
Reset time
27.5.2
Control B
The CTRLB register contains the mode and source settings for the CRC. It is not writable when the CRC
is busy or when an NMI has been triggered.
Name: CTRLB
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
MODE[1:0]
Access
Reset
0
SRC[1:0]
R/W
R/W
R/W
R/W
0
0
0
0
Bits 5:4 – MODE[1:0]: CRC Flash Access Mode
The MODE bit field selects the priority of the CRC module in the system when accessing Flash, either in
the background or completely stalling the CPU until the CRC is completed. It is also possible to select the
CONTINUOUS mode, which will make the CRC module restart at the beginning of the selected section
after finishing a section. The CONTINUOUS mode will stop if a failure occurs. To otherwise stop a
CONTINUOUS mode, write the ENABLE or RESET bit in the CRCSCAN.CTRLA register.
The CRC can be enabled during internal reset initialization to verify Flash sections before letting the CPU
start (see device datasheet fuse description). If the CRC is enabled during internal reset initialization, the
MODE bit field will read out as BACKGROUND when normal code execution starts.
Value
0x0
0x2
0x3
other
Name
PRIORITY
Description
The CRC module runs a single check with priority to Flash. The CPU is
halted until the CRC completes.
BACKGROUND The CRC module runs a single check with lowest priority to Flash.
CONTINUOUS The CRC module runs continuous checks in the background. After
completing a successful check it restarts.
Reserved
Bits 1:0 – SRC[1:0]: CRC Source
The SRC bit field selects which section of the Flash the CRC module should check. To set up section
sizes, please refer to the fuse description.
The CRC can be enabled during internal reset initialization to verify Flash sections before letting the CPU
start (see device datasheet fuse description). If the CRC is enabled during internal reset initialization, the
SRC bit field will read out as FLASH, BOOTAPP or BOOT when normal code execution starts (depending
on the configuration).
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Value
0x0
0x1
0x2
0x3
Name
FLASH
Description
The CRC is performed on the entire Flash (boot, application code and
application data sections).
BOOTAPP The CRC is performed on the boot and application code sections of Flash.
BOOT
The CRC is performed on the boot section of Flash.
Reserved.
Related Links
FUSES - Configuration and User Fuses
Reset time
27.5.3
Status
The status register contains the busy and OK information. It is not writable, only readable.
Name: STATUS
Offset: 0x02
Reset: 0x02
Property:
Bit
7
6
5
4
3
2
1
0
OK
BUSY
Access
R
R
Reset
1
0
Bit 1 – OK: CRC OK
When this bit is read as 1, the previous CRC completed successfully. The bit is set to '1' from Reset, but
is cleared to '0' when enabling. As long as the CRC module is busy, it will be read '0'. When running
continuously, the CRC status must be assumed OK until it fails or is stopped by the user.
Bit 0 – BUSY: CRC Busy
When this bit is read as 1, the CRC module is busy. As long as the module is busy, the access to the
control registers are limited. See CTRLA and CTRLB for more information.
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28.
CCL – Configurable Custom Logic
28.1
Features
•
•
•
•
•
•
•
•
28.2
Glue logic for general purpose PCB design
Up to two Programmable LookUp Tables LUT[1:0]
Combinatorial Logic Functions: Any logic expression which is a function of up to three inputs.
Sequential Logic Functions:
Gated D Flip-Flop, JK Flip-Flop, gated D Latch, RS Latch
Flexible Lookup Table Inputs Selection:
– I/Os
– Events
– Subsequent LUT Output
– Internal Peripherals
• Analog Comparator
• Timer/Counters
• USART
• SPI
Clocked by system clock or other peripherals
Output can be connected to IO pins or Event System
Optional synchronizer, filter, or edge detector available on each LUT output
Overview
The Configurable Custom Logic (CCL) is a programmable logic peripheral which can be connected to the
device pins, to events, or to other internal peripherals. The CCL can serve as "glue logic" between the
device peripherals and external devices. The CCL can eliminate the need for external logic components,
and can also help the designer to overcome real-time constrains by combining core independent
peripherals to handle the most time critical parts of the application independent of the CPU.
The CCL peripheral has one pair of Lookup Tables (LUT). Each LUT consists of three inputs, a truth
table, and a filter/edge detector. Each LUT can generate an output as a user programmable logic
expression with three inputs. Inputs can be individually masked.
The output can be generated from the inputs combinatorially, and can be filtered to remove spikes. An
optional Sequential module can be enabled. The inputs to the Sequential module are individually
controlled by two independent, adjacent LUT (LUT0/LUT1) outputs, enabling complex waveform
generation.
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28.2.1
Block Diagram
Figure 28-1. Configurable Custom Logic
LUT0
INSEL
Internal
Events
I/O
Peripherals
FILTSEL
TRUTH
Filter/
Synch
CLKSRC
EDGEDET
Edge
Detector
LUT0-OUT
CLK_MUX_OUT
LUT0-IN[2]
clkCCL
SEQSEL
Sequential
ENABLE
LUT1
INSEL
Internal
Events
I/O
Peripherals
FILTSEL
TRUTH
Filter/
Synch
CLKSRC
LUT1-IN[2]
clkCCL
EDGEDET
Edge
Detector
LUT1-OUT
CLK_MUX_OUT
ENABLE
28.2.2
Signal Description
Pin Name
Type
Description
LUTn-OUT
Digital output
Output from lookup table
LUTn-IN[2:0]
Digital input
Input to lookup table
Refer to I/O Multiplexing and Considerations for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
Related Links
I/O Multiplexing and Considerations
28.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 28-1. CCL System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
No
EVSYS
Debug
Yes
UPDI
28.2.3.1 Clocks
By default, the CCL is using the peripheral clock of the device (CLK_PER).
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Alternatively, the CCL can be clocked by a peripheral input that is available on LUT n input line 2
(LUTn_IN[2]). This is configured by writing a '1' to the Clock Source Selection bit (CLKSRC) in the LUTn
Control A register (CCL.LUTnCTRLA). The sequential block is clocked by the same clock as that of its
even LUT in the LUT pair (SEQn.clk = LUT2n.clk). It is advised to disable the peripheral by writing a '0' to
the Enable bit (ENABLE) in the Control A register (CCL.CTRLA) before configuring the CLKSRC bit in
CCL.LUTnCTRLA.
Alternatively, the input line 2 (IN[2]) of a LUT can be used to clock the LUT and the corresponding
Sequential block. This is enabled by writing a '1' to the Clock Source Selection bit (CLKSRC) in the LUTn
Control A register (CCL.LUTnCTRLA).
The CCL must be disabled before changing the LUT clock source: write a '0' to the Enable bit (ENABLE)
in Control A register (CCL.CTRLA).
Related Links
CLKCTRL - Clock Controller
28.2.3.2 I/O Lines
Using the CCL I/O lines requires the I/O pins to be configured. Refer to PORT - I/O Pin Configuration for
details.
Related Links
PORT - I/O Pin Configuration
28.2.3.3 Interrupts
Not applicable.
28.2.3.4 Events
The events are connected to the Event System. Refer to EVSYS – Event System for details on how to
configure the Event System.
Related Links
EVSYS - Event System
28.2.3.5 Debug Operation
When the CPU is halted in debug mode the CCL continues normal operation. If the CCL is configured in
a way that requires it to be periodically serviced by the CPU, improper operation or data loss may result
during debugging.
28.3
Functional Description
28.3.1
Initialization
The following bits are enable-protected, meaning that they can only be written when the corresponding
even LUT is disabled (ENABLE=0 in CCL.LUT0CTRLA):
•
Sequential Selection (SEQSEL) in Sequential Control 0 register (CCL.SEQCTRL0)
The following registers are enable-protected, meaning that they can only be written when the
corresponding LUT is disabled (ENABLE=0 in CCL.LUT0CTRLA):
•
LUT n Control x register, except ENABLE bit (CCL.LUTnCTRLx)
Enable-protected bits in the CCL.LUTnCTRLx registers can be written at the same time as ENABLE in
CCL.LUTnCTRLx is written to '1', but not at the same time as ENABLE is written to '0'.
Enable-protection is denoted by the Enable-Protected property in the register description.
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28.3.2
Operation
28.3.2.1 Enabling, Disabling and Resetting
The CCL is enabled by writing a '1' to the ENABLE bit in the Control register (CCL.CTRLA). The CCL is
disabled by writing a '0' to that ENABLE bit.
Each LUT is enabled by writing a '1' to the LUT Enable bit (ENABLE) in the LUT n Control A register
(CCL.LUTnCTRLA). Each LUT is disabled by writing a '0' to the ENABLE bit in CCL.LUTnCTRLA.
28.3.2.2 Lookup Table Logic
The lookup table in each LUT unit can generate a combinational logic output as a function of up to three
inputs IN[2:0]. Unused inputs can be masked (tied low). The truth table for the combinational logic
expression is defined by the bits in the CCL.TRUTHn registers. Each combination of the input bits
(IN[2:0]) corresponds to one bit in the TRUTHn register, as shown in the table:
Table 28-2. Truth Table of LUT
IN[2]
IN[1]
IN[0]
OUT
0
0
0
TRUTH[0]
0
0
1
TRUTH[1]
0
1
0
TRUTH[2]
0
1
1
TRUTH[3]
1
0
0
TRUTH[4]
1
0
1
TRUTH[5]
1
1
0
TRUTH[6]
1
1
1
TRUTH[7]
28.3.2.3 Truth Table Inputs Selection
Input Overview
The inputs can be individually:
•
•
•
•
Masked
Driven by peripherals:
– Analog comparator output (AC)
– Timer/Counters waveform outputs (TC)
Driven by internal events from Event System
Driven by other CCL sub-modules
The Input Selection for each input y of LUT n is configured by writing the Input y Source Selection bit in
the LUT n Control x=[B,C] registers
•
INSEL0 in CCL.LUTnCTRLB
•
INSEL1 in CCL.LUTnCTRLB
•
INSEL2 in CCL.LUTnCTRLC.
Internal Feedback Inputs (FEEDBACK)
When selected (INSELy=FEEDBACK in CCL.LUTnCTRLx), the Sequential (SEQ) output is used as input
for the corresponding LUT.
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The output from an internal sequential module can be used as input source for the LUT, see figure below
for an example for LUT0 and LUT1. The sequential selection for each LUT follows the formula:
IN 2N � = SEQ �
IN 2N+1 � = SEQ �
With N representing the sequencer number and i=0,1 representing the LUT input index.
For details, refer to Sequential Logic.
Figure 28-2. Feedback Input Selection
Linked LUT (LINK)
When selecting the LINK input option, the next LUT's direct output is used as the LUT input. In general,
LUT[n+1] is linked to the input of LUT[n]. As example LUT1 is the input for LUT0.
Figure 28-3. Linked LUT Input Selection
LUT0
SEQ 0
CTRL
(ENABLE)
LUT1
Internal Events Inputs Selection (EVENT)
Asynchronous events from the Event System can be used as input to the LUT. Two event input lines
(EVENT0 and EVENT1) are available, and can be selected as LUT input. Before selecting the EVENT
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input option by writing to the LUT CONTROL A or B register (CCL.LUTnCTRLB or LUTnCTRLC), the
Event System must be configured.
I/O Pin Inputs (IO)
When selecting the IO option, the LUT input will be connected to its corresponding IO pin. Refer to the I/O
Multiplexing section for more details about where the LUTnINy are located.
Figure 28-4. I/O Pin Input Selection
Peripherals
The different peripherals on the three input lines of each LUT are selected by writing to the respective
LUT n Input y bit fields in the LUT n Control B and C registers:
•
INSEL0 in CCL.LUTnCTRLB
•
INSEL1 in CCL.LUTnCTRLB
•
INSEL2 in CCL.LUTnCTRLC.
Related Links
I/O Multiplexing and Considerations
PORT - I/O Pin Configuration
CLKCTRL - Clock Controller
AC – Analog Comparator
TCA - 16-bit Timer/Counter Type A
TCD - 12-bit Timer/Counter Type D
USART - Universal Synchronous and Asynchronous Receiver and Transmitter
SPI - Serial Peripheral Interface
TWI - Two Wire Interface
I/O Multiplexing and Considerations
28.3.2.4 Filter
By default, the LUT output is a combinational function of the LUT inputs. This may cause some short
glitches when the inputs change value. These glitches can be removed by clocking through filters, if
demanded by application needs.
The Filter Selection bits (FILTSEL) in the LUT Control registers (CCL.LUTnCTRLA) define the digital filter
options. When a filter is enabled, the output will be delayed by two to five CLK cycles (peripheral clock or
alternative clock). One clock cycle after the corresponding LUT is disabled, all internal filter logic is
cleared.
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Figure 28-5. Filter
FILTSEL
Input
OUT
Q
D
R
Q
D
R
Q
D
R
D
G
Q
R
CLK_MUX_OUT
CLR
28.3.2.5 Edge Detector
The edge detector can be used to generate a pulse when detecting a rising edge on its input. To detect a
falling edge, the TRUTH table should be programmed to provide inverted output.
The edge detector is enabled by writing '1' to the Edge Selection bit (EDGEDET) in the LUT n Control A
register (CCL.LUTnCTRLA). In order to avoid unpredictable behavior, a valid filter option must be enabled
as well.
Edge detection is disabled by writing a '0' to EDGEDET in CCL.LUTnCTRLA. After disabling a LUT, the
corresponding internal Edge Detector logic is cleared one clock cycle later.
Figure 28-6. Edge Detector
CLK_MUX_OUT
28.3.2.6 Sequential Logic
Each LUT pair can be connected to an internal Sequential block. A Sequential block can function as
either D flip-flop, JK flip-flop, gated D-latch, or RS-latch. The function is selected by writing the Sequential
Selection bits (SEQSEL) in Sequential Control register (CCL.SEQCTRLn).
The Sequential block receives its input from the either LUT, filter or edge detector, depending on the
configuration.
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The Sequential block is clocked by the same clock as the corresponding LUT, which is either the
peripheral clock or input line 2 (IN[2]). This is configured by the Clock Source bit (CLKSRC) in the LUT n
Control A register (CCL.LUTnCTRLA).
When the even LUT (LUT0) is disabled, the latch is asynchronously cleared, during which the flip-flop
reset signal (R) is kept enabled for one clock cycle. In all other cases, the flip-flop output (OUT) is
refreshed on rising edge of the clock, as shown in the respective Characteristics tables.
Gated D Flip-Flop (DFF)
The D-input is driven by the even LUT output (LUT0), and the G-input is driven by the odd LUT output
(LUT1).
Figure 28-7. D Flip-Flop
even LUT
CLK_MUX_OUT
odd LUT
Table 28-3. DFF Characteristics
R
G
D
OUT
1
X
X
Clear
0
1
1
Set
0
Clear
X
Hold state (no change)
0
JK Flip-Flop (JK)
The J-input is driven by the even LUT output (LUT0), and the K-input is driven by the odd LUT output
(LUT1).
Figure 28-8. JK Flip-Flop
even LUT
CLK_MUX_OUT
odd LUT
Table 28-4. JK Characteristics
R
J
K
OUT
1
X
X
Clear
0
0
0
Hold state (no change)
0
0
1
Clear
0
1
0
Set
0
1
1
Toggle
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Gated D-Latch (DLATCH)
The D-input is driven by the even LUT output (LUT0), and the G-input is driven by the odd LUT output
(LUT1).
Figure 28-9. D-Latch
even LUT
D
odd LUT
G
Q
OUT
Table 28-5. D-Latch Characteristics
G
D
OUT
0
X
Hold state (no change)
1
0
Clear
1
1
Set
RS Latch (RS)
The S-input is driven by the even LUT output (LUT0), and the R-input is driven by the odd LUT output
(LUT1).
Figure 28-10. RS-Latch
even LUT
S
odd LUT
R
Q
OUT
Table 28-6. RS-latch Characteristics
S
R
OUT
0
0
Hold state (no change)
0
1
Clear
1
0
Set
1
1
Forbidden state
28.3.2.7 Clock Source Settings
The Filter, Edge Detector and Sequential logic are by default clocked by the system clock (CLK_PER). It
is also possible to use the LUT input 2 (IN[2]) to clock these blocks (CLK_MUX_OUT in figure Figure
28-11). This is configured by writing the Clock Source bit (CLKSRC) in the LUT Control A register
(CCL.LUTnCTRLA) to '1'.
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Figure 28-11. Clock Source Settings
Edge
Detector
IN[2]
Filter
CLK_MUX_OUT
CLK_CCL
CLKSRC
LUT0
Edge
Detector
IN[2]
Sequential
logic
Filter
CLK_MUX_OUT
CLK_CCL
CLKSRC
LUT1
When the Clock Source bit (CLKSRC) is '1', IN[2] is used to clock the corresponding Filter and Edge
Detector (CLK_MUX_OUT). The Sequential logic is clocked by CLK_MUX_OUT of the even LUT in the
pair. When CLKSRC bit is '1', IN[2] is treated as MASKed (low) in the TRUTH table.
The CCL peripheral must be disabled while changing the clock source to avoid undetermined outputs
from the peripheral.
28.3.3
Events
The CCL can generate the following output events:
•
LUTnOUT: Lookup Table Output Value
The CCL can take the following actions on an input event:
•
INx: The event is used as input for the TRUTH table.
Related Links
EVSYS - Event System
28.3.4
Sleep Mode Operation
Writing the Run In Standby bit (RUNSTDBY) in the Control A register (CCL.CTRLA) to '1' will allow the
system clock to be enabled in Standby sleep mode.
