ATmega3208/3209
ATmega3208/3209 Data Sheet
Introduction
The ATmega3208/3209 microcontrollers are part of the megaAVR® 0-series, which uses the AVR® processor with
hardware multiplier running at up to 20 MHz, and offers a wide range of Flash sizes up to 48 KB, up to 6 KB of
SRAM, and 256 bytes of EEPROM in 28-, 32-, 40-, or 48-pin packages. The series uses the latest technologies from
Microchip with a flexible and low-power architecture, including Event System and SleepWalking, accurate analog
features, and advanced peripherals.
The devices described in this data sheet offer 32 KB in a 28/32/48-pin package.
megaAVR® 0-series Overview
The figure below shows the megaAVR® 0-series devices, laying out pin count variants and memory sizes:
•
•
Vertical migration is possible without code modification, as these devices are fully pin and feature compatible
Horizontal migration to the left reduces the pin count and, therefore, the available features
Figure 1. megaAVR® 0-series Overview
Flash
48 KB
ATmega4808
32 KB
ATmega3208
ATmega3209
16 KB
ATmega1608
ATmega1609
8 KB
ATmega808
ATmega809
28
32
ATmega4809
40
48
Pins
Devices with different Flash memory sizes typically also have different SRAM and EEPROM.
The name of a device in the megaAVR 0-series is decoded as follows:
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 1
ATmega3208/3209
Figure 2. megaAVR® Device Designations
AT mega 4809 - MFR - VAO
Variant Suffix
AVR product family
Flash size in KB
Series name
Pin count
VAO = Automotive
Blank = Industrial
Carrier Type
R=Tape & Reel
Blank=Tube or Tray
Temperature Range
9=48 pins (PDIP: 40 pins)
8=32 pins (SSOP: 28 pins)
F=-40°C to +125°C (extended)
U=-40°C to +85°C (industrial)
Package Type
A=TQFP
M=QFN (UQFN/VQFN)
P=PDIP
X=SSOP
Memory Overview
Table 1. Memory Overview
Memory Type
ATmega808,
ATmega809
ATmega1608,
ATmega1609
ATmega3208,
ATmega3209
ATmega4808,
ATmega4809
Flash
8 KB
16 KB
32 KB
48 KB
SRAM
1 KB
2 KB
4 KB
6 KB
EEPROM
256B
256B
256B
256B
User row
32B
32B
64B
64B
Peripheral Overview
Table 2. Peripheral Overview
Feature
ATmega808
ATmega1608
ATmega3208
ATmega4808
ATmega808
ATmega1608
ATmega3208
ATmega4808
ATmega4809
ATmega809
ATmega1609
ATmega3209
ATmega4809
Pins
28
32
40
48
Max. frequency
(MHz)
20
20
20
20
16-bit Timer/Counter
type A (TCA)
1
1
1
1
16-bit Timer/Counter
type B (TCB)
3
3
4
4
12-bit Timer/Counter
type D (TCD)
-
-
-
-
Real-Time Counter
(RTC)
1
1
1
1
USART
3
3
4
4
SPI
1
1
1
1
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
...........continued
Feature
ATmega808
ATmega1608
ATmega3208
ATmega4808
ATmega808
ATmega1608
ATmega3208
ATmega4808
ATmega4809
ATmega809
ATmega1609
ATmega3209
ATmega4809
Pins
28
32
40
48
1(1)
1(1)
1(1)
1(1)
ADC (channels)
1 (8)
1 (12)
1 (16)
1 (16)
DAC (outputs)
-
-
-
-
AC (inputs)
1 (4p/3n)
1 (4p/3n)
1 (4p/3n)
1 (4p/3n)
Peripheral Touch
Controller (PTC)
(self-cap/mutual cap
channels)
-
-
-
-
Custom Logic (LUTs)
1 (4)
1 (4)
1 (4)
1 (4)
Window Watchdog
1
1
1
1
Event System
channels
6
6
8
8
General purpose I/O
23
27
33
41
PORT
PA[0:7], PC[0:3],
PD[0:7], PF[0,1,6]
PA[0:7], PC[0:3],
PD[0:7], PF[0:6]
PA[0:7], PC[0:5],
PD[0:7], PE[0:3],
PF[0:6]
PA[0:7], PB[0:5],
PC[0:7], PD[0:7],
PE[0:3], PF[0:6]
Asynchronous
external interrupts
6
7
8
10
CRCSCAN
1
1
1
1
Unified Program and
Debug Interface
(UPDI) activated by
dedicated pin
1
1
1
1
TWI
1.
(I2C)
TWI can operate as master and slave at the same time on different pins.
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Preliminary Datasheet
DS40002174A-page 3
ATmega3208/3209
Features
•
•
•
•
AVR® CPU:
– Single-cycle I/O access
– Two-level interrupt controller
– Two-cycle hardware multiplier
Memories:
– 32 KB In-system self-programmable Flash memory
– 256B EEPROM
– 6 KB SRAM
– Write/Erase endurance:
• Flash 10,000 cycles
• EEPROM 100,000 cycles
– Data retention: 40 years at 55°C
System:
– Power-on Reset (POR) circuit
– Brown-out Detector (BOD)
– Clock options:
• 16/20 MHz low-power internal oscillator
• 32.768 kHz Ultra Low-Power (ULP) internal oscillator
• 32.768 kHz external crystal oscillator
• External clock input
– Single-pin Unified Program Debug 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
Peripherals:
– One 16-bit Timer/Counter type A (TCA) with a dedicated period register and three compare channels
– Up to four 16-bit Timer/Counters type B (TCB) with input capture
– One 16-bit Real-Time Counter (RTC) running from an external crystal or an internal RC oscillator
– Up to four USARTs with fractional baud rate generator, auto-baud, and start-of-frame detection
– Master/slave Serial Peripheral Interface (SPI)
– Master/slave TWI with dual address match
• Can operate simultaneously as master and slave
• Standard mode (Sm, 100 kHz)
• Fast mode (Fm, 400 kHz)
• Fast mode plus (Fm+, 1 MHz)
– Event System for core independent and predictable inter-peripheral signaling
– Configurable Custom Logic (CCL) with up to four programmable Look-up Tables (LUT)
– One Analog Comparator (AC) with a scalable reference input
– One 10-bit 150 ksps Analog-to-Digital Converter (ADC)
– Five selectable internal voltage references: 0.55V, 1.1V, 1.5V, 2.5V, and 4.3V
– CRC code memory scan hardware
• Optional automatic CRC scan before code execution is allowed
– Watchdog Timer (WDT) with Window mode, with a separate on-chip oscillator
– External interrupt on all general purpose pins
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 4
ATmega3208/3209
•
•
•
•
•
I/O and Packages:
– Up to 41 programmable I/O lines
– 28-pin SSOP
– 32-pin VQFN 5x5 and TQFP 7x7
– 48-pin UQFN 6x6 and TQFP 7x7
Temperature Ranges:
– Industrial: -40°C to +85°C
– Extended: -40°C to +125°C
Speed Grades -40°C to +105°C:
– 0-5 MHz @ 1.8V – 5.5V
– 0-10 MHz @ 2.7V – 5.5V
– 0-20 MHz @ 4.5V – 5.5V
Speed Grades -40°C to +125°C:
– 0-8 MHz @ 2.7V - 5.5V
– 0-16 MHz @ 4.5V - 5.5V
VAO variants available: Designed, manufactured, tested, and qualified in accordance with AEC-Q100
requirements for automotive applications.
© 2020 Microchip Technology Inc.
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ATmega3208/3209
Table of Contents
Introduction.....................................................................................................................................................1
megaAVR® 0-series Overview....................................................................................................................... 1
1.
2.
Memory Overview........................................................................................................................ 2
Peripheral Overview..................................................................................................................... 2
Features......................................................................................................................................................... 4
1.
Silicon Errata and Data Sheet Clarification Document..........................................................................12
2.
Block Diagram.......................................................................................................................................13
3.
Pinout.................................................................................................................................................... 14
3.1.
3.2.
3.3.
4.
I/O Multiplexing and Considerations..................................................................................................... 17
4.1.
5.
Features..................................................................................................................................... 24
Overview.................................................................................................................................... 24
Architecture................................................................................................................................ 24
Arithmetic Logic Unit (ALU)........................................................................................................ 25
Functional Description................................................................................................................26
Register Summary - CPU...........................................................................................................31
Register Description................................................................................................................... 31
Memories.............................................................................................................................................. 35
7.1.
7.2.
7.3.
7.4.
7.5.
7.6.
7.7.
7.8.
7.9.
7.10.
8.
Numerical Notation.....................................................................................................................19
Memory Size and Type...............................................................................................................19
Frequency and Time...................................................................................................................19
Registers and Bits...................................................................................................................... 20
ADC Parameter Definitions........................................................................................................ 21
AVR® CPU............................................................................................................................................ 24
6.1.
6.2.
6.3.
6.4.
6.5.
6.6.
6.7.
7.
Multiplexed Signals.................................................................................................................... 17
Conventions.......................................................................................................................................... 19
5.1.
5.2.
5.3.
5.4.
5.5.
6.
28-Pin SSOP.............................................................................................................................. 14
32-Pin VQFN/TQFP................................................................................................................... 15
48-Pin UQFN/TQFP................................................................................................................... 16
Overview.................................................................................................................................... 35
Memory Map.............................................................................................................................. 35
In-System Reprogrammable Flash Program Memory................................................................36
SRAM Data Memory.................................................................................................................. 37
EEPROM Data Memory............................................................................................................. 37
User Row (USERROW)............................................................................................................. 37
Signature Row (SIGROW)......................................................................................................... 37
Fuses (FUSE).............................................................................................................................50
Memory Section Access from CPU and UPDI on Locked Device..............................................59
I/O Memory.................................................................................................................................60
Peripherals and Architecture.................................................................................................................63
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Preliminary Datasheet
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ATmega3208/3209
8.1.
8.2.
8.3.
9.
Peripheral Module Address Map................................................................................................ 63
Interrupt Vector Mapping............................................................................................................ 65
System Configuration (SYSCFG)...............................................................................................66
NVMCTRL - Nonvolatile Memory Controller......................................................................................... 69
9.1.
9.2.
9.3.
9.4.
9.5.
Features..................................................................................................................................... 69
Overview.................................................................................................................................... 69
Functional Description................................................................................................................70
Register Summary - NVMCTRL................................................................................................. 75
Register Description................................................................................................................... 75
10. CLKCTRL - Clock Controller................................................................................................................. 83
10.1.
10.2.
10.3.
10.4.
10.5.
Features..................................................................................................................................... 83
Overview.................................................................................................................................... 83
Functional Description................................................................................................................85
Register Summary - CLKCTRL.................................................................................................. 89
Register Description................................................................................................................... 89
11. SLPCTRL - Sleep Controller................................................................................................................. 99
11.1.
11.2.
11.3.
11.4.
11.5.
Features..................................................................................................................................... 99
Overview.................................................................................................................................... 99
Functional Description................................................................................................................99
Register Summary - SLPCTRL................................................................................................ 102
Register Description................................................................................................................. 102
12. RSTCTRL - Reset Controller.............................................................................................................. 104
12.1.
12.2.
12.3.
12.4.
12.5.
Features................................................................................................................................... 104
Overview.................................................................................................................................. 104
Functional Description..............................................................................................................104
Register Summary - RSTCTRL................................................................................................107
Register Description................................................................................................................. 107
13. CPUINT - CPU Interrupt Controller..................................................................................................... 110
13.1.
13.2.
13.3.
13.4.
13.5.
Features................................................................................................................................... 110
Overview...................................................................................................................................110
Functional Description.............................................................................................................. 111
Register Summary - CPUINT................................................................................................... 117
Register Description................................................................................................................. 117
14. EVSYS - Event System.......................................................................................................................122
14.1.
14.2.
14.3.
14.4.
14.5.
Features................................................................................................................................... 122
Overview.................................................................................................................................. 122
Functional Description..............................................................................................................123
Register Summary - EVSYS.................................................................................................... 127
Register Description................................................................................................................. 127
15. PORTMUX - Port Multiplexer.............................................................................................................. 132
15.1. Overview.................................................................................................................................. 132
15.2. Register Summary - PORTMUX.............................................................................................. 133
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ATmega3208/3209
15.3. Register Description................................................................................................................. 133
16. PORT - I/O Pin Configuration..............................................................................................................140
16.1.
16.2.
16.3.
16.4.
16.5.
16.6.
16.7.
Features................................................................................................................................... 140
Overview.................................................................................................................................. 140
Functional Description..............................................................................................................141
Register Summary - PORTx.....................................................................................................145
Register Description - Ports..................................................................................................... 145
Register Summary - VPORTx.................................................................................................. 157
Register Description - Virtual Ports.......................................................................................... 157
17. BOD - Brown-out Detector.................................................................................................................. 162
17.1.
17.2.
17.3.
17.4.
17.5.
Features................................................................................................................................... 162
Overview.................................................................................................................................. 162
Functional Description..............................................................................................................163
Register Summary - BOD.........................................................................................................165
Register Description................................................................................................................. 165
18. VREF - Voltage Reference..................................................................................................................172
18.1.
18.2.
18.3.
18.4.
18.5.
Features................................................................................................................................... 172
Overview.................................................................................................................................. 172
Functional Description..............................................................................................................172
Register Summary - VREF.......................................................................................................173
Register Description................................................................................................................. 173
19. WDT - Watchdog Timer.......................................................................................................................176
19.1.
19.2.
19.3.
19.4.
19.5.
Features................................................................................................................................... 176
Overview.................................................................................................................................. 176
Functional Description..............................................................................................................177
Register Summary - WDT........................................................................................................ 180
Register Description................................................................................................................. 180
20. TCA - 16-bit Timer/Counter Type A.....................................................................................................183
20.1.
20.2.
20.3.
20.4.
20.5.
20.6.
20.7.
Features................................................................................................................................... 183
Overview.................................................................................................................................. 183
Functional Description..............................................................................................................186
Register Summary - TCAn in Normal Mode.............................................................................195
Register Description - Normal Mode........................................................................................ 195
Register Summary - TCAn in Split Mode................................................................................. 215
Register Description - Split Mode.............................................................................................215
21. TCB - 16-bit Timer/Counter Type B.....................................................................................................231
21.1.
21.2.
21.3.
21.4.
21.5.
Features................................................................................................................................... 231
Overview.................................................................................................................................. 231
Functional Description..............................................................................................................233
Register Summary - TCB......................................................................................................... 241
Register Description................................................................................................................. 241
22. RTC - Real-Time Counter................................................................................................................... 252
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22.1. Features................................................................................................................................... 252
22.2. Overview.................................................................................................................................. 252
22.3. Clocks.......................................................................................................................................253
22.4. RTC Functional Description..................................................................................................... 253
22.5. PIT Functional Description....................................................................................................... 254
22.6. Crystal Error Correction............................................................................................................255
22.7. Events...................................................................................................................................... 255
22.8. Interrupts.................................................................................................................................. 256
22.9. Sleep Mode Operation............................................................................................................. 256
22.10. Synchronization........................................................................................................................256
22.11. Debug Operation...................................................................................................................... 257
22.12. Register Summary - RTC.........................................................................................................258
22.13. Register Description.................................................................................................................258
23. USART - Universal Synchronous and Asynchronous Receiver and Transmitter................................275
23.1.
23.2.
23.3.
23.4.
23.5.
Features................................................................................................................................... 275
Overview.................................................................................................................................. 275
Functional Description..............................................................................................................276
Register Summary - USARTn.................................................................................................. 291
Register Description................................................................................................................. 291
24. SPI - Serial Peripheral Interface..........................................................................................................308
24.1.
24.2.
24.3.
24.4.
24.5.
Features................................................................................................................................... 308
Overview.................................................................................................................................. 308
Functional Description..............................................................................................................310
Register Summary - SPIn.........................................................................................................317
Register Description................................................................................................................. 317
25. TWI - Two-Wire Interface.................................................................................................................... 324
25.1.
25.2.
25.3.
25.4.
25.5.
Features................................................................................................................................... 324
Overview.................................................................................................................................. 324
Functional Description..............................................................................................................325
Register Summary - TWIn........................................................................................................337
Register Description................................................................................................................. 337
26. CRCSCAN - Cyclic Redundancy Check Memory Scan...................................................................... 355
26.1.
26.2.
26.3.
26.4.
26.5.
Features................................................................................................................................... 355
Overview.................................................................................................................................. 355
Functional Description..............................................................................................................356
Register Summary - CRCSCAN...............................................................................................359
Register Description................................................................................................................. 359
27. CCL – Configurable Custom Logic......................................................................................................363
27.1.
27.2.
27.3.
27.4.
27.5.
Features................................................................................................................................... 363
Overview.................................................................................................................................. 363
Functional Description..............................................................................................................365
Register Summary - CCL......................................................................................................... 373
Register Description................................................................................................................. 373
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Preliminary Datasheet
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ATmega3208/3209
28. AC - Analog Comparator.....................................................................................................................384
28.1.
28.2.
28.3.
28.4.
28.5.
Features................................................................................................................................... 384
Overview.................................................................................................................................. 384
Functional Description..............................................................................................................385
Register Summary - AC........................................................................................................... 387
Register Description................................................................................................................. 387
29. ADC - Analog-to-Digital Converter...................................................................................................... 393
29.1.
29.2.
29.3.
29.4.
29.5.
Features................................................................................................................................... 393
Overview.................................................................................................................................. 393
Functional Description..............................................................................................................396
Register Summary - ADCn.......................................................................................................403
Register Description................................................................................................................. 403
30. UPDI - Unified Program and Debug Interface.....................................................................................421
30.1.
30.2.
30.3.
30.4.
30.5.
Features................................................................................................................................... 421
Overview.................................................................................................................................. 421
Functional Description..............................................................................................................423
Register Summary....................................................................................................................441
Register Description................................................................................................................. 441
31. Instruction Set Summary.....................................................................................................................452
32. Electrical Characteristics.....................................................................................................................458
32.1. Disclaimer.................................................................................................................................458
32.2. Absolute Maximum Ratings .....................................................................................................458
32.3. General Operating Ratings ......................................................................................................458
32.4. Power Considerations.............................................................................................................. 460
32.5. Power Consumption................................................................................................................. 461
32.6. Wake-Up Time..........................................................................................................................462
32.7. Peripherals Power Consumption..............................................................................................463
32.8. BOD and POR Characteristics................................................................................................. 464
32.9. External Reset Characteristics................................................................................................. 465
32.10. Oscillators and Clocks..............................................................................................................465
32.11. I/O Pin Characteristics..............................................................................................................467
32.12. USART..................................................................................................................................... 469
32.13. SPI........................................................................................................................................... 470
32.14. TWI...........................................................................................................................................471
32.15. VREF........................................................................................................................................473
32.16. ADC..........................................................................................................................................474
32.17. AC............................................................................................................................................ 477
32.18. UPDI.........................................................................................................................................479
32.19. Programming Time...................................................................................................................479
33. Typical Characteristics........................................................................................................................ 481
33.1.
33.2.
33.3.
33.4.
Power Consumption................................................................................................................. 481
GPIO........................................................................................................................................ 490
VREF Characteristics............................................................................................................... 497
BOD Characteristics.................................................................................................................499
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Preliminary Datasheet
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33.5.
33.6.
33.7.
33.8.
ADC Characteristics................................................................................................................. 502
AC Characteristics....................................................................................................................512
OSC20M Characteristics..........................................................................................................514
OSCULP32K Characteristics................................................................................................... 516
34. Ordering Information........................................................................................................................... 518
35. Package Drawings.............................................................................................................................. 520
35.1.
35.2.
35.3.
35.4.
35.5.
35.6.
Online Package Drawings........................................................................................................ 520
28-Pin SSOP............................................................................................................................ 521
32-Pin TQFP............................................................................................................................ 525
32-Pin VQFN............................................................................................................................ 529
48-Pin TQFP............................................................................................................................ 533
48-Pin UQFN............................................................................................................................536
36. Data Sheet Revision History............................................................................................................... 540
36.1. Rev.A - 01/2020........................................................................................................................540
36.2. Appendix - Obsolete Revision History......................................................................................540
The Microchip Website...............................................................................................................................544
Product Change Notification Service..........................................................................................................544
Customer Support...................................................................................................................................... 544
Product Identification System.....................................................................................................................545
Microchip Devices Code Protection Feature.............................................................................................. 545
Legal Notice............................................................................................................................................... 545
Trademarks................................................................................................................................................ 546
Quality Management System..................................................................................................................... 546
Worldwide Sales and Service.....................................................................................................................547
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Preliminary Datasheet
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ATmega3208/3209
Silicon Errata and Data Sheet Clarification ...
1.
Silicon Errata and Data Sheet Clarification Document
Our intention is to provide our customers with the best documentation possible to ensure successful use of Microchip
products. Between data sheet updates, a Silicon Errata and Data Sheet Clarification Document will contain the most
recent information for the data sheet. The ATmega3208/3209 Silicon Errata and Data Sheet Clarification Document is
available at the device product page on https://www.microchip.com.
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Preliminary Datasheet
DS40002174A-page 12
ATmega3208/3209
Block Diagram
2.
Block Diagram
UPDI
UPDI
CRC
M
SRAM
CPU
OCD
M
Flash
M
S
BUS Matrix
S
AINPn
AINNn
OUT
AINn
VREFA
EVOUTx
LUTn-INn
LUTn-OUT
WOn
WO
ACn
GPIOR
EVSYS
CCL
TCAn
TCBn
RXD
TXD
XCK
XDIR
USARTn
MISO
MOSI
SCK
SS
SPIn
SDA (master)
SCL (master)
SDA (slave)
SCL (slave)
NVMCTRL
PORTS
ADCn
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
EEPROM
S
S
CPUINT
I
N
/
O
U
T
D
A
T
A
B
U
S
System
Management
RSTCTRL
PAn
PBn
PCn
PDn
PEn
PFn
Detectors/
References
RESET
RST
POR
Bandgap
BOD/
VLM
CLKCTRL
SLPCTRL
Clock Generation
CLKOUT
WDT
OSC20M
EXTCLK
OSC32K
RTC
TOSC1
XOSC32K
TOSC2
TWIn
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ATmega3208/3209
Pinout
3.
Pinout
3.1
28-Pin SSOP
PA7
1
28
PA6
PC0
2
27
PA5
PC1
3
26
PA4
PC2
4
25
PA3
PC3
5
24
PA2
PD0
6
23
PA1
PD1
7
22
PA0 (EXTCLK)
PD2
8
21
GND
PD3
9
20
VDD
PD4
10
19
UPDI
PD5
11
18
PF6
PD6
12
17
PF1 (TOSC2)
PD7
13
16
PF0 (TOSC1)
AVDD
14
15
GND
Power
Functionality
Input supply
Programming, debug
Ground
Clock, crystal
GPIO on VDD power domain
TWI
GPIO on AVDD power domain
Digital functions only
Analog functions
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ATmega3208/3209
Pinout
PA2
PA1
PA0 (EXTCLK)
GND
VDD
UPDI
PF6
PF5
32
31
30
29
28
27
26
25
32-Pin VQFN/TQFP
PA6
4
21
PF1 (TOSC2)
PA7
5
20
PF0 (TOSC1)
PC0
6
19
GND
PC1
7
18
AVDD
PC2
8
17
PD7
Power
PD6
PD5
PD4
16
PF2
15
22
14
3
13
PA5
PD3
PF3
12
23
PD2
2
11
PA4
PD1
PF4
10
24
PD0
1
9
PA3
PC3
3.2
Functionality
Input supply
Programming, debug
Ground
Clock, crystal
GPIO on VDD power domain
TWI
GPIO on AVDD power domain
Digital functions only
Analog functions
Note: The center pad underneath the QFN packages can be connected to PCB ground or left electrically
unconnected. Solder or glue it to the board to ensure good mechanical stability. If the center pad is not attached, the
package might loosen from the board.
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Preliminary Datasheet
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ATmega3208/3209
Pinout
PA4
PA3
PA2
PA1
PA0 (EXTCLK)
GND
VDD
UPDI
PF6
PF5
PF4
PF3
48
47
46
45
44
43
42
41
40
39
38
37
48-Pin UQFN/TQFP
6
31
PE1
PB3
7
30
PE0
PB4
8
29
GND
PB5
9
28
AVDD
PC0
10
27
PD7
PC1
11
26
PD6
PC2
12
25
PD5
Power
PC7
PC6
24
PB2
PD4
PE2
23
32
PD3
5
22
PB1
PD2
PE3
21
33
PD1
4
20
PB0
PD0
PF0 (TOSC1)
19
34
18
3
17
PA7
PC5
PF1 (TOSC2)
16
35
PC4
2
15
PA6
GND
PF2
14
36
VDD
1
13
PA5
PC3
3.3
Functionality
Input supply
Programming, debug
Ground
Clock, crystal
GPIO on VDD power domain
TWI
GPIO on AVDD power domain
Digital functions only
Analog functions
Note: The center pad underneath the QFN packages can be connected to PCB ground or left electrically
unconnected. Solder or glue it to the board to ensure good mechanical stability. If the center pad is not attached, the
package might loosen from the board.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 16
ATmega3208/3209
I/O Multiplexing and Considerations
4.
I/O Multiplexing and Considerations
4.1
Multiplexed Signals
TQFP48/
UQFN48
TQFP32/
VQFN32
SSOP28
Pin name(1,2)
Special
44
30
22
PA0
EXTCLK
45
31
23
PA1
46
32
24
PA2
TWI
0,XCK
SDA(MS)
0-WO2
0-WO
47
1
25
PA3
TWI
0,XDIR
SCL(MS)
0-WO3
1-WO
48
2
26
PA4
0,TxD(3)
MOSI
0-WO4
1
3
27
PA5
0,RxD(3)
MISO
0-WO5
2
4
28
PA6
0,XCK(3)
SCK
3
5
1
PA7
0,XDIR(3)
SS
ADC0
CLKOUT
AC0
OUT
USARTn
SPI0
TWI0
TCA0
0,TxD
0-WO0
0,RxD
0-WO1
TCBn
EVSYS
CCL-LUTn
0-IN0
0-IN1
EVOUTA
0-IN2
0-OUT
0-OUT(3)
EVOUTA(3)
4
PB0
3,TxD
0-WO0(3)
5
PB1
3,RxD
0-WO1(3)
6
PB2
3,XCK
0-WO2(3)
7
PB3
3,XDIR
0-WO3(3)
8
PB4
3,TxD(3)
0-WO4(3)
2-WO(3)
0-WO5(3)
3-WO
EVOUTB
PB5
3,RxD(3)
10
6
2
PC0
1,TxD
MOSI(3)
0-WO0(3)
2-WO
1-IN0
11
7
3
PC1
1,RxD
MISO(3)
0-WO1(3)
3-WO(3)
1-IN1
SDA(MS)(3)
0-WO2(3)
SCL(MS)(3)
0-WO3(3)
9
12
8
4
PC2
TWI
1,XCK
SCK(3)
13
9
5
PC3
TWI
1,XDIR
SS(3)
14
VDD
15
GND
16
PC4
1,TxD(3)
0-WO4(3)
17
PC5
1,RxD(3)
0-WO5(3)
18
PC6
1,XCK(3)
19
PC7
1,XDIR(3)
1-OUT(3)
0-WO0(3)
10
6
PD0
AIN0
21
11
7
PD1
AIN1
P3
0-WO1(3)
22
12
8
PD2
AIN2
P0
0-WO2(3)
23
13
9
PD3
AIN3
N0
0-WO3(3)
24
14
10
PD4
AIN4
P1
0-WO4(3)
25
15
11
PD5
AIN5
N1
0-WO5(3)
26
16
12
PD6
27
17
13
PD7
28
18
14
AVDD
29
19
15
GND
AIN6
P2
AIN7
N2
PE0
AIN8
MOSI(3)
0-WO0(3)
PE1
AIN9
MISO(3)
0-WO1(3)
AIN10
SCK(3)
0-WO2(3)
AIN11
SS(3)
0-WO3(3)
33
PE3
2-IN1
EVOUTD
2-IN2
2-OUT
2-OUT(3)
31
PE2
2-IN0
EVOUTD(3)
30
32
1-IN2
1-OUT
EVOUTC(3)
20
VREFA
EVOUTC
EVOUTE
34
20
16
PF0
TOSC1
2,TxD
0-WO0(3)
3-IN0
35
21
17
PF1
TOSC2
2,RxD
0-WO1(3)
3-IN1
36
22
PF2
TWI
AIN12
2,XCK
SDA(S)(3)
37
23
PF3
TWI
AIN13
2,XDIR
SCL(S)(3)
© 2020 Microchip Technology Inc.
Preliminary Datasheet
0-WO2(3)
0-WO3(3)
EVOUTF
3-IN2
3-OUT
DS40002174A-page 17
ATmega3208/3209
I/O Multiplexing and Considerations
...........continued
SSOP28
Pin name(1,2)
TQFP48/
UQFN48
TQFP32/
VQFN32
38
24
PF4
AIN14
39
25
PF5
AIN15
40
26
18
PF6
41
27
19
UPDI
42
28
20
VDD
43
29
21
GND
Special
RESET
ADC0
AC0
USARTn
SPI0
TWI0
TCA0
TCBn
2,TxD(3)
0-WO4(3)
0-WO(3)
2,RxD(3)
0-WO5(3)
1-WO(3)
EVSYS
2,XCK(3)
CCL-LUTn
3-OUT(3)
Note:
1. Pin names are of type Pxn, with x being the PORT instance (A,B,C, ...) 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. Alternate pin positions. For selecting the alternate positions, refer to the PORTMUX documentation.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Conventions
5.
Conventions
5.1
Numerical Notation
Table 5-1. Numerical Notation
5.2
Symbol
Description
165
Decimal number
0b0101
Binary number
‘0101’
Binary numbers are given without prefix if unambiguous
0x3B24
Hexadecimal number
X
Represents an unknown or do not care value
Z
Represents a high-impedance (floating) state for either a
signal or a bus
Memory Size and Type
Table 5-2. Memory Size and Bit Rate
5.3
Symbol
Description
KB
kilobyte (210B = 1024B)
MB
megabyte (220B = 1024 KB)
GB
gigabyte (230B = 1024 MB)
b
bit (binary ‘0’ or ‘1’)
B
byte (8 bits)
1 kbit/s
1,000 bit/s rate
1 Mbit/s
1,000,000 bit/s rate
1 Gbit/s
1,000,000,000 bit/s rate
word
16-bit
Frequency and Time
Table 5-3. Frequency and Time
Symbol
Description
kHz
1 kHz = 103 Hz = 1,000 Hz
MHz
1 MHz = 106 Hz = 1,000,000 Hz
GHz
1 GHz = 109 Hz = 1,000,000,000 Hz
ms
1 ms = 10-3s = 0.001s
µs
1 µs = 10-6s = 0.000001s
ns
1 ns = 10-9s = 0.000000001s
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Conventions
5.4
Registers and Bits
Table 5-4. Register and Bit Mnemonics
Symbol
Description
R/W
Read/Write accessible register bit. The user can read from and write to this bit.
R
Read-only accessible register bit. The user can only read this bit. Writes will be ignored.
W
Write-only accessible register bit. The user can only write this bit. Reading this bit will return an
undefined value.
BITFIELD
Bitfield names are shown in uppercase. Example: INTMODE.
BITFIELD[n:m]
A set of bits from bit n down to m. Example: PINA[3:0] = {PINA3, PINA2, PINA1, PINA0}.
Reserved
Reserved bits, bit fields, and bit field values are unused and reserved for future use. For
compatibility with future devices, always write reserved bits to ‘0’ when the register is written.
Reserved bits will always return zero when read.
PERIPHERALn
If several instances of the peripheral exist, the peripheral name is followed by a single number to
identify one instance. Example: USARTn is the collection of all instances of the USART module,
while USART3 is one specific instance of the USART module.
PERIPHERALx
If several instances of the peripheral exist, the peripheral name is followed by a single capital
letter (A-Z) to identify one instance. Example: PORTx is the collection of all instances of the
PORT module, while PORTB is one specific instance of the PORT module.