If RUNSTDBY is '0' the system clock will be disabled in Standby sleep mode. If the Filter, Edge Detector
or Sequential logic are enabled, the LUT output will be forced to zero in Standby sleep mode. In Idle
sleep mode, the TRUTH table decoder will continue operation and the LUT output will be refreshed
accordingly, regardless of the RUNSTDBY bit.
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If the Clock Source bit (CLKSRC) in the LUT n Control A register (CCL.LUTnCTRLA) is written to '1', the
LUT input 2 (IN[2]) will always clock the Filter, Edge Detector and Sequential block. The availability of the
IN[2] clock in sleep modes will depend on the sleep settings of the peripheral employed.
28.3.5
Configuration Change Protection
Not applicable.
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28.4
Register Summary - CCL
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
SEQCTRL0
7:0
RUNSTDBY
ENABLE
SEQSEL[3:0]
0x02
...
Reserved
0x04
0x05
LUT0CTRLA
7:0
0x06
LUT0CTRLB
7:0
0x07
LUT0CTRLC
7:0
0x08
TRUTH0
7:0
0x09
LUT1CTRLA
7:0
0x0A
LUT1CTRLB
7:0
0x0B
LUT1CTRLC
7:0
0x0C
TRUTH1
7:0
EDGEDET
CLKSRC
FILTSEL[1:0]
OUTEN
ENABLE
INSEL1[3:0]
INSEL0[3:0]
INSEL2[3:0]
TRUTH[7:0]
EDGEDET
CLKSRC
FILTSEL[1:0]
OUTEN
ENABLE
INSEL1[3:0]
INSEL0[3:0]
INSEL2[3:0]
TRUTH[7:0]
28.5
Register Description
28.5.1
Control A
Name: CTRLA
Offset: 0x00 [ID-00000485]
Reset: 0x00
Property:
Bit
7
Access
Reset
6
5
4
3
2
1
0
RUNSTDBY
ENABLE
R/W
R/W
0
0
Bit 6 – RUNSTDBY: Run in Standby
This bit indicates if the peripheral clock (CLK_PER) is kept running in Standby sleep mode. The setting is
ignored for configurations where the CLK_PER is not required. For details refer to Sleep Mode Operation.
Value
0
1
Description
System clock is not required in standby sleep mode.
System clock is required in standby sleep mode.
Bit 0 – ENABLE: Enable
Value
0
1
28.5.2
Description
The peripheral is disabled.
The peripheral is enabled.
Sequential Control 0
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Name: SEQCTRL0
Offset: 0x01 [ID-00000485]
Reset: 0x00
Property: Enable-Protected
Bit
7
6
5
4
3
2
1
0
SEQSEL[3:0]
Access
Reset
R/W
R/W
R/W
R/W
0
0
0
0
2
1
Bits 3:0 – SEQSEL[3:0]: Sequential Selection
These bits select the sequential configuration.
Value
0x0
0x1
0x2
0x3
0x4
Other
28.5.3
Name
DISABLE
DFF
JK
LATCH
RS
-
Description
Sequential logic is disabled
D flip flop
JK flip flop
D latch
RS latch
Reserved
LUT n Control A
Name: LUT0CTRLA, LUT1CTRLA
Offset: 0x05 + n*0x04 [n=0..1]
Reset: 0x00
Property: Enable-Protected
Bit
Access
Reset
7
6
EDGEDET
CLKSRC
5
4
R/W
R/W
R/W
0
0
0
FILTSEL[1:0]
3
0
OUTEN
ENABLE
R/W
R/W
R/W
0
0
0
Bit 7 – EDGEDET: Edge Detection
Value
0
1
Description
Edge detector is disabled.
Edge detector is enabled.
Bit 6 – CLKSRC: Clock Source Selection
This bit selects whether the peripheral clock (CLK_PER) or any input present on input line 2 (IN[2]) is
used as clock (CLK_MUX_OUT) for a LUT.
The CLK_MUX_OUT of the even LUT is used for clocking the Sequential block of a LUT pair.
Value
0
1
Description
CLK_PER is clocking the LUT.
IN[2] is clocking the LUT.
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Bits 5:4 – FILTSEL[1:0]: Filter Selection
These bits select the LUT output filter options:
Filter Selection
Value
0x0
0x1
0x2
0x3
Name
DISABLE
SYNCH
FILTER
-
Description
Filter disabled
Synchronizer enabled
Filter enabled
Reserved
Bit 3 – OUTEN: Output Enable
This bit enables the LUT output to the LUTnOUT pin. When written to '1', the pin configuration of the
PORT I/O-Controller is overridden.
Value
0
1
Description
Output to pin disabled.
Output to pin enabled.
Bit 0 – ENABLE: LUT Enable
Value
0
1
28.5.4
Description
The LUT is disabled.
The LUT is enabled.
LUT n Control B
SPI connections to the CCL work only in master SPI mode.
USART connections to the CCL work only in asynchronous/synchronous USART master mode.
Name: LUT0CTRLB, LUT1CTRLB
Offset: 0x06 + n*0x04 [n=0..1]
Reset: 0x00
Property: Enable-Protected
Bit
7
6
5
4
3
2
INSEL1[3:0]
Access
Reset
1
0
INSEL0[3:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:4 – INSEL1[3:0]: LUT n Input 1 Source Selection
These bits select the source for input 1 of LUT n:
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
MASK
FEEDBACK
LINK
EVENT0/EVENT1
EVENT2/EVENT3
IO
AC0
TCB0
© 2017 Microchip Technology Inc.
Description
Masked input
Feedback input
Linked other LUT as input source
Event 0 as input source for LUT0 / Event 1 as input source for LUT1
Event 2 as input source for LUT0 / Event 3 as input source for LUT1
I/O pin LUTn-IN1 input source
AC0 OUT input source
TCB WO input source
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Value
0x8
0x9
0xA
0xB
0xC
0xD
0xE
Name
TCA0
TCD0
USART0
SPI0
AC1
TCB1
AC2
Description
TCA WO1 input source
TCD WOB input source
USART TXD input source
SPI MOSI input source
AC1 OUT input source
TCB 1 W0 input source
AC2 OUT input source
Bits 3:0 – INSEL0[3:0]: LUT n Input 0 Source Selection
These bits select the source for input 0 of LUT n:
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC
0xD
0xE
Other
28.5.5
Name
MASK
FEEDBACK
LINK
EVENT0/EVENT1
EVENT2/EVENT3
IO
AC0
TCB0
TCA0
TCD0
USART0
SPI0
AC1
TCB1
AC2
-
Description
Masked input
Feedback input
Linked other LUT as input source
Event 0 as input source for LUT0 / Event 1 as input source for LUT1
Event 2 as input source for LUT0 / Event 3 as input source for LUT1
I/O pin LUTn-IN0 input source
AC0 OUT input source
TCB WO input source
TCA WO0 input source
TCD WOA input source
USART XCK input source
SPI SCK input source
AC1 OUT input source
TCB 1 W0 input source
AC2 OUT input source
Reserved
LUT n Control C
Name: LUT0CTRLC, LUT1CTRLC
Offset: 0x07 + n*0x04 [n=0..1]
Reset: 0x00
Property: Enable-Protected
Bit
7
6
5
4
3
2
1
0
INSEL2[3:0]
Access
R/W
R/W
R/W
R/W
0
0
0
0
Reset
Bits 3:0 – INSEL2[3:0]: LUT n Input 2 Source Selection
These bits select the source for input 2 of LUT n:
Value
0x0
0x1
0x2
Name
MASK
FEEDBACK
LINK
© 2017 Microchip Technology Inc.
Description
Masked input
Feedback input
Linked other LUT as input source
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Value
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
other
28.5.6
Name
EVENT0
EVENT1
IO
AC0
TCB0
TCA0
TCD0
SPI0
-
Description
Event input source 0
Event input source 1
I/O pin LUTn-IN2 input source
AC0 OUT input source
TCB WO input source
TCA WO2 input source
TCD WOA input source
Reserved
SPI MISO input source
Reserved
TRUTHn
Name: TRUTH0, TRUTH1
Offset: 0x08 + n*0x04 [n=0..1]
Reset: 0x00
Property: Enable-Protected
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
TRUTH[7:0]
Access
Reset
Bits 7:0 – TRUTH[7:0]: Truth Table
These bits define the value of truth logic as a function of inputs IN[2:0].
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8-bit AVR Microcontroller
29.
AC – Analog Comparator
29.1
Features
•
•
•
•
•
•
•
•
•
29.2
Three instances of the AC controller, AC0, AC1, and AC2
50ns response time for supply voltage above 2.7V
Zero-cross detection
Selectable hysteresis:
– None
– 10mV
– 25mV
– 50mV
Analog comparator output available on pin
Comparator output inversion available
Flexible input selection:
– 4 Positive pins
– 2 Negative pins
– Output from the DAC
– Internal reference voltage
Interrupt generation on:
– Rising edge
– Falling edge
– Both egdes
Event generation:
– Comparator output
Overview
The Analog Comparator (AC) compares the voltage levels on two inputs and gives a digital output based
on this comparison. The AC can be configured to generate interrupt requests and/or Events upon several
different combinations of input change.
The dynamic behavior of the AC can be adjusted by a hysteresis feature. The hysteresis can be
customized to optimize the operation for each application.
The input selection includes analog port pins, DAC output and internal references. The analog
comparator output state can also be output on a pin for use by external devices.
The AC has one positive input and one negative input. The positive input source is one of a selection of 4
analog input pins. The negative inputs are chosen either from analog input pins or from internal inputs,
such as an internal voltage reference.
The digital output from the comparator is '1' when the difference between the positive and the negative
input voltage is positive, and '0' otherwise.
This device provides three instances of the AC controller, AC0, AC1, and AC2.
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29.2.1
Block Diagram
Figure 29-1. Analog Comparator
AC Controller
AINP0
MUXCTRLA
:
Invert
+
AINPn
Controller
Logic
AC
AINN0
OUT
-
:
AINNn
Hysteresis
Enable
VREF
Event
System
CTRLA
DAC
Note: Refer to Signal Description for the number of AINN and AINP.
29.2.2
Signal Description
Signal
Description
Type
AINN0
Negative Input 0
Analog
AINN1
Negative Input 1
Analog
AINP0
Positive Input 0
Analog
AINP1
Positive Input 1
Analog
AINP2
Positive Input 2
Analog
AINP3
Positive Input 3
Analog
OUT
Comparator Output for AC
Digital
Related Links
I/O Multiplexing and Considerations
29.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 29-1. AC System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
I/O Lines and Connections
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Debug Operation
Clocks
Interrupts
Events
29.2.3.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
CLKCTRL - Clock Controller
29.2.3.2 I/O Lines and Connections
I/O pins AINN0-AINN1, AINP0- AINP3 are all analog inputs to the AC.
For correct operation, the pins must be configured in the Port and Port Multiplexing peripherals.
It is recommended to disable the GPIO input when using the AC.
Related Links
I/O Multiplexing and Considerations
29.2.3.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
Related Links
CPUINT - CPU Interrupt Controller
SREG
Interrupts
29.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
EVSYS - Event System
29.2.3.5 Debug Operation
This peripheral is unaffected by entering debug mode.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
UPDI - Unified Program and Debug Interface
29.3
Functional Description
29.3.1
Initialization
For basic operation, follow these steps:
•
Configure the desired input pins in the PORT peripheral.
•
Select the positive and negative input sources by writing the Positive and Negative Input MUX
Selection bit fields (MUXPOS and MUXNEG) in the Mux Control A register (AC.MUXCTRLA).
•
Optional: Enable the output to pin by writing a '1' to the Output Pad Enable bit (OUTEN) in the
Control A register (AC.CTRLA).
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•
Enable the AC by writing a '1' to the ENABLE bit in AC.CTRLA.
During the start-up time after enabling the AC, the output of the AC may be invalid.
The start-up time of the AC by itself is at most 2.5µs. If a internal referance is used, the referance start-up
time is normally longer than the AC startup time. The VREF startup time is at most 60 µs.
29.3.2
Operation
29.3.2.1 Input Hysteresis
Applying an input hysteresis helps preventing constant toggling of the output when the noise-afflicted
input signals are close to each other.
The input hysteresis can either be disabled or have one of three levels. The hysteresis is configured by
writing to the Hysteresis Mode Select bit field (HYSMODE) in the Control A register (AC.CTRLA).
29.3.2.2 Input Sources
The AC has one positive and one negative input. The inputs can be pins and internal sources, such as a
voltage reference.
Each input is selected by writing to the Positive and Negative Input MUX Selection bit field (MUXPOS and
MUXNEG) in the MUX Control A register (AC.MUXTRLA).
Pin Inputs
The following Analog input pins on the port can be selected as input to the analog comparator
•
•
•
•
•
•
AINN0
AINN1
AINP0
AINP1
AINP2
AINP3
Internal Inputs
Two internal inputs are available for the analog comparator:
•
•
Output from the DAC
DAC and AC voltage reference
Related Links
VREF - Voltage Reference
29.3.2.3 Low Power Mode
For power-conscious applications, the AC provides a Low Power with reduced power consumption and
increased propagation delay.
29.3.3
Events
The AC will generate the following Event automatically when the AC is enabled:
•
Comparator output Event
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29.3.4
Interrupts
Table 29-2. Available Interrupt Vectors and Sources
Offset Name
0x00
Vector Description
Conditions
COMP0 Analog comparator interrupt AC output is toggling as configured by INTMODE in
AC.CTRLA
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Status register
(AC.STATUS).
An interrupt source is enabled or disabled by writing to the corresponding bit in the peripheral's Interrupt
Control register (AC.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the Interrupt
Flag is set. The interrupt request remains active until the Interrupt Flag is cleared. See the AC.STATUS
register description for details on how to clear Interrupt Flags.
Related Links
CPUINT - CPU Interrupt Controller
SREG
Interrupts
29.3.5
Sleep Mode Operation
In Idle sleep mode the AC will continue to operate normal. in all sleep modes in which CLK_PER is
available.
In Standby sleep mode, the AC is disabled by default. If the Run in Standby Sleep Mode bit
(RUNSTDBY) in the Control A register (AC.CTRLA) is written to '1', the AC will continue to operate, but
the Status register will not be updated, and no Interrupts are generated , but events and the pad output
will be updated.
In Power Down sleep mode, the AC and the output to pad are disabled.
29.3.6
Configuration Change Protection
Not applicable.
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29.4
Register Summary - AC
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
RUNSTDBY
7:0
INVERT
0x01
Reserved
0x02
MUXCTRLA
OUTEN
INTMODE[1:0]
HYSMODE[1:0]
MUXPOS[1:0]
ENABLE
MUXNEG[1:0]
0x03
...
Reserved
0x05
0x06
INTCTRL
7:0
0x07
STATUS
7:0
CMP
STATE
29.5
Register Description
29.5.1
Control A
CMP
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
Access
Reset
7
6
5
4
3
2
RUNSTDBY
OUTEN
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
INTMODE[1:0]
1
HYSMODE[1:0]
0
ENABLE
Bit 7 – RUNSTDBY: Run in Standby Mode
Writing a '1' to this bit allows the AC to continue operation in Standby sleep mode. Since the clock is
stopped, interrupts and status flags are not updated.
Value
0
1
Description
In Standby sleep mode, the peripheral is halted
In Standby sleep mode, the peripheral continues operation
Bit 6 – OUTEN: Analog Comparator Output Pad Enable
Writing this bit to '1' makes the OUT signal available on the pin.
Bits 5:4 – INTMODE[1:0]: Interrupt Modes
Writing to these bits selects what edge(s) of the AC output an interrupt request is triggered.
Value
0x0
0x1
0x2
0x3
Name
BOTHEDGE
NEGEDGE
POSEDGE
Description
both negative and positive edge
Reserved
Negative edge
Positive edge
Bits 2:1 – HYSMODE[1:0]: Hysteresis Mode Select
Writing these bits selects the hysteresis mode for the AC input.
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Value
0x0
0x1
0x2
0x3
Name
OFF
10
25
50
Description
OFF
±10mV
±25mV
±50mV
Bit 0 – ENABLE: Enable AC
Writing this bit to '1' enables the AC.
29.5.2
Mux Control A
AC.MUXCTRLA controls Analog Comparator Muxes
Name: MUXCTRLA
Offset: 0x02
Reset: 0x00
Property:
Bit
7
6
5
4
INVERT
Access
Reset
3
2
1
MUXPOS[1:0]
0
MUXNEG[1:0]
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 7 – INVERT: Invert AC Output
Writing a '1' to this bit enables inversion of the output of the AC. This effectively inverts the input to all the
peripherals connected to the signal, and also affects the internal status signals.
Bits 4:3 – MUXPOS[1:0]: Positive Input MUX Selection
Writing to this bit field selects the input signal to the positive input of the AC.
Value
0
1
1
1
Name
AINP0
AINP1
AINP2
AINP3
Description
Positive Pin 0
Positive Pin 1
Positive Pin 2
Positive Pin 3
Bits 1:0 – MUXNEG[1:0]: Negative Input MUX Selection
Writing to this bit field selects the input signal to the negative input of the AC.
Value
0x0
0x1
0x2
0x3
29.5.3
Name
AINN0
AINN1
VREF
DAC
Description
Negative Pin 0
Negative Pin 1
Voltage Reference
DAC output. Instance n of the AC will use instance n of the DAC: for example AC0
will use DAC0 and AC1 will use DAC1.
Interrupt Control
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Name: INTCTRL
Offset: 0x06
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
CMP
Access
R/W
Reset
0
Bit 0 – CMP: Analog Comparator Interrupt Enable
Writing this bit to '1' enables Analog Comparator Interrupt.
29.5.4
Status
Name: STATUS
Offset: 0x07
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
STATE
CMP
Access
R
R/W
Reset
0
0
Bit 4 – STATE: Analog Comparator State
This shows current status of the OUT signal from the AC. This will have a synchronizer delay to get
updated in the I/O register (3 cycles).
Bit 0 – CMP: Analog Comparator Interrupt Flag
This is the interrupt flag for AC. Writing a '1' to this bit will clear the Interrupt flag.
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30.
ADC - Analog to Digital Converter
30.1
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
30.2
10-bit resolution
±2 LSB absolute accuracy
6.5 - 260μs conversion time
Up to 115ksps
Up to twelve multiplexed single-ended input channels
Temperature sensor input channel
0V to VDD ADC input voltage range
Multiple internal ADC reference voltage between 0.55V and VDD
External reference input VAREF
Single Conversion mode
Interrupt available on ADC conversion complete
Optional Event triggered conversion
Optional interrupt on conversion results
Compare function for accurate monitoring or user defined thresholds (window comparator mode)
Accumulation up to 64 samples per conversion
Overview
The Analog-to-Digital Converter (ADC) peripheral features a 10-bit successive approximation ADC (SAR),
with a sampling rate up to 115ksps. The ADC is connected to a 12-channel Analog Multiplexer which
allows twelve single-ended voltage inputs. The single-ended voltage inputs refer to 0V (GND). The ADC
input channel can either be internal (e.g. a voltage reference) or external through the analog input pins.
An ADC conversion can be started by software, or by using the Event System (EVSYS) to route an event
from other peripherals. Making it possible to do periodic sampling of input signals, trigger an ADC
conversion on a special condition, or triggering an ADC conversion in standby sleep mode. A window
compare feature is available for monitoring the input signal, and can be configured to only trigger an
interrupt on user defined thresholds for under, over, inside or outside a window, with minimum software
intervention required.
The ADC input signal is fed through a sample-and-hold circuit which ensures that the input voltage to the
ADC is held at a constant level during sampling.
The ADC supports sampling in bursts where a configurable number of conversion results are
accumulated into a single ADC result (Sample Accumulation). Further, a sample delay can be configured
to tune the ADC sampling frequency associated with a single burst. This is to tune the sampling
frequency away from any harmonic noise aliased with the ADC sampling frequency (within the burst) from
the sampled signal. An automatic sampling delay variation feature can be used to randomize this delay to
slightly change the time between samples.
Selectable voltage references from the internal Voltage Reference (VREF) peripheral, VDD supply
voltage, or external VREF pin (VREFA).
This device has two instances of the ADC, ADC0 and ADC1.
When the Peripheral Touch Controller (PTC) is enabled, ADC0 is fully controlled by the PTC peripheral.
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Block Diagram
Figure 30-1. Block Diagram
..
.
ADC
DAC
"enable"
VREF
TEMPREF
RES
"accumulate"
AINn
VREF
"convert"
AIN0
AIN1
Internal reference
VREFA
VDD
"sample"
30.2.1
>
<
WCOMP
(IRQ)
Control Logic
MUXPOS
RESRDY
(IRQ)
CTRLA
EVCTRL
COMMAND
WINLT
WINHT
The analog input channel is selected by writing to the MUXPOS bits in the MUXPOS register
(ADC.MUXPOS). Any of the ADC input pins, GND, internal Voltage Reference (VREF), or temperature
sensor, can be selected as single ended input to the ADC. The ADC is enabled by writing a '1' to the ADC
ENABLE bit in the Control A register (ADC.CTRLA). Voltage reference and input channel selections will
not go into effect before the ADC is enabled. The ADC does not consume power when the ENABLE bit in
ADC.CTRLA is zero.
The ADC generates a 10-bit result which can be read from the Result Register (ADC.RES). The result is
presented right adjusted.
30.2.2
Signal Description
Pin Name
Type
Description
AIN[11:0]
Analog input
analog input to be converted
VREFA
Analog input
analog reference input
Related Links
Configuration Summary
I/O Multiplexing and Considerations
30.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 30-1. ADC System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
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Dependency
Applicable
Peripheral
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
30.2.3.1 Clocks
The ADC uses the peripheral clock CLK_PER, and has an internal prescaler to generate the ADC clock
source CLK_ADC.
Related Links
CLKCTRL - Clock Controller
Clock generation
30.2.3.2 I/O Lines and Connections
The I/O-pins (AINx and VREF) are configured by the PORT - I/O Pin Controller.
The digital input buffer should be disabled on the pin used as input for the ADC to disconnect the digital
domain from the analog domain to obtain the best possible ADC results. This is configured by the PORT I/O Pin Controller.
Related Links
PORT - I/O Pin Configuration
30.2.3.3 Interrupts
Using the interrupts of this peripheral requires the Interrupt Controller to be configured first.
Related Links
CPUINT - CPU Interrupt Controller
SREG
Interrupts
30.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
EVSYS - Event System
30.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in debugging
mode will halt normal operation of the peripheral.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
30.2.4
Definitions
An ideal n-bit single-ended ADC converts a voltage linearly between GND and VREF in 2n steps (LSBs).
The lowest code is read as 0, and the highest code is read as 2n-1. Several parameters describe the
deviation from the ideal behavior:
Offset Error
The deviation of the first transition (0x000 to 0x001) compared to the ideal
transition (at 0.5 LSB). Ideal value: 0 LSB.
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Figure 30-2. Offset Error
Output Code
Ideal ADC
Actual ADC
Offset
Error
Gain Error
VREF Input Voltage
After adjusting for offset, the gain error is found as the deviation of the last
transition (0x3FE to 0x3FF) compared to the ideal transition (at 1.5 LSB below
maximum). Ideal value: 0 LSB.
Figure 30-3. Gain Error
Gain
Error
Output Code
Ideal ADC
Actual ADC
VREF
Integral NonLinearity (INL)
Input Voltage
After adjusting for offset and gain error, the INL is the maximum deviation of an
actual transition compared to an ideal transition for any code. Ideal value: 0 LSB.
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Figure 30-4. Integral Non-Linearity
Output Code
INL
Ideal ADC
Actual ADC
VREF
Differential NonLinearity (DNL)
Input Voltage
The maximum deviation of the actual code width (the interval between two
adjacent transitions) from the ideal code width (1 LSB). Ideal value: 0 LSB.
Figure 30-5. Differential Non-Linearity
Output Code
0x3FF
1 LSB
DNL
0x000
0
VREF
Input Voltage
Quantization Error Due to the quantization of the input voltage into a finite number of codes, a range
of input voltages (1 LSB wide) will code to the same value. Always ±0.5 LSB.
Absolute
Accuracy
The maximum deviation of an actual (unadjusted) transition compared to an ideal
transition for any code. This is the compound effect of all aforementioned errors.
Ideal value: ±0.5 LSB.
30.3
Functional Description
30.3.1
Initialization
The following steps are recommended in order to initialize ADC operation:
1. Configure the resolution by writing to the Resolution Selection bit (RESSEL) in the Control A
register (ADC.CTRLA).
2. Optional: Configure the number of samples to be accumulated per conversion by writing the
Sample Accumulation Number Select bits (SAMPNUM) in the Control B register (ADC.CTRLB).
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3.
4.
5.
6.
7.
Configure a voltage reference by writing to the Reference Selection bit (REFSEL) in the Control C
register (ADC.CTRLC). Default is the internal Voltage Reference of the device (VREF, as
configured there).
Configure the CLK_ADC by writing to the Prescaler bit field (PRESC) in the Control C register
(ADC.CTRLC).
Configure an input by writing to the MUXPOS bit field in the MUXPOS register (ADC.MUXPOS).
Optional: Enable Start Event input by writing a '1' to the Start Event Input bit (STARTEI) in the
Event Control register (ADC.EVCTRL). Configure the Event System accordingly.
Enable the ADC by writing a '1' to the ENABLE bit in ADC.CTRLA.
Following these steps will initialize the ADC for basic measurements, which can be triggered by an Event
(if configured) or by writing a '1' to the Start Conversion bit (STCONV) in the Command register
(ADC..COMMAND).
30.3.2
Operation
30.3.2.1 Starting a Conversion
Once the input channel is selected by writing to the MUXPOS register (ADC.MUXPOS), a conversion is
triggered by writing a '1' to the ADC Start Conversion bit (STCONV) in the Command register
(ADC.COMMAND). This bit is one as long as the conversion is in progress. In single conversion mode,
STCONV is cleared by hardware when the conversion is completed.
If a different input channel is selected while a conversion is in progress, the ADC will finish the current
conversion before changing the channel.
Depending on the Accumulator setting, the conversion result is from a single sensing operation, or from a
sequence of accumulated samples. Once the triggered operation is finished, the Result Ready flag
(RESRDY) in the Interrupt Flag register (ADC.INTFLAG) is set. And the corresponding interrupt vector is
executed if the Result Ready Interrupt Enable bit (RESRDY) in the Interrupt Control register
(ADC.INTCTRL) is one and the Global Interrupt Enable bit is one.
A single conversion can be started by writing a '1' to the STCONV bit in ADC.COMMAND. The STCONV
bit can be used to determine if a conversion is in progress, the STCONV bit will be set during a
conversion, and cleared once the conversion is complete.
The RESRDY interrupt flag in ADC.INTFLAG will be set even if the specific interrupt is disabled, allowing
software to check for finished conversion by polling the flag. A conversion can thus be triggered without
causing an interrupt.
Alternatively, a conversion can be triggered by an event, this is enabled by writing a '1' to the Start Event
Input bit (STARTEI) in the Event Control register (ADC.EVCTRL). Any incoming event routed to the ADC
thorugh the Event System (EVSYS) will trigger an ADC conversion. This provides a method to start
conversions at predictable intervals or at specific conditions.
The event trigger input is edge sensitive, when an event occurs, STCONV in ADC.COMMAND is set.
STCONV will be cleared when the conversion is complete.
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30.3.2.2 Clock generation
Figure 30-6. ADC Prescaler
ENABLE
"START"
Reset
8-bit PRESCALER
CTRLC
CLK_PER/256
CLK_PER/128
CLK_PER/64
CLK_PER/32
CLK_PER/16
CLK_PER/8
CLK_PER/4
CLK_PER/2
CLK_PER
PRESC
ADC clock source
(CLK_ADC)
The ADC requires an input clock frequency between 50kHz and 1.5MHz for maximum resolution. If a
lower resolution than 10 bits is selected, the input clock frequency to the ADC can be higher than 1.5MHz
to get a higher sample rate.
The ADC module contains a prescaler which generates the ADC clock (CLK_ADC) from any CPU clock
(CLK_PER) above 100kHz. The prescaling is selected by writing to the Prescaler bits (PRESC) in the
Control C register (ADC.CTRLC). The prescaler starts counting from the moment the ADC is switched on
by writing a '1' to the ENABLE bit in ADC.CTRLA. The prescaler keeps running as long as the ENABLE
bit is one, the prescaler counter is reset to zero when the ENABLE bit is zero.
When initiating a conversion by writing a '1' to the Start Conversion bit (STCONV) in the Command
register (ADC.COMMAND) or from event, the conversion starts at the following rising edge of the
CLK_ADC clock cycle. The prescaler is kept reset as long as there is no ongoing conversion. This
assures a fixed delay from the trigger to the actual start of a conversion in CLK_PER cycles as:
PRESCfactor
+2
2
Figure 30-7. Start conversion and clock generation
StartDelay =
CLK_PER
STCONV
CLK_PER/2
CLK_PER/4
CLK_PER/8
30.3.2.3 Conversion timing
A normal conversion takes 13 CLK_ADC cycles. The actual sample-and-hold takes place 2 CLK_ADC
cycles after the start of a conversion. Start of conversion is initiated by writing a '1' to the STCONV bit in
ADC.COMMAND. When a conversion is complete, the result is available in the Result register
(ADC.RES), and the Result Ready interrupt flag is set (RESRDY in ADC.INTFLAG). The interrupt flag will
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be cleared when the result is read from the Result registers, or by writing a '1' to the RESRDY bit in
ADC.INTFLAG.
Figure 30-8. ADC Timing Diagram - Single Conversion
2
3
4
6
8
5
7
1
Cycle Number
9
10
11
13
12
ADC clock
ADC enable
STCONV
RESRDY IF
RESH
RESL
Result MSB
Result LSB
conversion
complete
sample
Both sampling time and sampling length can be adjusted using Sample Delay bit field in Control D
(ADC.CTRLD) and sampling Sample Length bit field in the Sample Control register (ADC.SAMPCTRL).
Both of these control the ADC sampling time in number of CLK_ADC cycles. This allows sampling highimpedance sources without relaxing conversion speed. See register description for further information.
Total sampling time is given by:
SampleTime =
2 + SAMPDLY + SAMPLEN
�CLK_ADC
Figure 30-9. ADC timing Diagram - Single conversion with delays
1
2
3
4
5
6
7
8
9
10
11
12
13
CLK_ADC
ENABLE
STCONV
RES
Result
INITDLY
(0 – 256
CLK_ADC cycles)
SAMPDLY
(0 – 15
CLK_ADC cycles)
SAMPLEN
(0 – 31
CLK_ADC cycles)
30.3.2.4 Changing Channel or Reference Selection
The MUXPOS bits the ADC.MUXPOS register and the REFSEL bits in the ADC.CTRLC register are
buffered through a temporary register to which the CPU has random access. This ensures that the
channel and reference selections only take place at a safe point during the conversion. The channel and
reference selections are continuously updated until a conversion is started.
Once the conversion starts, the channel and reference selections are locked to ensure sufficient sampling
time for the ADC. Continuous updating resumes in the last CLK_ADC clock cycle before the conversion
completes (RESRDY in ADC.INTFLAGS is set). The conversion starts on the following rising CLK_ADC
clock edge after the STCONV bit is written to '1'.
ADC Input Channels
When changing channel selection, the user should observe the following guideline to ensure that the
correct channel is selected:
The channel should be selected before starting the conversion. The channel selection may be changed
one ADC clock cycle after writing '1' to the STCONV bit.
After switching the input channel the ADC requires a settling time, please refer to the electrical
characteristics section for details.
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ADC Voltage Reference
The reference voltage for the ADC (VREF) controls the conversion range of the ADC. Input voltages that
exceed the selected VREF will be converted to the maximum result value of the ADC, for an ideal 10-bit
ADC this is 0x3FF. VREF can be selected by writing the Reference Selection bits (REFSEL) in the Control
C register (ADC.CTRLC) as either VDD, external reference VREFA, or an internal reference. VDD is
connected to the ADC through a passive switch.
When using external reference voltage VREFA, ADCnREFSEL[0:2] in the corresponding VREF.CTRLn
register should be configured to the selection closest, but above applied reference voltage. For external
references higher than 4.3V, use ADCnREFSEL[0:2] = 0x3
The internal reference is generated from an internal bandgap reference through an internal amplifier,
controlled by the Voltage Reference (VREF) peripheral.
Related Links
VREF - Voltage Reference
Analog Input Circuitry
The analog input circuitry is illustrated in the Figure below. An analog source applied to ADCn is
subjected to the pin capacitance and input leakage of that pin (represented by IH and IL), regardless of
whether that channel is selected as input for the ADC. When the channel is selected, the source must
drive the S/H capacitor through the series resistance (combined resistance in the input path).
The ADC is optimized for analog signals with an output impedance of approximately 10kΩ or less. If such
a source is used, the sampling time will be negligible. If a source with higher impedance is used, the
sampling time will depend on how long the source needs to charge the S/H capacitor, which can vary
substantially.
Figure 30-10. Analog Input Schematic
IIH
ADCn
Rin
Cin
IIL
VDD/2
30.3.2.5 ADC Conversion Result
After the conversion is complete (RESRDY is set), the conversion result RES is available in the ADC
Result Register (ADC.RES). The result for a 10-bit conversion is given as:
RES =
1023 × �IN
�REF
where VIN is the voltage on the selected input pin and VREF the selected voltage reference (see
description for REFSEL in ADC.CTRLC and ADC.MUXPOS).
30.3.2.6 Temperature Measurement
The temperature measurement is based on an on-chip temperature sensor. For a temperature
measurement, follow these steps:
1. Configure the internal voltage reference to 1.1V: in VREF.CTRLA, write ADC0REFSEL=0x1 for
ADC0. For ADC1, write ADC1REFSEL=0x1 in VREF.CTRLC.
2. Select the internal voltage reference by writing the REFSEL bits in ADC.CTRLC to 0x0.
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3.
4.
5.
6.
7.
8.
Select the ADC Temperature sensor channel by writing the MUXPOS bits in the MUXPOS register
(ADC.MUXPOS) to 0x1E. This enables the temperature sensor.
In ADC.CTRLD Select INITDLY ≥ 32µs × �CLK_ADC
In ADC.SAMPCTRL Select SAMPLEN ≥ 32µs × �CLK_ADC
In ADC.CTRLC Select SAMPCAP = 5pF
Acquire the temperature sensor output voltage by starting a conversion.
Process the measurement result as described below.
The measured voltage has a linear relationship to the temperature. Due to process variations, the
temperature sensor output voltage varies between individual devices at the same temperature. The
individual compensation factors are determined during the production test and saved in the Signature
Row:
•
SIGROW.TEMPSENSE0 is an gain/slope correction
•
SIGROW.TEMPSENSE1 is a offset correction
In order to achieve accurate results, the result of the temperature sensor measurement must be
processed in the application software using factory calibration values. The temperature (in Kelvin) is
calculated by this rule:
Temp = (((RESH > 8
RESH and RESL are the high and low byte of the Result register (ADC.RES), and TEMPSENSEn are the
respective values from the Signature row.