Reset
Value of a register after a Power-on Reset. This is also the value of registers in a peripheral after
performing a software Reset of the peripheral, except for the Debug Control registers.
SET/CLR/TGL
Registers with SET/CLR/TGL suffix allow the user to clear and set bits in a register without doing
a read-modify-write operation.
Each SET/CLR/TGL register is paired with the register it is affecting. Both registers in a register
pair return the same value when read.
Example: In the PORT peripheral, the OUT and OUTSET registers form such a register pair. The
contents of OUT will be modified by a write to OUTSET. Reading OUT and OUTSET will return
the same value.
Writing a ‘1’ to a bit in the CLR register will clear the corresponding bit in both registers.
Writing a ‘1’ to a bit in the SET register will set the corresponding bit in both registers.
Writing a ‘1’ to a bit in the TGL register will toggle the corresponding bit in both registers.
5.4.1
Addressing Registers from Header Files
In order to address registers in the supplied C header files, the following rules apply:
1.
2.
3.
4.
A register is identified by ., e.g., CPU.SREG, USART2.CTRLA,
or PORTB.DIR.
The peripheral name is given in the “Peripheral Address Map” in the “Peripherals and Architecture” section.
is obtained by substituting any n or x in the peripheral name with the correct
instance identifier.
When assigning a predefined value to a peripheral register, the value is constructed following the rule:
___gc
is , but remove any instance identifier.
can be found in the “Name” column in the tables in the Register Description sections
describing the bit fields of the peripheral registers.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 20
ATmega3208/3209
Conventions
Example 5-1. Register Assignments
// EVSYS channel 0 is driven by TCB3 OVF event
EVSYS.CHANNEL0 = EVSYS_CHANNEL0_TCB3_OVF_gc;
// USART0 RXMODE uses Double Transmission Speed
USART0.CTRLB = USART_RXMODE_CLK2X_gc;
Note: For peripherals with different register sets in different modes, and
must be followed by a mode name, for example:
// TCA0 in Normal Mode (SINGLE) uses waveform generator in frequency mode
TCA0.SINGLE.CTRL=TCA_SINGLE_WGMODE_FRQ_gc;
5.5
ADC Parameter Definitions
An ideal n-bit single-ended ADC converts a voltage linearly between GND and VREF in 2n steps (LSb). 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.
Figure 5-1. 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 (e.g.,
0x3FE to 0x3FF for a 10-bit ADC) compared to the ideal transition (at 1.5 LSb below
maximum). Ideal value: 0 LSb.
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Preliminary Datasheet
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ATmega3208/3209
Conventions
Figure 5-2. 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.
Figure 5-3. Integral Nonlinearity
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 5-4. Differential Nonlinearity
Output Code
0x3FF
1 LSb
DNL
0x000
0
© 2020 Microchip Technology Inc.
VREF
Preliminary Datasheet
Input Voltage
DS40002174A-page 22
ATmega3208/3209
Conventions
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 errors mentioned before. Ideal value: ±0.5
LSb.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 23
ATmega3208/3209
AVR® CPU
6.
AVR® CPU
6.1
Features
•
•
•
•
•
•
•
•
6.2
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 64 KB of unified memory
Efficient support for 8-, 16-, and 32-bit arithmetic
Configuration Change Protection for system-critical features
Native On-Chip Debugging (OCD) support
– Two hardware breakpoints
– Change of flow, interrupt, and software breakpoints
– Run-time readout of Stack Pointer (SP) register, Program Counter (PC), and Status register
– Register file read- and writable in stopped mode
Overview
All AVR devices use the AVR 8-bit 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.
6.3
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 a single-level pipeline. 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.
Refer to the Instruction Set Summary chapter for a summary of all AVR instructions.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 24
ATmega3208/3209
AVR® CPU
Figure 6-1. 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
6.4
ALU
Arithmetic Logic Unit (ALU)
The Arithmetic Logic Unit (ALU) supports arithmetic and logic operations between registers, or between a constant
and a register. Also, single-register operations can 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
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 25
ATmega3208/3209
AVR® CPU
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 are supported, and the instruction set allows for efficient implementation of 32-bit arithmetic. The hardware
multiplier supports signed and unsigned multiplication and fractional format.
6.4.1
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 fractional number
A multiplication takes two CPU clock cycles.
6.5
6.5.1
Functional Description
Program Flow
After reset, the CPU will execute instructions from the lowest address in the Flash program memory, 0x0000. The
Program Counter (PC) addresses 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 use 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.
6.5.2
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 executions enabled by the Harvard architecture and the fast-access register file
concept. This is the basic pipelining concept enabling up to 1 MIPS/MHz performance with high efficiency.
Figure 6-2. The Parallel Instruction Fetches and 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.
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Preliminary Datasheet
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ATmega3208/3209
AVR® CPU
Figure 6-3. Single Cycle ALU Operation
T1
T2
T3
T4
clkCPU
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
6.5.3
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 the program flow in order to perform conditional operations.
CPU.SREG is updated after all ALU operations, as specified in the Instruction Set Summary section. This will in
many cases remove the need for using the dedicated compare instructions, resulting in a 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.
6.5.4
Stack and Stack Pointer
The stack is used for storing return addresses after interrupts and subroutine calls. Also, it can be used for storing
temporary data. The Stack Pointer (SP) always points to the top of the stack. The SP is defined by the Stack Pointer
bits in the Stack Pointer register (CPU.SP). The CPU.SP is implemented as two 8-bit registers that are accessible in
the I/O memory space.
Data are pushed and popped from the stack using the PUSH and POP instructions. The stack grows from higher to
lower memory locations. This means that pushing data onto the stack decreases the SP, and popping data off the
stack increases the SP. The SP 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 the SRAM start address (See the SRAM Data Memory section in the
Memories chapter for the SRAM start address), and it must be defined before any subroutine calls are executed and
before interrupts are enabled. See the table below for SP details.
Table 6-1. Stack Pointer Instructions
Instruction Stack Pointer
Description
PUSH
Decremented by 1 Data are pushed onto the stack
CALL
ICALL
RCALL
Decremented by 2 A return address is pushed onto the stack with a subroutine call or interrupt
POP
Incremented by 1
Data are popped from the stack
RET RETI
Incremented by 2
A return address is popped from the stack with a return from subroutine or return
from interrupt
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 16-bit 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 two.
The SP is decremented by ‘1’ when data are pushed on the stack with the PUSH instruction, and incremented by ‘1’
when data are popped off the stack using the POP instruction.
To prevent corruption when updating the SP from software, a write to SPL will automatically disable interrupts for up
to four instructions or until the next I/O memory write, whichever comes first.
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Preliminary Datasheet
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ATmega3208/3209
AVR® CPU
6.5.5
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.
Figure 6-4. AVR® CPU General Purpose Working Registers
0 Addr.
7
0x00
R0
0x01
R1
0x02
R2
...
0x0D
0x0E
0x0F
0x10
0x11
R13
R14
R15
R16
R17
...
X-register Low Byte
0x1A
X-register High Byte
0x1B
Y-register Low Byte
0x1C
Y-register High Byte
0x1D
Z-register Low Byte
0x1E
Z-register High Byte
0x1F
The register file is located in a separate address space and is, therefore, not accessible through instructions
operation on data memory.
R26
R27
R28
R29
R30
R31
6.5.5.1
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-, Y-, and Z-registers, while
the LPM instructions can only use the Z-register. Indirect calls and jumps (ICALL and IJMP ) also use the Z-register.
Refer to the instruction set or Instruction Set Summary for more information about how the X-, Y-, and Z-registers are
used.
Figure 6-5. The X-, Y-, and Z-Registers
Bit (individually)
7
X-register
15
Bit (individually)
7
Y-register
Bit (individually)
© 2020 Microchip Technology Inc.
R29
7
8
7
0
7
8
7
7
R31
0
7
8
7
0
0
R28
0
YL
ZH
15
R26
XL
YH
15
Z-register
Bit (Z-register)
0
XH
Bit (X-register)
Bit (Y-register)
R27
0
R30
0
ZL
Preliminary Datasheet
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DS40002174A-page 28
ATmega3208/3209
AVR® CPU
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.
6.5.6
Accessing 16-Bit Registers
The AVR data bus has a width of eight bits, 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. The high byte will now be 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 be read and written directly from user software.
6.5.7
Configuration Change Protection (CCP)
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 protected self-programming.
6.5.7.1
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.
6.5.7.2
Sequence for Execution of Self-Programming
In order to execute self-programming (the execution of writes to the NVM controller's command register), the
following steps are required:
1.
2.
The software temporarily 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.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 29
ATmega3208/3209
AVR® CPU
6.5.8
On Chip Debug Capabilities
The AVR CPU includes native OCD support. It includes some powerful debug capabilities to enable profiling and
detailed information about the CPU state. It is possible to alter the CPU state and resume code execution. In addition,
normal debug capabilities like hardware Program Counter breakpoints, breakpoints on change of flow instructions,
breakpoints on interrupts, and software breakpoints (BREAK instruction) are present. Refer to the Unified Program
and Debug Interface (UPDI) chapter for details about OCD.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 30
ATmega3208/3209
AVR® CPU
6.6
Offset
0x00
...
0x03
0x04
0x05
...
0x0C
Register Summary - CPU
Name
Reserved
CCP
7:0
CCP[7:0]
7:0
15:8
7:0
SP[7:0]
SP[15:8]
Reserved
0x0D
SP
0x0F
SREG
6.7
Bit Pos.
I
T
H
S
V
N
Z
C
Register Description
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Preliminary Datasheet
DS40002174A-page 31
ATmega3208/3209
AVR® CPU
6.7.1
Configuration Change Protection
Name:
Offset:
Reset:
Property:
Bit
7
CCP
0x04
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
CCP[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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 ‘0’.
Value
Name
Description
0x9D
SPM
Allow Self-Programming
0xD8
IOREG
Un-protect protected I/O registers
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Preliminary Datasheet
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ATmega3208/3209
AVR® CPU
6.7.2
Stack Pointer
Name:
Offset:
Reset:
Property:
SP
0x0D
Top of stack
-
The CPU.SP holds the Stack Pointer (SP) that points to the top of the stack. After reset, the SP points to the highest
internal SRAM address.
Only the number of bits required to address the available data memory including external memory (up to 64 KB) is
implemented for each device. Unused bits will always read as ‘0’.
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.
To prevent corruption when updating the SP from software, a write to CPU.SPL will automatically disable interrupts
for the next four instructions or until the next I/O memory write, whichever comes first.
Bit
15
14
13
12
11
10
9
8
R/W
R/W
R/W
R/W
3
2
1
0
R/W
R/W
R/W
R/W
SP[15:8]
Access
Reset
Bit
R/W
R/W
R/W
R/W
7
6
5
4
SP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
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.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
AVR® CPU
6.7.3
Status Register
Name:
Offset:
Reset:
Property:
SREG
0x0F
0x00
-
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 influenced by the different instructions, see the Instruction
Set Summary chapter.
Bit
Access
Reset
7
I
R/W
0
6
T
R/W
0
5
H
R/W
0
4
S
R/W
0
3
V
R/W
0
2
N
R/W
0
1
Z
R/W
0
0
C
R/W
0
Bit 7 – I Global Interrupt Enable
Writing a ‘1’ to this bit enables 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.
This bit can be set and cleared by software with the SEI and CLI instructions.
Changing the I flag through the I/O register results 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.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Memories
7.
Memories
7.1
Overview
The main memories of the ATmega3208/3209are SRAM data memory, EEPROM data memory, and Flash program
memory. Also, the peripheral registers are located in the I/O memory space.
7.2
Memory Map
The figure below shows the memory map for the largest device in the megaAVR 0-series. Refer to the subsequent
subsections for details on memory sizes and start addresses for devices with smaller memory sizes.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Memories
Figure 7-1. Memory Map: Flash 48 KB, Internal SRAM 6 KB, EEPROM 256B
Code space
0x0000
Data space
64 I/O Registers
0x0000 – 0x003F
960 Ext I/O Registers
0x0040 – 0x0FFF
NVM I/O Registers and
data
0x1000 – 0x13FF
0x1400
EEPROM 256B
0x1500
(Reserved)
0x2800
Flash code
48KB
Internal SRAM
6KB
0x3FFF
0x4000
Flash code
48KB
0xFFFF
7.3
In-System Reprogrammable Flash Program Memory
The ATmega3208/3209 contains 32 KB On-Chip In-System Reprogrammable Flash memory for program storage.
Since all AVR instructions are 16 or 32 bits wide, the Flash is organized with a 16-bit data width. For write protection,
the Flash program memory space can be divided into three sections: Bootloader section, application code section,
and application data section. Code placed in one section may be restricted from writing to addresses in other
sections, see the NVMCTRL documentation for more details.
The Program Counter can to address the whole program memory. The procedure for writing Flash memory is
described in detail in the documentation of the Nonvolatile Memory Controller (NVMCTRL) peripheral.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Memories
The Flash memory is mapped into the data space and is accessible with normal LD/ST instructions. For LD/ST
instructions, the Flash is mapped from address 0x4000. The Flash memory can be read with the LPM instruction. For
the LPM instruction, the Flash start address is 0x0000.
The ATmega3208/3209 has a CRC module that is a master on the bus.
Table 7-1. Physical Properties of Flash Memory
7.4
Property
ATmega3208 ATmega3209
Size
32 KB
Page size
128B
Number of pages
256
Start address in Data Space
0x4000
Start address in Code Space
0x0000
SRAM Data Memory
The primary task of the SRAM memory is to store application data. It is not possible to execute code from SRAM.
Table 7-2. Physical Properties of SRAM
7.5
Property
ATmega3208 ATmega3209
Size
4 KB
Start address
0x3000
EEPROM Data Memory
The primary task of the EEPROM memory is to store nonvolatile application data. The EEPROM memory supports
single-byte read and write. The EEPROM is controlled by the Nonvolatile Memory Controller (NVMCTRL).
Table 7-3. Physical Properties of EEPROM
7.6
Property
ATmega3208 ATmega3209
Size
256B
Page size
64B
Number of pages
4
Start address
0x1400
User Row (USERROW)
In addition to the EEPROM, the ATmega3208/3209 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. The USERROW can be used for the final configuration without
having programming or debugging capabilities enabled.
7.7
Signature Row (SIGROW)
The content of the Signature Row fuses (SIGROW) is preprogrammed and cannot be altered. SIGROW holds
information such as device ID, serial number, and factory calibration values.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Memories
All AVR microcontrollers have a three-byte device ID that identifies the device. This device ID can be read in both
serial and parallel mode, also when the device is locked. The three bytes reside in the Signature Row. The signature
bytes are given in the following table.
Table 7-4. Device ID
Device Name
Signature Bytes Address
0x00
0x01
0x02
ATmega3209
0x1E
0x95
0x31
ATmega3208
0x1E
0x95
0x30
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Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.1
Signature Row Summary
Offset
Name
Bit Pos.
0x00
DEVICEID0
7:0
DEVICEID[7:0]
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x0C
0x0D
...
0x17
0x18
0x19
0x1A
0x1B
0x1C
...
0x1F
0x20
0x21
0x22
0x23
0x24
0x25
DEVICEID1
DEVICEID2
SERNUM0
SERNUM1
SERNUM2
SERNUM3
SERNUM4
SERNUM5
SERNUM6
SERNUM7
SERNUM8
SERNUM9
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
DEVICEID[7:0]
DEVICEID[7:0]
SERNUM[7:0]
SERNUM[7:0]
SERNUM[7:0]
SERNUM[7:0]
SERNUM[7:0]
SERNUM[7:0]
SERNUM[7:0]
SERNUM[7:0]
SERNUM[7:0]
SERNUM[7:0]
7.7.2
Reserved
OSCCAL16M0
OSCCAL16M1
OSCCAL20M0
OSCCAL20M1
7:0
7:0
7:0
7:0
OSCCAL16M[6:0]
OSCCAL16MTCAL[3:0]
OSCCAL20M[6:0]
OSCCAL20MTCAL[3:0]
Reserved
TEMPSENSE0
TEMPSENSE1
OSC16ERR3V
OSC16ERR5V
OSC20ERR3V
OSC20ERR5V
7:0
7:0
7:0
7:0
7:0
7:0
TEMPSENSE[7:0]
TEMPSENSE[7:0]
OSC16ERR3V[7:0]
OSC16ERR5V[7:0]
OSC20ERR3V[7:0]
OSC20ERR5V[7:0]
Signature Row Description
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.1
Device ID n
Name:
Offset:
Reset:
Property:
DEVICEIDn
0x00 + n*0x01 [n=0..2]
[Device ID]
-
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].
Bit
7
6
5
Access
Reset
R
x
R
x
R
x
4
3
DEVICEID[7:0]
R
R
x
x
2
1
0
R
x
R
x
R
x
Bits 7:0 – DEVICEID[7:0] Byte n of the Device ID
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.2
Serial Number Byte n
Name:
Offset:
Reset:
Property:
SERNUMn
0x03 + n*0x01 [n=0..9]
[device serial number]
-
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].
Bit
7
6
5
4
3
2
1
0
R
x
R
x
R
x
R
x
SERNUM[7:0]
Access
Reset
R
x
R
x
R
x
R
x
Bits 7:0 – SERNUM[7:0] Serial Number Byte n
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.3
OSC16 Calibration byte
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
OSCCAL16M0
0x18
[Factory oscillator calibration value]
-
6
5
4
R
x
R
x
R
x
3
OSCCAL16M[6:0]
R
x
2
1
0
R
x
R
x
R
x
Bits 6:0 – OSCCAL16M[6:0] OSC16 Calibration
These bits contains factory calibration values for the internal 16 MHz oscillator. If the OSCCFG fuse is configured to
run the device at 16 MHz, this byte is automatically copied to the OSC20MCALIBA register during Reset to calibrate
the internal 16 MHz RC Oscillator.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.4
OSC16 Temperature Calibration byte
Name:
Offset:
Reset:
Property:
Bit
7
OSCCAL16M1
0x19
[Factory oscillator temperature calibration value]
-
6
Access
Reset
5
4
3
R
x
2
1
OSCCAL16MTCAL[3:0]
R
R
x
x
0
R
x
Bits 3:0 – OSCCAL16MTCAL[3:0] OSC16 Temperature Calibration
These bits contain factory temperature calibration values for the internal 16 MHz oscillator. If the OSCCFG fuse is
configured to run the device at 16 MHz, this byte is automatically written into the OSC20MCALIBB register during
Reset to ensure correct frequency of the calibrated RC Oscillator.
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Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.5
OSC20 Calibration byte
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
OSCCAL20M0
0x1A
[Factory oscillator calibration value]
-
6
5
4
R
x
R
x
R
x
3
OSCCAL20M[6:0]
R
x
2
1
0
R
x
R
x
R
x
Bits 6:0 – OSCCAL20M[6:0] OSC20 Calibration
These bits contain factory calibration values for the internal 20 MHz oscillator. If the OSCCFG fuse is configured to
run the device at 20 MHz, this byte is automatically written into the OSC20MCALIBA register during Reset to ensure
correct frequency of the calibrated RC Oscillator.
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Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.6
OSC20 Temperature Calibration byte
Name:
Offset:
Reset:
Property:
Bit
7
OSCCAL20M1
0x1B
[Factory oscillator temperature calibration value]
-
6
Access
Reset
5
4
3
R
x
2
1
OSCCAL20MTCAL[3:0]
R
R
x
x
0
R
x
Bits 3:0 – OSCCAL20MTCAL[3:0] OSC20 Temperature Calibration
These bits contain factory temperature calibration values for the internal 20 MHz oscillator. If the OSCCFG fuse is
configured to run the device at 20 MHz, this byte is automatically written into the OSC20MCALIBB register during
Reset to ensure correct frequency of the calibrated RC Oscillator.
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Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.7
Temperature Sensor Calibration n
Name:
Offset:
Reset:
Property:
TEMPSENSEn
0x20 + n*0x01 [n=0..1]
[Temperature sensor calibration value]
-
These bytes contain correction factors for temperature measurements by the ADC. SIGROW.TEMPSENSE0 is a
correction factor for the gain/slope (unsigned), and SIGROW.TEMPSENSE1 is a correction factor for the offset
(signed).
Bit
7
6
5
Access
Reset
R
x
R
x
R
x
4
3
TEMPSENSE[7:0]
R
R
x
x
2
1
0
R
x
R
x
R
x
Bits 7:0 – TEMPSENSE[7:0] Temperature Sensor Calibration Byte n
Refer to the ADC section for a description of how to use this register.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.8
OSC16 Error at 3V
Name:
Offset:
Reset:
Property:
OSC16ERR3V
0x22
[Oscillator frequency error value]
-
Bit
7
6
5
Access
Reset
R
x
R
x
R
x
4
3
OSC16ERR3V[7:0]
R
R
x
x
2
1
0
R
x
R
x
R
x
Bits 7:0 – OSC16ERR3V[7:0] OSC16 Error at 3V
This byte contains the signed oscillator frequency error value when running at internal 16 MHz at 3V, as measured
during production.
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Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.9
OSC16 Error at 5V
Name:
Offset:
Reset:
Property:
OSC16ERR5V
0x23
[Oscillator frequency error value]
-
Bit
7
6
5
Access
Reset
R
x
R
x
R
x
4
3
OSC16ERR5V[7:0]
R
R
x
x
2
1
0
R
x
R
x
R
x
Bits 7:0 – OSC16ERR5V[7:0] OSC16 Error at 5V
This byte contains the signed oscillator frequency error value when running at internal 16 MHz at 5V, as measured
during production.
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Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.10 OSC20 Error at 3V
Name:
Offset:
Reset:
Property:
OSC20ERR3V
0x24
[Oscillator frequency error value]
-
Bit
7
6
5
Access
Reset
R
x
R
x
R
x
4
3
OSC20ERR3V[7:0]
R
R
x
x
2
1
0
R
x
R
x
R
x
Bits 7:0 – OSC20ERR3V[7:0] OSC20 Error at 3V
This byte contains the signed oscillator frequency error value when running at internal 20 MHz at 3V, as measured
during production.
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Preliminary Datasheet
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ATmega3208/3209
Memories
7.7.2.11 OSC20 Error at 5V
Name:
Offset:
Reset:
Property:
OSC20ERR5V
0x25
[Oscillator frequency error value]
-
Bit
7
6
5
Access
Reset
R
x
R
x
R
x
4
3
OSC20ERR5V[7:0]
R
R
x
x
2
1
0
R
x
R
x
R
x
Bits 7:0 – OSC20ERR5V[7:0] OSC20 Error at 5V
This byte contains the signed oscillator frequency error value when running at internal 20 MHz at 5V, as measured
during production.
7.8
Fuses (FUSE)
Fuses hold the device configuration and are a part of the nonvolatile memory. The fuses are available from device
power-up. The fuses can be read by the CPU or the UPDI, but can only be programmed or cleared by the UPDI. The
configuration values stored in the fuses are copied to their respective target registers at the end of the start-up
sequence.
The fuses are preprogrammed but can be altered by the user. Altered fuse values will be effective only after a Reset.
Note: When writing the fuses, all reserved bits must be written to ‘0’.
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Preliminary Datasheet
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ATmega3208/3209
Memories
7.8.1
Fuse Summary - FUSE
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
...
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
WDTCFG
BODCFG
OSCCFG
7:0
7:0
7:0
7.8.2
WINDOW[3:0]
LVL[2:0]
PERIOD[3:0]
SAMPFREQ
ACTIVE[1:0]
OSCLOCK
SLEEP[1:0]
FREQSEL[1:0]
Reserved
SYSCFG0
SYSCFG1
APPEND
BOOTEND
Reserved
LOCKBIT
7:0
7:0
7:0
7:0
7:0
CRCSRC[1:0]
RSTPINCFG
EESAVE
SUT[2:0]
APPEND[7:0]
BOOTEND[7:0]
LOCKBIT[7:0]
Fuse Description
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 51
ATmega3208/3209
Memories
7.8.2.1
Watchdog Configuration
Name:
Offset:
Reset:
Property:
Bit
7
WDTCFG
0x00
Initial factory value 0x00
-
6
5
4
3
2
WINDOW[3:0]
Access
Reset
R
x
R
x
1
0
R
x
R
x
PERIOD[3:0]
R
x
R
x
R
x
R
x
Bits 7:4 – WINDOW[3:0] Watchdog Window Time-out Period
This value is loaded into the WINDOW bit field of the Watchdog Control A (WDT.CTRLA) register during Reset.
Bits 3:0 – PERIOD[3:0] Watchdog Time-out Period
This value is loaded into the PERIOD bit field of the Watchdog Control A (WDT.CTRLA) register during Reset.
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Preliminary Datasheet
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ATmega3208/3209
Memories
7.8.2.2
BOD Configuration
Name:
Offset:
Reset:
Property:
BODCFG
0x01
Initial factory value 0x00
-
The settings of the BOD will be reloaded from this Fuse after a Power-on Reset. For all other Resets, the BOD
configuration remains unchanged.
Bit
Access
Reset
7
R
x
6
LVL[2:0]
R
x
5
R
x
4
SAMPFREQ
R
x
3
2
1
ACTIVE[1:0]
R
x
0
SLEEP[1:0]
R
x
R
x
R
x
Bits 7:5 – LVL[2:0] BOD Level
This value is loaded into the LVL bit field of the BOD Control B (BOD.CTRLB) register during Reset.
Value
Name
Description
0x0
BODLEVEL0
1.8V
0x2
BODLEVEL2
2.6V
0x7
BODLEVEL7
4.3V
Other
Reserved
Note:
• Refer to BOD and POR Characteristics in the Electrical Characteristics section for further details
• Values in the description are typical values
Bit 4 – SAMPFREQ BOD Sample Frequency
This value is loaded into the SAMPFREQ bit of the BOD Control A (BOD.CTRLA) register during Reset.
Value
Description
0x0
Sample frequency is 1 kHz
0x1
Sample frequency is 125 Hz
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 (BOD.CTRLA) register during Reset.
Value
Description
0x0
Disabled
0x1
Enabled
0x2
Sampled
0x3
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 (BOD.CTRLA) register during Reset.
Value
Description
0x0
Disabled
0x1
Enabled
0x2
Sampled
0x3
Reserved
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Preliminary Datasheet
DS40002174A-page 53
ATmega3208/3209
Memories
7.8.2.3
Oscillator Configuration
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
OSCLOCK
R
x
OSCCFG
0x02
Initial factory value 0x02
-
6
5
4
3
2
1
0
FREQSEL[1:0]
R
R
x
x
Bit 7 – OSCLOCK Oscillator Lock
This fuse bit is loaded to LOCK in CLKCTRL.OSC20MCALIBB during Reset.
Value
Description
0x0
Calibration registers of the 20 MHz oscillator can be modified at run-time
0x1
Calibration registers of the 20 MHz oscillator are locked at run-time
Bits 1:0 – FREQSEL[1:0] Frequency Select
These bits select the operation frequency of the internal RC Oscillator (OSC20M) and determine the respective
factory calibration values to be written to CAL20M in CLKCTRL.OSC20MCALIBA and TEMPCAL20M in
CLKCTRL.OSC20MCALIBB.
Value
Description
0x0
Reserved
0x1
Run at 16 MHz
0x2
Run at 20 MHz
0x3
Reserved
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Preliminary Datasheet
DS40002174A-page 54
ATmega3208/3209
Memories
7.8.2.4
System Configuration 0
Name:
Offset:
Reset:
Property:
Bit
SYSCFG0
0x05
Initial factory value 0xC0
-
7
6
5
4
CRCSRC[1:0]
Access
Reset
R
x
R
x
3
RSTPINCFG
R
x
2
1
0
EESAVE
R
x
Bits 7:6 – CRCSRC[1:0] CRC Source
See the CRC description for more information about the functionality.
Value
Name
Description
0x0
FLASH
CRC of full Flash (boot, application code, and application data)
0x1
BOOT
CRC of boot section
0x2
BOOTAPP
CRC of application code and boot sections
0x3
NOCRC
No CRC
Bit 3 – RSTPINCFG Reset Pin Configuration
This bit selects the pin configuration for the Reset pin.
Value
Description
0x0
GPIO
0x1
RESET
Bit 0 – EESAVE EEPROM Save During Chip Erase
If the device is locked, the EEPROM is always erased by a chip erase, regardless of this bit.
Value
Description
0x0
EEPROM erased by chip erase
0x1
EEPROM not erased by chip erase
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 55
ATmega3208/3209
Memories
7.8.2.5
System Configuration 1
Name:
Offset:
Reset:
Property:
Bit
7
SYSCFG1
0x06
Initial factory value 0x07
-
6
5
4
3
Access
Reset
2
R
x
1
SUT[2:0]
R
x
0
R
x
Bits 2:0 – SUT[2:0] Start-Up Time Setting
These bits select the start-up time between power-on and code execution.
Value
Description
0x0
0 ms
0x1
1 ms
0x2
2 ms
0x3
4 ms
0x4
8 ms
0x5
16 ms
0x6
32 ms
0x7
64 ms
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 56
ATmega3208/3209
Memories
7.8.2.6
Application Code End
Name:
Offset:
Reset:
Property:
Bit
7
APPEND
0x07
Initial factory value 0x00
-
6
5
4
3
2
1
0
R
x
R
x
R
x
R
x
APPEND[7:0]
Access
Reset
R
x
R
x
R
x
R
x
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 plus application code size. The remaining Flash will be application data. A value of 0x00
defines the Flash from BOOTEND*256 to the end of Flash as the application code section. When both
FUSE.APPEND and FUSE.BOOTEND are 0x00 the entire Flash is BOOT section.
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Preliminary Datasheet
DS40002174A-page 57
ATmega3208/3209
Memories
7.8.2.7
Boot End
Name:
Offset:
Reset:
Property:
BOOTEND
0x08
Initial factory value 0x00
-
Bit
7
6
5
Access
Reset
R
x
R
x
R
x
4
3
BOOTEND[7:0]
R
R
x
x
2
1
0
R
x
R
x
R
x
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.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 58
ATmega3208/3209
Memories
7.8.2.8
Lockbits
Name:
Offset:
Reset:
Property:
Bit
LOCKBIT
0x0A
Initial factory value 0xC5
-
7
6
5
4
3
2
1
0
R
x
R
x
R
x
R
x
LOCKBIT[7:0]
Access
Reset
R
x
R
x
R
x
R
x
Bits 7:0 – LOCKBIT[7:0] Lockbits
The UPDI cannot access the system bus when the part is locked. The UPDI can then only read the internal Control
and Status (CS) space of the UPDI and the Asynchronous System Interface (ASI). Refer to the UPDI section for
additional details.
Value
Description
0xC5
Valid key - the device is open
other
Invalid key - the device is locked
7.9
Memory Section Access from CPU and UPDI on Locked Device
The device can be locked so that the memories cannot be read using the UPDI. The locking protects both the Flash
(all BOOT, APPCODE, and APPDATA sections), SRAM, and the EEPROM including the FUSE data. This prevents
successful reading of application data or code using the debugger interface. Regular memory access from within the
application still is enabled.
The device is locked by writing any invalid key to the LOCKBIT bit field in FUSE.LOCKBIT.
Table 7-5. Memory Access in Unlocked Mode (FUSE.LOCKBIT Valid)(1)
Memory Section
CPU Access
UPDI Access
Read
Write
Read
Write
SRAM
Yes
Yes
Yes
Yes
Registers
Yes
Yes
Yes
Yes
Flash
Yes
Yes
Yes
Yes
EEPROM
Yes
Yes
Yes
Yes
USERROW
Yes
Yes
Yes
Yes
SIGROW
Yes
No
Yes
No
Other Fuses
Yes
No
Yes
Yes
Table 7-6. Memory Access in Locked Mode (FUSE.LOCKBIT Invalid)(1)
Memory Section
CPU Access
UPDI Access
Read
Write
Read
Write
SRAM
Yes
Yes
No
No
Registers
Yes
Yes
No
No
Flash
Yes
Yes
No
No
EEPROM
Yes
Yes
No
No
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 59
ATmega3208/3209
Memories
...........continued
Memory Section
CPU Access
UPDI Access
Read
Write
Read
Write
USERROW
Yes
Yes
No
Yes(2)
SIGROW
Yes
No
No
No
Other Fuses
Yes
No
No
No
Note:
1. Read operations marked No in the tables may appear to be successful, but the data is corrupt. Hence, any
attempt of code validation through the UPDI will fail on these memory sections.