It is recommended to follow these steps in user code:
int8_t sigrow_offset = SIGROW.TEMPSENSE1; // Read signed value from signature row
uint8_t sigrow_gain = SIGROW.TEMPSENSE0;
// Read unsigned value from signature row
uint16_t adc_reading = 0;
// ADC conversion result with 1.1 V internal reference
uint32_t temp = adc_reading - sigrow_offset;
temp *= sigrow_gain; // Result might overflow 16 bit variable (10bit+8bit)
temp += 0x80;
// Add 1/2 to get correct rounding on division below
temp >>= 8;
// Divide result to get Kelvin
uint16_t temperature_in_K = temp;
Related Links
TEMPSENSEn
30.3.2.7 Window Comparator Mode
The ADC can raise the WCOMP flag in the Interrupt and Flag register (ADC.INTFLAG) and request an
interrupt (WCOMP) when the result of a conversion is above and/or below certain thresholds. The
available modes are:
•
The result is under a threshold
•
The result is over a threshold
•
The result is inside a window (above a lower threshold, but below the upper one)
•
The result is outside a window (either under the lower or above the upper threshold)
The thresholds are defined by writing to the Window Comparator Threshold registers (ADC.WINLT and
ADC.WINHT). Writing to the Window Comparator Mode bit field (WINCM) in the Control E register
(ADC.CTRLE) selects the conditions when the flag is raised and/or the interrupt is requested.
Assuming the ADC is already configured to run, follow these steps to use the Window Comparator Mode:
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1.
2.
3.
Choose which Window Comparator to use (see WINCM description in ADC.CTRLE), and set the
required threshold(s) by writing to ADC.WINLT and/or ADC.WINHT.
Optional: enable the interrupt request by writing a '1' to the Window Comparator Interrupt Enable bit
(WCOMP) in the Interrupt Control register (ADC.INTCTRL)
Enable the Window Comparator and select a mode by writing a non-zero value to the WINCM bit
field in ADC.CTRLE.
When accumulating multiple samples, the comparison between the result and the threshold will happen
after the last sample was acquired. Consequently, the flag is only raised once, after taking the last sample
of the accumulation.
30.3.2.8 PTC Operation
When the Peripheral Touch Controller (PTC) is enabled, it takes complete control of ADC0.
When the PTC is disabled, ADC0 is available as a normal ADC.
Refer to the QTouch Library user guide for more details on using the PTC.
Related Links
Functional Description
30.3.3
Events
An ADC conversion can be triggered automatically by an event input if the Start Event Input bit
(STARTEI) in the Event Control register (ADC.EVCTRL) is written to '1'.
See also the description of the Asynchronous User Channel n Input Selection in the Event System
(EVSYS.ASYNCUSERn).
Related Links
ASYNCUSER0, ASYNCUSER1, ASYNCUSER2, ASYNCUSER3, ASYNCUSER4, ASYNCUSER5,
ASYNCUSER6, ASYNCUSER7, ASYNCUSER8, ASYNCUSER9, ASYNCUSER10
30.3.4
Interrupts
Table 30-2. Available Interrupt Vectors and Sources
Offset Name
Vector Description
Conditions
0x00
RESRDY Result Ready interrupt
The conversion result is available in the Result
register (ADC.RES).
0x02
WCOMP Window Comparator interrupt As defined by WINCM in ADC.CTRLE.
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Interrupt Flags register
of the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the Interrupt
Flag is set. The interrupt request remains active until the Interrupt Flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear Interrupt Flags.
30.3.5
Sleep Mode Operation
The ADC is by default disabled In Standby sleep mode.
The ADC can stay fully operational in Standby sleep mode if the Run in Standby bit (RUNSTDBY) in the
Control A register (ADC.CTRLA) is written to '1'.
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
When the device is entering Standby sleep mode when RUNSTDBY is one, the ADC will stay active,
hence any ongoing conversions will be completed, and interrupts will be executed as configured.
In Standby sleep mode an ADC conversion must be triggered via the Event System (EVSYS). The
peripheral clock is requested if needed and is turned off after the conversion is completed.
When an input Event trigger occurs, the positive edge will be detected, the Start Conversion bit
(STCONV) in the Command register (ADC.COMMAND) set, and the conversion will start. When the
conversion is completed, the Result Ready Flag (RESRDY) in the Interrupt Flags register
(ADC.INTFLAGS) is set and the STCONV bit in ADC.COMMAND is cleared.
The reference source and supply infrastructure need time to stabilize when activated in Standby sleep
mode. Configure a delay for the start of the first conversion by writing a non-zero value to the Initial Delay
bits (INITDLY) in the Control D register (ADC.CTRLD).
In Power Down sleep mode, no conversions are possible. Any ongoing conversions are halted and will be
resumed when going out of sleep. At end of conversion, the Result Ready Flag (RESRDY) will be set, but
the content of the result registers (ADC.RES) is invalid since the ADC was halted in the middle of a
conversion.
Related Links
SLPCTRL - Sleep Controller
30.3.6
Synchronization
Not applicable.
30.3.7
Configuration Change Protection
Not applicable.
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8-bit AVR Microcontroller
30.4
Register Summary - ADC
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
CTRLC
7:0
SAMPCAP
0x03
CTRLD
7:0
INITDLY[2:0]
0x04
CTRLE
7:0
RUNSTBY
RESSEL
ENABLE
SAMPNUM[2:0]
REFSEL[1:0]
PRESC[2:0]
ASDV
SAMPDLY[3:0]
WINCM[2:0]
0x05
SAMPCTRL
7:0
SAMPLEN[4:0]
0x06
MUXPOS
7:0
MUXPOS[4:0]
0x07
Reserved
0x08
COMMAND
7:0
0x09
EVCTRL
7:0
0x0A
INTCTRL
7:0
WCOMP
WCOMP
0x0B
INTFLAGS
7:0
0x0C
DBGCTRL
7:0
0x0D
TEMP
7:0
STCONV
STARTEI
RESRDY
RESRDY
DBGRUN
TEMP[7:0]
0x0E
...
Reserved
0x0F
0x10
RES
0x11
0x12
WINLT
0x13
0x14
WINHT
0x15
7:0
RES[7:0]
15:8
RES[15:8]
7:0
WINLT[7:0]
15:8
WINLT[15:8]
7:0
WINHT[7:0]
15:8
WINHT[15:8]
30.5
Register Description
30.5.1
Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
7
6
5
4
3
RUNSTBY
Access
Reset
2
1
0
RESSEL
ENABLE
R/W
R
R
R
R
R/W
R/W
0
0
0
0
0
0
0
Bit 7 – RUNSTBY: Run in Standby
This bit determines whether the ADC needs to run when the chip is in standby sleep mode.
Bit 2 – RESSEL: Resolution Selection
This bit selects the ADC resolution.
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8-bit AVR Microcontroller
Value
0
1
Description
Full 10-bit resolution. The 10-bit ADC results are accumulated or stored to the ADC Result
register (ADC.RES).
8-bit resolution. The conversion results are truncated to 8 bits (MSBs) before they are
accumulated or stored to the ADC Result register (ADC.RES). The two least significant bits
are discarded.
Bit 0 – ENABLE: ADC Enable
Value
0
1
30.5.2
Description
ADC is disabled.
ADC is enabled.
Control B
Name: CTRLB
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
Access
R
R
R
R
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SAMPNUM[2:0]
Bits 2:0 – SAMPNUM[2:0]: Sample Accumulation Number Select
These bits select how many consecutive ADC sampling results are accumulated automatically. When this
bit is written to a value greater than 0x0, the according number of consecutive ADC sampling results are
accumulated into the ADC Result register (RES) in one complete conversion.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
30.5.3
Name
NONE
ACC2
ACC4
ACC8
ACC16
ACC32
ACC64
-
Description
No accumulation.
2 results accumulated.
4 results accumulated.
8 results accumulated.
16 results accumulated.
32 results accumulated.
64 results accumulated.
Reserved.
Control C
Name: CTRLC
Offset: 0x02
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
7
6
5
SAMPCAP
4
3
2
1
REFSEL[1:0]
0
PRESC[2:0]
Access
R
R/W
R/W
R/W
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit 6 – SAMPCAP: Sample Capacitance Selection
This bit selects the sample capacitance, and hence, the input impedance. The best value is dependent on
the reference voltage and the application's electrical properties.
Value
0
1
Description
Recommended for reference voltage values below 1V.
Reduced size of sampling capacitance. Recommended for higher reference voltages.
Bits 5:4 – REFSEL[1:0]: Reference Selection
These bits selects the voltage reference for the ADC.
Value
0x0
0x1
0x2
Other
Name
INTERNAL
VDD
VREFA
-
Description
Internal reference
VDD
External reference VREFA
Reserved.
Bits 2:0 – PRESC[2:0]: Prescaler
These bits defines the division factor from peripheral clock (CLK_PER) to the ADC clock (CLK_ADC).
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
30.5.4
Name
DIV2
DIV4
DIV8
DIV16
DIV32
DIV64
DIV128
DIV256
Description
CLK_PER divided by 2
CLK_PER divided by 4
CLK_PER divided by 8
CLK_PER divided by 16
CLK_PER divided by 32
CLK_PER divided by 64
CLK_PER divided by 128
CLK_PER divided by 256
Control D
Name: CTRLD
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
INITDLY[2:0]
Access
Reset
4
3
2
ASDV
1
0
SAMPDLY[3:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:5 – INITDLY[2:0]: Initialization Delay
These bits defines the initialization/startup delay before the first sample when enabling the ADC or
changing to internal reference voltage. Setting this delay will ensure that the reference, muxes, etc are
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8-bit AVR Microcontroller
ready before starting the first conversion. The initialization delay will also take place when waking up from
deep sleep to do a measurement.
The delay is expressed as a number of CLK_ADC cycles.
Value
0x0
0x1
0x2
0x3
0x4
0x5
Other
Name
DLY0
DLY16
DLY32
DLY64
DLY128
DLY256
-
Description
Delay 0 CLK_ADC cycles.
Delay 16 CLK_ADC cycles.
Delay 32 CLK_ADC cycles.
Delay 64 CLK_ADC cycles.
Delay 128 CLK_ADC cycles.
Delay 256 CLK_ADC cycles.
Reserved
Bit 4 – ASDV: Automatic Sampling Delay Variation
Writing this bit to '1' enables automatic sampling delay variation between ADC conversions. The purpose
of varying sampling instant is to randomize the sampling instant and thus avoid standing frequency
components in frequency spectrum. The value of the SAMPDLY bits is automatically incremented by one
after each sample.
When the Automatic Sampling Delay Variation is enabled and the SAMPDLY value reaches 0xF, it wraps
around to 0x0.
Value
0
1
Name
ASVOFF
ASVON
Description
The Automatic Sampling Delay Variation is disabled.
The Automatic Sampling Delay Variation is enabled.
Bits 3:0 – SAMPDLY[3:0]: Sampling Delay Selection
These bits define the delay between consecutive ADC samples. The programmable Sampling Delay
allows modifying the sampling frequency during hardware accumulation, to suppress periodic noise
sources that may otherwise disturb the sampling. The SAMPDLY field can be also modified automatically
from sampling cycle to another, by setting the ASDV bit. The delay is expressed as CLK_ADC cycles and
is given directly by the bitfield setting. The sampling cap is kept open during the delay.
30.5.5
Control E
Name: CTRLE
Offset: 0x4
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
Access
R
R
R
R
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
WINCM[2:0]
Bits 2:0 – WINCM[2:0]: Window Comparator Mode
This field enable and define when the interrupt flag is set in Window Comparator mode. RESULT is the
16-bit accumulator result. WINLT and WINHT are 16-bit lower threshold value and 16-bit higher threshold
value, respectively.
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8-bit AVR Microcontroller
Value
0x0
0x1
0x2
0x3
0x4
Other
30.5.6
Name
NONE
BELOW
ABOVE
INSIDE
OUTSIDE
-
Description
No Window Comparison (default)
RESULT < WINLT
RESULT > WINHT
WINLT < RESULT < WINHT
RESULT < WINLT or RESULT >WINHT)
Reserved
Sample Control
Name: SAMPCTRL
Offset: 0x5
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
SAMPLEN[4:0]
Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 4:0 – SAMPLEN[4:0]: Sample Length
These bits extend the ADC sampling length in number of CLK_ADC cycles. By default the sampling time
is two CLK_ADC cycles. Increasing the sampling length allows sampling sources with higher impedance.
The total conversion time increased with the selected sampling length.
30.5.7
MUXPOS
Name: MUXPOS
Offset: 0x06
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
MUXPOS[4:0]
Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 4:0 – MUXPOS[4:0]: MUXPOS
This bit field selects which single ended analog input is connected to the ADC. If these bits are changed
during a conversion, the change will not take effect until this conversion is complete.
Value
0x00
0x01
0x02
0x03
0x04
0x05
0x06
Name
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
© 2017 Microchip Technology Inc.
Description
ADC input pin 0
ADC input pin 1
ADC input pin 2
ADC input pin 3
ADC input pin 4
ADC input pin 5
ADC input pin 6
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8-bit AVR Microcontroller
Value
0x07
0x08
0x09
0x0A
0x0B
0x1B
0x1C
0x1D
0x1E
0x1F
Other
30.5.8
Name
AIN7
AIN8
AIN9
AIN10
AIN11
PTC
DAC0
INTREF
TEMPSENSE
GND
-
Description
ADC input pin 7
ADC input pin 8
ADC input pin 9
ADC input pin 10
ADC input pin 11
ADC0: Reserved / ADC1: DAC2
DAC0
Internal reference (from VREF peripheral)
ADC0: Temperature sensor / ADC1: DAC1
0V (GND)
Reserved
Command
Name: COMMAND
Offset: 0x08
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
STCONV
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
Bit 0 – STCONV: Start Conversion
Writing a '1' to this bit will start a single measurement. STCONV will read as '1' as long as a conversion is
in progress. When the conversion is complete, this bit is automatically cleared.
Writing the bit to '0' during an ongoing conversion will stop the conversion.
30.5.9
Event Control
Name: EVCTRL
Offset: 0x09
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
STARTEI
Bit 0 – STARTEI: Start Event Input
This bit enables event input as source for conversion start.
30.5.10 Interrupt Control
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8-bit AVR Microcontroller
Name: INTCTRL
Offset: 0x0A
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
WCOMP
RESRDY
Access
R
R
R
R
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit 1 – WCOMP: Window Comparator Interrupt Enable
Writing a '1' to this bit enables window comparator interrupt.
Bit 0 – RESRDY: Result Ready Interrupt Enable
Writing a '1' to this bit enables result ready interrupt.
30.5.11 Interrupt Flags
Name: INTFLAGS
Offset: 0x0B
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
WCOMP
RESRDY
Access
R
R
R
R
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit 1 – WCOMP: Window Comparator Interrupt Flag
This window comparator flag is set when the measurement is complete and if the result match the
selected window comparator mode defined by WINCM (ADCn.CTRLE). The comparison is done at end of
conversion. The flag is cleared by either writing a '1' to the bit position or by reading the result register
(ADCn.RES). Writing a '0' to this bit has no effect.
Bit 0 – RESRDY: Result Ready Interrupt Flag
The result ready interrupt flag is set when a measurement is complete and a new result is ready. The flag
is cleared by either writing a '1' to the bit location or by reading the result register (ADCn.RES). Writing a
'0' to this bit has no effect.
30.5.12 Debug Run
Name: DBGCTRL
Offset: 0x0C
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
DBGRUN
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
Bit 0 – DBGRUN: Debug Run
Value
0
1
Description
The peripheral is halted in break debug mode and ignores events.
The peripheral will continue to run in break debug mode when the CPU is halted.
30.5.13 Temporary
The Temporary register is used by the CPU for single-cycle, 16-bit access to the 16-bit registers of this
peripheral. It can also be read and written by software. See also Accessing 16-bit Registers. There is one
common Temporary register for all the 16-bit registers of this peripheral.
Name: TEMP
Offset: 0x0D
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
TEMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – TEMP[7:0]: Temporary
Temporary register for read/write operations in 16-bit registers.
30.5.14 Result
The RESL and RESH register pair represents the 16-bit value, RES. The low byte [7:0] (suffix L) is
accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset + 0x01. For
more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
If the analog input is higher than the reference level of the ADC, the 10 bit ADC result will be equal the
max value of 0x3FF. Likewise, if the input is below 0V, the ADC result will be 0x000. As the ADC cannot
produce a result above 0x3FF values, the accumulated value will never exceed 0xFFC0 even after
maximum allowed 64 accumulations.
Name: RES
Offset: 0x10
Reset: 0x00
Property:
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Datasheet Preliminary
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8-bit AVR Microcontroller
Bit
15
14
13
12
11
10
9
8
RES[15:8]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
RES[7:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 15:8 – RES[15:8]: Result high byte
These bits constitute the MSB of RES register, where the msb is RES[15]. The ADC itself has 10-bit
output, ADC[9:0], where the msb is ADC[9]. The data format in ADC and Digital Accumulation is 1’s
complement, where 0x0000 represents the zero and 0xFFFF represent the largest number (full scale).
Bits 7:0 – RES[7:0]: Result low byte
These bits constitute the LSB of ADC/Accumulator Result, (RES) register. The data format in ADC and
Digital Accumulation is 1’s complement, where 0x0000 represents the zero and 0xFFFF represent the
largest number (full scale).
30.5.15 Window Comparator Low Threshold
This register is the 16-bit Low Threshold for the digital comparator monitoring the RES register. The ADC
itself has 10-bit output, RES[9:0], where the msb is RES[9]. The data format in ADC and Digital
Accumulation is one’s complement, where 0x0000 represents the zero and 0xFFFF represent the largest
number (full scale).
The WINLTH and WINLTL register pair represent the 16-bit value, WINLT. The low byte [7:0] (suffix L) is
accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset + 0x01. For
more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
When accumulating samples, the window comparator thresholds are applied on the accumulated value
and not on each sample.
Name: WINLT
Offset: 0x12
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
WINLT[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
WINLT[7:0]
Access
Reset
Bits 15:8 – WINLT[15:8]: Window Comparator Low Threshold high byte
These bits hold the MSB of the 16-bit register.
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Datasheet Preliminary
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8-bit AVR Microcontroller
Bits 7:0 – WINLT[7:0]: Window Comparator Low Threshold low byte
These bits hold the LSB of the 16-bit register.
30.5.16 Window Comparator High Threshold
This register is the 16-bit High Threshold for the digital comparator monitoring the RES register. The ADC
itself has 10-bit output, RES[9:0], where the msb is RES[9]. The data format in ADC and Digital
Accumulation is one’s complement, where 0x0000 represents the zero and 0xFFFF represent the largest
number (full scale).
The WINHTH and WINHTL register pair represent the 16-bit value, WINHT. The low byte [7:0] (suffix L) is
accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset + 0x01. For
more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.
Name: WINHT
Offset: 0x14
Reset: 0x00
Property:
Bit
15
14
13
12
11
10
9
8
WINHT[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
WINHT[7:0]
Access
Reset
Bits 15:8 – WINHT[15:8]: Window Comparator High Threshold high byte
These bits hold the MSB of the 16-bit register.
Bits 7:0 – WINHT[7:0]: Window Comparator High Threshold low byte
These bits hold the LSB of the 16-bit register.
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
31.
DAC - Digital to Analog Converter
31.1
Features
•
•
•
•
•
31.2
8-bit resolution
Up to 350ksps conversion rate
High drive capabilities (DAC0)
Functioning as input to Analog Comparator (AC) or ADC
Three instances of the peripheral: DAC0, DAC1, DAC2
Overview
The Digital-to-Analog Converter (DAC) converts a digital value written to the Data register (DAC.DATA) to
an analogue voltage. The conversion range is between GND and the selected reference voltage.
The DAC features an 8-bit Resistor String type DAC, capable of converting 350,000 samples per second
(350ksps). The DAC uses the internal Voltage Reference (VREF) as upper limit for conversion. The DAC
has one continuous time output with high drive capabilities, which is able to drive 5kΩ and/or 30pF load.
The DAC conversion can be started from the application by writing to the data conversion registers.
This device has three instances of the DAC peripheral, DAC0, DAC1, and DAC2.
31.2.1
Block Diagram
Figure 31-1. DAC Block Diagram
other
peripherals
DATA
DAC
8
OUT
Output
Driver
VREF
ENABLE
CTRLA
OUTEN
Note: Only DAC0 has an output driver for an external pin.
31.2.2
Signal Description
Signal
Description
Type
OUT
DAC output
Analog
Note: Only DAC0 has an output driver for an external pin.
Related Links
I/O Multiplexing and Considerations
31.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
© 2017 Microchip Technology Inc.
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8-bit AVR Microcontroller
Table 31-1. DAC System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
No
-
Events
No
-
Debug
Yes
UPDI
Related Links
Clocks
I/O Lines and Connections
Debug Operation
31.2.3.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
CLKCTRL - Clock Controller
31.2.3.2 I/O Lines and Connections
Using the I/O lines of the peripheral requires configuration of the I/O pins.
Table 31-2. I/O Lines
Instance
Signal
I/O Line
Peripheral Function
DAC
OUT
PA6
A
The DAC0 has one analog output pin (OUT) that must be configured before it can be used.
A DAC is also internally connected to the AC and to the ADC. To use this internal OUT as input, both
output and input must be configured in their respective registers.
Note: Only DAC0 has an output driver for an external pin.
Related Links
PORT - I/O Pin Configuration
AC – Analog Comparator
ADC - Analog to Digital Converter
31.2.3.3 Events
Not applicable.
31.2.3.4 Interrupts
Not applicable.
31.2.3.5 Debug Operation
This peripheral is unaffected by entering debug mode.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
PORT - I/O Pin Configuration
31.3
Functional Description
31.3.1
Initialization
To operate the DAC, the following steps are required:
•
•
•
•
•
Select the DAC reference voltage in the Voltage Reference (VREF) peripheral by writing the DAC
and AC Reference Selection bits (DAC0REFSEL) in the Control A register of the Voltage Reference
(VREF.CTRLA) for DAC0. For DAC1, use DAC1REFSEL in VREF.CTRLC. For DAC2, use
DAC2REFSEL in VREF.CTRLD.
The conversion range is between GND and the selected reference voltage.
Configure the further usage of the DAC output:
– Configure an internal peripheral (e.g. AC, ADC) to use the DAC output. See the according
peripheral's documentation.
– Enable the output to a pin by writing a '1' to the Output Enable bit (OUTEN) in the Control A
register (DAC.CTRLA). This requires configuration of the Port peripheral.
For DAC0, either one or both options are valid. Other instances of the DAC only support internal
signaling.
Write an initial digital value to the Data register (DAC.DATA).
Enable the DAC by writing a '1' to the ENABLE bit in the Control A register (DAC.CTRLA).
Related Links
VREF - Voltage Reference
AC – Analog Comparator
ADC - Analog to Digital Converter
31.3.2
Operation
31.3.2.1 Enabling, Disabling and Resetting
The DAC is enabled by writing a '1' to the ENABLE bit in the Control A register (DAC.CTRLA), and
disabled by writing a '0' to this bit.
The OUT output to a pin is enabled by writing the Output Enable bit (OUTEN) in the CTRLA register
(DAC.CTRLA).
31.3.2.2 Starting a Conversion
When the DAC is enabled (ENABLE=1 in DAC.CTRLA), a conversion starts as soon as the Data register
(DAC.DATA) is written.
When the DAC is disabled (ENABLE=0 in DAC.CTRLA), writing DAC.DATA does not trigger a
conversion. Instead, the conversion starts on writing a '1' to ENABLE in DAC.CTRLA.
31.3.2.3 DAC as Source For Internal Peripherals
The analog output of the DAC is internally connected to both the AC and the ADC, and is available to
these other peripherals when the DAC is enabled (ENABLE=1 in DAC.CTRLA). When the DAC analog
output is only being used internally, it is not necessary to enable the pin output driver (i.e. OUTEN=0 in
DAC.CTRLA is acceptable).
Note: Only DAC0 has an output driver for an external pin.
Related Links
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
AC – Analog Comparator
ADC - Analog to Digital Converter
31.3.3
Sleep Mode Operation
If the Run in Standby bit (RUNSTDBY) in the Control A register (DAC.CTRLA) is written to '1' and
CLK_PER is available, the DAC will continue to operate in Standby sleep mode. If RUNSTDBY bit is
zero, the DAC will stop the conversion in Standby sleep mode.
If conversion is stopped in Standby sleep mode, the DAC and the output buffer are disabled to reduce
power consumption. When the device is exiting Standby sleep mode, the DAC and the output buffer (if
configured by OUTEN=1 in DAC.CTRLA) are enabled again. Therefore, a certain start-up time is required
before a new conversion is initiated.
In Power Down sleep mode, the DAC and output buffer are disabled to reduce power consumption.
Note: Only DAC0 has an output driver for an external pin.
31.3.4
Configuration Change Protection
Not applicable.
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Datasheet Preliminary
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8-bit AVR Microcontroller
31.4
Register Summary - DAC
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
DATA
7:0
RUNSTDBY
OUTEN
ENABLE
DATA[7:0]
31.5
Register Description
31.5.1
Control A
Name: CTRLA
Offset: 0x00
Reset: 0x00
Property:
Bit
Access
7
6
RUNSTDBY
OUTEN
ENABLE
R/W
R/W
R/W
0
0
0
Reset
5
4
3
2
1
0
Bit 7 – RUNSTDBY: Run in Standby Mode
If this bit is written to '1', the DAC or Output Buffer will not automatically be disabled when the device is
entering Standby sleep mode.
Note: Only DAC0 has an output driver for an external pin.
Bit 6 – OUTEN: Output Buffer Enable
Writing a '1' to this bit enables the Output Buffer and sends the OUT signal to a pin.
Note: Only DAC0 has an output driver for an external pin.
Bit 0 – ENABLE: DAC Enable
Writing a '1' to this bit enables the DAC.
31.5.2
DATA
Name: DATA
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
DATA[7:0]
Access
Reset
Bits 7:0 – DATA[7:0]: Data
These bits contains the digital data which will be converted to an analog voltage.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
32.
PTC - Peripheral Touch Controller
32.1
Overview
The Peripheral Touch Controller (PTC) acquires signals in order to detect touch on capacitive sensors.
The external capacitive touch sensor is typically formed on a PCB, and the sensor electrodes are
connected to the analog front end of the PTC through the I/O pins in the device. The PTC supports both
self- and mutual-capacitance sensors.
In mutual-capacitance mode, sensing is done using capacitive touch matrices in various X-Y
configurations, including indium tin oxide (ITO) sensor grids. The PTC requires one pin per X-line and one
pin per Y-line.
In self-capacitance mode, the PTC requires only one pin (Y-line) for each touch sensor.
The number of available pins and the assignment of X- and Y-lines is depending on both package type
and device configuration. Refer to the Configuration Summary and I/O Multiplexing table for details.
Related Links
Configuration Summary
I/O Multiplexing and Considerations
32.2
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Low-power, high-sensitivity, environmentally robust capacitive touch buttons, sliders, wheels
Supports wake-up on touch from power-save sleep mode
Supports mutual capacitance and self-capacitance sensing
– Mix-and-match mutual-and self-capacitance sensors
One pin per electrode – no external components
Load compensating charge sensing
– Parasitic capacitance compensation and adjustable gain for superior sensitivity
Zero drift over the temperature and VDD range
– Auto calibration and re-calibration of sensors
Single-shot charge measurement
Hardware noise filtering and noise signal de-synchronization for high conducted immunity
Driven shield for better noise immunity and moisture tolerance
– Any PTC X/Y line can be used for the driven shield
– All enabled sensors will be driven at the same potential as the sensor scanned
Selectable channel change delay allows choosing the settling time on a new channel, as required
Acquisition-start triggered by command or through auto-triggering feature
Low CPU utilization through interrupt on acquisition-complete
Using ADC peripheral for signal conversion and acquisition
Supported by Atmel|START and Atmel Studio documentation.
Related Links
Configuration Summary
I/O Multiplexing and Considerations
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
32.3
Block Diagram
Figure 32-1. PTC Block Diagram Mutual-Capacitance
Input
Control
Compensation
Circuit
Y0
RS
Y1
Charge
Integrator
Ym
IRQ
ADC
System
10
Result
CX0Y0
X0
X Line Driver
X1
C XnYm
Xn
Figure 32-2. PTC Block Diagram Self-Capacitance
Input
Control
Compensation
Circuit
Y0
Y1
CY0
RS
Charge
Integrator
Ym
IRQ
ADC
System
10
Result
CYm
Shield Driver
X Line Driver
32.4
Signal Description
Table 32-1. Signal Description for PTC
Name
Type
Description
Y[m:0]
Analog
Y-line (Input/Output)
X[n:0]
Digital
X-line (Output)
Note: The number of X and Y lines are device dependent. Refer to Configuration Summary for details.
Refer to I/O Multiplexing and Considerations for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
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Datasheet Preliminary
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8-bit AVR Microcontroller
Related Links
Configuration Summary
I/O Multiplexing and Considerations
32.5
System Dependencies
In order to use this Peripheral, configure the other components of the system as described in the
following sections.
32.5.1
I/O Lines
The I/O lines used for analog X-lines and Y-lines must be connected to external capacitive touch sensor
electrodes. External components are not required for normal operation. However, to improve the EMC
performance, a series resistor of 1kΩ or more can be used on X-lines and Y-lines.
32.5.1.1 Mutual-Capacitance Sensor Arrangement
A mutual-capacitance sensor is formed between two I/O lines - an X electrode for transmitting and Y
electrode for sensing. The mutual capacitance between the X and Y electrode is measured by the
Peripheral Touch Controller.
Figure 32-3. Mutual Capacitance Sensor Arrangement
Sensor Capacitance Cx,y
MCU
X0
X1
Xn
Cx0,y0
Cx0,y1
Cx0,ym
Cx1,y0
Cx1,y1
Cx1,ym
Cxn,y0
Cxn,y1
Cxn,ym
PTC
PTC
Module
Module
Y0
Y1
Ym
32.5.1.2 Self-Capacitance Sensor Arrangement
A self-capacitance sensor is connected to a single pin on the Peripheral Touch Controller through the Y
electrode for sensing the signal. The sense electrode capacitance is measured by the Peripheral Touch
Controller.
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8-bit AVR Microcontroller
Figure 32-4. Self-capacitance Sensor Arrangement
MCU
Sensor Capacitance Cy
Y0
Cy0
Y1
Cy1
PTC
Module
Ym
Cym
For more information about designing the touch sensor, refer to Buttons, Sliders and Wheels Touch
Sensor Design Guide.
32.5.2
Clocks
The PTC is clocked by the CLK_PER clock. See the Related Links for details on configuring CLK_PER.
Related Links
CLKCTRL - Clock Controller
32.5.3
Analog-Digital Converter (ADC)
The PTC is using the ADC for signal conversion and acquisition. The ADC must be enabled and
configured appropriatly in order to allow correct behavior of the PTC.
Related Links
ADC - Analog to Digital Converter
32.6
Functional Description
In order to access the PTC, the user must use Atmel|START to configure and link the QTouch Library
firmware with the application software. QTouch Library can be used to implement buttons, sliders, wheels
in a variety of combinations on a single interface.
Figure 32-5. QTouch Library Usage
Custom Code
Compiler
Link
Application
QTouch
Library
For more information about QTouch Library, refer to the QTouch Library Peripheral Touch Controller User
Guide.
© 2017 Microchip Technology Inc.
Datasheet Preliminary
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8-bit AVR Microcontroller
33.
UPDI - Unified Program and Debug Interface
Related Links
Debug Operation
33.1
Features
•
•
•
33.2
Programming
– External programming through UPDI 1-wire (1W) interface
• Enable programming by 12V or fuse
• Uses the RESET pin of the device for programming
• No GPIO pins occupied during operation
• Asynchronous Half-Duplex UART protocol towards the programmer
Debugging
– Memory mapped access to device address space (NVM, RAM, I/O)
– No limitation on device clock frequency
– Unlimited number of user program breakpoints
– 2 Hardware Breakpoints
– Run-time readout of program counter (PC), Stack Pointer (SP) and CPU Status register
(CPU_SREG) for code profiling
– Program Flow Control
• Go, Stop, Reset, Step Into
– Non-intrusive run-time chip monitoring without accessing system registers
• Monitor CRC status and sleep status
Unified Programming and Debug Interface (UPDI)
– Built in error detection with error signature readout
– Frequency Measurement of internal oscillators using the Event System
Overview
The Unified Program and Debug Interface (UPDI) is an proprietary interface for external programming
and on-chip debugging of a device.
The UPDI supports programming of nonvolatile memory (NVM) space; FLASH, EEPROM, fuses, lockbits
and the user row. In addition the UPDI can access the entire I/O and data space of the device. See the
NVM Controller documentation for programming via the NVM controller and executing NVM controller
commands.
Programming and debugging is done through the UPDI Physical interface (UPDI PHY), which is a 1-wire
UART based half-duplex interface using the RESET pin for data reception and transmission. Clocking of
UPDI PHY is done by an internal oscillator. Enabling of the 1-wire interface, by disabling the reset
functionality, is either done by 12V programming or by fusing the RESET pin to UPDI by setting the
RESET Pin Configuration (RSTPINCFG) bits in FUSE.SYSCFG0. The UPDI Access layer grants access
to the Bus Matrix, with memory mapped access to system blocks such as Memories, NVM, and
peripherals.
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Datasheet Preliminary
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8-bit AVR Microcontroller
The Asynchronous System Interface (ASI) provides direct interface access to On-Chip Debugging (OCD),
NVM and System Management features. This gives the debugger direct access to system information,
without requesting bus access.
Related Links
NVMCTRL - Non Volatile Memory Controller
Enabling of KEY Protected Interfaces
33.2.1
Block Diagram
Figure 33-1. UPDI Block Diagram
ASI
Memories
UPDI PAD
(RX/TX Data)
UPDI
Physical
layer
Bus Matrix
UPDI Controller
UPDI
Access
layer
NVM
Peripherals
ASI Access
ASI Internal Interfaces
OCD
NVM
Controller
System
Management
33.2.2
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 33-1. UPDI System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
No
-
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
I/O Lines and Connections
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8-bit AVR Microcontroller
Power Management
33.2.2.1 Clocks
The UPDI Physical (UPDI PHY) layer and UPDI Access (UPDI ACC) layer can operate on different clock
domains. The UPDI PHY layer clock is derived from an internal oscillator, and the UPDI ACC layer clock
is the same as the system clock. There is a synchronization boundary between the UPDI PHY layer and
UPDI ACC layer, which ensures correct operation between the clock domains. The UPDI clock output
frequency is selected through the ASI, and the default UPDI clock start-up frequency is 4MHz after
enabling the UPDI. The UPDI clock frequency is changed by writing the UPDICLKSEL bits in ASI_CTRLA
register.