2. In Locked mode, the USERROW can be written blindly using the Fuse Write command, but the current
USERROW values cannot be read out.
Important: The only way to unlock a device is a CHIPERASE, which will erase all device memories to
factory default so that no application data is retained.
7.10
I/O Memory
All ATmega3208/3209 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 ‘0’ 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 ATmega3208/3209 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 ATmega3208/3209 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 reside in the address range 0x1C - 0x1F, are directly bit-accessible using the SBI, CBI, SBIS, and
SBIC instructions.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 60
ATmega3208/3209
Memories
7.10.1
Register Summary
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
GPIOR0
GPIOR1
GPIOR2
GPIOR3
7:0
7:0
7:0
7:0
7.10.2
GPIOR[7:0]
GPIOR[7:0]
GPIOR[7:0]
GPIOR[7:0]
Register Description
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 61
ATmega3208/3209
Memories
7.10.2.1 General Purpose I/O Register n
Name:
Offset:
Reset:
Property:
GPIOR
0x00 + n*0x01 [n=0..3]
0x00
-
These are general purpose registers that can be used to store data, such as global variables and flags, in the bit
accessible I/O memory space.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
GPIOR[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – GPIOR[7:0] GPIO Register Byte
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Peripherals and Architecture
8.
Peripherals and Architecture
8.1
Peripheral Module Address Map
The address map shows the base address for each peripheral. For a complete register description and summary for
each peripheral module, refer to the respective module section.
Table 8-1. Peripheral Module Address Map
Base Address
Name
Description
28-Pin
32-Pin
48-Pin
0x0000
VPORTA
Virtual Port A
X
X
X
0x0004
VPORTB
Virtual Port B
0x0008
VPORTC
Virtual Port C
X
X
X
0x000C
VPORTD
Virtual Port D
X
X
X
0x0010
VPORTE
Virtual Port E
0x0014
VPORTF
Virtual Port F
X
X
X
0x001C
GPIO
General Purpose I/O X
registers
X
X
0x0030
CPU
CPU
X
X
X
0x0040
RSTCTRL
Reset Controller
X
X
X
0x0050
SLPCTRL
Sleep Controller
X
X
X
0x0060
CLKCTRL
Clock Controller
X
X
X
0x0080
BOD
Brown-out Detector
X
X
X
0x00A0
VREF
Voltage Reference
X
X
X
0x0100
WDT
Watchdog Timer
X
X
X
0x0110
CPUINT
Interrupt Controller
X
X
X
0x0120
CRCSCAN
Cyclic Redundancy
Check Memory
Scan
X
X
X
0x0140
RTC
Real-Time Counter
X
X
X
0x0180
EVSYS
Event System
X
X
X
0x01C0
CCL
Configurable
Custom Logic
X
X
X
0x0400
PORTA
Port A Configuration X
X
X
0x0420
PORTB
Port B Configuration
0x0440
PORTC
Port C Configuration X
X
X
0x0460
PORTD
Port D Configuration X
X
X
0x0480
PORTE
Port E Configuration
0x04A0
PORTF
Port F Configuration
X
X
X
0x05E0
PORTMUX
Port Multiplexer
X
X
X
© 2020 Microchip Technology Inc.
X
X
X
X
Preliminary Datasheet
DS40002174A-page 63
ATmega3208/3209
Peripherals and Architecture
...........continued
Base Address
Name
Description
28-Pin
32-Pin
48-Pin
0x0600
ADC0
Analog-to-Digital
Converter
X
X
X
0x0680
AC0
Analog Comparator
0
X
X
X
0x0800
USART0
Universal
X
Synchronous
Asynchronous
Receiver Transmitter
0
X
X
0x0820
USART1
Universal
X
Synchronous
Asynchronous
Receiver Transmitter
1
X
X
0x0840
USART2
Universal
X
Synchronous
Asynchronous
Receiver Transmitter
2
X
X
0x0860
USART3
Universal
Synchronous
Asynchronous
Receiver Transmitter
3
0x08A0
TWI0
Two-Wire Interface
X
X
X
0x08C0
SPI0
Serial Peripheral
Interface
X
X
X
0x0A00
TCA0
Timer/Counter Type
A instance 0
X
X
X
0x0A80
TCB0
Timer/Counter Type
B instance 0
X
X
X
0x0A90
TCB1
Timer/Counter Type
B instance 1
X
X
X
0x0AA0
TCB2
Timer/Counter Type
B instance 2
X
X
X
0x0AB0
TCB3
Timer/Counter Type
B instance 3
0x0F00
SYSCFG
System
Configuration
X
X
X
0x1000
NVMCTRL
Nonvolatile Memory
Controller
X
X
X
0x1100
SIGROW
Signature Row
X
X
X
0x1280
FUSE
Device-specific
fuses
X
X
X
0x1300
USERROW
User Row
X
X
X
© 2020 Microchip Technology Inc.
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X
Preliminary Datasheet
DS40002174A-page 64
ATmega3208/3209
Peripherals and Architecture
8.2
Interrupt Vector Mapping
Each of the 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 ‘Interrupts’ 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 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 in the peripheral's Interrupt
Control (peripheral.INTCTRL) register.
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.
Note: Interrupts must be enabled globally for interrupt requests to be generated.
Table 8-2. Interrupt Vector Mapping
Vector Number
Vector Address
Peripheral Source
28-Pin
32-Pin
40-Pin
48-Pin
0
0x00
RESET
X
X
X
X
1
0x02
NMI - Non-Maskable Interrupt from CRC
X
X
X
X
2
0x04
VLM - Voltage Level Monitor
X
X
X
X
3
0x06
RTC - Overflow or compare match
X
X
X
X
4
0x08
PIT - Periodic interrupt
X
X
X
X
5
0x0A
CCL - Configurable Custom Logic
X
X
X
X
6
0x0C
PORTA - External interrupt
X
X
X
X
7
0x0E
TCA0 - Overflow
X
X
X
X
8
0x10
TCA0 - Underflow (Split mode)
X
X
X
X
9
0x12
TCA0 - Compare channel 0
X
X
X
X
10
0x14
TCA0 - Compare channel 1
X
X
X
X
11
0x16
TCA0 - Compare channel 2
X
X
X
X
12
0x18
TCB0 - Capture
X
X
X
X
13
0x1A
TCB1 - Capture
X
X
X
X
14
0x1C
TWI0 - Slave
X
X
X
X
15
0x1E
TWI0 - Master
X
X
X
X
16
0x20
SPI0 - Serial Peripheral Interface 0
X
X
X
X
17
0x22
USART0 - Receive Complete
X
X
X
X
18
0x24
USART0 - Data Register Empty
X
X
X
X
19
0x26
USART0 - Transmit Complete
X
X
X
X
20
0x28
PORTD - External interrupt
X
X
X
X
21
0x2A
AC0 – Compare
X
X
X
X
22
0x2C
ADC0 – Result Ready
X
X
X
X
23
0x2E
ADC0 - Window Compare
X
X
X
X
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Peripherals and Architecture
...........continued
Vector Number
Vector Address
24
8.3
Peripheral Source
28-Pin
32-Pin
40-Pin
48-Pin
0x30
PORTC - External interrupt
X
X
X
X
25
0x32
TCB2 - Capture
X
X
X
X
26
0x34
USART1 - Receive Complete
X
X
X
X
27
0x36
USART1 - Data Register Empty
X
X
X
X
28
0x38
USART1 - Transmit Complete
X
X
X
X
29
0x3A
PORTF - External interrupt
X
X
X
X
30
0x3C
NVM - Ready
X
X
X
X
31
0x3E
USART2 - Receive Complete
X
X
X
X
32
0x40
USART2 - Data Register Empty
X
X
X
X
33
0x42
USART2 - Transmit Complete
X
X
X
X
34
0x44
PORTB - External interrupt
35
0x46
PORTE - External interrupt
X
X
36
0x48
TCB3 - Capture
X
X
37
0x4A
USART3 - Receive Complete
X
X
38
0x4C
USART3 - Data Register Empty
X
X
39
0x4E
USART3 - Transmit Complete
X
X
System Configuration (SYSCFG)
The system configuration contains the revision ID of the part. The revision ID is readable from the CPU, making it
useful for implementing application changes between part revisions.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
Peripherals and Architecture
8.3.1
Register Summary
Offset
Name
Bit Pos.
0x00
0x01
Reserved
REVID
7:0
8.3.2
REVID[7:0]
Register Description - SYSCFG
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Preliminary Datasheet
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ATmega3208/3209
Peripherals and Architecture
8.3.2.1
Device Revision ID Register
Name:
Offset:
Reset:
Property:
REVID
0x01
[revision ID]
-
This register is read-only and displays the device revision ID.
Bit
7
6
5
4
3
2
1
0
R
R
R
R
REVID[7:0]
Access
Reset
R
R
R
R
Bits 7:0 – REVID[7:0] Revision ID
These bits contain the device revision. 0x00 = A, 0x01 = B, and so on.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
NVMCTRL - Nonvolatile Memory Controller
9.
NVMCTRL - Nonvolatile 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:
– 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 and can 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
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Preliminary Datasheet
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ATmega3208/3209
NVMCTRL - Nonvolatile Memory Controller
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).
Figure 9-2. Flash Sections
FLASHSTART : 0x4000
BOOT
BOOTEND>0: 0x4000+BOOTEND*256
APPLICATION
CODE
APPEND>0: 0x4000+APPEND*256
APPLICATION
DATA
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. 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 9-1. 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
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NVMCTRL - Nonvolatile Memory Controller
Note:
• See also the BOOTEND and APPEND descriptions.
• Interrupt vectors are by default located after the BOOT section. This can be changed in the interrupt controller.
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 lockbits (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
9.3.2.1
Memory Access
Read
Reading of the Flash and EEPROM is done by using load instructions with an 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 a time. The Least Significant bits
(LSb) 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 enters a sleep mode. Programming an unerased Flash page will corrupt its content.
The Flash can either be written with the erase and write separately, or one command handling both:
Alternative 1:
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NVMCTRL - Nonvolatile Memory Controller
•
•
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 an 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. Confirm that any previous operation is completed by reading the Busy Flags (EEBUSY and FBUSY) in the
NVMCTRL.STATUS register.
2. Write the NVM command unlock to the Configuration Change Protection register in the CPU (CPU.CCP).
3. Write the desired command value to the CMD bits in the Control A register (NVMCTRL.CTRLA) within the next
four instructions.
9.3.2.4.1 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.
9.3.2.4.2 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 have to be updated before executing the command. The CPU can continue running code while the
operation is ongoing.
The page buffer will automatically be cleared after the operation is finished.
9.3.2.4.3 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 automatically be cleared after the operation is finished.
9.3.2.4.4 Page Buffer Clear Command
The Page Buffer Clear command clears the page buffer. The contents of the page buffer will be all 1’s after the
operation. The CPU will be halted when the operation executes (seven CPU cycles).
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NVMCTRL - Nonvolatile Memory Controller
9.3.2.4.5 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 Flash will not be protected by Boot Section Lock
(BOOTLOCK) or Application Code Section Write Protection (APCWP) in NVMCTRL.CTRLB. The memory will be all
1’s after the operation.
9.3.2.4.6 EEPROM Erase Command
The EEPROM Erase command erases the EEPROM. The EEPROM will be all 1’s after the operation. The CPU will
be halted while the EEPROM is being erased.
9.3.2.4.7 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:
1. A regular write sequence to the Flash, which requires a minimum voltage to operate correctly.
2. 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:
•
•
•
9.3.4
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 don’t match the required detection level, an external low VDD Reset
protection circuit can be used. If a Reset occurs while a write operation is ongoing, the write operation will be
aborted.
Interrupts
Table 9-2. Available Interrupt Vectors and Sources
Offset
Name
Vector Description
Conditions
0x00
EEREADY
NVM
The EEPROM is ready for new write/erase operations.
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.
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NVMCTRL - Nonvolatile Memory Controller
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). To write to these registers, a
certain key must first be written to the CPU.CCP register, followed by a write access to the protected bits within four
CPU instructions.
Attempting to write to a protected register without following the appropriate CCP unlock sequence leaves the
protected register unchanged.
The following registers are under CCP:
Table 9-3. NVMCTRL - Registers under Configuration Change Protection
Register
Key
NVMCTRL.CTRLA
SPM
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NVMCTRL - Nonvolatile Memory Controller
9.4
Register Summary - NVMCTRL
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
0x05
CTRLA
CTRLB
STATUS
INTCTRL
INTFLAGS
Reserved
7:0
7:0
7:0
7:0
7:0
0x06
DATA
0x08
ADDR
9.5
7:0
15:8
7:0
15:8
WRERROR
CMD[2:0]
BOOTLOCK
EEBUSY
APCWP
FBUSY
EEREADY
EEREADY
DATA[7:0]
DATA[15:8]
ADDR[7:0]
ADDR[15:8]
Register Description
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NVMCTRL - Nonvolatile Memory Controller
9.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
Configuration Change Protection
6
5
4
3
Access
Reset
2
R/W
0
1
CMD[2:0]
R/W
0
0
R/W
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
Name
Description
0x0
No command
0x1
WP
Write page buffer to memory (NVMCTRL.ADDR selects which memory)
0x2
ER
Erase page (NVMCTRL.ADDR selects which memory)
0x3
ERWP Erase and write page (NVMCTRL.ADDR selects which memory)
0x4
PBC
Page buffer clear
0x5
CHER Chip erase: erase Flash and EEPROM (unless EESAVE in FUSE.SYSCFG is '1')
0x6
EEER
EEPROM Erase
0x7
WFU
Write fuse (only accessible through UPDI)
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NVMCTRL - Nonvolatile Memory Controller
9.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
7
CTRLB
0x01
0x00
-
6
5
4
3
Access
Reset
2
1
BOOTLOCK
R/W
0
0
APCWP
R/W
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 be written from the boot section only. It can only be cleared to ’0’ by a Reset.
This bit will take effect only 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.
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NVMCTRL - Nonvolatile Memory Controller
9.5.3
Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x02
0x00
-
6
5
4
3
Access
Reset
2
WRERROR
R
0
1
EEBUSY
R
0
0
FBUSY
R
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.
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NVMCTRL - Nonvolatile Memory Controller
9.5.4
Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x03
0x00
-
6
5
4
3
Access
Reset
2
1
0
EEREADY
R/W
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.
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NVMCTRL - Nonvolatile Memory Controller
9.5.5
Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x04
0x00
-
6
5
4
3
2
1
0
EEREADY
R/W
0
Access
Reset
Bit 0 – EEREADY EEREADY Interrupt Flag
This flag is set continuously as long as the EEPROM is not busy. This flag is cleared by writing a '1' to it.
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NVMCTRL - Nonvolatile Memory Controller
9.5.6
Data
Name:
Offset:
Reset:
Property:
DATA
0x06
0x00
-
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.
Bit
15
14
13
12
11
10
9
8
R/W
0
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
DATA[15:8]
Access
Reset
Bit
R/W
0
R/W
0
R/W
0
R/W
0
7
6
5
4
DATA[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 15:0 – DATA[15:0] Data Register
This register is used by the UPDI for fuse write operations.
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NVMCTRL - Nonvolatile Memory Controller
9.5.7
Address
Name:
Offset:
Reset:
Property:
ADDR
0x08
0x00
-
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.
Bit
15
14
13
12
11
10
9
8
R/W
0
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
ADDR[15:8]
Access
Reset
Bit
R/W
0
R/W
0
R/W
0
R/W
0
7
6
5
4
ADDR[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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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CLKCTRL - Clock Controller
10.
CLKCTRL - Clock Controller
10.1
Features
•
•
•
•
10.2
All clocks and clock sources are automatically enabled when requested by peripherals
Internal Oscillators:
– 16/20 MHz Oscillator (OSC20M)
– 32 KHz Ultra Low-Power Oscillator (OSCULP32K)
External Clock Options:
– 32.768 kHz 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 I/O 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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CLKCTRL - Clock Controller
10.2.1
Block Diagram - CLKCTRL
Figure 10-1. CLKCTRL Block Diagram
NVM
RAM
CPU
CLK_CPU
Other
Peripherals
CLKOUT
CLK_PER
RTC
WDT
INT
BOD
TCD
PRESCALER
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
32 KHz ULP
Int. Oscillator
32.768 kHz
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 I/O bus, and all peripherals connected to the I/O 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.
– CLK_BOD is used by the BOD. It will be requested when the BOD is enabled in Sampled mode.
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.
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CLKCTRL - Clock Controller
10.2.2
Signal Description
Signal
Type
Description
CLKOUT
Digital output
CLK_PER output
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 a 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.
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
32 KHz Osc.
32.768 kHz crystal Osc.
External clock
CLK_MAIN
Main Clock Prescaler
(Div 1, 2, 4, 8, 16, 32,
64, 6, 10, 24, 48)
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.
10.3.3
Main Clock After Reset
After any reset, CLK_MAIN is provided by the 16/20 MHz Oscillator (OSC20M) and with a prescaler division factor of
6. The actual frequency of the OSC20M is determined by the Frequency Select bits (FREQSEL) of the Oscillator
Configuration fuse (FUSE.OSCCFG). Refer to the description of FUSE.OSCCFG for details of the possible
frequencies after reset.
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CLKCTRL - Clock Controller
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 32 KHz Crystal Oscillator
Control A register (CLKCTRL.XOSC32KCTRLA) before it can serve as a clock source.
The respective Oscillator Status bits in the Main Clock Status register (CLKCTRL.MCLKSTATUS) indicate whether
the clock source is running and stable.
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.
10.3.4.1.1 16/20 MHz 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).
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.
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 locked if this oscillator is used as the main clock
source and the Lock Enable bit (LOCKEN) in the Control B register (CLKCTRL.OSC20MCALIBB) is ‘1’.
The calibration bits are protected by the Configuration Change Protection Mechanism, requiring a timed write
procedure for changing the main clock and prescaler settings.
Refer to the Electrical Characteristics section for the start-up time.
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 a wider operating range,
the relative factory stored frequency error after calibrations can be used. The four errors are measured at different
settings and are available in the signature row as signed byte values.
•
•
•
•
SIGROW.OSC16ERR3V is the frequency error from 16 MHz measured at 3V
SIGROW.OSC16ERR5V is the frequency error from 16 MHz measured at 5V
SIGROW.OSC20ERR3V is the frequency error from 20 MHz measured at 3V
SIGROW.OSC20ERR5V is the frequency error from 20 MHz 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 seven LSb the lower bits of the Q1.10.
BAUDact��� = BAUD����� +
BAUD����� * �����������
1024
The minimum legal BAUD register value is 0x40, the target BAUD register value should therefore not be lower than
0x4A to ensure that the compensated BAUD value stays within the legal range, even for parts with negative
compensation values. The example code below demonstrates how to apply this value for more accurate USART
baud rate:
#include
/* Baud rate compensated with factory stored frequency error */
/* Asynchronous communication without Auto-baud (Sync Field) */
/* 16MHz Clock, 3V and 600 BAUD
*/
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 86
ATmega3208/3209
CLKCTRL - Clock Controller
int8_t sigrow_val
int32_t baud_reg_val
= SIGROW.OSC16ERR3V;
= 600;
assert (baud_reg_val >= 0x4A);
value with max neg comp
baud_reg_val *= (1024 + sigrow_val);
baud_reg_val /= 1024;
USART0.BAUD = (int16_t) baud_reg_val;
// read signed error
// ideal BAUD register value
// Verify legal min BAUD register
// sum resolution + error
// divide by resolution
// set adjusted baud rate
10.3.4.1.2 32 KHz Oscillator (OSCULP32K)
The 32 KHz 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 provides the 1 KHz signal for the Real-Time Counter (RTC), the Watchdog Timer (WDT), and the
Brown-out Detector (BOD).
The start-up time of this oscillator is the oscillator start-up time plus four oscillator cycles. Refer to the Electrical
Characteristics chapter for the start-up time.
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 32.768 kHz Crystal Oscillator (XOSC32K).
• Instead of a crystal oscillator, TOSC1 can be configured to accept an external clock source.
10.3.4.2.1 32.768 kHz 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 32 KHz 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 two cycles.
10.3.4.2.2 External Clock (EXTCLK)
The EXTCLK 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 two cycles when first requested.
10.3.5
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). To write to these registers, a
certain key must first be written to the CPU.CCP register, followed by a write access to the protected bits within four
CPU instructions.
Attempting to write to a protected register without following the appropriate CCP unlock sequence leaves the
protected register unchanged.
The following registers are under CCP:
Table 10-1. CLKCTRL - Registers Under Configuration Change Protection
Register
Key
CLKCTRL.MCLKCTRLB
IOREG
CLKCTRL.MCLKLOCK
IOREG
CLKCTRL.XOSC32KCTRLA
IOREG
CLKCTRL.MCLKCTRLA
IOREG
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Preliminary Datasheet
DS40002174A-page 87
ATmega3208/3209
CLKCTRL - Clock Controller
...........continued
Register
Key
CLKCTRL.OSC20MCTRLA
IOREG
CLKCTRL.OSC20MCALIBA
IOREG
CLKCTRL.OSC20MCALIBB
IOREG
CLKCTRL.OSC32KCTRLA
IOREG
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Preliminary Datasheet
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ATmega3208/3209
CLKCTRL - Clock Controller
10.4
Register Summary - CLKCTRL
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
...
0x0F
0x10
0x11
0x12
0x13
...
0x17
0x18
0x19
...
0x1B
0x1C
MCLKCTRLA
MCLKCTRLB
MCLKLOCK
MCLKSTATUS
7:0
7:0
7:0
7:0
10.5
CLKOUT
CLKSEL[1:0]
PEN
LOCKEN
SOSC
PDIV[3:0]
EXTS
XOSC32KS
OSC32KS
OSC20MS
Reserved
OSC20MCTRLA
OSC20MCALIBA
OSC20MCALIBB
7:0
7:0
7:0
RUNSTDBY
CAL20M[6:0]
LOCK
TEMPCAL20M[3:0]
Reserved
OSC32KCTRLA
7:0
RUNSTDBY
Reserved
XOSC32KCTRLA
7:0
CSUT[1:0]
SEL
RUNSTDBY
ENABLE
Register Description
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Preliminary Datasheet
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ATmega3208/3209
CLKCTRL - Clock Controller
10.5.1
Main Clock Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CLKOUT
R/W
0
MCLKCTRLA
0x00
0x00
Configuration Change Protection
6
5
4
3
2
1
0
CLKSEL[1:0]
R/W
R/W
0
0
Bit 7 – CLKOUT System Clock Out
When this bit is written to ‘1’, the system clock is output to the 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).
Value
Name
Description
0x0
OSC20M
16/20 MHz internal oscillator
0x1
OSCULP32K
32 KHz internal ultra low-power oscillator
0x2
XOSC32K
32.768 kHz external crystal oscillator
0x3
EXTCLK
External clock
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Preliminary Datasheet
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ATmega3208/3209
CLKCTRL - Clock Controller
10.5.2
Main Clock Control B
Name:
Offset:
Reset:
Property:
Bit
7
MCLKCTRLB
0x01
0x11
Configuration Change Protection
6
5
4
3
2
1
R/W
0
R/W
0
PDIV[3:0]
Access
Reset
R/W
1
R/W
0
0
PEN
R/W
1
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.
The user software must ensure a correct configuration of the input frequency (CLK_MAIN) and prescaler settings,
such that the resulting frequency of CLK_PER never exceeds the allowed maximum (see Electrical Characteristics).
Value
Description
Value
Division
0x0
2
0x1
4
0x2
8
0x3
16
0x4
32
0x5
64
0x8
6
0x9
10
0xA
12
0xB
24
0xC
48
other
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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Preliminary Datasheet
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ATmega3208/3209
CLKCTRL - Clock Controller
10.5.3
Main Clock Lock
Name:
Offset:
Reset:
Property:
Bit
7
MCLKLOCK
0x02
Based on OSCLOCK in FUSE.OSCCFG
Configuration Change Protection
6
5
4
3
Access
Reset
2
1
0
LOCKEN
R/W
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.
At reset, the LOCKEN bit is loaded based on the OSCLOCK bit in FUSE.OSCCFG.
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Preliminary Datasheet
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ATmega3208/3209
CLKCTRL - Clock Controller
10.5.4
Main Clock Status
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
EXTS
R
0
MCLKSTATUS
0x03
0x00
-
6
XOSC32KS
R
0
5
OSC32KS
R
0
4
OSC20MS
R
0
3
2
1
0
SOSC
R
0
Bit 7 – EXTS External Clock Status
Value
Description
0
EXTCLK has not started
1
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 oscillator
RUNSTDBY bit is set but the oscillator is unused/not requested, this bit will be 0.
Value
Description
0
XOSC32K is not stable
1
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 oscillator
RUNSTDBY bit is set but the oscillator is unused/not requested, this bit will be 0.
Value
Description
0
OSCULP32K is not stable
1
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 oscillator
RUNSTDBY bit is set but the oscillator is unused/not requested, this bit will be 0.
Value
Description
0
OSC20M is not stable
1
OSC20M is stable
Bit 0 – SOSC Main Clock Oscillator Changing
Value
Description
0
The clock source for CLK_MAIN is not undergoing a switch
1
The clock source for CLK_MAIN is undergoing a switch and will change as soon as the new source is
stable
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Preliminary Datasheet
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ATmega3208/3209
CLKCTRL - Clock Controller
10.5.5
16/20 MHz Oscillator Control A
Name:
Offset:
Reset:
Property:
Bit
7
OSC20MCTRLA
0x10
0x00
Configuration Change Protection
6
5
4
3
Access
Reset
2
1
RUNSTDBY
R/W
0
0
Bit 1 – RUNSTDBY Run Standby
This bit forces 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 four 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.
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Preliminary Datasheet
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ATmega3208/3209
CLKCTRL - Clock Controller
10.5.6
16/20 MHz Oscillator Calibration A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
OSC20MCALIBA
0x11
Based on FREQSEL in FUSE.OSCCFG
Configuration Change Protection
6
5
4
R/W
x
R/W
x
R/W
x
3
CAL20M[6:0]
R/W
x
2
1
0
R/W
x
R/W
x
R/W
x
Bits 6:0 – CAL20M[6:0] Calibration
These bits change the frequency around the current center frequency of the OSC20M for fine-tuning.
At reset, the factory calibrated values are loaded based on the FREQSEL bit in FUSE.OSCCFG.
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Preliminary Datasheet
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ATmega3208/3209
CLKCTRL - Clock Controller
10.5.7
16/20 MHz Oscillator Calibration B
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
LOCK
R
x
OSC20MCALIBB
0x12
Based on FUSE.OSCCFG
Configuration Change Protection
6
5
4
3
R/W
x
2
1
TEMPCAL20M[3:0]
R/W
R/W
x
x
0
R/W
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, the factory calibrated values are loaded based on the FREQSEL bits in FUSE.OSCCFG.
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Preliminary Datasheet
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ATmega3208/3209
CLKCTRL - Clock Controller
10.5.8
32 KHz Oscillator Control A
Name:
Offset:
Reset:
Property:
Bit
7
OSC32KCTRLA
0x18
0x00
Configuration Change Protection
6
5
4
3
Access
Reset
2
1
RUNSTDBY
R/W
0
0
Bit 1 – RUNSTDBY Run Standby
This bit forces 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 the oscillator start-up time.
When not requested by peripherals, no oscillator output is provided.
It takes four 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.
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Preliminary Datasheet
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ATmega3208/3209
CLKCTRL - Clock Controller
10.5.9
32.768 kHz Crystal Oscillator Control A
Name:
Offset:
Reset:
Property:
XOSC32KCTRLA
0x1C
0x00
Configuration Change Protection
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 re-enabling the
XOSC32K with new settings.
Bit
7
6
5
4
3
CSUT[1:0]
Access
Reset
R/W
0
R/W
0
2
SEL
R/W
0
1
RUNSTDBY
R/W
0
0
ENABLE
R/W
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
Name
Description
0x0
1K
1k cycles
0x1
16K
16k cycles
0x2
32K
32k cycles
0x3
64K
64k cycles
Bit 2 – SEL Source Select
This bit selects the external source type. It is write protected when the oscillator is enabled (ENABLE=1).
Value
Description
0
External crystal
1
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 has already 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.
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.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
SLPCTRL - Sleep Controller
11.
SLPCTRL - Sleep Controller
11.1
Features
•
•
•
11.2
Power management for adjusting power consumption and functions
Three sleep modes:
– Idle
– Standby
– Power-Down
Configurable Standby Sleep mode where peripherals can be configured as ON or OFF.
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 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.
All sleep modes are available and can be entered from active mode. In active mode, the CPU is executing application
code. When the device enters sleep mode, program execution is stopped and interrupts or a reset is used to wake
the device again. The application code decides which sleep mode to enter and when.
Interrupts are used to wake 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 take the
device out of a sleep mode.
The content of the register file, SRAM and registers are kept during sleep. If a Reset occurs during sleep, the device
will reset, start, and execute from the Reset vector.
11.2.1
Block Diagram
Figure 11-1. Sleep Controller in System
SLEEP Instruction
SLPCTRL
Interrupt Request
CPU
Sleep State
Interrupt Request
Peripheral
11.3
11.3.1
Functional Description
Initialization
To put the device into a sleep mode, follow these steps:
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
SLPCTRL - Sleep Controller
•
Configure and enable the interrupts that shall be able to wake the device from sleep. Also, enable global
interrupts.
WARNING
•
11.3.2
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.
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
Standby
PowerDown
The CPU stops executing code, no peripherals are disabled.
All interrupt sources can wake the device.
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.
BOD, WDT, and PIT (a component of the RTC) are active.
The only wake-up sources are the pin change interrupt, PIT, VLM, TWI address match and CCL.
Table 11-1. Sleep Mode Activity Overview
Group
Peripheral
Active in Sleep Mode
Clock
Active Clock
Domain
Oscillators
Idle
Standby
Power-Down
CPU
CLK_CPU
Peripherals
CLK_PER
X
RTC
CLK_RTC
X
X(1)
CCL
CLK_PER(2)
X
X(1)
ADCn
CLK_PER
X
X(1)
TCBn
CLK_PER
X
X(1)
PIT (RTC)
CLK_RTC
X
X
X
BOD (VLM)
CLK_BOD
X
X
X
WDT
CLK_WDT
X
X
X
Main Clock Source
X
X(1)
PIT and RTC Clock Source
X
X(1)
X(3)
BOD Oscillator
X
X
X
WDT Oscillator
X
X
X
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Preliminary Datasheet
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ATmega3208/3209
SLPCTRL - Sleep Controller
...........continued
Group
Peripheral
Active in Sleep Mode
Clock
Wake-Up
Sources
Idle
Standby
Power-Down
INTn and Pin Change
X
X
X
TWI Address Match
X
X
X
PIT (RTC)
X
X
X
CCL
X
X(1)
X(4)
RTC
X
X(1)
UART Start-of-Frame
X
X(1)
TCBn
X
X(1)
ADCn Window
X
X(1)
ACn
X
X(1)
All other Interrupts
X
Note:
1. RUNSTBY bit of the corresponding peripheral must be set to enter the active state.
2. CCL can select between multiple clock sources.
3. PIT only
4. CCL can wake up the device if no internal clock source is required.
11.3.2.2 Wake-Up Time
The normal wake-up time for the device is six 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 32 KHz oscillator and RTC clock may be running if it is used by the
BOD or WDT. All other clock sources will be OFF.
Table 11-2. 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 ensures correct supply voltage whenever code is executed.
11.3.3
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 periodic service by the CPU through interrupts or similar, improper operation
or data loss may result during halted debugging.