Figure 33-2. UPDI clock domains
ASI
SYNCH
UPDI Controller
UPDI
Physical
layer
Clock
Controller
UPDI clk
source
~
UPDI
Access
layer
Clock
Controller
Clk_UPDI
Clk_sys
Clk_sys
UPDI
CLKSEL
~
Related Links
CLKCTRL - Clock Controller
33.2.2.2 I/O Lines and Connections
To operate the UPDI, the RESET pin must be set to UPDI Mode. This is not done through the PORT I/O
Pin Configuration as for regular I/O Pins, but through setting the RESET pin Configuration (RSTPINCFG)
bits in FUSE.SYSCFG0 as described in UPDI Enable with Fuse Override of RESET pin, or by following
the UPDI 12V enable sequence from UPDI Enable with 12V Override of RESET pin. Pull enable, input
enable and output enable settings are automatically controlled by the UPDI when active.
33.2.2.3 Events
The events of this peripheral are connected to the Event System.
Related Links
EVSYS - Event System
33.2.2.4 Power Management
The UPDI physical layer continues to operate in any sleep mode and is always accessible for a
connected debugger, but read/write access to the system bus is restricted in sleep modes where the CPU
clock is switched off. The UPDI can be enabled at any time, independent of the system sleep state. See
Sleep Mode Operation for details on UPDI operation duing sleep modes.
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33.3
Functional Description
33.3.1
Principle of Operation
Communication through the UPDI is based on standard UART communication, using a fixed frame
format, and automatic baud rate detection for clock and data recovery. In addition to the data frame, there
are several control frames which are important to the communication. The supported frame formats are
presented in Figure 33-3.
Figure 33-3. Supported UPDI Frame formats
DATA
St
0
1
2
3
4
5
6
7
P
S1 S2
P
S1 S2
P
S1 S2
IDLE
BREAK
SYNCH (0x55)
St
Synch Part
End_synch
ACK (0x40)
St
Data
Frame
IDLE
Frame
BREAK
SYNCH
ACK
Consist of 1 start bit (always low), 8 data bits, 1 parity bit (even parity) and two stop bits
(always high). If the start bit, parity bit or stop bits have an incorrect value, an error will be
detected and signalized by the UPDI. The parity bit check in the UPDI can be disabled by
writing the PARD bit in UPDI.CTRLA, in which case the parity generation from the debugger
can be ignored.
Special frame which consist of 12 high bits. This is the same as keeping the transmission line
in an IDLE state.
Special frame which consist of 12 low bits. The BREAK frame is used to reset the UPDI back
to its default state, and is typically used for error recovery.
The SYNCH frame (0x55) is used by the baud rate generator to set the baud rate for the
coming transmission. A SYNCH character is always expected by the UPDI in front of every
new instruction, and after a successful BREAK has been transmitted.
The Acknowledge (ACK) character is transmitted from the UPDI whenever a ST or STS
instruction has successfully crossed the synchronization boundary, and have gained bus
access. When an ACK is received by the debugger, the next transmission can start.
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33.3.1.1 UPDI UART
All transmission and reception of serial data on the UPDI is achieved using the UPDI frames presented in
Figure 33-3. Communication is initiated from the master (debugger) side, and every transmission must
start with a SYNCH character upon which the UPDI can recover the transmission baud rate, and store
this setting for the coming data. The baud rate set by the SYNCH character will be used for both
reception and transmission for the instruction byte received after the SYNCH. See UPDI Instruction Set
for details on when the next SYNCH character is expected in the instruction stream.
There is no writable baud rate register in the UPDI, so the baud rate sampled from the SYNCH character
is used for data recovery by sampling the start bit, and do a majority voting on the middle samples. This
process is repeated for all bits in the frame, including the parity bit and two stop bits. The baud generator
uses 16 samples, and the majority voting is done on sample 7,8 and 9.
Figure 33-4. UPDI UART Start Bit and Data/Parity/Stop bit sampling
RxD
IDLE
Sample
0 0
START
1
2
3
4
5
6
7
RxD
BIT 0
8 9 10 11 12 13 14 15 16 1
2
3
BIT n
Sample
1
2
3
4
5
6
7
8 9 10 11 12 13 14 15 16 1
The transmission Baud Rate must be set up in relation to the selected UPDI clock, which can be adjusted
by UPDICLKSEL in UPDI.ASI_CTRLA. See Table 33-2 for recommended maximum and minimum baud
rate settings.
Table 33-2. Recommended UART Baud Rate based on UPDICLKSEL setting
UPDICLKSEL[1:0]
MAX Recommended Baud Rate MIN Recommended Baud Rate
0x1 (16MHz)
0.9Mbps
0.300kbps
0x2 (8MHz)
450kbps
0.150kbps
0x3 (4MHz) - Default
225kbps
0.075kbps
The UPDI baud rate generator utilizes fractional baud counting to minimize the transmission error. With
the fixed frame format used by the UPDI, the maximum and recommended receiver transmission error
limits can be seen in the following table:
Table 33-3. Receiver Baud Rate Error
Data + parity bits
Rslow
Rfast
Max Total Error
(%)
Recommended
max RX error (%)
9
96.39
104.76
+4.76 / -3.61
+1.5 / -1.5
33.3.1.2 BREAK Character
The BREAK character is used to reset the internal state of the UPDI to the default setting. This is useful if
the UPDI enters an error state due to communication error, or when synchronization between the
debugger and the UPDI is lost.
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8-bit AVR Microcontroller
A single BREAK character is enough to reset the UPDI, but in some special cases where the BREAK
character is sent when the UPDI has not yet entered the error state, a double BREAK character might be
needed. A double BREAK is guaranteed to reset the UPDI from any state. When sending a double
BREAK it is required to have at least one stop bit between the BREAK characters.
No SYNCH character is required before the BREAK, because the BREAK is used to reset the UPDI from
any state. This means that the UPDI will sample the BREAK based on the last stored baud rate setting,
derived from the last received valid SYNCH character. If the communication error was due to incorrect
sampling of the SYNCH character, the baud rate is unknown to the connected debugger. For this reason
the BREAK character should be transmitted at the slowest recommended baud rate setting for the
selected UPDI clock according to Table 33-4:
Table 33-4. Recommended BREAK Character Duration
33.3.2
UPDICLKSEL[1:0]
Recommended BREAK Character Duration
0x1 (16MHz)
6.15ms
0x2 (8MHz)
12.30ms
0x3 (4MHz) - Default
24.60ms
Operation
The UPDI must be enabled before the UART communication can start:
•
UPDI Enable with 12V Override of RESET pin
•
UPDI Enable with Fuse Override of RESET pin
33.3.2.1 UPDI Enable with Fuse Override of RESET pin
When the RESET Pin Configuration (RSTPINCFG) bits in FUSE.SYSCFG0 are 0x1, the RESET pin will
be overridden, and the UPDI will take control of the pin and configure it as input with pull-up. When the
pull-up is detected by a connected debugger, the UPDI enable sequence, as depicted below, is started.
Figure 33-5. UPDI Enable sequence with UPDI PAD Enabled by Fuse
1 Fuse read in. Pull-up enabled. Ready to receive init.
Internal oscillator ready; Communication channel
ready.
2
1
RESET
Hi-Z
St
Handshake / BREAK
[10 – 200us]
D1
D2
D3
D4
D5
D6
D7
Sp
SYNC (0x55)
(Autobaud)
(Ignore)
UPDI.r x d
UPDI.t x d
D0
2
Hi-Z
Hi-Z
10 – 200us
d eb u g g er .
UPDI.t x d
Hi-Z
Hi-Z
200ns
When the pull-up is detected, the debugger initiates the enable sequence by driving the line low for a
minimum of 200ns and a maximum of 1us to ensure that the line is released from the debugger before
the UPDI enable sequence is done.
The negative edge is detected by the UPDI, which requests the UPDI clock. The UPDI will continue to
drive the line low until the clock is stable and ready for the UPDI to use. The duration of this will vary,
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depending on the status of the oscillator when the UPDI is enabled. A start-up time between 10us and
200us can be expected. After this duration, the data line will be released by the UPDI, and pulled-high.
When the Debugger detects that the line is high, the initial SYNCH character (0x55) must be sent to
properly enable the UPDI for communication. If the start bit of the SYNCH character is not sent within
13.5ms, the UPDI will disable itself, and the enable sequence must be repeated. This time is based on
counted cycles on the 4MHz UPDI clock, which is default when enabling the UPDI. The disable is
performed to avoid the UPDI being enabled unintentionally.
After successful SYNCH character transmission, the first instruction frame can be transmitted.
33.3.2.2 UPDI Enable with 12V Override of RESET pin
GPIO or Reset functionality on the RESET pin can be overridden by the UPDI by using 12V
programming. By applying a 12V pulse to the RESET pin, the pin functionality is switched to UPDI,
independent of RSTPINCFG in FUSE.SYSCFG0. It is recommended to always reset the device before
starting the 12V enable sequence.
During power-up, the Power-on Reset (POR) must be released before the 12V pulse can be applied. The
duration of the pulse is recommended in the range from 100us to 1ms, before tri-stating. When applying
the rising edge of the 12V pulse, the UPDI will be reset. After tri-stating, the UPDI will remain in reset until
the RESET pin is driven low by the debugger. This will release the UPDI reset, and initiate the same
enable sequence as explained in UPDI Enable with Fuse Override of RESET pin.
The following figure shows the 12V enable sequence.
Figure 33-6. UPDI Enable Sequence by 12V Programming
1 RESET pin disabled; UPDI pin function enabled.
Internal oscillator ready; Communication channel
2
ready.
1
RESET /
(PDI12V)
St
(Hi-Z)
Handshake / BREAK
[10 – 200us]
D1
D2
D3
D4
D5
D6
D7
Sp
SYNC (0x55)
(Autobaud)
(Ignore)
UPDI.r x d
UPDI.t x d
D0
2
Hi-Z
Hi-Z
10 – 200us
d eb u g g er .
UPDI.t x d
Hi-Z
Hi-Z
200ns
d eb u g g er .
UPDI.o 12v
When enabled by 12V, only a POR will disable the UPDI configuration on the RESET pin, and restore the
default setting. If issuing a UPDI disable command through the UPDIDIS bit in UPDI.CTRLB, the UPDI
will be reset and the clock request will be canceled, but the RESET pin will remain in UPDI configuration.
33.3.2.3 UPDI Disable
Any programming or debug session should be terminated by writing the UPDIDIS bit in UPDI.CTRLB.
Writing this bit will reset the UPDI including any decoded KEYs, and disable the oscillator request for the
module. If the disable operation is not performed, the UPDI will stay enabled and request its oscillator,
causing increased power consumption for the application.
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During the enable sequence the UPDI can disable itself in case of a faulty enable sequence. There are
two cases which will cause an automatic disable.
•
A SYNCH character is not sent within 13.5ms after the initial enable pulse described in UPDI
Enable with Fuse Override of RESET pin.
•
The first SYNCH character after an initiated enable is too short or too long to register as a valid
SYNCH character. See Table 33-2 for recommended baud rate operating ranges.
33.3.2.4 Output Enable Timer Protection for GPIO Configuration
When the RESET Pin Configuration (RSTPINCFG) bits in FUSE.SYSCFG0 are 0x0, the RESET pin
configured as GPIO. To avoid the potential conflict between the GPIO actively driving the output and a
12V UPDI enable sequence initiation, a timer protection is disabling the output enable for a minimum time
of 8.8ms after each System Reset.
It is always recommended to issue a System Reset before entering the 12V programming sequence.
33.3.2.5 UPDI Communication Error Handling
The UPDI contains a comprehensive error detection system, to be able to provide information to the
debugger when recovering from an error scenario. The error detection consist of detecting physical
transmission errors like start bit error, parity error, contention error and frame error, to more high level
errors like access timeout error. See UPDI_STATUSB.PESIG for an overview of the available error
signatures.
Whenever the UPDI detects an error, it will immediately transfer to an internal error state to avoid
unwanted system communication. In the error state the UPDI will ignore all incoming data requests,
except if a BREAK character is transmitted. The following procedure should always be applied when
recovering from an error condition.
•
Send a BREAK character. See BREAK Character for recommended BREAK character handling.
•
Send a SYNCH character at the desired baud rate for the next data transfer. Upon receiving a
BREAK, the UPDI oscillator setting in UPDI.ASI_CTRLA is reset to the 4MHz default UPDI clock
selection. This affects the baud rate range of the UPDI according to Table 33-2 .
•
Do a Load Control Status (LDCS) to UPDI.STATUSB register to read the PESIG field. PESIG will
give information about the occurred error, and the error signature will be cleared when read.
•
The UPDI is now recovered from the error state, and ready to receive the next SYNCH character
and instruction.
33.3.2.6 Direction Change
In order to ensure correct timing for half-duplex UART operation, the UPDI has a built in Guard Time
mechanism to relax the timing when changing direction from RX mode to TX mode. The Guard Time is a
number of IDLE bits inserted before the next start bit is transmitted. The number of IDLE bits can be
configured through GTVAL in UPDI.CTRLA. The duration of each IDLE bit is given by the baud rate used
by the current transmission.
It is not recommended to use GTVAL setting 0x7, with no additional IDLE bits.
Figure 33-7. UPDI Direction Change by inserting IDLE bits
RX Data Frame
St
R X D a ta F ra m e
Dir Change
P
Data from
debugger to UPDI
© 2017 Microchip Technology Inc.
S1
S2
I D L E b it s
TX Data Frame
St
T X D a ta F r a m e
G uard Tim e #
IDLE bits inserted
Datasheet Preliminary
P
S1
S2
Data from UPDI to
debugger
DS40001893B-page 394
8-bit AVR Microcontroller
The UPDI Guard Time is the minimum IDLE time that the connected debugger will experience when
waiting for data from the UPDI. Because of the asynchronous interface to the system, as presented in
Clocks, the ratio between the UPDI clock and the system clock will affect the synchronization time, and
how long it takes before the UPDI can transmit data. In the cases where the synchronization delay is
shorter than the current Guard Time setting, the Guard Time will be given by GTVAL directly.
33.3.3
UPDI Instruction Set
Communication through the UPDI is based on a small instruction set. The instructions are used to access
the internal UPDI and ASI Control and Status (CS) space, as well as the memory mapped system space.
All instructions are byte instructions, and must be preceded by a SYNCH character to determine the baud
rate for the communication. See UPDI UART for information about setting the baud rate for the
transmission. The following Figure gives an overview of the UPDI instruction set.
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Datasheet Preliminary
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8-bit AVR Microcontroller
Figure 33-8. UPDI Instruction Set Overview
Opcode
L DS
STS
0
0
0
1
Size A
0
0
0
0
Opcode
LD
ST
0
0
0
1
Ptr
1
1
Size B
Size A/B
0
STCS
1
1
0
1
0
0
0
0
0
LD S
0
0
1
LD
0
1
0
STS
0
1
1
ST
1
0
0
L D C S ( L D S C o n t r o l/ S ta t u s )
1
0
1
REPEAT
1
1
0
S T C S ( S T S C o n tr o l/ S ta t u s )
1
1
1
KEY
S ize A - A d d re s s s ize
0
CS Address
L DCS
OPCODE
0
0
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
P tr - P o in ter a c c es s
0
0
* (p tr)
0
1
* (p tr+ + )
1
0
p tr
1
1
R e s e rv e d
S ize B - D ata s ize
Size B
REPEA T
1
0
1
0
0
0
SIB
K EY
1
1
1
0
0
Size C
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
C S A d d r e s s (C S - C o n t r o l /S t a t u s r e g .)
0
0
0
0
R eg 0
0
0
0
1
R eg 1
0
0
1
0
R eg 2
0
0
1
1
R eg 3
0
1
0
0
R e g 4 (A S I C S s p a c e )
......
1
1
1
1
R e s e rv e d
S ize C - K ey s ize
0
0
0
1
6 4 b it s ( 8 B y t e s )
1 2 8 b it s ( 1 6 B y t e s )
1
0
R e s e rv e d
1
1
R e s e rv e d
S IB – S y s t e m I n f o r m a t i o n B l o c k s e l .
© 2017 Microchip Technology Inc.
0
R e c e iv e K E Y
1
S e n d S IB
Datasheet Preliminary
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8-bit AVR Microcontroller
33.3.3.1 LDS - Load Data from Data Space Using Direct Addressing
The LDS instruction is used to load data form the bus matrix and into the serial shift register for serial read
out. The LDS instruction is based on direct addressing, and the address must be given as an operand to
the instruction for the data transfer to start. Maximum supported size for address and data is 16 bit. LDS
supports repeated memory access when combined with the REPEAT instruction.
As shown in Figure 33-9, after issuing the SYNCH character followed by the LDS instruction, the number
of desired address bytes, as indicated by the SizeA field in the instruction, must be transmitted. The
output data size is selected by the SizeB field, and is issued after the specified Guard Time. When
combined with the REPEAT instruction, the address must be sent in for each iteration of the repeat,
meaning after each time the output data sampling is done. There is no automatic address increment
when using REPEAT with LDS, as it uses a direct addressing protocol.
Figure 33-9. LDS Instruction Operation
OPCODE
Size A
Size B
S ize A - A d d re s s s ize
0
L DS
0
0
0
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
S ize B - D ata s ize
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
ADR SIZE
Synch
(0x55)
LDS
A d r_ 0
Rx
A d r_ n
D a ta _ 0
D a ta _ n
Tx
ΔGT
33.3.3.2 STS - Store Data to Data Space Using Direct Addressing
The STS instruction is used to store data that is shifted serially into the PHY layer to the bus matrix
address space. The STS instruction is based on direct addressing, where the address is the first set of
operands, and data is the second set. The size of the address and data operands are given by the size
fields presented in the Figure below. Maximum size for both address and data is 16 bit.
STS supports repeated memory access when combined with the REPEAT instruction.
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8-bit AVR Microcontroller
Figure 33-10. STS Instruction Operation
OPCODE
Size A
Size B
S ize A - A d d re s s s ize
0
STS
1
0
0
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
S ize B - D ata s ize
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
ADR SIZE
Synch
(0x55)
STS
A d r_ 0
DATA SIZE
A d r_ n
D a ta _ 0
Rx
D a ta _ n
ACK
ΔGT
ACK
Tx
ΔGT
The transfer protocol for an STS instruction is depicted in the Figure as well, following this sequence:
1.
2.
3.
4.
The address is sent.
An Acknowledge (ACK) is sent back from the UPDI if the transfer was successful.
The number of bytes as specified in the STS instruction is sent.
A new ACK is received after the data has been successfully transferred.
33.3.3.3 LD - Load Data from Data Space Using Indirect Addressing
The LD instruction is used to load data form the bus matrix and into the serial shift register for serial read
out. The LD instruction is based on indirect addressing, which means that the address pointer in the UPDI
needs to be written prior to bus matrix access. Automatic pointer post increment operation is supported,
and is useful when the LD instruction is used with REPEAT. It is also possible to do a LD of the UPDI
pointer register. Maximum supported size for address and data load is 16 bit.
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8-bit AVR Microcontroller
Figure 33-11. LD Instruction Operation
OPCODE
LD
Synch
(0x55)
0
0
Ptr
1
Size A/B
P tr - P o in ter a c c es s
0
0
0
* (p tr)
0
1
* (p tr+ + )
1
0
p tr
1
1
R e s e rv e d
S ize A - A d d re s s s ize
S ize B - D ata s ize
0
0
B y te
0
0
B y te
0
1
W o rd (2 B y te s )
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
0
R e s e rv e d
1
1
R e s e rv e d
1
1
R e s e rv e d
LD
DATA SIZE
D a ta _ 0
Rx
D a ta _ n
Tx
ΔGT
The Figure above shows an example of a typical LD sequence, where data is received after the Guard
Time period. Loading data from the UPDI pointer register follows the same transmission protocol.
33.3.3.4 ST - Store Data from Data Space Using Indirect Addressing
The ST instruction is used to store data that is shifted serially into the PHY layer to the bus matrix address
space. The ST instruction is based on indirect addressing, which means that the address pointer in the
UPDI needs to be written prior to bus matrix access. Automatic pointer post increment operation is
supported, and is useful when the ST instruction is used with REPEAT. ST is also used to store the UPDI
address pointer into the pointer register. Maximum supported size for storing address and data is 16 bit.
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8-bit AVR Microcontroller
Figure 33-12. ST Instruction Operation
OPCODE
ST
0
1
Ptr
1
Size A/B
P tr - P o in ter a c c es s
0
0
0
* (p tr)
0
1
* (p tr+ + )
1
0
p tr
1
1
R e s e rv e d
S ize A - A d d re s s s ize
S ize B - D ata s ize
0
0
B y te
0
0
B y te
0
1
W o rd (2 B y te s )
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
0
R e s e rv e d
1
1
R e s e rv e d
1
1
R e s e rv e d
ADDRESS_SIZE
Synch
(0x55)
ST
ADR _0
ADR _n
Rx
ACK
Tx
ΔGT
Block SIZE
Synch
(0x55)
ST
D a ta _ 0
Rx
D a ta _ n
ACK
Tx
ΔGT
The Figure above gives an example of ST to the UPDI pointer register, and store of regular data. In both
cases an Acknowledge (ACK) is sent back by the UPDI if the store was successful, and a SYNCH
character is sent before each instruction. To write the UPDI pointer register, the following procedure
should be followed.
•
Set the PTR field in the ST instruction to the signature 0x2
•
Set the address size field SizeA to the desired address size
•
After issuing the ST instruction, send SizeA bytes of address data
•
Wait for the ACK character which signifies a successful write to the address register
After the address register is written, sending data is done in a similar fashion
•
Set the PTR field in the ST instruction to the signature 0x0 to write to the address specified by the
UPDI pointer register. If the PTR field is set to 0x1, the UPDI pointer is automatically updated to the
next address according to the data size SizeD field of the instruction after the write is executed.
•
Set the SizeD field in the instruction to the desired data size.
•
After sending the ST instruction, send SizeD bytes of address data
•
Wait for the ACK character which signifies a successful write to the bus matrix
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When used with the REPEAT, it is recommended to set up the address register with the start address for
the block to be written, and use pointer post increment register to automatically increase the address for
each repeat cycle. When using repeat, the data frame of SizeD data bytes can be sent after each
received ACK.
33.3.3.5 LCDS - Load Data from Control and Status Register Space
The LCDS instruction is used to load data from the UPDI and ASI CS-space. LCDS is based on direct
addressing, where the address is part of the instruction opcode. The total address space for LCDS is 16
byte, and can only access the internal UPDI register space. This instruction only supports byte access,
and data size is not configurable.
Figure 33-13. LCDS Instruction Operation
OPCODE
L DCS
1
0
CS Address
0
CS Address (CS - Control/Status reg.)
0 0 0 0 Reg 0
0 0 0 1 Reg 1
0 0 1 0 Reg 2
0 0 1 1 Reg 3
0 1 0 0 Reg 4 (ASI CS Space)
......
1 1 1 1 Reserved
0
Synch
(0x55)
LDCS
Rx
Data
Tx
Δgt
The Figure above shows a typical example of LCDS data transmission. A data byte from the LCDS space
is transmitted from the UPDI after the Guard-Time is completed.
33.3.3.6 STCS (Store Data to Control and Status register space)
The STCS instruction is used to store data to the UPDI and ASI CS-space. STCS is based on direct
addressing, where the address is part of the instruction opcode. The total address space for STCS is 16
byte, and can only access the internal UPDI register space. This instruction only supports byte access,
and data size is not configurable.
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8-bit AVR Microcontroller
Figure 33-14. STCS instruction operation
OPCODE
STCS
1
1
CS Address
0
C S A d d r e s s (C S - C o n t r o l /S t a t u s r e g .)
0
Synch
(0x55)
STCS
0
0
0
0
R eg 0
0
0
0
1
R eg 1
0
0
1
0
R eg 2
0
0
1
1
R eg 3
0
1
0
0
R e g 4 (A S I C S S p a c e )
......
1
1
1
1
R e s e rv e d
D a ta
Rx
Tx
Figure 33-14 shows the data frame transmitted after the SYNCH and instruction frames. There is no
response generated from the STCS instruction, as is the case for ST and STS.
33.3.3.7 REPEAT - Set Instruction Repeat Counter
The REPEAT instruction is used to store the repeat count value into the UPDI repeat counter register.
When instructions are used with REPEAT, protocol overhead for SYNCH- and Instruction Frame can be
omitted on all instructions except the first instruction after the REPEAT is issued. REPEAT is most useful
for memory instructions (LD,ST,LDS,STS), but all instructions can be repeated, except the REPEAT
instruction itself.
The DATA_SIZE opcode field refers to the size of the repeat value. Only byte size (up to 255 repeats) is
supported. The instruction that is loaded directly after the REPEAT instruction will be repeated RPT_0
times. The instruction will be issued a total of RPT_0 + 1 times. An ongoing repeat can only be aborted
by sending a BREAK character.
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8-bit AVR Microcontroller
Figure 33-15. REPEAT Instruction Operation
OPCODE
REPEA T
1
0
Size B
1
0
0
0
S ize B - D ata s ize
0
0
B y te
0
1
R e s e rv e d
1
0
R e s e rv e d
1
1
R e s e rv e d
REPEAT SIZE
Synch
(0x55)
REPEA T
RPT_0
Rpt nr of Blocks of DATA_SIZE
DATA_SIZE
Synch
(0x55)
ST
(p t r + + )
D a ta _ 0
D a ta _ n
DATA_SIZE
DATA_SIZE
D a ta B _ 1
D a ta B _ n
Rx
ACK
Δd
ACK
Δd
Δd
Δd
Tx
Δd
The Figure above gives an example of repeat operation with a ST instruction using pointer post increment
operation. After the REPEAT instruction is sent with RPT_0 = n, the first ST instruction is issued with
SYNCH- and Instruction frame, while the next n ST-instructions are executed by only sending in data
bytes according to the ST operand DATA_SIZE, and maintaining the Acknowledge (ACK) handshake
protocol.
If using indirect addressing instructions (LD/ST) it is recommended to always use the pointer post
increment option when combined with REPEAT . Otherwise the same address will be accessed in all
repeated access operations. For direct addressing instructions (LDS/STS), the address must always be
transmitted as specified in the instruction protocol, before data can be received (LDS) or sent (STS).
33.3.3.8 KEY - Set Activation KEY
The KEY instruction is used for communicating KEY bytes to the UPDI, opening up for executing
protected features on the device. See Table 33-5for an overview over functions that are activated by
KEYs. For the KEY instruction, only 64bit KEY size is supported. If the System Information Block (SIB)
field of the KEY instruction is set, the KEY instruction returns the SIB instead of expecting incoming KEY
bytes. Maximum supported size for SIB is 128bits.
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8-bit AVR Microcontroller
Figure 33-16. KEY Instruction Operation
SIB
K EY
1
1
1
0
Size C
0
S ize C - K ey s ize
0
0
6 4 b it s ( 8 B y t e s )
0
1
1 2 8 b it s ( 1 6 B y t e s ) ( S IB o n ly )
1
0
R e s e rv e d
1
1
R e s e rv e d
S IB – S y s t e m I n f o r m a t i o n B l o c k s e l .
0
Send KEY
1
R e c e iv e S I B
KEY SIZE
Synch
(0x55)
K EY
KEY_0
KEY_n
Rx
Tx
Synch
(0x55)
Rx
K EY
S IB _ 0
Δgt
S IB _ n
Tx
SIB SIZE
The Figure above shows the transmission of a KEY, and the reception of a SIB. In both cases, the
SIZE_C field in the opcode determines the number of frames to be sent or received. There is no
response after sending a KEY to the UPDI. When requesting the SIB, data will be transmitted from the
UPDI according to the current Guard Time setting.
33.3.4
System Clock Measurement with UPDI
It is possible to use the UPDI to get a accurate measurement of the system clock frequency, by using the
UPDI event connected to TCB with Input Capture capabilities. A recommended setup flow for this feature
is given by the following steps:
•
Set up TCB.CTRLB with setting CNTMODE=0x3, Input Capture frequency measurement mode.
See for details.
•
Write CAPTEI=1 in TCB.EVCTRL to enable Event Interrupt. Keep EDGE = 0 in TCB.EVCTRL.
•
Configure the Event System as described in Events
•
For the SYNCH character used to generate the UPDI events, it is recommended to use a slow
baud rate in the range of 10kbps - 50kbps to get a more accurate measurement on the value
captured by the timer between each UPDI event. One particular thing is that if the capture is set up
to trigger an interrupt, the first captured value should be ignored. The second captured value based
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8-bit AVR Microcontroller
•
on the input event should be used for the measurement. See the figure below for an example using
10kbps UPDI SYNCH character pulses, giving a capture window of 200µs for the Timer.
It is possible to read out the captured value directly after the SYNCH character, by reading the
TCB.CC register, or the value can be written to memory by the CPU once the capture is done.
Figure 33-17. UPDI System Clock Measurement Events
Ignore first
capture event
200us
UPDI_
Input
TCB_CC
33.3.5
CAPT_1
CAPT_2
CAPT_3
Interbyte Delay
When loading data with the UPDI, or reading out the System Information Block, the output data will
normally come out with two IDLE bits between each transmitted byte for a multibyte transfer. Depending
on the application on the receiver side, data might be coming out too fast when there is no extra IDLE bits
between each byte. By enabling the IBDLY feature in UPDI.CTRLB, two extra stop bits will be inserted
between each byte to relax the sampling time for the debugger. Interbyte delay works in the same way as
guard time, by inserting extra IDLE bits, but only a fixed number of IDLE bits and only for multibyte
transfers. The first transmitted byte after a direction change will be subject to the regular Guard Time
before it is transmitted, and the interbyte delay is not added to this time.
Figure 33-18. Interbyte Delay exemple with LD and RPT
Too fast transm ission, no interbyte delay
RX
Debugger
Data
TX
RPT
CNT
LD*(ptr)
GT
Debugger
Processing
S
D0
B
D1
S
B
D2
D1lots
D0
S
B
D3
S
B
D4
D1lost
D2
S
B
D5
S
B
D4
Data sam pling ok with interbyte delay
RX
Debugger
Data
TX
RPT
CNT
Debugger
Processing
LD*(ptr)
GT
S IB
B
D0
D0
S IB
B
D1
D1
D2
D2
S IB
B
D3
S
B
D3
In Figure 33-18, GT denotes the Guard Time insertion, SB are stop bits and IB is the inserted interbyte
delay. The rest of the frames are data and instructions.
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33.3.6
System Information Block
The System Information Block (SIB) can be read out at any time by setting the SIB bit in the KEY
instruction from KEY - Set Activation KEY. The SIB provides a compact form of providing information for
the debugger which is vital in identifying and setting up the proper communication channel with the part.
The output of the SIB should be interpreted as ASCII symbols. KEY size field should be set to 16byte
when reading out the complete SIB, and 8 byte size can be used to read out only the Family_ID. See
Figure 33-19 for SIB format description, and which data that is available at different readout sizes.
Figure 33-19. System Information Block format
16 8
33.3.7
[Byte][Bits]
[6:0] [55:0]
[7][7:0]
[10:8][23:0]
[13:11][23:0]
[14][7:0]
[15][7:0]
Field Name
Family_ID
Reserved
NVM_VERSION
OCD_VERSION
RESERVED
DBG_OSC_FREQ
Enabling of KEY Protected Interfaces
Access to some internal interfaces and features are protected by the UPDI KEY mechanism. To activate
a KEY, the correct KEY data must be transmitted by using the KEY instruction as described in KEY
instruction. Table 33-5 describes the available KEYs, and the condition required when doing operation
with the KEY active. There is no requirement when shifting in the KEY, but you would for instance
normally run a Chiperase before enabling the NVMPROG KEY, to unlock the device for debug. But if the
NVMPROGKEY is shifted in first, it will not be reset by shifting in the Chiperase KEY afterwards.
Table 33-5. KEY Activation Overview
KEY name
Description
Requirements for
operation
Reset
Chiperase
Start NVM Chiperase.
Clear Lockbits
None
UPDI Disable / UPDI
Reset
NVMPROG
Activate NVM
Programming
Lockbits Cleared.
Programming Done /
ASI_SYS_STATUS.NVM UPDI Reset
PROG set.
USERROW-Write
Program User Row on
Locked part
Lockbits Set.
Write to KEY status bit /
ASI_SYS_STATUS.URO UPDI Reset
WPROG set
Table 33-6 gives an overview of the available KEY signatures that must be shifted in to activate the
interfaces.
Table 33-6. KEY Activation Signatures
KEY name
KEY signature (LSB written
first)
Size
Chiperase
0x4E564D4572617365
64bit
NVMPROG
0x4E564D50726F6720
64bit
USERROW-Write
0x4E564D5573267465
64bit
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33.3.7.1 Chip Erase
The following steps should be followed to issue a Chip Erase.
1. Enter the CHIPERASE KEY by using the KEY instruction. See Table 33-6 for the CHIPERASE
signature.
2. Optional: Read the Chip Erase bit in the AS Key Status register (CHIPERASE in
UPDI.ASI_KEY_STATUS) to see that the KEY is successfully activated.
3. Write the Reset signature into the UPDI.ASI_RESET_REQ register. This will issue a System Reset.
4. Write 0x00 to the ASI Reset Request register (UPDI.ASI_RESET_REQ) to clear the System Reset.
5. Read the Lock Status bit in the ASI System Status register (LOCKSTATUS in
UPDI.ASI_SYS_STATUS).
6. Chip Erase is done when LOCKSTATUS == 0 in UPDI.ASI_SYS_STATUS. If LOCKSTATUS == 1,
go to point 5 again.
After a successful Chip Erase, the Lockbits will be cleared, and the UPDI will have full access to the
system. Until Lockbits are cleared, the UPDI cannot access the system bus, and only CS-space
operations can be performed. See User Row Programming.
Caution: During Chip Erase, the BOD is forced ON (ACTIVE=0x1 in BOD.CTRLA), and uses
the BOD Level from the BOD Configuration fuse (LVL in BOD.CTRLB = LVL in
FUSE.BODCFG). If the supply voltage VDD is below that threshold level, the device is
unserviceable until VDD is increased adequately.
33.3.7.2 NVM Programming
If the device is unlocked, it is possible to write directly to the NVM Controller using the UPDI - this will
lead to unpredictable code execution if the CPU is active during the NVM programming. To avoid this, the
following NVM Programming sequence should be executed.
1.
Follow the Chiperase procedure as described in Chip Erase. If the part is already unlocked, this
point can be skipped.
2. Enter the NVMPROG KEY by using the KEY instruction. See Table 33-6 for the NVMPROG
signature.