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Preliminary Datasheet
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ATmega3208/3209
SLPCTRL - Sleep Controller
11.4
Register Summary - SLPCTRL
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
11.5
SMODE[1:0]
SEN
Register Description
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Preliminary Datasheet
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ATmega3208/3209
SLPCTRL - Sleep Controller
11.5.1
Control A
Name:
Offset:
Reset:
Property:
CTRLA
0x00
0x00
-
Bit
7
6
5
4
3
Access
Reset
R
0
R
0
R
0
R
0
R
0
2
1
SMODE[1:0]
R/W
R/W
0
0
0
SEN
R/W
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
Name
Description
0x0
IDLE
Idle Sleep mode enabled
0x1
STANDBY
Standby Sleep mode enabled
0x2
PDOWN
Power-Down Sleep mode enabled
other
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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Preliminary Datasheet
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ATmega3208/3209
RSTCTRL - Reset Controller
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:
– Power supply Reset sources: Brown-out Detect (BOD), Power-on Reset (POR)
– User Reset sources: External Reset pin (RESET), Watchdog Reset (WDT), Software Reset (SW), and
UPDI Reset.
12.2
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
VDD
POR
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
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.
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RSTCTRL - Reset Controller
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.
After Reset from any source, all registers that are loaded from fuses are reloaded.
12.3.2
Operation
12.3.2.1 Reset Sources
There are two kinds of sources for Resets:
• Power supply Resets, which are caused by changes in the power supply voltage: Power-on Reset (POR) and
Brown-out Detector (BOD).
• User Resets, which are issued by the application, by the debug operation, or by pin changes (Software Reset,
Watchdog Reset, UPDI Reset, and external Reset pin RESET).
12.3.2.1.1 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 reaches the POR threshold voltage. The POR is always enabled and will also detect when the VDD falls below the
threshold voltage.
12.3.2.1.2 Brown-Out Detector (BOD) Reset
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 the application it is forced to a
minimum level in order to ensure a safe operation during internal Reset and chip erase.
12.3.2.1.3 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.
12.3.2.1.4 External Reset
The external Reset is enabled by a fuse, see the RSTPINCFG field in FUSE.SYSCFG0.
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.
12.3.2.1.5 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 time-out period, a Watchdog Reset will be issued. See the WDT
documentation for further details.
12.3.2.1.6 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. See the UPDI chapter
on how to generate a UPDI Reset request.
12.3.2.1.7 Domains Affected By Reset
The following logic domains are affected by the various resets:
Table 12-1. Logic Domains Affected by Various Resets
Reset Type
Fuses are
Reloaded
POR
X
BOD
X
Software Reset X
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TCD Pin
Override
Functionality
Available
Reset of TCD
Pin Override
Settings
Reset of BOD Reset of UPDI Reset of
Configuration
Other Volatile
Logic
X
X
X
X
Preliminary Datasheet
X
X
X
X
X
DS40002174A-page 105
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RSTCTRL - Reset Controller
...........continued
Reset Type
Fuses are
Reloaded
External Reset X
Watchdog
X
Reset
UPDI Reset
X
TCD Pin
Override
Functionality
Available
Reset of TCD
Pin Override
Settings
Reset of BOD Reset of UPDI Reset of
Configuration
Other Volatile
Logic
X
X
X
X
X
X
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 Brown-out Detector (BOD)
is active as long as the supply voltage is below the Reset source threshold.
When all the Reset sources are released, an internal Reset initialization of the device is done. This time will be
increased with the start-up time given by the start-up time fuse setting (SUT in FUSE.SYSCFG1). The internal Reset
initialization time will also increase if the CRCSCAN is configured to run at start-up (CRCSRC in FUSE.SYSCFG0).
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). To write to these registers, a
certain key must first be written to the CPU.CCP register, followed by a write access to the protected bits within four
CPU instructions.
Attempting to write to a protected register without following the appropriate CCP unlock sequence leaves the
protected register unchanged.
The following registers are under CCP:
Table 12-2. RSTCTRL - Registers Under Configuration Change Protection
Register
Key
RSTCTRL.SWRR
IOREG
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RSTCTRL - Reset Controller
12.4
Register Summary - RSTCTRL
Offset
Name
Bit Pos.
0x00
0x01
RSTFR
SWRR
7:0
7:0
12.5
UPDIRF
SWRF
WDRF
EXTRF
BORF
PORF
SWRE
Register Description
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RSTCTRL - Reset Controller
12.5.1
Reset Flag Register
Name:
Offset:
Reset:
Property:
RSTFR
0x00
0xXX
-
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).
Bit
7
6
Access
Reset
5
UPDIRF
R/W
x
4
SWRF
R/W
x
3
WDRF
R/W
x
2
EXTRF
R/W
x
1
BORF
R/W
x
0
PORF
R/W
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' to it.
After a POR, only the POR flag is set and all the other flags are cleared. No other flags can be set before a full
system boot is run after the POR.
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RSTCTRL - Reset Controller
12.5.2
Software Reset Register
Name:
Offset:
Reset:
Property:
Bit
7
SWRR
0x01
0x00
Configuration Change Protection
6
5
4
3
Access
Reset
2
1
0
SWRE
R/W
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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CPUINT - CPU Interrupt Controller
13.
CPUINT - CPU Interrupt Controller
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
Non-Maskable Interrupts (NMI) for Critical Functions
Two Interrupt Priority Levels: 0 (normal) and 1 (high)
– One of the Interrupt Requests can optionally be assigned as a Priority Level 1 interrupt
– Optional Round Robin Priority Scheme for Priority Level 0 Interrupts
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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CPUINT - CPU Interrupt Controller
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
13.3
13.3.1
STATUS
LVL0PRI
LVL1VEC
Global
Interrupt
Enable
CPU.SREG
Wake-up
Sleep
Controller
Functional Description
Initialization
An interrupt must be initialized in the following order:
1.
2.
3.
13.3.2
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).
– 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 Interrupt vector placement is dependent on the value of Interrupt Vector Select bit (IVSEL) in the Control A
register (CPUINT.CTRLA). Refer to the IVSEL description in CPUINT.CTRLA for the possible locations.
If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular program code can
be placed at these locations.
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CPUINT - CPU Interrupt Controller
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, two cycles to store the Program Counter to the stack, and three cycles(1) to jump to the interrupt
handler (JMP).
After the Program Counter is pushed on the stack, the program vector for the interrupt is executed. See Figure 13-2,
first diagram.
The jump to the interrupt handler takes three clock cycles(1). If an interrupt occurs during execution of a multicycle
instruction, this instruction is completed before the interrupt is served. See Figure 13-2, second diagram.
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. See
Figure 13-2, third diagram.
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.
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CPUINT - CPU Interrupt Controller
Figure 13-2. Interrupt Execution of a Single-Cycle Instruction, Multicycle Instruction, and From Sleep(1)
Single-Cycle Instruction
Multicycle Instruction
Sleep
Note:
1. Devices with 8 KB of Flash or less use RJMP instead of JMP, which takes only two clock cycles.
13.3.2.4 Interrupt Priority
All interrupt vectors are assigned to one of three possible priority levels, as shown in the table. An interrupt request
from a high priority source will interrupt any ongoing interrupt handler from a normal priority source. When returning
from the high priority interrupt handler, the execution of the normal priority interrupt handler will resume.
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CPUINT - CPU Interrupt Controller
Table 13-1. Interrupt Priority Levels
Priority
Level
Source
Highest
Non Maskable Interrupt (NMI)
Device-dependent and statically
assigned
...
High Priority (Level 1)
One vector is optionally user
selectable as Level 1
Lowest
Normal Priority (Level 0)
The remaining interrupt vectors
13.3.2.4.1 Non-Maskable Interrupts (NMI)
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 an 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 the 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.
13.3.2.4.2 High Priority Interrupt
It is possible to assign one interrupt request to level 1 (high priority) by writing its interrupt vector number to the
CPUINT.LVL1VEC register. This interrupt request will have higher priority than the other (normal priority) interrupt
requests.
13.3.2.4.3 Normal Priority Interrupts
All interrupt vectors other than NMI are assigned to priority level 0 (normal) by default. The user may override this by
assigning one of these vectors as a high priority vector. The device will have many normal priority vectors, and some
of these may be pending at the same time. Two different scheduling schemes are available to choose which of the
pending normal priority interrupts to service first: Static and round robin.
The following sections use the ordered sequence IVEC to explain these scheduling schemes. IVEC is the Interrupt
Vector Mapping as listed in the Peripherals and Architecture chapter. IVEC0 is the reset vector, IVEC1 is the NMI
vector, and so on. In a vector table with n+1 elements, the vector with the highest vector number is denoted IVECn.
Reset, non-maskable interrupts and high-level interrupts are included in the IVEC map, but will be disregarded by the
normal priority interrupt scheduler as they are not normal priority interrupts.
Scheduling of Normal Priority Interrupts
Static Scheduling
If several level 0 interrupt requests are pending at the same time, the one with the highest priority is scheduled for
execution first. The CPUINT.LVL0PRI register makes it possible to change the default priority. The reset value for
CPUINT.LVL0PRI is zero, resulting in a default priority as shown in Figure 13-3. As the figure shows, IVEC0 has the
highest priority, and IVECn has the lowest priority.
The default priority can be changed by writing to the CPUINT.LVL0PRI register. The value written to the register will
identify the vector number with the lowest priority. The next interrupt vector in IVEC will have the highest priority, see
Figure 13-4. In this figure, the value Y has been written to CPUINT.LVL0PRI, so that interrupt vector Y+1 has the
highest priority. Note that in this case, the priorities will "wrap" so that IVEC0 has lower priority than IVECn.
Refer to the Interrupt Vector Mapping of the device for available interrupt requests and their interrupt vector number.
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CPUINT - CPU Interrupt Controller
Figure 13-3. Static Scheduling when CPUINT.LVL0PRI is zero
Lowest Address
IVEC 0
Highest Priority
IVEC 1
:
:
:
IVEC Y
IVEC Y+1
:
:
:
Highest Address
IVEC n
Lowest Priority
Figure 13-4. Static Scheduling when CPUINT.LVL0PRI is Different From Zero
Lowest Address
IVEC 0
IVEC 1
:
:
:
IVEC Y
Lowest Priority
IVEC Y+1
Highest Priority
:
:
:
Highest Address
IVEC n
Round Robin Scheduling
Static scheduling may cause starvation, i.e. some interrupts might never be serviced. To avoid this, the CPUINT
offers round robin scheduling for normal priority (LVL0) interrupts. In round robin scheduling, CPUINT.LVL0PRI
contains the number of the vector number in IVEC with the lowest priority. This register is automatically updated by
hardware with the interrupt vector number for the last acknowledged LVL0 interrupt. This interrupt vector will,
therefore, have the lowest priority next time one or more LVL0 interrupts are pending. Figure 13-5 explains the new
priority ordering after IVEC Y was the last interrupt to be acknowledged, and after IVEC Y+1 was the last interrupt to
be acknowledged.
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).
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CPUINT - CPU Interrupt Controller
Figure 13-5. Round Robin Scheduling
IVEC Y was last acknowledged
interrupt
IVEC Y+1 was last acknowledged
interrupt
IVEC 0
IVEC 0
:
:
:
:
:
:
IVEC Y
Lowest Priority
IVEC Y
IVEC Y+1
Highest Priority
IVEC Y+1
Lowest Priority
IVEC Y+2
Highest Priority
:
:
:
IVEC n
:
:
:
IVEC n
13.3.2.5 Compact Vector Table
The Compact Vector Table (CVT) is a feature to allow 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
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). To write to these registers, a
certain key must first be written to the CPU.CCP register, followed by a write access to the protected bits within four
CPU instructions.
Attempting to write to a protected register without following the appropriate CCP unlock sequence leaves the
protected register unchanged.
The following registers are under CCP:
Table 13-2. INTCTRL - Registers under Configuration Change Protection
Register
Key
IVSEL in CPUINT.CTRLA
IOREG
CVT in CPUINT.CTRLA
IOREG
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CPUINT - CPU Interrupt Controller
13.4
Register Summary - CPUINT
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
CTRLA
STATUS
LVL0PRI
LVL1VEC
7:0
7:0
7:0
7:0
13.5
IVSEL
CVT
NMIEX
LVL1EX
LVL0RR
LVL0EX
LVL0PRI[7:0]
LVL1VEC[7:0]
Register Description
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CPUINT - CPU Interrupt Controller
13.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CTRLA
0x00
0x00
Configuration Change Protection
6
IVSEL
R/W
0
5
CVT
R/W
0
4
3
2
1
0
LVL0RR
R/W
0
Bit 6 – IVSEL Interrupt Vector Select
If the boot section is defined, it will be placed before the 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
Description
0
Interrupt vectors are placed at the start of the application section of the Flash.
1
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
Description
0
Compact Vector Table function is disabled
1
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
Description
0
Priority is fixed for priority level 0 interrupt requests: The lowest interrupt vector address has the
highest priority.
1
Round Robin priority scheme is enabled for priority level 0 interrupt requests.
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CPUINT - CPU Interrupt Controller
13.5.2
Status
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
NMIEX
R
0
STATUS
0x01
0x00
-
6
5
4
3
2
1
LVL1EX
R
0
0
LVL0EX
R
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.
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CPUINT - CPU Interrupt Controller
13.5.3
Interrupt Priority Level 0
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
LVL0PRI
0x02
0x00
-
7
6
5
R/W
0
R/W
0
R/W
0
4
3
LVL0PRI[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – LVL0PRI[7:0] Interrupt Priority Level 0
This register is used to modify the priority of the LVL0 interrupts. See Scheduling of Normal Priority Interrupts for
more information.
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CPUINT - CPU Interrupt Controller
13.5.4
Interrupt Vector with Priority Level 1
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
LVL1VEC
0x03
0x00
-
7
6
5
R/W
0
R/W
0
R/W
0
4
3
LVL1VEC[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
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.
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EVSYS - Event System
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 8 parallel Event channels available
Each channel is driven by one event generator and can have multiple event users
Events can be sent and/or received by most peripherals, and by software
The event system works in Active, Idle, and Standby Sleep modes
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 event signal can be routed on each channel. Multiple peripherals can use events from the same channel.
The EVSYS can directly connect peripherals such as ADCs, 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.
14.2.1
Block Diagram
Figure 14-1. Block Diagram
Event channel n
STROBEx[n]
From event
generators
.
.
.
0
D QD Q
CHANNELn
To channel
mux for async
event user
1
To channel
mux for sync
event user
Is
async?
The block diagram shows the operation of an event channel. A multiplexer controlled by EVSYS.CHANNELn at the
input selects which of the event sources to route onto the event channel. Each event channel has two subchannels;
One asynchronous subchannel and one synchronous subchannel. A synchronous user will listen to the synchronous
subchannel, an asynchronous user will listen to the asynchronous subchannel.
An event signal from an asynchronous source will be synchronized by the event system before being routed to the
synchronous subchannel. An asynchronous event signal to be used by a synchronous consumer must last for at least
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EVSYS - Event System
one peripheral clock cycle to guarantee that it will propagate through the synchronizer. The synchronizer will delay
such an event by 2-3 clock cycles depending on when the event occurs.
Figure 14-2. Example of Event Source, Generator, User, and Action
Event Generator
Event User
Timer/Counter
ADC
Compare Match
Over-/Underflow
|
Channel Sweep
Event
Routing
Network
Single
Conversion
Error
Event Action Selection
Event Source
14.2.2
Event Action
Signal Description
Signal
Type
Description
EVOUTn
Digital output
Event output, one output per I/O Port
14.3
Functional Description
14.3.1
Initialization
To use events, both the event system, the generating peripheral and peripheral(s) using the event must be set up
appropriately.
1.
2.
3.
14.3.2
Configure the generating peripheral appropriately. As an example, if the generating peripheral is a timer, set
the prescaling, compare register, etc. so that the desired event is generated.
Configure the event user peripheral(s) appropriately. As an example, if the ADC is the event user, set the ADC
prescaler, resolution, conversion time, etc. as desired, and configure ADC conversion to start on the reception
of an event.
Configure the event system to route the desired source. In this case, the Timer/Compare match to the desired
event channel. This may, for example, be channel 0, which is accomplished by writing to EVSYS.CHANNEL0.
Configure the ADC to listen to this channel, by writing to EVSYS.USERn, where n is the index allocated to the
ADC.
Operation
14.3.2.1 Event User Multiplexer Setup
Each event user has one dedicated event user multiplexer selecting which event channel to listen to. The application
configures these multiplexers by writing to the corresponding User Channel Input Selection n (EVSYS.USERn)
register.
14.3.2.2 Event System Channel
An event channel can be connected to one of the event generators. Event channels can be connected to either
asynchronous generators or synchronous generators.
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Preliminary Datasheet
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EVSYS - Event System
The source for each event channel is configured by writing to the respective Channel n Input Selection register
(EVSYS.CHANNELn).
14.3.2.3 Event Generators
Each event channel has several possible event generators, only one of which can be selected at a time. The event
generator trigger for a channel is selected by writing to the respective channel register (EVSYS.CHANNELn). By
default, the channels are not connected to any event generator. For details on event generation, refer to the
documentation of the corresponding peripheral.
A generated event is either synchronous or asynchronous to clocks in the device, depending on the generator. An
asynchronous event can be generated in sleep modes when clocks are not running. Such events can also be
generated outside the normal edges of the (prescaled) clocks in the system, making the system respond faster than
the selected clock frequency would suggest.
Generator Event
Generating Clock Length of Event
Domain
Constraints for Synchronous
User
UPDI
SYNC character
CLK_PDI
Waveform: SYNC char on Synchronizing clock in user
PDI RX input
must be fast enough to ensure
synchronized to CLK_PDI that the event is seen by the
user
RTC
Overflow
CLK_RTC
Pulse: 1 * CLK_RTC
Compare Match
CLK_RTC
Pulse: 1 * CLK_RTC
None
PIT
RTC Prescaled clock CLK_RTC
Level
CCL-LUT
LUT output
Asynchronous
Depends on CCL
configuration
The clock source used for CCL
must be slower or equal to
CLK_PER or input signals to
CCL are stable for at least
Tclk_per
AC
Comparator result
Asynchronous
Level: Typically ≥1 us
The frequency of input signals
to AC must be ≤fclk_per to
ensure that the event is seen
by the synchronous user
ADC
Result ready
CLK_ADC
Pulse: 1 * CLK_PER
None
PORT
Pin input
Asynchronous
Level: Externally
controlled
The input signal must be stable
for longer than fclk_per
USART
USART Baud clock
TXCLK
Level
None
SPI
SPI Master clock
SCK
Level
None
TCA
Overflow
CLK_PER
Pulse: 1 * CLK_PER
None
Underflow in split
mode
CLK_PER
Pulse: 1 * CLK_PER
Compare match ch 0 CLK_PER
Pulse: 1 * CLK_PER
Compare match ch 1 CLK_PER
Pulse: 1 * CLK_PER
Compare match ch 2 CLK_PER
Pulse: 1 * CLK_PER
CAPT interrupt flag
set
Pulse: 1 * CLK_PER
TCB
CLK_PER
None
14.3.2.4 Event Users
Each event user must be configured to select the event channel to listen to. An event user may require the event
signal to be either synchronous or asynchronous to the system clock. An asynchronous event user can respond to
events in sleep modes when clocks are not running. Such events can also be responded to outside the normal edges
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EVSYS - Event System
of the (prescaled) clocks in the system, making the event user respond faster than the clock frequency would
suggest. For details on the requirements of each peripheral, refer to the documentation of the corresponding
peripheral.
User
Module/Event Mode
Input Format
Asynchronous
TCAn
CNT_POSEDGE
Edge
No
CNT_ANYEDGE
Edge
No
CNT_HIGHLVL
Level
No
UPDOWN
Level
No
Time-out check
Edge
No
Input Capture on Event
Edge
No
Input Capture Frequency Measurement
Edge
No
Input Capture Pulse-Width Measurement
Edge
No
Input Capture Frequency and Pulse Width Measurement
Edge
No
Single-Shot
Edge
Yes
USARTn
IrDA Mode
Level
No
CCLLUTnx
LUTn input x or clock signal
Level
Yes
ADCn
ADC start on event
Edge
Yes
EVOUTx
Forward event signal to pin
Level
Yes
TCBn
14.3.2.5 Synchronization
Events can be either synchronous or asynchronous to the system clock. Each event system channel has two
subchannels; one asynchronous and one synchronous. Both subchannels are available to all event users, each user
is hardwired to listen to one or the other.
The asynchronous subchannel is identical to the event output from the generator. If the event generator generates a
signal that is asynchronous to the system clock, the signal on the asynchronous subchannel will be asynchronous. If
the event generator generates a signal that is synchronous to the system clock, the signal on the asynchronous
subchannel will also be synchronous.
The synchronous subchannel is identical to the event output from the generator if the event generator generates a
signal that is synchronous to the system clock. If the event generator generates a signal that is asynchronous to the
system clock, this signal is first synchronized before being routed onto the synchronous subchannel. Synchronization
will delay the event by two system cycles. The event system automatically performs this synchronization if an
asynchronous generator is selected for an event channel, no explicit configuration is needed.
14.3.2.6 Software Event
The application can generate a software event. Software events on channel n are issued by writing a ‘1’ to the
STROBE[n] bit in the EVSYS.STROBEx register. A software event appears as a pulse on the event system channel,
inverting the current event system value for one clock cycle.
Event users see software events as no different from those produced by event generating peripherals. When the
STROBE[n] bit in the EVSYS.STROBEx register is written to ‘1’, an event will be generated on the respective
channel, and received and processed by the event user.
14.3.3
Sleep Mode Operation
When configured, the event system will work in all sleep modes. One exception is software events which require a
system clock.
Asynchronous event users are able to respond to an event without their clock running, i.e. in Standby Sleep mode.
Synchronous event users require their clock to be running to be able to respond to events. Such users will only work
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EVSYS - Event System
in Idle Sleep mode or in Standby Sleep mode if configured to run in Standby mode by setting the RUNSTBY bit in the
appropriate register.
Asynchronous event generators are able to generate an event without their clock running, i.e. in Standby Sleep
mode. Synchronous event generators require their clock to be running to be able to generate events. Such
generators will only work in Idle Sleep mode or in Standby Sleep mode if configured to run in Standby mode by
setting the RUNSTBY bit in the appropriate register.
14.3.4
Debug Operation
This peripheral is unaffected by entering Debug mode.
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EVSYS - Event System
14.4
Register Summary - EVSYS
Offset
Name
Bit Pos.
0x00
0x01
...
0x0F
0x10
0x11
0x12
0x13
0x14
0x15
0x16
0x17
0x18
...
0x1F
0x20
...
0x37
STROBEx
7:0
STROBE[7:0]
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
GENERATOR[7:0]
GENERATOR[7:0]
GENERATOR[7:0]
GENERATOR[7:0]
GENERATOR[7:0]
GENERATOR[7:0]
GENERATOR[7:0]
GENERATOR[7:0]
USER0
7:0
CHANNEL[7:0]
USER23
7:0
CHANNEL[7:0]
14.5
Reserved
CHANNEL0
CHANNEL1
CHANNEL2
CHANNEL3
CHANNEL4
CHANNEL5
CHANNEL6
CHANNEL7
Reserved
Register Description
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EVSYS - Event System
14.5.1
Channel Strobe
Name:
Offset:
Reset:
Property:
STROBEx
0x00
0x00
-
Software Events
Write bits in this register in order to create software events.
Refer to the Peripheral Overview for the available number of event system channels.
Bit
7
6
5
4
3
2
1
0
W
0
W
0
W
0
W
0
STROBE[7:0]
Access
Reset
W
0
W
0
W
0
W
0
Bits 7:0 – STROBE[7:0] 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).
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EVSYS - Event System
14.5.2
Channel n Generator Selection
Name:
Offset:
Reset:
Property:
CHANNEL
0x10 + n*0x01 [n=0..7]
0x00
-
Each channel can be connected to one event generator. Not all generators can be connected to all channels. Refer to
the table below to see which generator sources that can be routed onto each channel, and the generator value that
must be written to EVSYS.CHANNELn to achieve this routing. The value 0x00 in EVSYS.CHANNELn turns the
channel OFF.
Bit
Access
Reset
7
6
5
R/W
0
R/W
0
R/W
0
4
3
GENERATOR[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – GENERATOR[7:0] Channel Generator Selection
GENERATOR
INPUT
Async/Sync
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
binary
hex
0000_0001
0x01
UPDI
Sync
UPDI
0000_0110
0x06
RTC_OVF
Async
OVF
0000_0111
0x07
RTC_CMP
Async
CMP
0000_1000
0x08
RTC_PIT0
Async
DIV8192
DIV512
DIV8192
DIV512
DIV8192
DIV512
DIV8192
DIV512
0000_1001
0x09
RTC_PIT1
Async
DIV4096
DIV256
DIV4096
DIV256
DIV4096
DIV256
DIV4096
DIV256
0000_1010
0x0A
RTC_PIT2
Async
DIV2048
DIV128
DIV2048
DIV128
DIV2048
DIV128
DIV2048
DIV128
0000_1011
0x0B
RTC_PIT3
Async
DIV1024
DIV64
DIV1024
DIV64
DIV1024
DIV64
DIV1024
DIV64
0001_00nn
0x10-0x13
CCL_LUTn
Async
LUTn
0010_0000
0x20
AC0
Async
OUT
0010_0100
0x24
ADC0
Sync
RESRDY
0100_0nnn
0x40-0x47
PORT0_PINn
Async
PORTA_PINn
PORTC_PINn
PORTE_PINn
0100_1nnn
0x48-0x4F
PORT1_PINn
Async
PORTB_PINn
PORTD_PINn
PORTF_PINn
0110_0nnn
0x60-0x67
USARTn
Sync
XCK
0110_1000
0x68
SPI0
Sync
SCK
1000_0000
0x80
TCA0_OVF_LUNF
Sync
OVF/LUNF
1000_0001
0x81
TCA0_HUNF
Sync
HUNF
1000_0100
0x84
TCA0_CMP0
Sync
CMP0
1000_0101
0x85
TCA0_CMP1
Sync
CMP1
1000_0110
0x86
TCA0_CMP2
Sync
CMP2
1010_nnn0
0xA0-0xAE
TCBn
Sync
CAPT
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Preliminary Datasheet
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EVSYS - Event System
14.5.3
User Channel Mux
Name:
Offset:
Reset:
Property:
USER
0x20 + n*0x01 [n=0..23]
0x00
-
Each event user can be connected to one channel. Several users can be connected to the same channel. The
following table lists all event system users, with their corresponding user ID number. This ID number corresponds to
the USER register index, e.g., the EVSYS.USER2 register controls the user with ID 2.
Bit
Access
Reset
USER #
User Name
Async/Sync
Description
0
CCLLUT0A
Async
CCL LUT0 event input A
1
CCLLUT0B
Async
CCL LUT0 event input B
2
CCLLUT1A
Async
CCL LUT1 event input A
3
CCLLUT1B
Async
CCL LUT1 event input B
4
CCLLUT2A
Async
CCL LUT2 event input A
5
CCLLUT2B
Async
CCL LUT2 event input B
6
CCLLUT3A
Async
CCL LUT3 event input A
7
CCLLUT3B
Async
CCL LUT3 event input B
8
ADC0
Async
ADC0 Trigger
9
EVOUTA
Async
EVSYS pin output A
10
EVOUTB
Async
EVSYS pin output B
11
EVOUTC
Async
EVSYS pin output C
12
EVOUTD
Async
EVSYS pin output D
13
EVOUTE
Async
EVSYS pin output E
14
EVOUTF
Async
EVSYS pin output F
15
USART0
Sync
USART0 event input
16
USART1
Sync
USART1 event input
17
USART2
Sync
USART2 event input
18
USART3
Sync
USART3 event input
19
TCA0
Sync
TCA0 event input
20
TCB0
Both
TCB0 event input
21
TCB1
Both
TCB1 event input
22
TCB2
Both
TCB2 event input
23
TCB3
Both
TCB3 event input
7
6
5
R/W
0
R/W
0
R/W
0
4
3
CHANNEL[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – CHANNEL[7:0] User Channel Selection
Describes which event system channel the user is connected to.
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Preliminary Datasheet
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EVSYS - Event System
Value
0
n
Description
OFF, no channel is connected to this event system user
Event user is connected to CHANNEL(n-1)
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ATmega3208/3209
PORTMUX - Port Multiplexer
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. Available options are described in detail in the PORTMUX register map and depend on the
actual pin and its properties.
For available pins and functionalities, refer to the “I/O Multiplexing and Considerations” section.
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PORTMUX - Port Multiplexer
15.2
Register Summary - PORTMUX
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
0x05
EVSYSROUTEA
CCLROUTEA
USARTROUTEA
TWISPIROUTEA
TCAROUTEA
TCBROUTEA
7:0
7:0
7:0
7:0
7:0
7:0
15.3
EVOUTF
USART3[1:0]
EVOUTE
USART2[1:0]
TWI0[1:0]
EVOUTD
EVOUTC
LUT3
LUT2
USART1[1:0]
TCB3
TCB2
EVOUTB
EVOUTA
LUT1
LUT0
USART0[1:0]
SPI0[1:0]
TCA0[2:0]
TCB1
TCB0
Register Description
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PORTMUX - Port Multiplexer
15.3.1
PORTMUX Control for Event System
Name:
Offset:
Reset:
Property:
Bit
7
EVSYSROUTEA
0x00
0x00
-
6
Access
Reset
5
EVOUTF
R/W
0
4
EVOUTE
R/W
0
3
EVOUTD
R/W
0
2
EVOUTC
R/W
0
1
EVOUTB
R/W
0
0
EVOUTA
R/W
0
Bit 5 – EVOUTF Event Output F
Write this bit to ‘1’ to select alternative pin location for Event Output F.
Value
Name
Description
0x0
DEFAULT
EVOUTF on PF2
0x1
Reserved
Bit 4 – EVOUTE Event Output E
Write this bit to ‘1’ to select alternative pin location for Event Output E.
Value
Name
Description
0x0
DEFAULT
EVOUTE on PE2
0x1
Reserved
Bit 3 – EVOUTD Event Output D
Write this bit to ‘1’ to select alternative pin location for Event Output D.
Value
Name
Description
0x0
DEFAULT
EVOUTD on PD2
0x1
ALT1
EVOUTD on PD7
Bit 2 – EVOUTC Event Output C
Write this bit to ‘1’ to select alternative pin location for Event Output C.
Value
Name
Description
0x0
DEFAULT
EVOUTC on PC2
0x1
ALT1
EVOUTC on PC7
Bit 1 – EVOUTB Event Output A
Write this bit to ‘1’ to select alternative pin location for Event Output B.
Value
Name
Description
0x0
DEFAULT
EVOUTB on PB2
0x1
Reserved
Bit 0 – EVOUTA Event Output A
Write this bit to ‘1’ to select alternative pin location for Event Output A.
Value
Name
Description
0x0
DEFAULT
EVOUTA on PA2
0x1
ALT1
EVOUTA on PA7
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PORTMUX - Port Multiplexer
15.3.2
PORTMUX Control for CCL
Name:
Offset:
Reset:
Property:
Bit
7
CCLROUTEA
0x01
0x00
-
6
Access
Reset
5
4
3
LUT3
R/W
0
2
LUT2
R/W
0
1
LUT1
R/W
0
0
LUT0
R/W
0
Bit 3 – LUT3 CCL LUT 3 Output
Write this bit to ‘1’ to select alternative pin location for CCL LUT 3.
Value
Name
Description
0x0
DEFAULT
CCL LUT3 on PF[3]
0x1
ALT1
CCL LUT3 on PF[6]
Bit 2 – LUT2 CCL LUT 2 Output
Write this bit to ‘1’ to select alternative pin location for CCL LUT 2.
Value
Name
Description
0x0
DEFAULT
CCL LUT2 on PD[3]
0x1
ALT1
CCL LUT2 on PD[6]
Bit 1 – LUT1 CCL LUT 1 Output
Write this bit to ‘1’ to select alternative pin location for CCL LUT 1.
Value
Name
Description
0x0
DEFAULT
CCL LUT1 on PC[3]
0x1
ALT1
CCL LUT1 on PC[6]
Bit 0 – LUT0 CCL LUT 0 Output
Write this bit to ‘1’ to select alternative pin location for CCL LUT 0.