3. Optional: Read the NVMPROG field in the KEY_STATUS register to see that the KEY has been
activated.
4. Write the Reset signature into the ASI_RESET_REQ register. This will issue a System Reset.
5. Write 0x00 to the Reset signature in ASI_RESET_REQ register to clear the System Reset.
6. Read NVMPROG in ASI_SYS_STATUS.
7. NVM Programming can start when NVMPROG == 1 in the ASI_SYS_STATUS register. If
NVMPROG == 0, go to point 6 again.
8. Write data to NVM through the UPDI.
9. Write the Reset signature into the ASI_RESET_REQ register. This will issue a System Reset.
10. Write 0x00 to the Reset signature in ASI_RESET_REQ register to clear the System Reset.
11. Programming is complete.
33.3.7.3 User Row Programming
The User Row Programming feature allows the user to program new values to the User Row
(USERROW) on a locked device. To program with this functionality enabled, the following sequence
should be followed.
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8-bit AVR Microcontroller
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Enter the USERROW-Write KEY located in Table 33-6 by using the KEY instruction. See Table 33-6
for the UROWWRITE signature.
Optional: Read the UROWWRITE bit field in UPDI.ASI_KEY_STATUS to see that the KEY has
been activated.
Write the Reset signature into the UPDI.ASI_RESET_REQ register. This will issue a System Reset.
Write 0x00 to the Reset signature in UPDI.ASI_RESET_REQ register to clear the System Reset.
Read UROWPROG bit in UPDI.ASI_SYS_STATUS.
User Row Programming can start when UROWPROG == 1. If UROWPROG == 0, go to point 5
again.
The writable area has a size of one EEPROM page, 32 byte, and it is only possible to write User
Row data to the first 32 byte addresses of the RAM. Addressing outside this memory range will
result in a non executed write. The data will map 1:1 with the User Row space, when the data is
copied into the User Row upon completion of the Programming sequence.
When all User Row data has been written to the RAM, write the UROWWRITEFINAL bit in
UPDI.ASI_SYS_CTRLA.
Read the UROWPROG bit in UPDI.ASI_SYS_STATUS.
The User Row Programming is completed when UROWPROG == 0. If UROWPROG == 1, go to
point 9 again.
Write the UROWWRITE bit in UPDI.ASI_KEY_STATUS.
Write the Reset signature into the UPDI.ASI_RESET_REQ register. This will issue a System Reset.
Write 0x00 to the Reset signature in UPDI.ASI_RESET_REQ register to clear the System Reset.
User Row Programming is complete.
It is not possible to read back data from the SRAM in this mode. Only writes to the first 32 bytes of the
SRAM is allowed.
33.3.8
Events
The UPDI is connected to the Event System (EVSYS) as described in ASYNCCH0, ASYNCCH1,
ASYNCCH2, ASYNCCH3.
The UPDI can generate the following output events:
•
SYNCH Character Positive Edge Event
This Event is set on the UPDI clock for each detected positive edge in the SYNCH character, and it is not
possible to disable this event from the UPDI. The recommended application for this Event is system clock
frequency measurement through the UPDI. Section System Clock Measurement with UPDI provides the
details on how to setup the system for this operation.
Related Links
EVSYS - Event System
33.3.9
Sleep Mode Operation
The UPDI physical layer runs independently of all sleep modes, and the UPDI is always accessible for a
connected debugger independent of the device sleep mode. If the system enters a sleep mode that turns
off the CPU clock, the UPDI will not be able to access the system bus and read memories and
peripherals. The UPDI physical layer clock is unaffected by the sleep mode settings, as long as the UPDI
is enabled. By reading the INSLEEP bit in UPDI.ASI_SYS_STATUS it is possible to monitor if the system
domain is in sleep mode. The INSLEEP bit is set if the system is in IDLE sleep mode or deeper.
It is possible to prevent the system clock from stopping when going into sleep mode, by writing the
CLKREQ bit in UPDI.ASI_SYS_CTRL to '1'. If this bit is set the system sleep mode state is emulated, and
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it is possible for the UPDI to access the system bus and read out peripheral registers even in the deepest
sleep modes.
CLKREQ in UPDI.ASI_SYS_CTRL is by default '1', which means that default operation is keeping the
system clock on during sleep modes.
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33.4
Register Summary - UPDI
Offset
Name
Bit Pos.
0x00
STATUSA
7:0
0x01
STATUSB
7:0
0x02
CTRLA
7:0
0x03
CTRLB
7:0
UPDIREV[3:0]
PESIG[2:0]
IBDLY
PARD
DTD
RSD
GTVAL[2:0]
NACKDIS
CCDETDIS
UPDIDIS
0x04
...
Reserved
0x06
0x07
ASI_KEY_STATUS
7:0
0x08
ASI_RESET_REQ
7:0
0x09
ASI_CTRLA
7:0
0x0A
ASI_SYS_CTRLA
7:0
0x0B
ASI_SYS_STATUS
7:0
0x0C
ASI_CRC_STATUS
7:0
33.5
UROWWRITE NVMPROG
CHIPERASE
RSTREQ[7:0]
UPDICLKSEL[1:0]
UROWWRITE
CLKREQ
_FINAL
RSTSYS
INSLEEP
NVMPROG UROWPROG
LOCKSTATUS
CRC_STATUS[2:0]
Register Description
These registers are only readable through the UPDI with special instructions, and are NOT readable
through the CPU.
Registers at offset addresses 0x0-0x3 are the UPDI Physical configuration registers
Registers at offset addresses 0x4-0xC are the ASI level registers.
33.5.1
Status A
Name: STATUSA
Offset: 0x00
Reset: 0x10
Property:
Bit
7
6
5
4
3
2
1
0
UPDIREV[3:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
1
0
0
0
0
Bits 7:4 – UPDIREV[3:0]: UPDI Revision
These bits are read-only and contain the revision of the current UPDI implementation.
33.5.2
Status B
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Name: STATUSB
Offset: 0x01
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
PESIG[2:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 2:0 – PESIG[2:0]: UPDI Error Signature
These bits describe the UPDI Error Signature, and is set when an internal UPDI error condition occurs.
The PESIG field is cleared on a read from the debugger.
Table 33-7. Valid Error Signatures
33.5.3
PESIG[2:0] Error Type
Error Description
0x0
No error
No error detected (Default)
0x1
Parity error
Wrong sampling of the parity bit
0x2
Frame error
Wrong Sampling of frame stop bits
0x3
Access Layer Timeout Error UPDI can get no data or response from the Access layer.
Examples of error cases are system domain in sleep or
system domain reset.
0x4
Clock recovery error
Wrong sampling of frame start bit
0x5
-
Reserved
0x6
Reserved
Reserved
0x7
Contention error
Signalize Driving Contention on the UPDI RXD/TXD line.
Control A
Name: CTRLA
Offset: 0x02
Reset: 0x00
Property:
Bit
Access
Reset
5
4
3
IBDLY
7
6
PARD
DTD
RSD
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
GTVAL[2:0]
Bit 7 – IBDLY: Inter-Byte Delay Enable
Writing a '1' to this bit enables a fixed inter-byte delay between each data byte transmitted from the UPDI
when doing multi-byte LD(S). The fixed length is two IDLE characters. Before the first transmitted byte will
use the regular GT delay used for direction change.
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Bit 5 – PARD: Parity Disable
Writing this bit to '1' will disable parity detection in the UPDI by just ignoring the Parity bit. This feature is
recommended only during testing.
Bit 4 – DTD: Disable Timeout Detection
Setting this bit disables the timeout detection on the PHY layer, which requests a response from the ACC
layer within a specified time (65536 UPDI clock cycles).
Bit 3 – RSD: Response Signature Disable
Writing a '1' to this bit will disable any response signatures generated by the UPDI. This is to reduce the
protocol overhead to a minimum when writing large blocks of data to the NVM space. Disabling the
Response Signature should be used with caution, and only when the delay experienced by the UPDI
when accessing the system bus is predictable, otherwise loss of data may occur.
Bits 2:0 – GTVAL[2:0]: Guard Time Value
This bit field selects the Guard Time Value that will be used by the UPDI when the transmission mode
switches from RX to TX. The Guard time is equal to the Baud Rate used in 1-Wire mode.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
33.5.4
Description
UPDI Guard Time: 128 cycles (default)
UPDI Guard Time: 64 cycles
UPDI Guard Time: 32 cycles
UPDI Guard Time: 16 cycles
UPDI Guard Time: 8 cycles
UPDI Guard Time: 4 cycles
UPDI Guard Time: 2 cycles
GT off (no extra Idle bits inserted)
Control B
Name: CTRLB
Offset: 0x03
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
NACKDIS
CCDETDIS
UPDIDIS
Access
R
R
R
R
R
R
Reset
0
0
0
0
0
0
1
0
Bit 4 – NACKDIS: Disable NACK Response
Writing this bit to '1' disables the NACK signature sent by the UPDI if a System Reset is issued during an
ongoing LD(S) and ST(S) operation.
Bit 3 – CCDETDIS: Collision and Contention Detection Disable
If this bit is written to '0', contention detection is enabled for 1W mode. This means that the UPDI can
detect a collision in an ongoing 1-Wire transmission.
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8-bit AVR Microcontroller
Bit 2 – UPDIDIS: UPDI Disable
Writing a '1' to this bit disables the UPDI PHY interface. The clock request from the UPDI is lowered, and
the UPDI is reset. All UPDI PHY configurations and KEYs will be reset when the UPDI is disabled.
33.5.5
ASI Key Status
Name: ASI_KEY_STATUS
Offset: 0x07
Reset: 0x00
Property:
Bit
7
6
5
4
3
UROWWRITE
NVMPROG
CHIPERASE
Access
R
R
R
Reset
0
0
0
2
1
0
Bit 5 – UROWWRITE: User Row Write Key Status
This bit is set to '1' if the UROWWRITE KEY is active. Otherwise this bit reads as zero.
Bit 4 – NVMPROG: NVM Programming
This bit is set to '1' if the NVMPROG KEY is active. This bit is automatically reset after the programming
sequence is done. Otherwise this bit reads as zero.
Bit 3 – CHIPERASE: Chip Erase
This bit is set to '1' if the CHIPERASE KEY is active. This bit will automatically be reset when the chip
erase sequence is completed. Otherwise this bit reads as zero.
33.5.6
ASI Reset Request
Name: ASI_RESET_REQ
Offset: 0x08
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
RSTREQ[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – RSTREQ[7:0]: Reset Request
A Reset is signalized to the System when writing the Reset signature 0x59h to this address.
Writing any other signature to this register will clear the Reset.
When reading this register, reading bit RSTREQ[0] will tell if the UPDI is holding an active Reset on the
system. If this bit is '1', the UPDI has an active Reset request to the system. All other bits will read as '0'.
The UPDI will not be reset when issuing a System Reset from this register.
33.5.7
ASI Control A
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8-bit AVR Microcontroller
Name: ASI_CTRLA
Offset: 0x09
Reset: 0x02
Property:
Bit
7
6
5
4
3
2
1
0
UPDICLKSEL[1:0]
Access
Reset
R/W
R/W
1
1
Bits 1:0 – UPDICLKSEL[1:0]: UPDI Clock Select
Writing these bits selects the UPDI clock output frequency. Default setting after reset and enable is 4MHz.
Any other clock output selection is only recommended when the BOD is at the highest level. For all other
BOD settings, the default 4MHz selection is recommended.
Value
0x0
0x1
0x2
0x3
33.5.8
Description
Reserved
16MHz UPDI clock
8MHz UPDI clock
4MHz UPDI clock (Default Setting)
ASI System Control A
Name: ASI_SYS_CTRLA
Offset: 0x0A
Reset: 0x00
Property:
Bit
7
6
5
4
3
2
1
0
UROWWRITE_
CLKREQ
FINAL
Access
R
R
R
R
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit 1 – UROWWRITE_FINAL : User Row Programming Done
This bit should be written through the UPDI when the user row data has been written to the RAM. Writing
this bit will start the process of programming the user row data to the FLASH.
If this bit is written before the User Row code is written to RAM by the UPDI, the CPU will progress
without the written data.
This bit is only writable if the Userrow-write KEY is successfully decoded.
Bit 0 – CLKREQ: Request System Clock
If this bit is written to '1', the ASI is requesting the system clock, independent of system sleep modes. This
makes it possible for the UPDI to access the ACC layer, also if the system is in sleep mode.
Writing a zero to this bit will lower the clock request.
This bit will be reset when the UPDI is disabled.
This bit is set by default when the UPDI is enabled in any mode (Fuse, 12V).
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33.5.9
ASI System Status
Name: ASI_SYS_STATUS
Offset: 0x0B
Reset: 0x01
Property:
Bit
7
6
5
4
3
2
RSTSYS
INSLEEP
NVMPROG
UROWPROG
1
LOCKSTATUS
0
Access
R
R
R
R
R
Reset
0
0
0
0
1
Bit 5 – RSTSYS: System Reset Active
If this bit is set, there is an active Reset on the system domain. If this bit is cleared, the system is not in
Reset.
This bit is cleared on read.
A reset held from the ASI_RESET_REQ register will also affect this bit.
Bit 4 – INSLEEP: System Domain in Sleep
If this bit is set, the system domain is in IDLE or deeper sleep mode. If this bit is cleared, the system is not
in sleep.
Bit 3 – NVMPROG: Start NVM Programming
If this bit is set, NVM Programming can start from the UPDI.
When the UPDI is done, it must reset the system through the UPDI Reset Register.
Bit 2 – UROWPROG : Start User Row Programming
If this bit is set, User Row Programming can start from the UPDI.
When the UPDI is done, it must write the UROWWRITE_FINAL bit in ASI_SYS_CTRLA.
Bit 0 – LOCKSTATUS: NVM Lock Status
If this bit is set, the device is locked. If a Chiperase is done, and the Lockbits are cleared, this bit will read
as zero.
33.5.10 ASI CRC Status
Name: ASI_CRC_STATUS
Offset: 0x0C
Reset: 0x00
Property:
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8-bit AVR Microcontroller
Bit
7
6
5
4
3
2
1
0
CRC_STATUS[2:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 2:0 – CRC_STATUS[2:0]: CRC Execution Status
These bits signalize the status of the CRC conversion. The bits are one-hot encoded.
Value
0x0
0x1
0x2
0x4
Other
Description
Not enabled
CRC enabled, busy
CRC enabled, done with OK signature
CRC enabled, done with FAILED signature
Reserved
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34.
Instruction Set Summary
Table 34-1. Arithmetic and Logic Instructions
Mnemonic
Operands
Description
ADD
Rd, Rr
Add without Carry
Rd
Op
←
Rd + Rr
Flags
Z,C,N,V,S,H
#Clocks
1
ADC
Rd, Rr
Add with Carry
Rd
←
Rd + Rr + C
Z,C,N,V,S,H
1
ADIW
Rd, K
Add Immediate to
Word
Rd
←
Rd + 1:Rd + K
Z,C,N,V,S
2
SUB
Rd, Rr
Subtract without
Carry
Rd
←
Rd - Rr
Z,C,N,V,S,H
1
SUBI
Rd, K
Subtract
Immediate
Rd
←
Rd - K
Z,C,N,V,S,H
1
SBC
Rd, Rr
Subtract with Carry
Rd
←
Rd - Rr - C
Z,C,N,V,S,H
1
SBCI
Rd, K
Subtract
Immediate with
Carry
Rd
←
Rd - K - C
Z,C,N,V,S,H
1
SBIW
Rd, K
Subtract
Immediate from
Word
Rd + 1:Rd
←
Rd + 1:Rd - K
Z,C,N,V,S
2
AND
Rd, Rr
Logical AND
Rd
←
Rd • Rr
Z,N,V,S
1
ANDI
Rd, K
Logical AND with
Immediate
Rd
←
Rd • K
Z,N,V,S
1
OR
Rd, Rr
Logical OR
Rd
←
Rd v Rr
Z,N,V,S
1
ORI
Rd, K
Logical OR with
Immediate
Rd
←
Rd v K
Z,N,V,S
1
EOR
Rd, Rr
Exclusive OR
Rd
←
Rd ⊕ Rr
Z,N,V,S
1
COM
Rd
One’s
Complement
Rd
←
$FF - Rd
Z,C,N,V,S
1
NEG
Rd
Two’s Complement
Rd
←
$00 - Rd
Z,C,N,V,S,H
1
SBR
Rd,K
Set Bit(s) in
Register
Rd
←
Rd v K
Z,N,V,S
1
CBR
Rd,K
Clear Bit(s) in
Register
Rd
←
Rd • ($FFh - K)
Z,N,V,S
1
INC
Rd
Increment
Rd
←
Rd + 1
Z,N,V,S
1
DEC
Rd
Decrement
Rd
←
Rd - 1
Z,N,V,S
1
TST
Rd
Test for Zero or
Minus
Rd
←
Rd • Rd
Z,N,V,S
1
CLR
Rd
Clear Register
Rd
←
Rd ⊕ Rd
Z,N,V,S
1
SER
Rd
Set Register
Rd
←
$FF
None
1
MUL
Rd,Rr
Multiply Unsigned
R1:R0
←
Rd x Rr (UU)
Z,C
2
MULS
Rd,Rr
Multiply Signed
R1:R0
←
Rd x Rr (SS)
Z,C
2
MULSU
Rd,Rr
Multiply Signed
with Unsigned
R1:R0
←
Rd x Rr (SU)
Z,C
2
FMUL
Rd,Rr
Fractional Multiply
Unsigned
R1:R0
←
Rd x Rr
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