Value
Name
Description
0x0
DEFAULT
CCL LUT0 on PA[3]
0x1
ALT1
CCL LUT0 on PA[6]
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PORTMUX - Port Multiplexer
15.3.3
PORTMUX Control for USART
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
USARTROUTEA
0x02
0x00
-
7
6
USART3[1:0]
R/W
R/W
0
0
5
4
USART2[1:0]
R/W
R/W
0
0
3
2
USART1[1:0]
R/W
R/W
0
0
1
0
USART0[1:0]
R/W
R/W
0
0
Bits 7:6 – USART3[1:0] USART 3 Communication
Write these bits to select alternative communication pins for USART 3.
Value
Name
Description
0x0
DEFAULT
USART3 on PB[3:0]
0x1
ALT1
USART3 on PB[5:4]
0x2
Reserved
0x3
NONE
Not connected to any pins
Bits 5:4 – USART2[1:0] USART 2 Communication
Write these bits to select alternative communication pins for USART 2.
Value
Name
Description
0x0
DEFAULT
USART2 on PF[3:0]
0x1
ALT1
USART2 on PF[6:4]
0x2
Reserved
0x3
NONE
Not connected to any pins
Bits 3:2 – USART1[1:0] USART 1 Communication
Write these bits to select alternative communication pins for USART 1.
Value
Name
Description
0x0
DEFAULT
USART1 on PC[3:0]
0x1
ALT1
USART1 on PC[7:4]
0x2
Reserved
0x3
NONE
Not connected to any pins
Bits 1:0 – USART0[1:0] USART 0 Communication
Write these bits to select alternative communication pins for USART 0.
Value
Name
Description
0x0
DEFAULT
USART0 on PA[3:0]
0x1
ALT1
USART0 on PA[7:4]
0x2
Reserved
0x3
NONE
Not connected to any pins
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PORTMUX - Port Multiplexer
15.3.4
PORTMUX Control for TWI and SPI
Name:
Offset:
Reset:
Property:
Bit
7
TWISPIROUTEA
0x03
0x00
-
6
5
4
3
2
1
TWI0[1:0]
Access
Reset
R/W
0
0
SPI0[1:0]
R/W
0
R/W
0
R/W
0
Bits 5:4 – TWI0[1:0] TWI 0 Communication
Write these bits to select alternative communication pins for TWI 0.
Value
Name
Description
0x0
DEFAULT
SCL/SDA on PA[3:2], Slave mode on PC[3:2] in dual TWI mode
0x1
ALT1
SCL/SDA on PA[3:2], Slave mode on PF[3:2] in dual TWI mode
0x2
ALT2
SCL/SDA on PC[3:2], Slave mode on PF[3:2] in dual TWI mode
0x3
Reserved
Bits 1:0 – SPI0[1:0] SPI 0 Communication
Write these bits to select alternative communication pins for SPI 0.
Value
Name
Description
0x0
DEFAULT
SPI on PA[7:4]
0x1
ALT1
SPI on PC[3:0]
0x2
ALT2
SPI on PE[3:0]
0x3
NONE
Not connected to any pins
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ATmega3208/3209
PORTMUX - Port Multiplexer
15.3.5
PORTMUX Control for TCA
Name:
Offset:
Reset:
Property:
Bit
7
TCAROUTEA
0x04
0x00
-
6
5
4
3
Access
Reset
2
R/W
0
1
TCA0[2:0]
R/W
0
0
R/W
0
Bits 2:0 – TCA0[2:0] TCA0 Output
Write these bits to select alternative output pins for TCA0.
Value
Name
Description
0x0
PORTA
TCA0 pins on PA[5:0]
0x1
PORTB
TCA0 pins on PB[5:0]
0x2
PORTC
TCA0 pins on PC[5:0]
0x3
PORTD
TCA0 pins on PD[5:0]
0x4
PORTE
TCA0 pins on PE[5:0]
0x5
PORTF
TCA0 pins on PF[5:0]
Other
Reserved
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ATmega3208/3209
PORTMUX - Port Multiplexer
15.3.6
PORTMUX Control for TCB
Name:
Offset:
Reset:
Property:
Bit
7
TCBROUTEA
0x05
0x00
-
6
Access
Reset
5
4
3
TCB3
R/W
0
2
TCB2
R/W
0
1
TCB1
R/W
0
0
TCB0
R/W
0
Bit 3 – TCB3 TCB3 Output
Write this bit to ‘1’ to select alternative output pin for 16-bit timer/counter B 3.
Value
Name
Description
0x0
DEFAULT
TCB3 on PB5
0x1
ALT1
TCB3 on PC1
Bit 2 – TCB2 TCB2 Output
Write this bit to ‘1’ to select alternative output pin for 16-bit timer/counter B 2.
Value
Name
Description
0x0
DEFAULT
TCB2 on PC0
0x1
ALT1
TCB2 on PB4
Bit 1 – TCB1 TCB1 Output
Write this bit to ‘1’ to select alternative output pin for 16-bit timer/counter B 1.
Value
Name
Description
0x0
DEFAULT
TCB1 on PA3
0x1
ALT1
TCB1 on PF5
Bit 0 – TCB0 TCB0 Output
Write this bit to ‘1’ to select alternative output pin for 16-bit timer/counter B 0.
Value
Name
Description
0x0
DEFAULT
TCB0 on PA2
0x1
ALT1
TCB0 on PF4
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PORT - I/O Pin Configuration
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. Each PORT instance has up
to eight I/O pins. The PORTs are named PORTA, PORTB, PORTC, etc. Refer to the “I/O Multiplexing and
Considerations” chapter in the device Data Sheet 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 (PORTx.DIR) and Data Output Value
(PORTx.OUT) registers to enable that pin as an output and to define the output state. For example, pin PA3 is
controlled by DIR[3] and OUT[3] of the PORTA instance.
The input value of a PORT pin is synchronized to the main clock and then made accessible as the data input value
(PORTx.IN). To reduce power consumption, these input synchronizers are not clocked if the Input Sense
Configuration bit field (ISC) in PORTx.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 and events 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 a 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.
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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
Interrupt
Interrupt
Generator
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
Pxn
I/O pin
I/O pin n on PORTx
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.
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Specific pins, such as those used for connecting a debugger, may be configured differently, as required by their
special function.
16.3.2
Operation
16.3.2.1 Basic Functions
Each I/O pin Pxn can be controlled by the registers in PORTx. 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 PORTx.DIR register to '1'. This can be done by writing bit n in
the PORTx.DIRSET register to '1', which will avoid disturbing the configuration of other pins in that group. The nth bit
in the PORTx.OUT register must be written to the desired output value.
Similarly, writing a PORTx.OUTSET bit to '1' will set the corresponding bit in the PORTx.OUT register to '1'. Writing a
bit in PORTx.OUTCLR to '1' will clear that bit in PORTx.OUT to zero. Writing a bit in PORTx.OUTTGL or PORTx.IN to
'1' will toggle that bit in PORTx.OUT.
To use pin n as an input, bit n in the PORTx.DIR register must be written to '0' to disable the output driver. This can
be done by writing bit n in the PORTx.DIRCLR register to '1', which will avoid disturbing the configuration of other
pins in that group. The input value can be read from bit n in register PORTx.IN as long as the ISC bit is not set to
INPUT_DISABLE.
Writing a bit to '1' in PORTx.DIRTGL will toggle that bit in PORTx.DIR and toggle the direction of the corresponding
pin.
16.3.2.2 Pin Configuration
The Pin n Configuration register (PORTx.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
PORTx.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 PORTx.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 PORTx.PINnCTRL.
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 re-enabling 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 a 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
16.3.2.3 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 memoryspecific instructions, such as bit-manipulation instructions, which are not valid for the extended I/O memory space
where the regular PORT registers reside.
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Table 16-1. 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
16.3.2.4 Peripheral Override
Peripherals such as USARTs and timers may be connected to I/O pins. Such peripherals will usually have a primary
and optionally also alternate I/O pin connection, selectable by PORTMUX. By configuring and enabling such
peripherals, the general-purpose I/O pin behavior normally controlled by PORT will be overridden by the peripheral in
a peripheral-dependent way. Some peripherals may not override all of the PORT registers, leaving the PORT module
to control some aspects of the I/O pin operation. Refer to the description of each peripheral for information on the
peripheral override. Any pin in a PORT which is not overridden by a peripheral will continue to operate as a generalpurpose I/O pin.
16.3.3
Interrupts
Table 16-2. Available Interrupt Vectors and Sources
Name
Vector Description Conditions
PORTx PORT interrupt
INTn in PORTx.INTFLAGS is raised as configured by ISC bit in PORTx.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 PORTx.PINnCTRL.
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 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.
Asynchronous Sensing Pin Properties
PORT 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
modes where no clocks are running.
Table 16-3. Behavior Comparison of Fully/Partly Asynchronous Sense Pin
Property
Synchronous or Partly Asynchronous Sense
Support
Full Asynchronous Sense
Support
Minimum pulse width
to trigger interrupt
Minimum one system clock cycle
Less than a system clock cycle
Waking the device
from sleep
From all interrupt sense configurations from sleep
modes with Main Clock running. Only from
BOTHEDGES or LEVEL interrupt sense
configuration from sleep modes with Main Clock
stopped.
From all interrupt sense
configurations from all sleep modes
Interrupt “dead time”
No new interrupt for three cycles after the previous
Less than a system clock cycle
Minimum Wake-up
pulse length
Value on pad must be kept until the system clock has Less than a system clock cycle
restarted
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16.3.4
Events
All PORT pins are asynchronous event system generators. PORT has as many event generators as there are PORT
pins in the device. Each event system output from PORT is the value present on the corresponding pin if the digital
input driver is enabled. If a pin input driver is disabled, the corresponding event system output is zero.
PORT has no event inputs.
16.3.5
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.
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16.4
Register Summary - PORTx
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
...
0x0F
0x10
0x11
0x12
0x13
0x14
0x15
0x16
0x17
DIR
DIRSET
DIRCLR
DIRTGL
OUT
OUTSET
OUTCLR
OUTTGL
IN
INTFLAGS
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
16.5
DIR[7:0]
DIRSET[7:0]
DIRCLR[7:0]
DIRTGL[7:0]
OUT[7:0]
OUTSET[7:0]
OUTCLR[7:0]
OUTTGL[7:0]
IN[7:0]
INT[7:0]
Reserved
PIN0CTRL
PIN1CTRL
PIN2CTRL
PIN3CTRL
PIN4CTRL
PIN5CTRL
PIN6CTRL
PIN7CTRL
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
INVEN
INVEN
INVEN
INVEN
INVEN
INVEN
INVEN
INVEN
PULLUPEN
PULLUPEN
PULLUPEN
PULLUPEN
PULLUPEN
PULLUPEN
PULLUPEN
PULLUPEN
ISC[2:0]
ISC[2:0]
ISC[2:0]
ISC[2:0]
ISC[2:0]
ISC[2:0]
ISC[2:0]
ISC[2:0]
Register Description - Ports
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16.5.1
Data Direction
Name:
Offset:
Reset:
Property:
Bit
7
DIR
0x00
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
DIR[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – DIR[7:0] Data Direction
This bit field controls output enable for the individual pins of the Port.
Writing a ‘1’ to PORTx.DIR[n] configures and enables pin n as an output pin.
Writing a ‘0’ to PORTx.DIR[n] configures pin n as an input-only pin. Its properties can be configured by writing to the
ISC bit in PORTx.PINnCTRL.
PORTx.DIRn controls only the output enable. Setting PORTx.DIR[n] to ‘1’ does not disable the pin input.
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16.5.2
Data Direction Set
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
DIRSET
0x01
0x00
-
7
6
5
R/W
0
R/W
0
R/W
0
4
3
DIRSET[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
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 PORTx.DIR[n] bit.
Reading this bit field will always return the value of PORTx.DIR.
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16.5.3
Data Direction Clear
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
DIRCLR
0x02
0x00
-
7
6
5
R/W
0
R/W
0
R/W
0
4
3
DIRCLR[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
0
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-only.
Writing a '1' to DIRCLR[n] will clear the corresponding bit in PORTx.DIR.
Reading this bit field will always return the value of PORTx.DIR.
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16.5.4
Data Direction Toggle
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
DIRTGL
0x03
0x00
-
7
6
5
R/W
0
R/W
0
R/W
0
4
3
DIRTGL[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
0
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 PORTx.DIR.
Reading this bit field will always return the value of PORTx.DIR.
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16.5.5
Output Value
Name:
Offset:
Reset:
Property:
Bit
7
OUT
0x04
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
OUT[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – OUT[7:0] Output Value
This bit field defines the data output value for the individual pins 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.
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16.5.6
Output Value Set
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
OUTSET
0x05
0x00
-
7
6
5
R/W
0
R/W
0
R/W
0
4
3
OUTSET[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
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 PORTx.OUT.
Reading this bit field will always return the value of PORTx.OUT.
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16.5.7
Output Value Clear
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
OUTCLR
0x06
0x00
-
7
6
5
R/W
0
R/W
0
R/W
0
4
3
OUTCLR[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
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 PORTx.OUT.
Reading this bit field will always return the value of PORTx.OUT.
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16.5.8
Output Value Toggle
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
OUTTGL
0x07
0x00
-
7
6
5
R/W
0
R/W
0
R/W
0
4
3
OUTTGL[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
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 PORTx.OUT.
Reading this bit field will always return the value of PORTx.OUT.
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PORT - I/O Pin Configuration
16.5.9
Input Value
Name:
Offset:
Reset:
Property:
Bit
7
IN
0x08
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
IN[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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. If the digital input buffers are disabled, the input is not sampled and cannot be read.
Writing to a bit of PORTx.IN will toggle the corresponding bit in PORTx.OUT.
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16.5.10 Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x09
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
INT[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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 PORTx.PINnCTRL.
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16.5.11 Pin n Control
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
INVEN
R/W
0
PINCTRL
0x10 + n*0x01 [n=0..7]
0x00
-
6
5
4
3
PULLUPEN
R/W
0
2
R/W
0
1
ISC[2:0]
R/W
0
0
R/W
0
Bit 7 – INVEN Inverted I/O Enable
Value
Description
0
Input and output values are not inverted
1
Input and output values are inverted
Bit 3 – PULLUPEN Pullup Enable
Value
Description
0
Pullup disabled for pin n
1
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
Name
Description
0x0
INTDISABLE
Interrupt disabled but input buffer enabled
0x1
BOTHEDGES
Interrupt enabled with sense on both edges
0x2
RISING
Interrupt enabled with sense on rising edge
0x3
FALLING
Interrupt enabled with sense on falling edge
0x4
INPUT_DISABLE
Interrupt and digital input buffer disabled
0x5
LEVEL
Interrupt enabled with sense on low level
other
Reserved
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16.6
Register Summary - VPORTx
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
DIR
OUT
IN
INTFLAGS
7:0
7:0
7:0
7:0
16.7
DIR[7:0]
OUT[7:0]
IN[7:0]
INT[7:0]
Register Description - Virtual Ports
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16.7.1
Data Direction
Name:
Offset:
Reset:
Property:
DIR
0x00
0x00
-
Writing to the Virtual PORT registers has the same effect as writing to the regular registers, but allows for memoryspecific instructions, such as bit-manipulation instructions, which are not valid for the extended I/O memory space
where the regular PORT registers reside.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
DIR[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – DIR[7:0] Data Direction
This bit field controls output enable for the individual pins of the Port.
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16.7.2
Output Value
Name:
Offset:
Reset:
Property:
OUT
0x01
0x00
-
Writing to the Virtual PORT registers has the same effect as writing to the regular registers, but allows for memoryspecific instructions, such as bit-manipulation instructions, which are not valid for the extended I/O memory space
where the regular PORT registers reside.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
OUT[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – OUT[7:0] Output Value
This bit field selects the data output value for the individual pins in the Port.
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16.7.3
Input Value
Name:
Offset:
Reset:
Property:
IN
0x02
0x00
-
Writing to the Virtual PORT registers has the same effect as writing to the regular registers, but allows for memoryspecific instructions, such as bit-manipulation instructions, which are not valid for the extended I/O memory space
where the regular PORT registers reside.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
IN[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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.
Writing to a bit of VPORTx.IN will toggle the corresponding bit in VPORTx.OUT.
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PORT - I/O Pin Configuration
16.7.4
Interrupt Flag
Name:
Offset:
Reset:
Property:
INTFLAGS
0x03
0x00
-
Writing to the Virtual PORT registers has the same effect as writing to the regular registers, but allows for memoryspecific instructions, such as bit-manipulation instructions, which are not valid for the extended I/O memory space
where the regular PORT registers reside.
Bit
7
6
5
4
3
2
1
0
R
0
R
0
R
0
R
0
INT[7:0]
Access
Reset
R
0
R
0
R
0
R
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 the ISC bits in PORTx.PINnCTRL.
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ATmega3208/3209
BOD - Brown-out Detector
17.
BOD - Brown-out Detector
17.1
Features
•
•
•
•
•
17.2
Brown-out Detection monitors the power supply to avoid operation below a programmable level
There are three modes:
– Enabled
– Sampled
– Disabled
Separate selection of mode for Active and Sleep modes
Voltage Level Monitor (VLM) with Interrupt
Programmable VLM Level Relative to the BOD Level
Overview
The Brown-out Detector (BOD) monitors the power supply and compares the voltage with two programmable brownout threshold levels. The brown-out threshold level defines when to generate a Reset. A Voltage Level Monitor (VLM)
monitors the power supply and 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 VLM threshold level is expressed as a percentage 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.
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ATmega3208/3209
BOD - Brown-out Detector
17.2.1
Block Diagram
Figure 17-1. BOD Block Diagram
VDD
BOD Level
and
Calibration
+
Bandgap
Brown-out
Detection
VLM Interrupt Level
Bandgap
17.3
Functional Description
17.3.1
Initialization
+
VLM Interrupt
Detection
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 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. When enabling VLM interrupt, the
interrupt flag will always be set if VLMCFG equals 0x2 and may be set if VLMCFG is configured to 0x0 or 0x1.
The VLM threshold is defined by writing the VLM Level bits (VLMLVL) in the Control A register (BOD.VLMCTRLA).
17.3.2
Interrupts
Table 17-1. Available Interrupt Vectors and Sources
Name Vector Description
VLM
Conditions
Voltage Level Monitor Supply voltage crossing the VLM threshold as configured by VLMCFG in
BOD.INTCTRL
The VLM interrupt will not be executed if the CPU is halted in debug mode.
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Preliminary Datasheet
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ATmega3208/3209
BOD - Brown-out Detector
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 (peripheral.INTCTRL) register.
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.
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
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). To write to these registers, a
certain key must first be written to the CPU.CCP register, followed by a write access to the protected bits within four
CPU instructions.
Attempting to write to a protected register without following the appropriate CCP unlock sequence leaves the
protected register unchanged.
The following registers are under CCP:
Table 17-2. Registers Under Configuration Change Protection
Register
Key
SLEEP in BOD.CTRLA
IOREG
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Preliminary Datasheet
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ATmega3208/3209
BOD - Brown-out Detector
17.4
Register Summary - BOD
Offset
Name
Bit Pos.
0x00
0x01
0x02
...
0x07
0x08
0x09
0x0A
0x0B
CTRLA
CTRLB
7:0
7:0
17.5
SAMPFREQ
ACTIVE[1:0]
SLEEP[1:0]
LVL[2:0]
Reserved
VLMCTRLA
INTCTRL
INTFLAGS
STATUS
7:0
7:0
7:0
7:0
VLMCFG[1:0]
VLMLVL[1:0]
VLMIE
VLMIF
VLMS
Register Description
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Preliminary Datasheet
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ATmega3208/3209
BOD - Brown-out Detector
17.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
Loaded from fuse
Configuration Change Protection
6
Access
Reset
5
4
SAMPFREQ
R
x
3
2
1
ACTIVE[1:0]
R
x
0
SLEEP[1:0]
R
x
R/W
x
R/W
x
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
Description
0x0
Sample frequency is 1 kHz
0x1
Sample frequency is 125 Hz
Bits 3:2 – ACTIVE[1:0] Active
These bits select 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.
Value
Description
0x0
Disabled
0x1
Enabled
0x2
Sampled
0x3
Enabled with wake-up halted until BOD is ready
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. The Reset
value is loaded from the SLEEP bits in FUSE.BODCFG.
These bits are under Configuration Change Protection (CCP).
Value
Description
0x0
Disabled
0x1
Enabled
0x2
Sampled
0x3
Reserved
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ATmega3208/3209
BOD - Brown-out Detector
17.5.2
Control B
Name:
Offset:
Reset:
Property:
CTRLB
0x01
Loaded from fuse
-
Bit
7
6
5
4
3
2
Access
Reset
R
0
R
0
R
0
R
0
R
0
R
x
1
LVL[2:0]
R
x
0
R
x
Bits 2:0 – LVL[2:0] BOD Level
These bits select the BOD threshold level.
The Reset value is loaded from the BOD Level bits (LVL) in the BOD Configuration Fuse (FUSE.BODCFG).
Value
Name
Description
0x0
BODLEVEL0
1.8V
0x2
BODLEVEL2
2.6V
0x7
BODLEVEL7
4.3V
Note:
• Refer to the BOD and POR Characteristics in Electrical Characteristics for further details.
• Values in the description are typical values.
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ATmega3208/3209
BOD - Brown-out Detector
17.5.3
VLM Control A
Name:
Offset:
Reset:
Property:
Bit
7
VLMCTRLA
0x08
0x00
-
6
5
4
3
2
Access
Reset
1
0
VLMLVL[1:0]
R/W
R/W
0
0
Bits 1:0 – VLMLVL[1:0] VLM Level
These bits select the VLM threshold relative to the BOD threshold (LVL in BOD.CTRLB).
Value
Description
0x0
VLM threshold 5% above BOD threshold
0x1
VLM threshold 15% above BOD threshold
0x2
VLM threshold 25% above BOD threshold
other
Reserved
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Preliminary Datasheet
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ATmega3208/3209
BOD - Brown-out Detector
17.5.4
Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x09
0x00
-
6
5
4
3
Access
Reset
2
1
VLMCFG[1:0]
R/W
R/W
0
0
0
VLMIE
R/W
0
Bits 2:1 – VLMCFG[1:0] VLM Configuration
These bits select which incidents will trigger a VLM interrupt.
Value
Description
0x0
Voltage crosses VLM threshold from above
0x1
Voltage crosses VLM threshold from below
0x2
Either direction is triggering an interrupt request
Other
Reserved
Bit 0 – VLMIE VLM Interrupt Enable
Writing a '1' to this bit enables the VLM interrupt.
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Preliminary Datasheet
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ATmega3208/3209
BOD - Brown-out Detector
17.5.5
VLM Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x0A
0x00
-
6
5
4
3
Access
Reset
2
1
0
VLMIF
R/W
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 is only updated when the BOD is enabled.
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BOD - Brown-out Detector
17.5.6
VLM Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x0B
0x00
-
6
5
4
3
Access
Reset
2
1
0
VLMS
R
0
Bit 0 – VLMS VLM Status
This bit is only valid when the BOD is enabled.
Value
Description
0
The voltage is above the VLM threshold level
1
The voltage is below the VLM threshold level
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ATmega3208/3209
VREF - Voltage Reference
18.
VREF - Voltage Reference
18.1
Features
•
•
18.2
Programmable Voltage Reference Sources:
– For ADC0 peripheral
– For AC0 peripheral
Each Reference Source Supports Different Voltages:
– 0.55V
– 1.1V
– 1.5V
– 2.5V
– 4.3V
– AVDD
Overview
The Voltage Reference buffer (VREF) provides control registers for selecting between multiple internal reference
levels. The internal references are generated from the internal bandgap.
When a peripheral that requires a voltage reference is enabled the corresponding voltage reference buffer and
bandgap is automatically enabled.
18.2.1
Block Diagram
Figure 18-1. VREF Block Diagram
Reference reque st
Reference enable
Reference se lect
Bandgap
Reference
Gen erator
Ban dgap
ena ble
18.3
18.3.1
0.55V
1.1V
1.5V
2.5V
4.3V
BUF
Inte rnal
Reference
Functional Description
Initialization
The output level from the reference buffer should be selected (ADC0REFSEL and AC0REFSEL in VREF.CTRLA)
before the respective modules are enabled. The reference buffer is then automatically enabled when requested by a
peripheral. Changing the reference while these modules are enabled could lead to unpredictable behavior.
The VREF module and reference voltage sources can be forced to be ON, independent of being required by a
peripheral, by writing to the respective Force Enable bits (ADC0REFEN, AC0REFEN) in the Control B
(VREF.CTRLB) register. This can be used to remove the reference start-up time, at the cost of increased power
consumption.
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Preliminary Datasheet
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ATmega3208/3209
VREF - Voltage Reference
18.4
Register Summary - VREF
Offset
Name
Bit Pos.
0x00
0x01
CTRLA
CTRLB
7:0
7:0
18.5
ADC0REFSEL[2:0]
AC0REFSEL[2:0]
ADC0REFEN AC0REFEN
Register Description
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Preliminary Datasheet
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ATmega3208/3209
VREF - Voltage Reference
18.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CTRLA
0x00
0x00
-
6
R/W
0
5
ADC0REFSEL[2:0]
R/W
0
4
3
R/W
0
2
R/W
0
1
AC0REFSEL[2:0]
R/W
0
0
R/W
0
Bits 6:4 – ADC0REFSEL[2:0] ADC0 Reference Select
These bits select the reference voltage for ADC0.
Value
Name
Description
0x0
0V55
0.55V internal reference
0x1
1V1
1.1V internal reference
0x2
2V5
2.5V internal reference
0x3
4V3
4.3V internal reference
0x4
1V5
1.5V internal reference
Other
Reserved
Note: Refer to VREF in the Electrical Characteristics section for further details.
Bits 2:0 – AC0REFSEL[2:0] AC0 Reference Select
These bits select the reference voltage for AC0.
Value
Name
Description
0x0
0V55
0.55V internal reference
0x1
1V1
1.1V internal reference
0x2
2V5
2.5V internal reference
0x3
4V3
4.3V internal reference
0x4
1V5
1.5V internal reference
0x5
Reserved
0x6
Reserved
0x7
AVDD
AVDD
Note: Refer to VREF in the Electrical Characteristics section for further details.
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Preliminary Datasheet
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ATmega3208/3209
VREF - Voltage Reference
18.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
7
CTRLB
0x01
0x00
-
6
5
4
3
Access
Reset
2
1
ADC0REFEN
R/W
0
0
AC0REFEN
R/W
0
Bit 1 – ADC0REFEN ADC0 Reference Force Enable
Writing a ‘1’ to this bit forces the voltage reference for ADC0 to be enabled, even if it is not requested.
Writing a ‘0’ to this bit allows to automatic enable/disable the reference source when not requested.
Bit 0 – AC0REFEN AC0 DACREF Reference Force Enable
Writing a ‘1’ to this bit forces the voltage reference for AC0 DACREF to be enabled, even if it is not requested.
Writing a ‘0’ to this bit allows to automatic enable/disable the reference source when not requested.
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ATmega3208/3209
WDT - Watchdog Timer
19.
WDT - Watchdog Timer
19.1
Features
•
•
•
•
•
•
•
19.2
Issues a System Reset if the Watchdog Timer is not Cleared Before its Time-out Period
Operating Asynchronously from System Clock Using an Independent Oscillator
Using the 1 KHz Output of the 32 KHz Ultra Low-Power Oscillator (OSCULP32K)
11 Selectable Time-out Periods, from 8 ms 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 the system 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 time-out period. If the WDT is not reset within the time-out 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 defines a time slot or "window" inside the time-out 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 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 CCP mechanism ensures that the WDT settings cannot be changed by accident. For increased safety, a
configuration for locking the WDT settings is available.
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ATmega3208/3209
WDT - Watchdog Timer
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.
19.3
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.
19.3.2
Clocks
A 1 KHz 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 the
WDT Control register will require synchronization between the clock domains.
19.3.3
Operation
19.3.3.1 Normal Mode
In Normal mode operation, a single time-out period is set for the WDT. If the WDT is not reset from software using the
WDR any time before the time-out occurs, the WDT will issue a system Reset.
A new WDT time-out period will be started each time the WDT is reset by WDR.
There are 11 possible WDT time-out periods (TOWDT), selectable from 8 ms to 8s by writing to the Period bit field
(PERIOD) in the Control A register (WDT.CTRLA).
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ATmega3208/3209
WDT - Watchdog Timer
Figure 19-2. Normal Mode Operation
WDT Count
Timely WDT Reset (WDR)
WDT Timeout
System Reset
Here:
TO WDT = 16 ms
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.
19.3.3.2 Window Mode
In Window mode operation, the WDT uses two different time-out periods; a closed Window Time-out period
(TOWDTW) and the normal time-out period (TOWDT):
• The closed window time-out period defines a duration from 8 ms 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 time-out period, which is also 8 ms 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 time-out period is the sum of the closed window and the open window time-out periods.
When enabling Window mode or when going out of Debug mode, the first closed period is activated after the first WDR
instruction.
If a second WDR is issued while a previous WDR is being synchronized, the second one will be ignored.
Figure 19-3. Window Mode Operation
WDT Count
Open
Timely WDT Reset (WDR)
Closed
WDR too early:
System Reset
Here:
TOWDTW =TOWDT = 8 ms
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.
19.3.3.3 Configuration Protection and Lock
The WDT provides two security mechanisms to avoid unintentional changes to the WDT settings:
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.
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WDT - Watchdog Timer
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.
19.3.4
Sleep Mode Operation
The WDT will continue to operate in any sleep mode where the source clock is active.
19.3.5
Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in Debugging mode will
halt the 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 is operating in Window mode, the first closed window time-out period will
be disabled, and a Normal mode time-out period is executed.
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 two to three 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). To write to these registers, a
certain key must first be written to the CPU.CCP register, followed by a write access to the protected bits within four
CPU instructions.
Attempting to write to a protected register without following the appropriate CCP unlock sequence leaves the
protected register unchanged.
The following registers are under CCP:
Table 19-1. 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)
Window Period bits in Control A register (CTRLA.WINDOW)
LOCK bit in STATUS register (STATUS.LOCK)
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ATmega3208/3209
WDT - Watchdog Timer
19.4
Register Summary - WDT
Offset
Name
Bit Pos.
0x00
0x01
CTRLA
STATUS
7:0
7:0
19.5
WINDOW[3:0]
LOCK
PERIOD[3:0]
SYNCBUSY
Register Description
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WDT - Watchdog Timer
19.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
R/W
x
CTRLA
0x00
From FUSE.WDTCFG
Configuration Change Protection
6
5
WINDOW[3:0]
R/W
R/W
x
x
4
3
R/W
x
R/W
x
2
1
PERIOD[3:0]
R/W
R/W
x
x
0
R/W
x
Bits 7:4 – WINDOW[3:0] Window
Writing a non-zero value to these bits enables the Window mode, and selects the duration of the closed period
accordingly.
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
1.024s
2.048s
4.096s
8.192s
Reserved
Bits 3:0 – PERIOD[3:0] Period
Writing a non-zero value to this bit enables the WDT, and selects the time-out period in Normal mode accordingly. In
Window mode, these bits select the duration of the open window.
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
Name
OFF
8CLK
16CLK
32CLK
64CLK
128CLK
256CLK
512CLK
1KCLK
2KCLK
4KCLK
8KCLK
-
© 2020 Microchip Technology Inc.
Description
0.008s
0.016s
0.032s
0.064s
0.128s
0.256s
0.512s
1.0s
2.0s
4.1s
8.2s
Reserved
Preliminary Datasheet
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ATmega3208/3209
WDT - Watchdog Timer
19.5.2
Status
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
LOCK
R/W
0
STATUS
0x01
0x00
Configuration Change Protection
6
5
4
3
2
1
0
SYNCBUSY
R
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 be cleared in Debug mode only.
If the PERIOD bits in WDT.CTRLA are different from zero after boot code, the lock will automatically be set.
This bit is under 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 the system after the synchronization is finished.
This bit is not under CCP.
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
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 in the figure
below.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
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
20.2.1
Waveform
Generation
CLK_PER
Event
System
PORTS
Timer Period
Prescaler
Block Diagram
The figure below shows a detailed block diagram of the timer/counter.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
Figure 20-2. Timer/Counter Block Diagram
Base Counter
Clock Select
CTRLA
PERBUF
Mode
CTRLB
PER
EVCTRL
Event
Action
‘‘count’’
‘‘clear’’
‘‘load’’
‘‘direction’’
Counter
CNT
=
=0
OVF
(INT Req. and Event)
Control Logic
Event
TOP
UPDATE
BV
BOTTOM
Compare Unit n
BV
CMPnBUF
Control Logic
CMPn
=
Waveform
Generation
‘‘match’’
WOn Out
CMPn
(INT Req. and Event)
The Counter register (TCAn.CNT), Period and Compare registers (TCAn.PER and TCAn.CMPm) and their
corresponding buffer registers (TCAn.PERBUF and TCAn.CMPBUFm) 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 TCAn.CMPm 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 as shown in the
figure below.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
Figure 20-3. Timer/Counter Clock Logic
CLK_PER
Prescaler
Event System
Event
CLKSEL
EVACT
(Encoding)
CLK_TCA
CNT
CNTxEI
20.2.2
Signal Description
Signal
Description
Type
WOn
Digital output
Waveform output
20.3
Functional Description
20.3.1
Definitions
The following definitions are used throughout the documentation:
Table 20-1. Timer/Counter Definitions
Name
Description
BOTTOM The counter reaches BOTTOM when it becomes 0x0000.
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.
The update condition is met when the timer/counter reaches BOTTOM or TOP, depending on the
UPDATE Waveform Generator mode. Buffered registers with valid buffer values will be updated unless the Lock
Update bit (LUPD) in TCAn.CTRLE has been set.
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. The latter can be the case when counting events.
20.3.2
Initialization
To start using the timer/counter in a basic mode, follow these steps:
1. Write a TOP value to the Period register (TCAn.PER).
2. Enable the peripheral by writing a ‘1’ to the ENABLE bit in the Control A register (TCAn.CTRLA).
The counter will start counting clock ticks according to the prescaler setting in the Clock Select bit field
(CLKSEL) in TCAn.CTRLA.
3. Optional: By writing a ‘1’ to the Enable Count on Event Input bit (CNTEI) in the Event Control register
(TCAn.EVCTRL), events are counted instead of clock ticks.
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
4.
20.3.3
The counter value can be read from the Counter bit field (CNT) in the Counter register (TCAn.CNT).
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 (TCAn.CTRLE), until it reaches TOP or BOTTOM. The clock ticks are given by the peripheral clock
(CLK_PER), prescaled according to the Clock Select bit field (CLKSEL) in the Control A register (TCAn.CTRLA).
When TOP is reached while the counter is counting up, the counter will wrap to ‘0’ at the next clock tick. When
counting down, the counter is reloaded with the Period register value (TCAn.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 (TCAn.CNT) when the counter is running. The write
access to TCAn.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 TCAn.CTRLE.
20.3.3.2 Double Buffering
The Period register value (TCAn.PER) and the Compare n register values (TCAn.CMPn) are all double-buffered
(TCAn.PERBUF and TCAn.CMPnBUF).
Each buffer register has a Buffer Valid flag (PERBV, CMPnBV) in the Control F register (TCAn.CTRLF), which
indicates that the buffer register contains a valid (new) value that can be copied into the corresponding Period or
Compare register. When the Period register and Compare n registers are used for a compare operation, the BV flag
is set when data are written to the buffer register and cleared on an UPDATE condition. This is shown for a Compare
register (CMPn) in the figure below.
Figure 20-5. Period and Compare Double Buffering
‘‘write enable’’
BV
UPDATE
EN
EN
‘‘data write’’
CMPnBUF
CMPn
CNT
=
‘‘match’’
Both the TCAn.CMPn and TCAn.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 (TCAn.PER).
No Buffering: If double-buffering is not used, any period update is immediate.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
Figure 20-6. Changing the Period Without Buffering
Counter wraparound
MAX
‘‘update’’
‘‘write’’
CNT
BOTTOM
New TOP written to
New TOP written to
PER that is higher
PER that is lower
than current CNT.
than current CNT.
A counter wraparound can occur in any mode of operation when counting up without buffering, as the TCAn.CNT and
TCAn.PER registers are continuously compared. If a new TOP value is written to TCAn.PER that is lower than the
current TCAn.CNT, the counter will wrap first, before a compare match occurs.
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.
New TOP written to
PER that is lower
than current CNT.
With Buffering: When double-buffering is used, the buffer can be written at any time and still maintain correct
operation. The TCAn.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.
Note: Buffering is used in figures illustrating TCA operation if not otherwise specified.
20.3.3.4 Compare Channel
Each Compare Channel n continuously compares the counter value (TCAn.CNT) with the Compare n register
(TCAn.CMPn). If TCAn.CNT equals TCAn.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 (TCAn.CMPnBUF) provides double-buffer capability equivalent to that for the period
buffer. The double-buffering synchronizes the update of the TCAn.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.
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Preliminary Datasheet
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TCA - 16-bit Timer/Counter Type A
20.3.3.4.1 Waveform Generation
The compare channels can be used for waveform generation on the corresponding port pins. The following
requirements must be met to make the waveform visible on the connected port pin:
1.
2.
A Waveform Generation mode must be selected by writing the WGMODE bit field in TCAn.CTRLB.
The TCA is counting clock ticks, not events (CNTEI = 0 in TCAn.EVCTRL).
3.
4.
The compare channels used must be enabled (CMPnEN = 1 in TCAn.CTRLB). This will override the output
value for the corresponding pin. An alternative pin can be selected by configuring the Port Multiplexer
(PORTMUX). Refer to the PORTMUX chapter for details.
The direction for the associated port pin n must be configured as an output (PORTx.DIR[n] = 1).
5.
Optional: Enable the inverted waveform output for the associated port pin n (INVEN = 1 in PORTx.PINnCTRL).
20.3.3.4.2 Frequency (FRQ) Waveform Generation
For frequency generation, the period time (T) is controlled by the TCAn.CMP0 register instead of the Period register
(TCAn.PER). The corresponding waveform generator output is toggled on each compare match between the
TCAn.CNT and TCAn.CMPm registers.
Figure 20-9. Frequency Waveform Generation
Period (T)
Direction change
CNT written
MAX
‘‘update’’
TOP
CNT
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 TCAn.CTRLA), and fCLK_PER is the peripheral clock
frequency.
The maximum frequency of the waveform generated is half of the peripheral clock frequency (fCLK_PER/2) when
TCAn.CMP0 is written to 0x0000 and no prescaling is used (N = 1, CLKSEL = 0x0 in TCAn.CTRLA).
20.3.3.4.3 Single-Slope PWM Generation
For single-slope Pulse-Width Modulation (PWM) generation the period (T) is controlled by TCAn.PER, while the
values of the TCAn.CMPm registers control the duty cycles of the generated waveforms. The figure below shows
how the counter counts from BOTTOM to TOP and then restarts from BOTTOM. The waveform generator output is
set at BOTTOM and cleared on the compare match between the TCAn.CNT and TCAn.CMPm registers.
CMPn = BOTTOM will produce a static low signal on WOn while CMPn > TOP will produce a static high signal on
WOn.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
Figure 20-10. Single-Slope Pulse-Width Modulation
Period (T)
CMPn=BOTTOM
CMPn>TOP
MAX
TOP
‘‘update’’
‘‘match’’
CNT
CMPn
BOTTOM
Output WOn
The TCAn.PER register defines the PWM resolution. The minimum resolution is 2 bits (TCA.PER = 0x0002), and the
maximum resolution is 16 bits (TCA.PER = MAX-1).
The following equation calculates the exact resolution in bits for single-slope PWM (RPWM_SS):
�PWM_SS =
log PER+2
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 and the TCA prescaler (CLKSEL in TCAn.CTRLA). It is calculated by the following equation
where N represents the prescaler divider used:
20.3.3.4.4 Dual-Slope PWM
For dual-slope PWM generation, the period (T) is controlled by TCAn.PER, while the values of TCAn.CMPm 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 upcounting and set on compare match when down-counting.
CMPn = BOTTOM will produce a static low signal on WOn, while CMPn = TOP will produce a static high signal on
WOn.
Figure 20-11. Dual-Slope Pulse-Width Modulation
Period (T)
CMPn=BOTTOM
CMPn=TOP
‘‘update’’
‘‘match’’
MAX
CMPn
CNT
TOP
BOTTOM
Waveform Output WOn
Using dual-slope PWM results in half the maximum operation frequency compared to single-slope PWM operation,
due to twice the number of timer increments per period.
The period register (TCAn.PER) defines the PWM resolution. The minimum resolution is 2 bits (TCAn.PER =
0x0003), and the maximum resolution is 16 bits (TCAn.PER = MAX).
The following equation calculates the exact resolution in bits for dual-slope PWM (RPWM_DS):
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
�PWM_DS =
log PER+1
log 2
�PWM_DS =
�CLK_PER
2� ⋅ PER
The PWM frequency depends on the period setting (TCAn.PER), the peripheral clock frequency (fCLK_PER) and the
prescaler divider used (CLKSEL in TCAn.CTRLA). It is calculated by the following equation:
N represents the prescaler divider used.
20.3.3.4.5 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 (PORTx.DIR[n] = 1). The TCA will override the port pin values when the compare channel is enabled
(CMPnEN = 1 in TCAn.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
INVEN
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 (TCAn.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 (TCAn.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 ‘0’.
A RESET command will set all timer/counter registers to their initial values. A RESET command can be issued only
when the timer/counter is not running (ENABLE = 0 in TCAn.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. Event controlled operation is not supported in Split mode.
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 20.6 Register Summary - TCAn in Split Mode).
Split Mode Differences Compared to Normal Mode
• Count:
– Down-count only
– Low Byte Timer Counter Register (TCAn.LCNT) and High Byte Timer Counter Register (TCAn.HCNT) are
independent
• Waveform Generation:
– Single-slope PWM only (WGMODE = SINGLESLOPE in TCAn.CTRLB)
• Interrupt:
– No change for Low Byte Timer Counter Register (TCAn.LCNT)
– Underflow interrupt for High Byte Timer Counter Register (TCAn.HCNT)
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TCA - 16-bit Timer/Counter Type A
•
•
•
– No compare interrupt or flag for High Byte Compare Register n (TCAn.HCMPn)
Event Actions: Not Compatible
Buffer Registers and Buffer Valid Flags: Unused
Register Access: Byte Access to All Registers
Block Diagram
Figure 20-13. Timer/Counter Block Diagram Split Mode
Base Counter
HPER
LPER
Clock Select
CTRLA
‘‘count high’’
‘‘load high’’
Counter
HCNT
‘‘count low’’
‘‘load low’’
LCNT
HUNF
Control Logic
(INT Req. and Event)
LUNF
(INT Req. and Event)
=0
BOTTOML
BOTTOMH
=0
Compare Unit n
LCMPn
=
Waveform
Generation
WOn Out
LCMPn
‘‘match’’
(INT Req. and Event)
Compare Unit n
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 changes, but their
values do not. For this reason, disabling the peripheral (ENABLE = 0 in TCAn.CTRLA) and doing a hard Reset (CMD
= RESET in TCAn.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:
1. Enable Split mode by writing a ‘1’ to the Split mode enable bit in the Control D register (SPLITM in
TCAn.CTRLD).
2. Write a TOP value to the Period registers (TCAn.PER).
3. Enable the peripheral by writing a ‘1’ to the ENABLE bit in the Control A register (TCAn.CTRLA).
The counter will start counting clock ticks according to the prescaler setting in the Clock Select bit field
(CLKSEL) in TCAn.CTRLA.
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
4.
20.3.4
The counter values can be read from the Counter bit field in the Counter registers (TCAn.CNT).
Events
The TCA can generate the events described in the table below. All event generators except TCAn_HUNF are shared
between Normal mode and Split mode operation.
Table 20-2. Event Generators in TCA
Generator Name
Peripheral
Description
Event
OVF_LUNF
HUNF
CMP0
TCAn
CMP1
CMP2
Normal mode: Overflow
Split mode: Low byte timer underflow
Normal mode: Not available
Split mode: High byte timer underflow
Normal mode: Compare Channel 0
match
Split mode: Low byte timer Compare
Channel 0 match
Normal mode: Compare Channel 1
match
Split mode: Low byte timer Compare
Channel 1 match
Normal mode: Compare Channel 2
match
Split mode: Low byte timer Compare
Channel 2 match
Event
Type
Generating
Clock Domain
Pulse
CLK_PER
One CLK_PER
period
Pulse
CLK_PER
One CLK_PER
period
Pulse
CLK_PER
One CLK_PER
period
Pulse
CLK_PER
One CLK_PER
period
Pulse
CLK_PER
One CLK_PER
period
Length of Event
Note: The conditions for generating an event are identical to those that will raise the corresponding interrupt flag in
the TCAn.INTFLAGS register for both Normal mode and Split mode.
The TCA has one event user for detecting and acting upon input events. The table below describes the event user
and the associated functionality.
Table 20-3. Event User in TCA
User Name
TCAn
Description
Input Detection
Async/Sync
Count on positive event
edge
Edge
Sync
Count on any event edge
Edge
Sync
Count while event signal is
high
Level
Sync
Event level controls count
direction, up when low and
down when high
Level
Sync
The specific actions described in the table above are selected by writing to the Event Action bits (EVACT) in the
Event Control register (TCAn.EVCTRL). Input events are enabled by writing a ‘1’ to the Enable Count on Event Input
bit (CNTEI in TCAn.EVCTRL).
Event inputs are not used in Split mode.
Refer to the Event System (EVSYS) chapter for more details regarding event types and Event System configuration.
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TCA - 16-bit Timer/Counter Type A
20.3.5
Interrupts
Table 20-4. Available Interrupt Vectors and Sources in Normal Mode
Name
OVF
Vector Description
Overflow or underflow interrupt
Conditions
The counter has reached TOP or BOTTOM.
CMP0 Compare Channel 0 interrupt
Match between the counter value and the Compare 0 register.
CMP1 Compare Channel 1 interrupt
Match between the counter value and the Compare 1 register.
CMP2 Compare Channel 2 interrupt
Match between the counter value and the Compare 2 register.
Table 20-5. Available Interrupt Vectors and Sources in Split Mode
Name
Vector Description
Conditions
LUNF
Low-byte Underflow interrupt Low byte timer reaches BOTTOM.
HUNF
High-byte Underflow interrupt High byte timer reaches BOTTOM.
LCMP0 Compare Channel 0 interrupt
Match between the counter value and the low byte of the Compare 0
register.
LCMP1 Compare Channel 1 interrupt
Match between the counter value and the low byte of the Compare 1
register.
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 (peripheral.INTCTRL) register.
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.
20.3.6
Sleep Mode Operation
The timer/counter will continue operation in Idle Sleep mode.
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TCA - 16-bit Timer/Counter Type A
20.4
Register Summary - TCAn in Normal Mode
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x0C
...
0x0D
0x0E
0x0F
0x10
...
0x1F
CTRLA
CTRLB
CTRLC
CTRLD
CTRLECLR
CTRLESET
CTRLFCLR
CTRLFSET
Reserved
EVCTRL
INTCTRL
INTFLAGS
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
0x20
CNT
0x22
...
0x25
Reserved
0x26
PER
0x28
CMP0
0x2A
CMP1
0x2C
CMP2
0x2E
...
0x35
Reserved
0x36
PERBUF
0x37
PERBUFH
0x38
CMP0nBUF
0x3A
CMP1nBUF
0x3C
CMP2nBUF
20.5
7:0
7:0
7:0
CLKSEL[2:0]
CMP2EN
CMP1EN
CMP0EN
ALUPD
CMP2OV
CMD[1:0]
CMD[1:0]
CMP2BV
CMP1BV
CMP2BV
CMP1BV
EVACT[2:0]
CMP2
CMP2
CMP1
CMP1
CMP0
CMP0
ENABLE
WGMODE[2:0]
CMP1OV
LUPD
LUPD
CMP0BV
CMP0BV
CMP0OV
SPLITM
DIR
DIR
PERBV
PERBV
CNTEI
OVF
OVF
Reserved
DBGCTRL
TEMP
7:0
7:0
TEMP[7:0]
DBGRUN
7:0
15:8
CNT[7:0]
CNT[15:8]
7:0
15:8
7:0
15:8
7:0
15:8
7:0
15:8
PER[7:0]
PER[15:8]
CMP[7:0]
CMP[15:8]
CMP[7:0]
CMP[15:8]
CMP[7:0]
CMP[15:8]
Reserved
7:0
PERBUF[7:0]
15:8
7:0
7:0
15:8
7:0
15:8
7:0
15:8
PERBUF[15:8]
PERBUF[15:8]
CMPBUF[7:0]
CMPBUF[15:8]
CMPBUF[7:0]
CMPBUF[15:8]
CMPBUF[7:0]
CMPBUF[15:8]
Register Description - Normal Mode
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
-
6
5
Access
Reset
4
3
R/W
0
2
CLKSEL[2:0]
R/W
0
1
R/W
0
0
ENABLE
R/W
0
Bits 3:1 – CLKSEL[2:0] Clock Select
These bits select the clock frequency for the timer/counter.
Value
Name
Description
0x0
DIV1
fTCA = fCLK_PER
0x1
DIV2
fTCA = fCLK_PER/2
0x2
DIV4
fTCA = fCLK_PER/4
0x3
DIV8
fTCA = fCLK_PER/8
0x4
DIV16
fTCA = fCLK_PER/16
0x5
DIV64
fTCA = fCLK_PER/64
0x6
DIV256
fTCA = fCLK_PER/256
0x7
DIV1024
fTCA = fCLK_PER/1024
Bit 0 – ENABLE Enable
Value
Description
0
The peripheral is disabled
1
The peripheral is enabled
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.2
Control B - Normal Mode
Name:
Offset:
Reset:
Property:
Bit
7
Access
Reset
CTRLB
0x01
0x00
-
6
CMP2EN
R/W
0
5
CMP1EN
R/W
0
4
CMP0EN
R/W
0
3
ALUPD
R/W
0
2
R/W
0
1
WGMODE[2:0]
R/W
0
0
R/W
0
Bits 4, 5, 6 – CMPEN Compare n Enable
In the FRQ and PWM Waveform Generation modes the Compare n Enable bits (CMPnEN) will make the waveform
output available on the pin corresponding to WOn, overriding the value in the corresponding PORT output register.
The corresponding pin direction must be configured as an output in the PORT peripheral.
Value
Description
0
Waveform output WOn will not be available on the corresponding pin
1
Waveform output WOn will override the output value of the corresponding pin
Bit 3 – ALUPD Auto-Lock Update
The Auto-Lock Update bit controls the Lock Update (LUPD) bit in the TCAn.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 the CMPnBUF register values are not transferred to
the CMPn registers until all enabled compare buffers are written.
Value
Description
0
LUPD in TCA.CTRLE is not altered by the system
1
LUPD in TCA.CTRLE is 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 the type of waveform generated.
No waveform generation is performed in the Normal mode of operation. For all other modes, the waveform generator
output will only be directed to the port pins if the corresponding CMPnEN bit has been set. The port pin direction must
be set as output.
Table 20-6. Timer Waveform Generation Mode
Value
Group Configuration
Mode of Operation
TOP
UPDATE
OVF
0x0
NORMAL
Normal
PER
TOP(1)
TOP(1)
0x1
FRQ
Frequency
CMP0
TOP(1)
TOP(1)
0x2
-
Reserved
-
-
-
0x3
SINGLESLOPE
Single-slope PWM
PER
BOTTOM
BOTTOM
0x4
-
Reserved
-
-
-
0x5
DSTOP
Dual-slope PWM
PER
BOTTOM
TOP
0x6
DSBOTH
Dual-slope PWM
PER
BOTTOM
TOP and BOTTOM
0x7
DSBOTTOM
Dual-slope PWM
PER
BOTTOM
BOTTOM
Note:
1. When counting up.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.3
Control C - Normal Mode
Name:
Offset:
Reset:
Property:
Bit
7
CTRLC
0x02
0x00
-
6
5
4
3
Access
Reset
2
CMP2OV
R/W
0
1
CMP1OV
R/W
0
0
CMP0OV
R/W
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.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.4
Control D
Name:
Offset:
Reset:
Property:
Bit
7
CTRLD
0x03
0x00
-
6
5
4
3
Access
Reset
2
1
0
SPLITM
R/W
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.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.5
Control Register E Clear - Normal Mode
Name:
Offset:
Reset:
Property:
CTRLECLR
0x04
0x00
-
This register can be used instead of a Read-Modify-Write (RMW) to clear individual bits by writing a ‘1’ to its bit
location.
Bit
7
6
5
4
3
2
CMD[1:0]
Access
Reset
R/W
0
R/W
0
1
LUPD
R/W
0
0
DIR
R/W
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 ‘0’.
Value
Name
Description
0x0
NONE
No command
0x1
UPDATE
Force update
0x2
RESTART
Force restart
0x3
RESET
Force hard Reset (ignored if the timer/counter 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
Description
0
The buffered registers are updated as soon as an UPDATE condition has occurred
1
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 it can also be
changed from software.
Value
Description
0
The counter is counting up (incrementing)
1
The counter is counting down (decrementing)
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.6
Control Register E Set - Normal Mode
Name:
Offset:
Reset:
Property:
CTRLESET
0x05
0x00
-
This register can be used instead of a Read-Modify-Write (RMW) to set individual bits by writing a ‘1’ to its bit
location.
Bit
7
6
5
4
3
2
CMD[1:0]
Access
Reset
R/W
0
R/W
0
1
LUPD
R/W
0
0
DIR
R/W
0
Bits 3:2 – CMD[1:0] Command
These bits are used for software control of update, restart and Reset the timer/counter. The command bits are always
read as ‘0’.
Value
Name
Description
0x0
NONE
No command
0x1
UPDATE
Force update
0x2
RESTART
Force restart
0x3
RESET
Force hard Reset (ignored if the timer/counter is enabled)
Bit 1 – LUPD Lock Update
Locking the update ensures that all buffers are valid before an update is performed.
Value
Description
0
The buffered registers are updated as soon as an UPDATE condition has occurred
1
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 it can also be
changed from software.
Value
Description
0
The counter is counting up (incrementing)
1
The counter is counting down (decrementing)
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.7
Control Register F Clear
Name:
Offset:
Reset:
Property:
CTRLFCLR
0x06
0x00
-
This register can be used instead of a Read-Modify-Write (RMW) to clear individual bits by writing a ‘1’ to its bit
location.
Bit
7
6
5
Access
Reset
4
3
CMP2BV
R/W
0
2
CMP1BV
R/W
0
1
CMP0BV
R/W
0
0
PERBV
R/W
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 TCAn.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 TCAn.PERBUF register. This bit is automatically cleared on an
UPDATE condition.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.8
Control Register F Set
Name:
Offset:
Reset:
Property:
CTRLFSET
0x07
0x00
-
This register can be used instead of a Read-Modify-Write (RMW) to set individual bits by writing a ‘1’ to its bit
location.
Bit
7
6
5
Access
Reset
4
3
CMP2BV
R/W
0
2
CMP1BV
R/W
0
1
CMP0BV
R/W
0
0
PERBV
R/W
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 TCAn.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 TCAn.PERBUF register. This bit is automatically cleared on an
UPDATE condition.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.9
Event Control
Name:
Offset:
Reset:
Property:
Bit
7
EVCTRL
0x09
0x00
-
6
Access
Reset
5
4
3
R/W
0
2
EVACT[2:0]
R/W
0
1
R/W
0
0
CNTEI
R/W
0
Bits 3:1 – EVACT[2:0] Event Action
These bits define what action the counter will take upon certain event conditions.
Value
Name
Description
0x0
EVACT_POSEDGE Count on positive event edge
0x1
EVACT_ANYEDGE Count on any event edge
0x2
EVACT_HIGHLVL Count prescaled clock cycles while the event signal is high
0x3
EVACT_UPDOWN Count prescaled clock cycles. The event signal controls the count direction, up
when low and down when high.
Other
Reserved
Bit 0 – CNTEI Enable Count on Event Input
Value
Description
0
Count on Event input is disabled
1
Count on Event input is enabled according to EVACT bit field
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.10 Interrupt Control Register - Normal Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
INTCTRL
0x0A
0x00
-
6
CMP2
R/W
0
5
CMP1
R/W
0
4
CMP0
R/W
0
3
2
1
0
OVF
R/W
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 the CMPn bit to ‘1’ enables the interrupt from Compare Channel n.
Bit 0 – OVF Timer Overflow/Underflow Interrupt Enable
Writing the OVF bit to ‘1’ enables the overflow/underflow interrupt.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.11 Interrupt Flag Register - Normal Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
INTFLAGS
0x0B
0x00
-
6
CMP2
R/W
0
5
CMP1
R/W
0
4
CMP0
R/W
0
3
2
1
0
OVF
R/W
0
Bit 6 – CMP2 Compare Channel 2 Interrupt Flag
See the CMP0 flag description.
Bit 5 – CMP1 Compare Channel 1 Interrupt Flag
See the CMP0 flag description.
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 is not cleared automatically. It will be cleared
only by writing a ‘1’ 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.
The OVF flag is not cleared automatically. It will be cleared only by writing a ‘1’ to its bit location.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.12 Debug Control Register
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x0E
0x00
-
6
5
4
3
2
Access
Reset
1
0
DBGRUN
R/W
0
Bit 0 – DBGRUN Run in Debug
Value
Description
0
The peripheral is halted in Break Debug mode and ignores events
1
The peripheral will continue to run in Break Debug mode when the CPU is halted
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.13 Temporary Bits for 16-Bit Access
Name:
Offset:
Reset:
Property:
TEMP
0x0F
0x00
-
The Temporary register is used by the CPU for single-cycle, 16-bit access to the 16-bit registers of this peripheral. It
can be read and written by software. Refer to 16-bit access in the AVR CPU chapter. There is one common
Temporary register for all the 16-bit registers of this peripheral.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
TEMP[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – TEMP[7:0] Temporary Bits for 16-bit Access
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.14 Counter Register - Normal Mode
Name:
Offset:
Reset:
Property:
CNT
0x20
0x00
-
The TCAn.CNTL and TCAn.CNTH register pair represents the 16-bit value, TCAn.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.
CPU and UPDI write access has priority over internal updates of the register.
Bit
15
14
13
12
11
10
9
8
R/W
0
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
CNT[15:8]
Access
Reset
Bit
R/W
0
R/W
0
R/W
0
R/W
0
7
6
5
4
CNT[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
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.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.15 Period Register - Normal Mode
Name:
Offset:
Reset:
Property:
PER
0x26
0xFFFF
-
TCAn.PER contains the 16-bit TOP value in the timer/counter in all modes of operation, except Frequency Waveform
Generation (FRQ).
The TCAn.PERL and TCAn.PERH register pair represents the 16-bit value, TCAn.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.
Bit
15
14
13
12
11
10
9
8
R/W
1
R/W
1
R/W
1
R/W
1
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
PER[15:8]
Access
Reset
Bit
R/W
1
R/W
1
R/W
1
R/W
1
7
6
5
4
PER[7:0]
Access
Reset
R/W
1
R/W
1
R/W
1
R/W
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.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.16 Compare n Register - Normal Mode
Name:
Offset:
Reset:
Property:
CMPn
0x28 + n*0x02 [n=0..2]
0x00
-
This register is continuously compared to the counter value. Normally, the outputs from the comparators are used to
generate waveforms.
TCAn.CMPn registers are updated with the buffer value from their corresponding TCAn.CMPnBUF register when an
UPDATE condition occurs.
The TCAn.CMPnL and TCAn.CMPnH register pair represents the 16-bit value, TCAn.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.
Bit
15
14
13
12
11
10
9
8
R/W
0
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
CMP[15:8]
Access
Reset
Bit
R/W
0
R/W
0
R/W
0
R/W
0
7
6
5
4
CMP[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
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.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.17 Period Buffer Register
Name:
Offset:
Reset:
Property:
PERBUF
0x36
0xFFFF
-
This register serves as the buffer for the Period register (TCAn.PER). Writing to this register from the CPU or UPDI
will set the Period Buffer Valid bit (PERBV) in the TCAn.CTRLF register.
The TCAn.PERBUFL and TCAn.PERBUFH register pair represents the 16-bit value, TCAn.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.
Bit
Access
Reset
Bit
Access
Reset
15
14
13
R/W
1
R/W
1
R/W
1
7
6
5
R/W
1
R/W
1
R/W
1
12
11
PERBUF[15:8]
R/W
R/W
1
1
4
3
PERBUF[7:0]
R/W
R/W
1
1
10
9
8
R/W
1
R/W
1
R/W
1
2
1
0
R/W
1
R/W
1
R/W
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.
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Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.18 Period Buffer Register High
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
PERBUFH
0x37
0xFF
-
7
6
5
R/W
1
R/W
1
R/W
1
4
3
PERBUF[15:8]
R/W
R/W
1
1
2
1
0
R/W
1
R/W
1
R/W
1
Bits 7:0 – PERBUF[15:8] Period Buffer High Byte
These bits hold the MSB of the 16-bit Period Buffer register. Refer to TCAn.PERBUFL register description for details.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
TCA - 16-bit Timer/Counter Type A
20.5.19 Compare n Buffer Register
Name:
Offset:
Reset:
Property:
CMPnBUF
0x38 + n*0x02 [n=0..2]
0x00
-
This register serves as the buffer for the associated Compare register (TCAn.CMPn). Writing to this register from the
CPU or UPDI will set the Compare Buffer valid bit (CMPnBV) in the TCAn.CTRLF register.
The TCAn.CMPnBUFL and TCAn.CMPnBUFH register pair represents the 16-bit value, TCAn.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.
Bit
Access
Reset
Bit
Access
Reset
15
14
13
R/W
0
R/W
0
R/W
0
7
6
5
R/W
0
R/W
0
R/W
0
12
11
CMPBUF[15:8]
R/W
R/W
0
0
4
3
CMPBUF[7:0]
R/W
R/W
0
0
10
9
8
R/W
0
R/W
0
R/W
0
2
1
0
R/W
0
R/W
0
R/W
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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TCA - 16-bit Timer/Counter Type A
20.6
Register Summary - TCAn in Split Mode
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
0x05
0x06
...
0x09
0x0A
0x0B
0x0C
...
0x0D
0x0E
0x0F
...
0x1F
0x20
0x21
0x22
...
0x25
0x26
0x27
0x28
0x29
0x2A
0x2B
0x2C
0x2D
CTRLA
CTRLB
CTRLC
CTRLD
CTRLECLR
CTRLESET
7:0
7:0
7:0
7:0
7:0
7:0
20.7
HCMP2EN
HCMP2OV
HCMP1EN
HCMP1OV
HCMP0EN
HCMP0OV
CLKSEL[2:0]
LCMP2EN
LCMP2OV
CMD[1:0]
CMD[1:0]
ENABLE
LCMP0EN
LCMP0OV
SPLITM
CMDEN[1:0]
CMDEN[1:0]
LCMP1EN
LCMP1OV
Reserved
INTCTRL
INTFLAGS
7:0
7:0
LCMP2
LCMP2
LCMP1
LCMP1
LCMP0
LCMP0
HUNF
HUNF
LUNF
LUNF
Reserved
DBGCTRL
7:0
DBGRUN
Reserved
LCNT
HCNT
7:0
7:0
LCNT[7:0]
HCNT[7:0]
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
LPER[7:0]
HPER[7:0]
LCMP[7:0]
HCMP[7:0]
LCMP[7:0]
HCMP[7:0]
LCMP[7:0]
HCMP[7:0]
Reserved
LPER
HPER
LCMP0
HCMP0
LCMP1
HCMP1
LCMP2
HCMP2
Register Description - Split Mode
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TCA - 16-bit Timer/Counter Type A
20.7.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
-
6
5
Access
Reset
4
3
R/W
0
2
CLKSEL[2:0]
R/W
0
1
R/W
0
0
ENABLE
R/W
0
Bits 3:1 – CLKSEL[2:0] Clock Select
These bits select the clock frequency for the timer/counter.
Value
Name
Description
0x0
DIV1
fTCA = fCLK_PER
0x1
DIV2
fTCA = fCLK_PER/2
0x2
DIV4
fTCA = fCLK_PER/4
0x3
DIV8
fTCA = fCLK_PER/8
0x4
DIV16
fTCA = fCLK_PER/16
0x5
DIV64
fTCA = fCLK_PER/64
0x6
DIV256
fTCA = fCLK_PER/256
0x7
DIV1024
fTCA = fCLK_PER/1024
Bit 0 – ENABLE Enable
Value
Description
0
The peripheral is disabled
1
The peripheral is enabled
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TCA - 16-bit Timer/Counter Type A
20.7.2
Control B - Split Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CTRLB
0x01
0x00
-
6
HCMP2EN
R/W
0
5
HCMP1EN
R/W
0
4
HCMP0EN
R/W
0
3
2
LCMP2EN
R/W
0
1
LCMP1EN
R/W
0
0
LCMP0EN
R/W
0
Bit 6 – HCMP2EN High byte Compare 2 Enable
See HCMP0EN.
Bit 5 – HCMP1EN High byte Compare 1 Enable
See HCMP0EN.
Bit 4 – HCMP0EN High byte Compare 0 Enable
Setting the HCMPnEN bit in the FRQ or PWM Waveform Generation mode of operation will override the port output
register for the corresponding WO[n+3] pin.
Bit 2 – LCMP2EN Low byte Compare 2 Enable
See LCMP0EN.
Bit 1 – LCMP1EN Low byte Compare 1 Enable
See LCMP0EN.
Bit 0 – LCMP0EN Low byte Compare 0 Enable
Setting the LCMPnEN bit in the FRQ or PWM Waveform Generation mode of operation will override the port output
register for the corresponding WOn pin.
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TCA - 16-bit Timer/Counter Type A
20.7.3
Control C - Split Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CTRLC
0x02
0x00
-
6
HCMP2OV
R/W
0
5
HCMP1OV
R/W
0
4
HCMP0OV
R/W
0
3
2
LCMP2OV
R/W
0
1
LCMP1OV
R/W
0
0
LCMP0OV
R/W
0
Bit 6 – HCMP2OV High byte Compare 2 Output Value
See HCMP0OV.
Bit 5 – HCMP1OV High byte Compare 1 Output Value
See HCMP0OV.
Bit 4 – HCMP0OV High byte Compare 0 Output Value
The HCMPnOV bit allows direct access to the output compare value of the waveform generator when the timer/
counter is not enabled. This is used to set or clear the WO[n+3] output value when the timer/counter is not running.
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 bit allows direct access to the output compare value of the waveform generator 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.
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TCA - 16-bit Timer/Counter Type A
20.7.4
Control D
Name:
Offset:
Reset:
Property:
Bit
7
CTRLD
0x03
0x00
-
6
5
4
3
Access
Reset
2
1
0
SPLITM
R/W
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.
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TCA - 16-bit Timer/Counter Type A
20.7.5
Control Register E Clear - Split Mode
Name:
Offset:
Reset:
Property:
CTRLECLR
0x04
0x00
-
This register can be used instead of a Read-Modify-Write (RMW) to clear individual bits by writing a ‘1’ to its bit
location.
Bit
7
6
5
4
3
2
CMD[1:0]
Access
Reset
R/W
0
R/W
0
1
0
CMDEN[1:0]
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 ‘0’.
Value
Name
Description
0x0
NONE
No command
0x1
Reserved
0x2
RESTART
Force restart
0x3
RESET
Force hard Reset (ignored if the timer/counter is enabled)
Bits 1:0 – CMDEN[1:0] Command Enable
These bits configure what timer/counters the command given by the CMD-bits will be applied to.
Value
Name
Description
0x0
NONE None
0x1
Reserved
0x2
Reserved
0x3
BOTH
Command (CMD) will be applied to both low byte and high byte timer/counter
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TCA - 16-bit Timer/Counter Type A
20.7.6
Control Register E Set - Split Mode
Name:
Offset:
Reset:
Property:
CTRLESET
0x05
0x00
-
This register can be used instead of a Read-Modify-Write (RMW) to set individual bits by writing a ‘1’ to its bit
location.
Bit
7
6
5
4
3
2
CMD[1:0]
Access
Reset
R/W
0
R/W
0
1
0
CMDEN[1:0]
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 ‘0’. The CMD bits must be used together with the Command Enable (CMDEN) bits. Using the RESET
command requires that both low byte and high byte timer/counter are selected with CMDEN.
Value
Name
Description
0x0
NONE
No command
0x1
Reserved
0x2
RESTART
Force restart
0x3
RESET
Force hard Reset (ignored if the timer/counter is enabled)
Bits 1:0 – CMDEN[1:0] Command Enable
These bits configure what timer/counters the command given by the CMD-bits will be applied to.
Value
Name
Description
0x0
NONE None
0x1
Reserved
0x2
Reserved
0x3
BOTH
Command (CMD) will be applied to both low byte and high byte timer/counter
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TCA - 16-bit Timer/Counter Type A
20.7.7
Interrupt Control Register - Split Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
INTCTRL
0x0A
0x00
-
6
LCMP2
R/W
0
5
LCMP1
R/W
0
4
LCMP0
R/W
0
3
2
1
HUNF
R/W
0
0
LUNF
R/W
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 the LCMPn bit to ‘1’ enables the low byte Compare Channel n interrupt.
Bit 1 – HUNF High byte Underflow Interrupt Enable
Writing the HUNF bit to ‘1’ enables the high byte underflow interrupt.
Bit 0 – LUNF Low byte Underflow Interrupt Enable
Writing the LUNF bit to ‘1’ enables the low byte underflow interrupt.
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TCA - 16-bit Timer/Counter Type A
20.7.8
Interrupt Flag Register - Split Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
INTFLAGS
0x0B
0x00
-
6
LCMP2
R/W
0
5
LCMP1
R/W
0
4
LCMP0
R/W
0
3
2
1
HUNF
R/W
0
0
LUNF
R/W
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 Low byte Compare Interrupt flag (LCMPn) is set on a compare match on the corresponding compare channel in
the low byte timer.
For all modes of operation, the LCMPn flag will be set when a compare match occurs between the Low Byte Timer
Counter register (TCAn.LCNT) and the corresponding compare register (TCAn.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.
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TCA - 16-bit Timer/Counter Type A
20.7.9
Debug Control Register
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x0E
0x00
-
6
5
4
3
2
Access
Reset
1
0
DBGRUN
R/W
0
Bit 0 – DBGRUN Run in Debug
Value
Description
0
The peripheral is halted in Break Debug mode and ignores events
1
The peripheral will continue to run in Break Debug mode when the CPU is halted
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TCA - 16-bit Timer/Counter Type A
20.7.10 Low Byte Timer Counter Register - Split Mode
Name:
Offset:
Reset:
Property:
LCNT
0x20
0x00
-
TCAn.LCNT contains the counter value for the low byte timer. CPU and UPDI write access has priority over count,
clear or reload of the counter.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
LCNT[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – LCNT[7:0] Counter Value for Low Byte Timer
These bits define the counter value of the low byte timer.
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TCA - 16-bit Timer/Counter Type A
20.7.11 High Byte Timer Counter Register - Split Mode
Name:
Offset:
Reset:
Property:
HCNT
0x21
0x00
-
TCAn.HCNT contains the counter value for the high byte timer. CPU and UPDI write access has priority over count,
clear or reload of the counter.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
HCNT[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – HCNT[7:0] Counter Value for High Byte Timer
These bits define the counter value in high byte timer.
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TCA - 16-bit Timer/Counter Type A
20.7.12 Low Byte Timer Period Register - Split Mode
Name:
Offset:
Reset:
Property:
LPER
0x26
0x00
-
The TCAn.LPER register contains the TOP value for the low byte timer.
Bit
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
LPER[7:0]
Access
Reset
R/W
1
R/W
1
R/W
1
R/W
1
Bits 7:0 – LPER[7:0] Period Value Low Byte Timer
These bits hold the TOP value for the low byte timer.
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TCA - 16-bit Timer/Counter Type A
20.7.13 High Byte Period Register - Split Mode
Name:
Offset:
Reset:
Property:
HPER
0x27
0x00
-
The TCAn.HPER register contains the TOP value for the high byte timer.
Bit
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
HPER[7:0]
Access
Reset
R/W
1
R/W
1
R/W
1
R/W
1
Bits 7:0 – HPER[7:0] Period Value High Byte Timer
These bits hold the TOP value for the high byte timer.
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TCA - 16-bit Timer/Counter Type A
20.7.14 Compare Register n For Low Byte Timer - Split Mode
Name:
Offset:
Reset:
Property:
LCMP
0x28 + n*0x02 [n=0..2]
0x00
-
The TCAn.LCMPn register represents the compare value of Compare Channel n for the low byte timer. This register
is continuously compared to the counter value of the low byte timer, TCAn.LCNT. Normally, the outputs from the
comparators are then used to generate waveforms.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
LCMP[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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 TCAn.LCNT.
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TCA - 16-bit Timer/Counter Type A
20.7.15 High Byte Compare Register n - Split Mode
Name:
Offset:
Reset:
Property:
HCMP
0x29 + n*0x02 [n=0..2]
0x00
-
The TCAn.HCMPn register represents the compare value of Compare Channel n for the high byte timer. This register
is continuously compared to the counter value of the high byte timer, TCAn.HCNT. Normally, the outputs from the
comparators are then used to generate waveforms.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
HCMP[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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 TCAn.HCNT.
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TCB - 16-bit Timer/Counter Type B
21.
TCB - 16-bit Timer/Counter Type B
21.1
Features
•
•
•
21.2
16-bit Counter Operation Modes:
– Periodic interrupt
– Time-out 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
Synchronize Operation with TCAn
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 that 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.
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TCB - 16-bit Timer/Counter Type B
21.2.1
Block Diagram
Figure 21-1. Timer/Counter Type B Block
Clock Select
CTRLA
Mode
CTRLB
EVCTRL
Event Action
Count
Counter
Clear
CNT
Events
Control
Logic
CAPT
(Interrupt Request
and Events)
BOTTOM
=0
CCMP
=
Waveform
Generation
Match
WO
The timer/counter can be clocked from the Peripheral Clock (CLK_PER), or a 16-bit Timer/Counter type A
(CLK_TCAn).
Figure 21-2. Timer/Counter Clock Logic
CTRLA
CLK_PER
DIV2
CLK_TCB
CLK_TCAn
Control
Logic
Events
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TCB - 16-bit Timer/Counter Type B
The Clock Select (CLKSEL) bit field in the Control A (TCBn.CTRLA) register selects one of the prescaler outputs
directly as the clock (CLK_TCB) input.
Setting the timer/counter to use the clock from a TCAn allows the timer/counter to run in sync with that TCAn.
By using the EVSYS, any event source, such as an external clock signal on any I/O pin, may be used as a control
logic input. When an event action controlled operation is used, the clock selection must be set to use an event
channel as the counter input.
21.2.2
Signal Description
Signal
Description
Type
WO
Digital Asynchronous Output
Waveform Output
21.3
Functional Description
21.3.1
Definitions
The following definitions are used throughout the documentation:
Table 21-1. Timer/Counter Definitions
Name
Description
BOTTOM
The counter reaches BOTTOM when it becomes 0x0000
MAX
The counter reaches maximum when it becomes 0xFFFF
TOP
The counter reaches TOP when it becomes equal to the highest value in the count sequence
CNT
Counter register value
CCMP
Capture/Compare register value
Note: 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:
1. Write a TOP value to the Compare/Capture (TCBn.CCMP) register.
2. Enable the counter by writing a ‘1’ to the ENABLE bit in the Control A (TCBn.CTRLA) register.
The counter will start counting clock ticks according to the prescaler setting in the Clock Select (CLKSEL) bit
field in the Control A (TCBn.CTRLA) register.
3. The counter value can be read from the Count (TCBn.CNT) register. The peripheral will generate a CAPT
interrupt and event when the CNT value reaches TOP.
3.1.
If the Compare/Capture register is modified to a value lower than the current Count register, the
peripheral will count to MAX and wrap around.
21.3.3
Operation
21.3.3.1 Modes
The timer can be configured to run in one of the eight different modes described in the sections below. The event
pulse needs to be longer than one system clock cycle in order to ensure edge detection.
21.3.3.1.1 Periodic Interrupt Mode
In the Periodic Interrupt mode, the counter counts to the capture value and restarts from BOTTOM. A CAPT interrupt
and event is generated when the counter is equal to TOP. If TOP is updated to a value lower than count upon
reaching MAX the counter restarts from BOTTOM.
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TCB - 16-bit Timer/Counter Type B
Figure 21-3. Periodic Interrupt Mode
CAPT
(Interrupt Request
MAX
and Event)
TOP
CNT
BOTTOM
TOP changed to
a value lower than CNT
CNT set to BOTTOM
21.3.3.1.2 Time-Out Check Mode
In the Time-Out Check mode, the peripheral starts counting on the first signal edge and stops on the next signal edge
detected on the event input channel. Start or Stop edge is determined by the Event Edge (EDGE) bit in the Event
Control (TCBn.EVCTRL) register. If the Count (TCBn.CNT) register reaches TOP before the second edge, a CAPT
interrupt and event will be generated. In Freeze state, after a Stop edge is detected, the counter will restart on a new
Start edge. If TOP is updated to a value lower than the Count (TCBn.CNT) register upon reaching MAX the counter
restarts from BOTTOM. Reading the Count (TCBn.CNT) register or Compare/Capture (TCBn.CCMP) register, or
writing the Run (RUN) bit in the Status (TCBn.STATUS) register in Freeze state will have no effect.
Figure 21-4. Time-Out Check Mode
Event Input
CAPT
(Interrupt Request
and Event)
Event Detector
MAX
TOP
CNT
BOTTOM
TOP changed to a value lower
than CNT
CNT set to
BOTTOM
21.3.3.1.3 Input Capture on Event Mode
In the Input Capture on Event mode, the counter will count from BOTTOM to MAX continuously. When an event is
detected the Count (TCBn.CNT) register value is transferred to the Compare/Capture (TCBn.CCMP) register and a
CAPT interrupt and event is generated. The Event edge detector that can be configured to trigger a capture on either
rising or falling edges.
The figure below shows the input capture unit configured to capture on the falling edge of the event input signal. The
CAPT Interrupt flag is automatically cleared after the low byte of the Compare/Capture (TCBn.CCMP) register has
been read.
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TCB - 16-bit Timer/Counter Type B
Figure 21-5. Input Capture on Event
Event Input
CAPT
(Interrupt Request
and Event)
Event Detector
MAX
CNT
BOTTOM
Copy CNT to
CCMP and CAPT
CNT set to
BOTTOM
Copy CNT to
CCMP and CAPT
It is recommended to write zero to the TCBn.CNT register when entering this mode from any other mode.
21.3.3.1.4 Input Capture Frequency Measurement Mode
In the Input Capture Frequency Measurement mode, the TCB captures the counter value and restarts on either a
positive or negative edge of the event input signal.
The CAPT Interrupt flag is automatically cleared after the low byte of the Compare/Capture (TCBn.CCMP) register
has been read.
The figure below illustrates this mode when configured to act on rising edge.
Figure 21-6. Input Capture Frequency Measurement
CAPT
(Interrupt Request
Event Input
and Event)
Event Detector
MAX
CNT
BOTTOM
Copy CNT to CCMP,
CAPT and restart
CNT set to
BOTTOM
Copy CNT to CCMP,
CAPT and restart
21.3.3.1.5 Input Capture Pulse-Width Measurement Mode
In the 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 CAPT
Interrupt flag is automatically cleared after the low byte of the Compare/Capture (TCBn.CCMP) register has been
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.
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ATmega3208/3209
TCB - 16-bit Timer/Counter Type B
Figure 21-7. Input Capture Pulse-Width Measurement
CAPT
Event Input
(Interrupt Request
and Event)
Edge Detector
MAX
CNT
BOTTOM
Start counter
Copy CNT to
CCMP and CAPT
Restart
counter
Copy CNT to
CCMP and CAPT
CNT set to
BOTTOM
21.3.3.1.6 Input Capture Frequency and Pulse-Width Measurement Mode
In the Input Capture Frequency and Pulse-Width Measurement mode, the timer will start counting when a positive
edge is detected on the event input signal. The count value is captured on the following falling edge. The counter
stops when the second rising edge of the event input signal is detected. This will set the interrupt flag.
The CAPT Interrupt flag is automatically cleared after the low byte of the Compare/Capture (TCBn.CCMP) register
has been read, and the timer/counter is ready for a new capture sequence. Therefore, the Count (TCBn.CNT)
register must be read before the Compare/Capture (TCBn.CCMP) register, since it is reset to BOTTOM at the next
positive edge of the event input signal.
Figure 21-8. Input Capture Frequency and Pulse-Width Measurement
Ignored until CPU
reads CCMP register
Trigger next capture
sequence
CAPT
(Interrupt Request
Event Input
and Event)
Event Detector
MAX
CNT
BOTTOM
Start
counter
Copy CNT to
CCMP
Stop counter and
CAPT
CPU reads the
CCMP register
21.3.3.1.7 Single-Shot Mode
The Single-Shot mode can be used to generate a pulse with a duration defined by the Compare (TCBn.CCMP)
register, every time a rising or falling edge is observed on a connected event channel.
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ATmega3208/3209
TCB - 16-bit Timer/Counter Type B
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 BOTTOM to TOP while driving its output high. The RUN bit in the Status
(TCBn.STATUS) register can be read to see if the counter is counting or not. When the Counter register reaches the
CCMP register value, the counter will stop, and the output pin will go low for at least one prescaler cycle. A new event
arriving during this time will be ignored. There is a two clock-cycle delay from when the event is received until the
output is set high.
The counter will start counting as soon as the module is enabled, even without triggering an event. This is prevented
by writing TOP to the Counter register. Similar behavior is seen if the Event Edge (EDGE) bit in the Event Control
(TCBn.EVCTRL) register is ‘1’ while the module is enabled. Writing TOP to the Counter register prevents this as well.
If the Event Asynchronous (ASYNC) bit in the Control B (TCBn.CTRLB) register is written to ‘1’ the timer will react
asynchronously to an incoming event. An edge on the event will immediately cause the output signal to be set. The
counter will still start counting two clock cycles after the event is received.
Figure 21-9. Single-Shot Mode
Ignored
Ignored
CAPT
(Interrupt Request
and Event)
Edge Detector
TOP
CNT
BOTTOM
Output
Event starts
counter
Counter reaches
TOP value
Event starts
counter
Counter reaches
TOP value
21.3.3.1.8 8-Bit PWM Mode
The TCB can be configured to run in 8-bit PWM mode, where each of the register pairs in the 16-bit Compare/
Capture (TCBn.CCMPH and TCBn.CCMPL) register are used as individual Compare registers. The period (T) is
controlled by CCMPH, while CCMPL controls the duty cycle of the waveform. The counter will continuously count
from BOTTOM to CCMPL, and the output will be set at BOTTOM and cleared when the counter reaches CCMPH.
CCMPH is the number of cycles for which the output will be driven high. CCMPL+1 is the period of the output pulse.
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ATmega3208/3209
TCB - 16-bit Timer/Counter Type B
Figure 21-10. 8-Bit PWM Mode
Period (T)
CCMPH=BOTTOM
CCMPH=TOP
CAPT
(Interrupt Request
CCMPH>TOP
and Event)
MAX
TOP
CCMPL
CNT
CCMPH
BOTTOM
Output
21.3.3.2 Output
Timer synchronization and output logic level are dependent on the selected Timer Mode (CNTMODE) bit field in
Control B (TCBn.CTRLB) register. In Single-Shot mode the timer/counter can be configured so that the signal
generation happens asynchronously to an incoming event (ASYNC = 1 in TCBn.CTRLB). The output signal is then
set immediately at the incoming event instead of being synchronized to the TCB clock. Even though the output is set
immediately, it will take two to three CLK_TCB cycles before the counter starts counting.
The different configurations and their impact on the output are listed in the table below.
Table 21-2. Output Configuration
CCMPEN
CNTMODE
ASYNC
0
The output is high when
the counter starts and the
output is low when the
counter stops
1
The output is high when
the event arrives and the
output is low when the
counter stops
Single-Shot mode
1
0
Output
8-bit PWM mode
Not applicable
8-bit PWM mode
Other modes
Not applicable
The output initial level sets
the CCMPINIT bit in the
TCBn.CTRLB register
Not applicable
Not applicable
No output
It is not recommended to change modes while the peripheral is enabled as this can produce an unpredictable output.
There is a possibility that an interrupt flag is set during the timer configuration. It is recommended to clear the Timer/
Counter Interrupt Flags (TCBn.INTFLAGS) register after configuring the peripheral.
21.3.3.3 Noise Canceler
The Noise Canceler improves the noise immunity by using a simple digital filter scheme. When the Noise Filter
(FILTER) bit in the Event Control (TCBn.EVCTRL) register 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.
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ATmega3208/3209
TCB - 16-bit Timer/Counter Type B
21.3.3.4 Synchronized with Timer/Counter Type A
The TCB can be configured to use the clock (CLK_TCA) of a Timer/Counter type A (TCAn) by writing to the Clock
Select bit field (CLKSEL) in the Control A register (TCBn.CTRLA). In this setting, the TCB will count on the exact
same clock source as selected in TCAn.
When the Synchronize Update (SYNCUPD) bit in the Control A (TCBn.CTRLA) register is written to ‘1’, the TCB
counter will restart when the TCAn counter restarts.
21.3.4
Events
The TCB can generate the events described in the following table:
Table 21-3. Event Generators in TCB
Generator Name
Peripheral
TCBn
Event
Description
CAPT CAPT flag set
Event Type
Generating Clock Domain
Pulse
CLK_PER
Length of Event
One CLK_PER period
The conditions for generating the CAPT and OVF events are identical to those that will raise the corresponding
interrupt flags in the Timer/Counter Interrupt Flags (TCBn.INTFLAGS) register. Refer to the Event System section for
more details regarding event users and Event System configuration.
The TCB can receive the events described in the following table:
Table 21-4. Event Users and Available Event Actions in TCB
User Name
Peripheral
Description
Input
Input Detection Async/Sync
Time-Out Check Count mode
Input Capture on Event Count mode
Input Capture Frequency Measurement Count mode
TCBn
CAPT
Input Capture Pulse-Width Measurement Count mode
Sync
Edge
Input Capture Frequency and Pulse-Width Measurement
Count mode
Single-Shot Count mode
Both
COUNT Event as clock source in combination with a count mode
Sync
CAPT and COUNT are TCB event users that detect and act upon input events.
The COUNT event user is enabled on the peripheral by modifying the Clock Select (CLKSEL) bit field in the Control A
(TCBn.CTRLA) register to EVENT, and setting up the Event System accordingly.
If the Capture Event Input Enable (CAPTEI) bit in the Event Control (TCBn.EVCTRL) register is written to ‘1’,
incoming events will result in an event action as defined by the Event Edge (EDGE) bit in Event Control
(TCBn.EVCTRL) register and the Timer Mode (CNTMODE) bit field in Control B (TCBn.CTRLB) register. The event
needs to last for at least one CLK_PER cycle to be recognized.
If the Asynchronous mode is enabled for Single-Shot mode, the event is edge-triggered and will capture changes on
the event input shorter than one system clock cycle.
21.3.5
Interrupts
Table 21-5. Available Interrupt Vectors and Sources
Name Vector Description Conditions
CAPT TCB interrupt
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Depending on the operating mode. See the description of the CAPT bit in the
TCBn.INTFLAG register.
Preliminary Datasheet
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ATmega3208/3209
TCB - 16-bit Timer/Counter Type 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 (peripheral.INTCTRL) register.
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.
21.3.6
Sleep Mode Operation
TCBn is by default disabled in Standby Sleep mode. It will be halted as soon as the Sleep mode is entered.
The module can stay fully operational in the Standby Sleep mode if the Run Standby (RUNSTDBY) bit in the
TCBn.CTRLA register is written to ‘1’.
All operations are halted in Power-Down Sleep mode.
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TCB - 16-bit Timer/Counter Type B
21.4
Register Summary - TCB
Offset
Name
Bit Pos.
0x00
0x01
0x02
...
0x03
0x04
0x05
0x06
0x07
0x08
0x09
CTRLA
CTRLB
7:0
7:0
RUNSTDBY
ASYNC
EVCTRL
INTCTRL
INTFLAGS
STATUS
DBGCTRL
TEMP
FILTER
0x0A
CNT
0x0C
CCMP
7:0
7:0
7:0
7:0
7:0
7:0
7:0
15:8
7:0
15:8
21.5
CCMPINIT
SYNCUPD
CCMPEN
CLKSEL[1:0]
CNTMODE[2:0]
ENABLE
Reserved
EDGE
CAPTEI
CAPT
CAPT
RUN
DBGRUN
TEMP[7:0]
CNT[7:0]
CNT[15:8]
CCMP[7:0]
CCMP[15:8]
Register Description
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ATmega3208/3209
TCB - 16-bit Timer/Counter Type B
21.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
Access
Reset
CTRLA
0x00
0x00
-
6
RUNSTDBY
R/W
0
5
4
SYNCUPD
R/W
0
3
2
1
CLKSEL[1:0]
R/W
R/W
0
0
0
ENABLE
R/W
0
Bit 6 – RUNSTDBY Run in 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 TCA0 is restarted or overflows. This can be used to
synchronize capture with the PWM period.
Bits 2:1 – CLKSEL[1:0] Clock Select
Writing these bits selects the clock source for this peripheral.
Value
Name
Description
0x0
CLKDIV1
CLK_PER
0x1
CLKDIV2
CLK_PER / 2
0x2
CLKTCA
Use CLK_TCA from TCA0
0x3
Reserved
Bit 0 – ENABLE Enable
Writing this bit to ‘1’ enables the Timer/Counter type B peripheral.
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TCB - 16-bit Timer/Counter Type B
21.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CTRLB
0x01
0x00
-
6
ASYNC
R/W
0
5
CCMPINIT
R/W
0
4
CCMPEN
R/W
0
3
2
R/W
0
1
CNTMODE[2:0]
R/W
0
0
R/W
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
Description
0
The output will go HIGH when the counter starts after synchronization
1
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
Description
0
Initial pin state is LOW
1
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
Description
0
Compare/Capture Output is ‘0’
1
Compare/Capture Output has a valid value
Bits 2:0 – CNTMODE[2:0] Timer Mode
Writing these bits selects the Timer mode.
Value
Name
Description
0x0
INT
Periodic Interrupt mode
0x1
TIMEOUT
Time-out Check mode
0x2
CAPT
Input Capture on Event mode
0x3
FRQ
Input Capture Frequency Measurement mode
0x4
PW
Input Capture Pulse-Width Measurement mode
0x5
FRQPW
Input Capture Frequency and Pulse-Width Measurement mode
0x6
SINGLE
Single-Shot mode
0x7
PWM8
8-Bit PWM mode
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TCB - 16-bit Timer/Counter Type B
21.5.3
Event Control
Name:
Offset:
Reset:
Property:
Bit
EVCTRL
0x04
0x00
-
7
Access
Reset
6
FILTER
R/W
0
5
4
EDGE
R/W
0
3
2
1
0
CAPTEI
R/W
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)
bit field in TCBn.CTRLB. “—” means that an event or edge has no effect in this mode.
Count Mode
Periodic Interrupt mode
Timeout Check mode
Input Capture on Event mode
Input Capture Frequency
Measurement mode
Input Capture Pulse-Width
Measurement mode
EDGE Positive Edge
Negative Edge
0
—
—
1
—
—
0
Start counter
Stop counter
1
Stop counter
Start counter
0
Input Capture, interrupt
—
1
—
Input Capture, interrupt
0
Input Capture, clear and restart
counter, interrupt
—
1
—
Input Capture, clear and restart
counter, interrupt
0
Clear and restart counter
Input Capture, interrupt
1
Input Capture, interrupt
Clear and restart counter
0
•
•
•
On the 1st Positive: Clear and restart counter
On the following Negative: Input Capture
On the 2nd Positive: Stop counter, interrupt
1
•
•
•
On the 1st Negative: Clear and restart counter
On the following Positive: Input Capture
On the 2nd Negative: Stop counter, interrupt
Input Capture Frequency and PulseWidth Measurement mode
Single-Shot mode
8-Bit PWM mode
0
Start counter
—
1
—
Start counter
0
—
—
1
—
—
Bit 0 – CAPTEI Capture Event Input Enable
Writing this bit to ‘1’ enables the input capture event.
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ATmega3208/3209
TCB - 16-bit Timer/Counter Type B
21.5.4
Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x05
0x00
-
6
5
4
3
Access
Reset
2
1
0
CAPT
R/W
0
Bit 0 – CAPT Capture Interrupt Enable
Writing this bit to ‘1’ enables interrupt on capture.
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TCB - 16-bit Timer/Counter Type B
21.5.5
Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
INTFLAGS
0x06
0x00
-
7
6
5
4
3
2
1
Access
Reset
0
CAPT
R/W
0
Bit 0 – CAPT Capture Interrupt Flag
This bit is set when a capture interrupt occurs. The interrupt conditions are dependent on the Counter Mode
(CNTMODE) bit field in the Control B (TCBn.CTRLB) register.
This bit is cleared by writing a ‘1’ to it or when the Capture register is read in Capture mode.
Table 21-6. Interrupt Sources Set Conditions by Counter Mode
Counter Mode
Interrupt Set Condition
Periodic Interrupt mode
Set when the counter reaches TOP
Timeout Check mode
Set when the counter reaches TOP
Single-Shot mode
Set when the counter reaches TOP
Input Capture Frequency
Measurement mode
Set on edge when the Capture register is
loaded and the counter restarts; the flag
clears when the capture is read
Input Capture on Event
mode
Set when an event occurs and the Capture
register is loaded; the flag clears when the
capture is read
Set on edge when the Capture register is
Input Capture Pulse-Width loaded; the previous edge initialized the
Measurement mode
count; the flag clears when the capture is
read
Input Capture Frequency
and Pulse-Width
Measurement mode
Set on the second edge (positive or
negative) when the counter is stopped; the
flag clears when the capture is read
8-Bit PWM mode
Set when the counter reaches CCML
© 2020 Microchip Technology Inc.
Preliminary Datasheet
TOP
Value
CAPT
CCMP
CNT == TOP
On Event, copy CNT to
CCMP, and restart
counting (CNT ==
BOTTOM)
-On Event, copy CNT to
CCMP, and continue
counting
CCML
CNT == CCML
DS40002174A-page 246
ATmega3208/3209
TCB - 16-bit Timer/Counter Type B
21.5.6
Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x07
0x00
-
6
5
4
3
2
1
Access
Reset
0
RUN
R
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 to ‘0’.
The bit is read-only and cannot be set by UPDI.
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TCB - 16-bit Timer/Counter Type B
21.5.7
Debug Control
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x08
0x00
-
6
5
4
3
2
Access
Reset
1
0
DBGRUN
R/W
0
Bit 0 – DBGRUN Debug Run
Value
Description
0
The peripheral is halted in Break Debug mode and ignores events
1
The peripheral will continue to run in Break Debug mode when the CPU is halted
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TCB - 16-bit Timer/Counter Type B
21.5.8
Temporary Value
Name:
Offset:
Reset:
Property:
TEMP
0x09
0x00
-
The Temporary register is used by the CPU for single-cycle, 16-bit access to the 16-bit registers of this peripheral. It
can be read and written by software. Refer to 16-bit access in the AVR CPU chapter. There is one common
Temporary register for all the 16-bit registers of this peripheral.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
TEMP[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – TEMP[7:0] Temporary Value
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TCB - 16-bit Timer/Counter Type B
21.5.9
Count
Name:
Offset:
Reset:
Property:
CNT
0x0A
0x00
-
The TCBn.CNTL and TCBn.CNTH register pair represents the 16-bit value TCBn.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.
CPU and UPDI write access has priority over internal updates of the register.
Bit
15
14
13
12
11
10
9
8
R/W
0
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
CNT[15:8]
Access
Reset
Bit
R/W
0
R/W
0
R/W
0
R/W
0
7
6
5
4
CNT[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
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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TCB - 16-bit Timer/Counter Type B
21.5.10 Capture/Compare
Name:
Offset:
Reset:
Property:
CCMP
0x0C
0x00
-
The TCBn.CCMPL and TCBn.CCMPH register pair represents the 16-bit value TCBn.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.
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/Time-Out and Single-Shot mode, this register acts as the TOP value
• In 8-bit PWM mode, TCBn.CCMPL and TCBn.CCMPH act as two independent registers
Bit
Access
Reset
Bit
15
14
13
R/W
0
R/W
0
R/W
0
7
6
5
12
11
CCMP[15:8]
R/W
R/W
0
0
4
10
9
8
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
CCMP[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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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ATmega3208/3209
RTC - Real-Time Counter
22.
RTC - Real-Time Counter
22.1
Features
•
•
•
•
•
•
•
•
•
22.2
16-bit resolution
Selectable clock sources
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
Crystal Error Correction
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 independently 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 KHz output from an external crystal. The RTC can also be clocked from an
external clock signal, the 32 KHz 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 32.768
kHz clock source, the maximum resolution is 30.5 μs, and timeout periods can be up to two seconds. With a
resolution of 1s, the maximum timeout period is more than 18 hours (65536 seconds).
The RTC also supports correction when operated using external crystal selection. An externally calibrated value will
be used for correction. The RTC can be adjusted by software to an accuracy of ±1PPM. The RTC correction
operation will either speed up (by skipping count) or slow down (by adding extra count) the prescaler to account for
the crystal error.
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 nth clock period. n can be selected from {4, 8, 16,.. 32768} for interrupts, and from {64, 128, 256,... 8192} for
events.
The PIT uses the same clock source (CLK_RTC) as the RTC function.
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22.2.1
Block Diagram
Figure 22-1. Block Diagram
EXTCLK
External Clock
TOSC1
TOSC2
32.768 kHz Crystal Osc
32.768 kHz Int. Osc
DIV32
RTC
PER
CLKSEL
CLK_RTC
Correction
counter
15-bit
prescaler
PIT
=
Overflow
=
Compare
CNT
CMP
Period
22.3
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 prescaler setting.
A 32.768 kHz crystal can be connected to the TOSC1 or TOSC2 pins, along with any required load capacitors.
Alternatively, an external digital clock can be connected to the TOSC1 pin.
22.4
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.
22.4.1
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).
22.4.1.1 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.
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The CLK_RTC clock configuration is used by both RTC and PIT functionality.
22.4.1.2 Configure RTC
To operate the RTC, follow these steps:
1.
2.
3.
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).
Configure the RTC-internal prescaler and enable the RTC by writing the desired value to the PRESCALER bit
field and a '1' to the RTC Enable bit (RTCEN) in the Control A register (RTC.CTRLA).
Note: The RTC peripheral is used internally during device start-up. Always check the Busy bits in the RTC.STATUS
and RTC.PITSTATUS registers, also on initial configuration.
22.4.2
Operation - RTC
22.4.2.1 Enabling, Disabling, and Resetting
The RTC is enabled by setting the Enable bit in the Control A register (ENABLE bit in RTC.CTRLA to 1). The RTC is
disabled by writing ENABLE bit in RTC.CTRLA to 0.
22.5
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.
22.5.1
Initialization
To operate the PIT, follow these steps:
1. Configure the RTC clock CLK_RTC as described in 22.4.1.1 Configure the Clock CLK_RTC.
2. Enable the interrupt by writing a '1' to the Periodic Interrupt bit (PI) in the PIT Interrupt Control register
(RTC.PITINTCTRL).
3. Select the period for the interrupt and enable the PIT by writing the desired value to the PERIOD bit field and a
'1' to the PIT Enable bit (PITEN) in the PIT Control A register (RTC.PITCTRLA).
Note: The RTC peripheral is used internally during device start-up. Always check the Busy bits in the RTC.STATUS
and RTC.PITSTATUS registers, also on initial configuration.
22.5.2
Operation - PIT
22.5.2.1 Enabling, Disabling, and Resetting
The PIT is enabled by setting the Enable bit in the PIT Control A register (the PITEN bit in RTC.PITCTRLA to 1). The
PIT is disabled by writing the PITEN bit in RTC.PITCTRLA to 0.
22.5.2.2 PIT Interrupt Timing
Timing of the First Interrupt
The PIT function and the RTC function are running off the same counter inside the prescaler, but both functions’
periods can be configured independently:
• The RTC period is configured by writing the PRESCALER bit field in RTC.CTRLA.
• The PIT period is configured by writing the PERIOD bit field in RTC.PITCTRLA.
The prescaler is OFF when both functions are OFF (RTC Enable bit (RTCEN) in RTC.CTRLA and PIT Enable bit
(PITEN) in RTC.PITCTRLA are zero), but it is running (i.e. its internal counter is counting) when either function is
enabled.
For this reason, the timing of the first PIT interrupt and the first RTC count tick will be unknown (anytime between
enabling and a full period).
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Continuous Operation
After the first interrupt, the PIT will continue toggling every ½ PIT period, resulting in a full PIT period signal.
Example 22-1. PIT Timing Diagram for PERIOD=CYC16
For PERIOD=CYC16 in RTC.PITCTRLA, the PIT output effectively follows the state of prescaler
counter bit 3, so the resulting interrupt output has a period of 16 CLK_RTC cycles.
The time between writing PITEN to ‘1’ and the first PIT interrupt can vary between virtually 0 and a
full PIT period of 16 CLK_RTC cycles. The precise delay between enabling the PIT and its first
output is depending on the prescaler’s counting phase: the depicted first interrupt in the lower
figure is produced by writing PITEN to ‘1’ at any time inside the leading time window.
Figure 22-2. Timing Between PIT Enable and First Interrupt
prescaler
counter
value (LSb)
..000000
..000001
..000010
..000011
..000100
..000101
..000110
..000111
..001000
..001001
..001010
..001011
..001100
..001101
..001110
..001111
..010000
..010001
..010010
..010011
..010100
..010101
..010110
..010111
..011000
..011001
..011010
..011011
..011100
..011101
..011110
..011111
..100000
..100001
..100010
..100011
..100100
..100101
..100110
..100111
..101000
..101001
..101010
..101011
..101100
..101101
..101110
..101111
CLK_RTC
prescaler bit 3
(CYC16)
Continuous Operation
PITENABLE=0
PIT output
time window for writing
PITENABLE=1
first PIT output
22.6
Crystal Error Correction
The prescaler for the RTC and PIT can do internal correction (when CORREN bit in RTC.CTRLA is ‘1’) on the crystal
clock by taking the PPM error value from the CALIB register.
The CALIB register must be written by the user based on information about the frequency error. Correction is done
within an interval of approximately 1 million cycles of the input clock. The correction operation is performed by adding
or removing one cycle. These single-cycle operations will be performed repeatedly the error number of times
(ERROR bits in RTC.CALIB) spread throughout the 1 million cycle correction interval.
The correction of the clock will be reflected in the RTC count value available through the RTC.CNTx registers or in
the PIT intervals.
If disabling the correction feature, an ongoing correction cycle will be completed before the function is disabled.
22.7
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. The generated
strobe is synchronous with CLK_RTC and lasts one CLK_RTC cycle.
Compare (CMP): Indicates a match between the counter value and the Compare register. The generated strobe
is synchronous with CLK_RTC and lasts one CLK_RTC cycle.
When enabled, the PIT generates the following 50% duty cycle clock signals on its event outputs:
•
•
•
Event 0: Clock period = 8192 RTC clock cycles
Event 1: Clock period = 4096 RTC clock cycles
Event 2: Clock period = 2048 RTC clock cycles
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•
•
•
•
•
Event 3: Clock period = 1024 RTC clock cycles
Event 4: Clock period = 512 RTC clock cycles
Event 5: Clock period = 256 RTC clock cycles
Event 6: Clock period = 128 RTC clock cycles
Event 7: Clock period = 64 RTC clock cycles
The event users are configured by the Event System (EVSYS).
22.8
Interrupts
Table 22-1. Available Interrupt Vectors and Sources
Name Vector Description
RTC
Real-time counter overflow and
compare match interrupt
Conditions
•
•
PIT
Periodic Interrupt Timer interrupt
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 by the PERIOD bits in
RTC.PITCTRLA.
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 (peripheral.INTCTRL) register.
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.
Note that:
• The RTC has two INTFLAGS registers: RTC.INTFLAGS and RTC.PITINTFLAGS.
• The RTC has two INTCTRL registers: RTC.INTCTRL and RTC.PITINTCTRL.
22.9
Sleep Mode Operation
The RTC will continue to operate in Idle Sleep mode. It will run in Standby Sleep mode if the RUNSTDBY bit in
RTC.CTRLA is set.
The PIT will continue to operate in any sleep mode.
22.10
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
an effect on the RTC or PIT, respectively. This synchronization time is described for each register in the Register
Description section.
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 these flags before writing to the mentioned registers.
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22.11
Debug Operation
RTC If the Debug Run bit (DBGRUN) in the Debug Control register (DBGCTRL) is ‘1’ the RTC will continue normal
operation.
If DBGRUN in DBGCTRL is ‘0’ and the CPU is halted, the RTC will halt operation and ignore incoming
events.
PIT
If the Debug Run bit (DBGRUN) in the PIT Debug Control register (PITDBGCTRL) is ‘1’ the PIT will continue
normal operation.
If DBGRUN in PITDBGCTRL is ‘0’ in debug mode and the CPU is halted, the PIT output will be low.
If the PIT output was high at the time, a new positive edge occurs to set the interrupt flag when re-starting
from a break. The result is an additional PIT interrupt that would not happen during normal operation.
If the PIT output was low at the break, the PIT will resume low without additional interrupt.
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22.12
Register Summary - RTC
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
CTRLA
STATUS
INTCTRL
INTFLAGS
TEMP
DBGCTRL
CALIB
CLKSEL
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
15:8
7:0
15:8
7:0
15:8
0x08
CNT
0x0A
PER
0x0C
CMP
0x0E
...
0x0F
0x10
0x11
0x12
0x13
0x14
0x15
22.13
RUNSTDBY
PRESCALER[3:0]
CMPBUSY
CORREN
PERBUSY
CNTBUSY
CMP
CMP
RTCEN
CTRLABUSY
OVF
OVF
TEMP[7:0]
DBGRUN
SIGN
ERROR[6:0]
CLKSEL[1:0]
CNT[7:0]
CNT[15:8]
PER[7:0]
PER[15:8]
CMP[7:0]
CMP[15:8]
Reserved
PITCTRLA
PITSTATUS
PITINTCTRL
PITINTFLAGS
Reserved
PITDBGCTRL
7:0
7:0
7:0
7:0
PERIOD[3:0]
7:0
PITEN
CTRLBUSY
PI
PI
DBGRUN
Register Description
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22.13.1 Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
RUNSTDBY
R/W
0
CTRLA
0x00
0x00
-
6
R/W
0
5
4
PRESCALER[3:0]
R/W
R/W
0
0
3
R/W
0
2
CORREN
R/W
0
1
0
RTCEN
R/W
0
Bit 7 – RUNSTDBY Run in Standby
Value
Description
0
RTC disabled in Standby sleep mode
1
RTC enabled in Standby sleep mode
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 CTRLABUSY flag in RTC.STATUS is cleared before writing to this
register.
Value
Name
Description
0x0
DIV1
RTC clock/1 (no prescaling)
0x1
DIV2
RTC clock/2
0x2
DIV4
RTC clock/4
0x3
DIV8
RTC clock/8
0x4
DIV16
RTC clock/16
0x5
DIV32
RTC clock/32
0x6
DIV64
RTC clock/64
0x7
DIV128
RTC clock/128
0x8
DIV256
RTC clock/256
0x9
DIV512
RTC clock/512
0xA
DIV1024
RTC clock/1024
0xB
DIV2048
RTC clock/2048
0xC
DIV4096
RTC clock/4096
0xD
DIV8192
RTC clock/8192
0xE
DIV16384
RTC clock/16384
0xF
DIV32768
RTC clock/32768
Bit 2 – CORREN Frequency Correction Enable
Value
Description
0
Frequency correction is disabled
1
Frequency correction is enabled
Bit 0 – RTCEN RTC Peripheral Enable
Value
Description
0
RTC peripheral disabled
1
RTC peripheral enabled
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22.13.2 Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x01
0x00
-
6
Access
Reset
5
4
3
CMPBUSY
R
0
2
PERBUSY
R
0
1
CNTBUSY
R
0
0
CTRLABUSY
R
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.
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.
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22.13.3 Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x02
0x00
-
6
5
4
3
Access
Reset
2
1
CMP
R/W
0
0
OVF
R/W
0
Bit 1 – CMP Compare Match Interrupt Enable
Enable interrupt-on-compare match (i.e., when the Counter value (CNT) matches the Compare value (CMP)).
Bit 0 – OVF Overflow Interrupt Enable
Enable interrupt-on-counter overflow (i.e., when the Counter value (CNT) matched the Period value (PER) and wraps
around to zero).
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22.13.4 Interrupt Flag
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x03
0x00
-
6
5
4
3
2
Access
Reset
1
CMP
R/W
0
0
OVF
R/W
0
Bit 1 – CMP Compare Match Interrupt Flag
This flag is set when the Counter value (CNT) matches the Compare value (CMP).
Writing a ‘1’ to this bit clears the flag.
Bit 0 – OVF Overflow Interrupt Flag
This flag is set when the Counter value (CNT) has reached the Period value (PER) and wrapped to zero.
Writing a ‘1’ to this bit clears the flag.
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22.13.5 Temporary
Name:
Offset:
Reset:
Property:
TEMP
0x4
0x00
-
The Temporary register is used by the CPU for single-cycle, 16-bit access to the 16-bit registers of this peripheral. It
can be read and written by software. Refer to 16-bit access in the AVR CPU chapter. There is one common
Temporary register for all the 16-bit registers of this peripheral.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
TEMP[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – TEMP[7:0] Temporary
Temporary register for read/write operations in 16-bit registers.
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22.13.6 Debug Control
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x05
0x00
-
6
5
4
3
2
Access
Reset
1
0
DBGRUN
R/W
0
Bit 0 – DBGRUN Debug Run
Value
Description
0
The peripheral is halted in Break Debug mode and ignores events
1
The peripheral will continue to run in Break Debug mode when the CPU is halted
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22.13.7 Crystal Frequency Calibration
Name:
Offset:
Reset:
Property:
CALIB
0x06
0x00
-
This register stores the error value and the type of correction to be done. This register is written by software with any
error value based on external calibration and/or temperature correction/s.
Bit
7
SIGN
R/W
0
Access
Reset
6
5
4
R/W
0
R/W
0
R/W
0
3
ERROR[6:0]
R/W
0
2
1
0
R/W
0
R/W
0
R/W
0
Bit 7 – SIGN Error Correction Sign Bit
This bit is used to indicate the direction of the correction.
Value
Description
0x0
Positive correction causing prescaler to count slower.
0x1
Negative correction causing prescaler to count faster. Requires that prescaler
configuration is set to minimum DIV2.
Bits 6:0 – ERROR[6:0] Error Correction Value
The number of correction clocks for each million RTC clock cycles interval (ppm).
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22.13.8 Clock Selection
Name:
Offset:
Reset:
Property:
Bit
7
CLKSEL
0x07
0x00
-
6
5
4
3
Access
Reset
2
1
0
CLKSEL[1:0]
R/W
R/W
0
0
Bits 1:0 – CLKSEL[1:0] Clock Select
Writing these bits select 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
Name
Description
0x0
INT32K
32.768 kHz from OSCULP32K
0x1
INT1K
1.024 kHz from OSCULP32K
0x2
TOSC32K
32.768 kHz from XOSC32K or external clock from TOSC1
0x3
EXTCLK
External clock from EXTCLK pin
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22.13.9 Count
Name:
Offset:
Reset:
Property:
CNT
0x08
0x0000
-
The RTC.CNTL and RTC.CNTH register pair represents the 16-bit value, 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 in the CPU chapter.
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 CNTBUSY flag in
RTC.STATUS is cleared before writing to this register.
Bit
15
14
13
12
11
10
9
8
R/W
0
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
CNT[15:8]
Access
Reset
Bit
R/W
0
R/W
0
R/W
0
R/W
0
7
6
5
4
CNT[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
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.
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22.13.10 Period
Name:
Offset:
Reset:
Property:
PER
0x0A
0xFFFF
-
The RTC.PERL and RTC.PERH register pair represents the 16-bit value, 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 in the CPU chapter.
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 PERBUSY flag in
RTC.STATUS is cleared before writing to this register.
Bit
15
14
13
12
11
10
9
8
R/W
1
R/W
1
R/W
1
R/W
1
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
PER[15:8]
Access
Reset
Bit
R/W
1
R/W
1
R/W
1
R/W
1
7
6
5
4
PER[7:0]
Access
Reset
R/W
1
R/W
1
R/W
1
R/W
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.
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22.13.11 Compare
Name:
Offset:
Reset:
Property:
CMP
0x0C
0x0000
-
The RTC.CMPL and RTC.CMPH register pair represents the 16-bit value, 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 in the CPU chapter.
Bit
15
14
13
12
11
10
9
8
R/W
0
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
CMP[15:8]
Access
Reset
Bit
R/W
0
R/W
0
R/W
0
R/W
0
7
6
5
4
CMP[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
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.
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22.13.12 Periodic Interrupt Timer Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
PITCTRLA
0x10
0x00
-
6
R/W
0
5
4
PERIOD[3:0]
R/W
R/W
0
0
3
2
R/W
0
1
0
PITEN
R/W
0
Bits 6:3 – PERIOD[3:0] Period
Writing this bit field selects the number of RTC clock cycles between each interrupt.
Value
Name
Description
0x0
OFF
No interrupt
0x1
CYC4
4 cycles
0x2
CYC8
8 cycles
0x3
CYC16
16 cycles
0x4
CYC32
32 cycles
0x5
CYC64
64 cycles
0x6
CYC128
128 cycles
0x7
CYC256
256 cycles
0x8
CYC512
512 cycles
0x9
CYC1024
1024 cycles
0xA
CYC2048
2048 cycles
0xB
CYC4096
4096 cycles
0xC
CYC8192
8192 cycles
0xD
CYC16384
16384 cycles
0xE
CYC32768
32768 cycles
0xF
Reserved
Bit 0 – PITEN Periodic Interrupt Timer Enable
Writing a '1' to this bit enables the Periodic Interrupt Timer.
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22.13.13 Periodic Interrupt Timer Status
Name:
Offset:
Reset:
Property:
Bit
7
PITSTATUS
0x11
0x00
-
6
5
4
3
2
1
Access
Reset
0
CTRLBUSY
R
0
Bit 0 – CTRLBUSY PITCTRLA Synchronization Busy
This bit indicates whether the RTC is busy synchronizing the Periodic Interrupt Timer Control A register
(RTC.PITCTRLA) in the RTC clock domain.
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22.13.14 PIT Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
PITINTCTRL
0x12
0x00
-
6
5
4
3
Access
Reset
2
1
0
PI
R/W
0
Bit 0 – PI Periodic interrupt
Value
Description
0
The periodic interrupt is disabled
1
The periodic interrupt is enabled
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22.13.15 PIT Interrupt Flag
Name:
Offset:
Reset:
Property:
Bit
7
PITINTFLAGS
0x13
0x00
-
6
5
4
3
Access
Reset
2
1
0
PI
R/W
0
Bit 0 – PI Periodic interrupt Flag
This flag is set when a periodic interrupt is issued.
Writing a ‘1’ clears the flag.
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22.13.16 Periodic Interrupt Timer Debug Control
Name:
Offset:
Reset:
Property:
Bit
7
PITDBGCTRL
0x15
0x00
-
6
5
4
3
2
Access
Reset
1
0
DBGRUN
R/W
0
Bit 0 – DBGRUN Debug Run
Writing this bit to '1' will enable the PIT to run in Debug mode while the CPU is halted.
Value
Description
0
The peripheral is halted in Break Debug mode and ignores events
1
The peripheral will continue to run in Break Debug mode when the CPU is halted
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23.
USART - Universal Synchronous and Asynchronous Receiver and
Transmitter
23.1
Features
•
•
•
•
•
•
•
•
•
•
•
•
23.2
Full-Duplex Operation
Half-Duplex Operation:
– One-Wire mode
– RS-485 mode
Asynchronous or Synchronous Operation
Supports Serial Frames with Five, Six, Seven, Eight or Nine Data Bits and One or Two Stop Bits
Fractional Baud Rate Generator:
– Can generate the desired baud rate from any system clock frequency
– No need for an external oscillator
Built-In Error Detection and Correction Schemes:
– Odd or even parity generation and parity check
– Buffer overflow and frame error detection
– Noise filtering including false Start bit detection and digital low-pass filter
Separate Interrupts for:
– Transmit complete
– Transmit Data register empty
– Receive complete
Master SPI Mode
Multiprocessor Communication Mode
Start-of-Frame Detection
IRCOM Module for IrDA® Compliant Pulse Modulation/Demodulation
LIN Slave Support
Overview
The Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) is a fast and flexible serial
communication peripheral. The USART supports a number of different modes of operation that can accommodate
multiple types of applications and communication devices. For example, the One-Wire Half-Duplex mode is useful
when low pin count applications are desired. The communication is frame-based, and the frame format can be
customized to support a wide range of standards.
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.
The transmitter consists of a single-write buffer, a Shift register, and control logic for different frame formats. The
receiver consists of a two-level receive buffer and a Shift register. The status information of the received data is
available for error checking. Data and clock recovery units ensure robust synchronization and noise filtering during
asynchronous data reception.
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23.2.1
Block Diagram
Figure 23-1. USART Block Diagram
CLOCK GENERATOR
BAUD
XCK
Baud Rate Generator
TRANSMITTER
XDIR
TX Shift Register
TXDATA
TXD
RECEIVER
RX Shift Register
RX Buffer
RXD
RXDATA
23.2.2
Signal Description
Signal
Type
Description
XCK
Output/input
Clock for synchronous operation
XDIR
Output
Transmit enable for RS-485
TxD
Output/input
Transmitting line (and receiving line in One-Wire mode)
RxD
Input
Receiving line
23.3
Functional Description
23.3.1
Initialization
Full Duplex Mode:
1.
2.
3.
4.
Set the baud rate (USARTn.BAUD).
Set the frame format and mode of operation (USARTn.CTRLC).
Configure the TXD pin as an output.
Enable the transmitter and the receiver (USARTn.CTRLB).
Note:
• For interrupt-driven USART operation, global interrupts must be disabled during the initialization
• Before doing a reinitialization with a changed baud rate or frame format, be sure that there are no ongoing
transmissions while the registers are changed
One-Wire Half Duplex Mode:
1.
2.
Internally connect the TXD to the USART receiver (the LBME bit in the USARTn.CTRLA register).
Enable internal pull-up for the RX/TX pin (the PULLUPEN bit in the PORTx.PINnCTRL register).
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3.
4.
5.
6.
Enable Open-Drain mode (the ODME bit in the USARTn.CTRLB register).
Set the baud rate (USARTn.BAUD).
Set the frame format and mode of operation (USARTn.CTRLC).
Enable the transmitter and the receiver (USARTn.CTRLB).
Note:
• When Open-Drain mode is enabled, the TXD pin is automatically set to output by hardware
• For interrupt-driven USART operation, global interrupts must be disabled during the initialization
• Before doing a reinitialization with a changed baud rate or frame format, be sure that there are no ongoing
transmissions while the registers are changed
23.3.2
Operation
23.3.2.1 Frame Formats
The USART data transfer is frame-based. A frame starts with a Start bit followed by one character of data bits. If
enabled, the Parity bit is inserted after the data bits and before the first Stop bit. After the Stop bit(s) of a frame, either
the next frame can follow immediately, or the communication line can return to the Idle (high) state. 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
The figure below illustrates the possible combinations of frame formats. Bits inside brackets are optional.
Figure 23-2. Frame Formats
FRAME
(IDLE)
St
0
1
2
3
4
[5]
[6]
[7]
[8]
[P]
Sp1 [Sp2]
St
Start bit, always low
(n)
Data bits (0 to 8)
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.
(St/IDLE)
23.3.2.2 Clock Generation
The clock used for shifting and sampling data bits is generated internally by the fractional baud rate generator or
externally from the Transfer Clock (XCK) pin.
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Figure 23-3. Clock Generation Logic Block Diagram
CLOCK GENERATOR
Sync
Register
Edge
Detector
CLK_PER
Fractional Baud Rate
Generator
BAUD
XCK
XCKO
Transmitter
TXCLK
Receiver
RXCLK
23.3.2.2.1 The Fractional Baud Rate Generator
In modes where the USART is not using the XCK input as a clock source, the fractional Baud Rate Generator is used
to generate the clock. Baud rate is given in terms of bits per second (bps) and is configured by writing the
USARTn.BAUD register. The baud rate (fBAUD) is generated by dividing the peripheral clock (fCLK_PER) by a division
factor decided by the BAUD register.
The fractional Baud Rate Generator features hardware that accommodates cases where fCLK_PER is not divisible by
fBAUD. Usually, this situation would lead to a rounding error. The fractional Baud Rate Generator expects the BAUD
register to contain the desired division factor left shifted by six bits, as implemented by the equations in Table 23-1.
The six LSbs will then hold the fractional part of the desired divisor. The fractional part of the BAUD register is used to
dynamically adjust fBAUD to achieve a closer approximation to the desired baud rate.
Since the baud rate cannot be higher than fCLK_PER, the integer part of the BAUD register needs to be at least 1.
Since the result is left shifted by six bits, the corresponding minimum value of the BAUD register is 64. The valid
range is, therefore, 64 to 65535.
In Synchronous mode, only the 10-bit integer part of the BAUD register (BAUD[15:6]) determines the baud rate, and
the fractional part (BAUD[5:0]) must, therefore, be written to zero.
The table below lists equations for translating baud rates into input values for the BAUD register. The equations take
fractional interpretation into consideration, so the BAUD values calculated with these equations can be written directly
to USARTn.BAUD without any additional scaling.
Table 23-1. Equations for Calculating Baud Rate Register Setting
Operating Mode
Asynchronous
Synchronous Master
Conditions
Baud Rate (Bits Per Seconds) USART.BAUD Register Value
Calculation
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64 × ����_���
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S is the number of samples per bit
• Asynchronous Normal mode: S = 16
• Asynchronous Double-Speed mode: S = 8
• Synchronous mode: S = 2
23.3.2.3 Data Transmission
The USART transmitter sends data by periodically driving the transmission line low. The data transmission is initiated
by loading the transmit buffer (USARTn.TXDATA) with the data to be sent. The data in the transmit buffer is moved to
the Shift register once it is empty and ready to send a new frame. After the Shift register is loaded with data, the data
frame will be transmitted.
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 (the TXCIF bit in the USARTn.STATUS register) is set, and the interrupt
is generated if it is enabled.
TXDATA can only be written when the Data Register Empty Interrupt Flag (the DREIF bit in the USARTn.STATUS
register) 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 (MSb) written to TXDATA are ignored. If 9-bit
characters are used, the DATA[8] bit in the USARTn.TXDATAH register has to be written before the DATA[7:0] bits in
the USARTn.TXDATAL register.
23.3.2.3.1 Disabling the Transmitter
When disabling the transmitter, the operation will not become effective until ongoing and pending transmissions are
completed (that is, 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 TXD pin, and the PORT module regains
control of the pin. The pin is automatically configured as an input by hardware regardless of its previous setting. The
pin can now be used as a normal I/O pin with no port override from the USART.
23.3.2.4 Data Reception
The USART receiver samples the reception line to detect and interpret the received data. The direction of the pin
must, therefore, be configured as an input by writing a ‘0’ to the corresponding bit in the Direction register
(PORTx.DIRn).
The receiver accepts data when a valid Start bit is detected. 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 (the RXCIF bit in the USARTn.STATUS register) is set, and the interrupt is
generated if enabled.
The RXDATA register is the part of the RX buffer that can be read by the application software when RXCIF is set.
When using frames with fewer than eight bits, the unused Most Significant bits (MSb) are read as zero. If 9-bit
characters are used, the DATA[8] bit in the USARTn.RXDATAH register must be read before the DATA[7:0] bits in the
USARTn.RXDATAL register.
23.3.2.4.1 Receiver Error Flags
The USART receiver features error detection mechanisms that uncover corruption of the transmission. These
mechanisms include the following:
• Frame Error detection - controls whether the received frame is valid
• Buffer Overflow detection - indicates data loss due to the receiver buffer being full and overwritten by the new
data
• Parity Error detection - checks the validity of the incoming frame by calculating its parity and comparing it to the
Parity bit
Each error detection mechanism controls one error flag that can be read in the RXDATAH register:
• Frame Error (FERR)
• Buffer Overflow (BUFOVF)
• Parity Error (PERR)
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The error flags are located in the RX buffer together with their corresponding frame. The RXDATAH register that
contains the error flags must be read before the RXDATAL register, since reading the RXDATAL register will trigger
the RX buffer to shift out the RXDATA bytes.
Note: If the Character Size bit field (the CHSIZE bits in the USARTn.CTRLC register) is set to nine bits, low byte
first (9BITL), the RXDATAH register will, instead of the RXDATAL register, trigger the RX buffer to shift out the
RXDATA bytes. The RXDATAL register must, in that case, be read before the RXDATAH register.
23.3.2.4.2 Disabling the Receiver
When disabling the receiver, the operation is immediate. The receiver buffer will be flushed, and data from ongoing
receptions will be lost.
23.3.2.4.3 Flushing the Receive Buffer
If the RX buffer has to be flushed during normal operation, repeatedly read the DATA location (USARTn.RXDATAH
and USARTn.RXDATAL registers) until the Receive Complete Interrupt Flag (the RXCIF bit in the
USARTn.RXDATAH register) is cleared.
23.3.3
Communication Modes
The USART is a flexible peripheral that supports multiple different communication protocols. The available modes of
operation can be split into two groups: Synchronous and asynchronous communication.
The synchronous communication relies on one device on the bus to be the master, providing the rest of the devices
with a clock signal through the XCK pin. All the devices use this common clock signal for both transmission and
reception, requiring no additional synchronization mechanism.
The device can be configured to run either as a master or a slave on the synchronous bus.
The asynchronous communication does not use a common clock signal. Instead, it relies on the communicating
devices to be configured with the same baud rate. When receiving a transmission, the hardware synchronization
mechanisms are used to align the incoming transmission with the receiving device peripheral clock.
Four different modes of reception are available when communicating asynchronously. One of these modes can
receive transmissions at twice the normal speed, sampling only eight times per bit instead of the normal 16. The
other three operating modes use variations of synchronization logic, all receiving at normal speed.
23.3.3.1 Synchronous Operation
23.3.3.1.1 Clock Operation
The XCK pin direction controls whether the transmission clock is an input (Slave mode) or an output (Master mode).
The corresponding port pin direction must be set to output for Master mode or to input for Slave mode
(PORTx.DIRn). The data input (on RXD) is sampled at the XCK clock edge which is opposite the edge where data
are transmitted (on TXD) as shown in the figure below.
Figure 23-4. Synchronous Mode XCK Timing
XCK
INVEN = 0
Data transmit (TxD)
Data sample (RxD)
XCK
INVEN = 1
Data transmit (TxD)
Data sample (RxD)
The I/O pin can be inverted by writing a ‘1’ to the Inverted I/O Enable (INVEN) bit in the Pin n Control register of the
port peripheral (PORTx.PINnCTRL). Using the inverted I/O setting for the corresponding XCK port pin, the XCK clock
edges used for sampling RxD and transmitting on TxD can be selected. If the inverted I/O is disabled (INVEN = 0),
the rising XCK clock edge represents the start of a new data bit, and the received data will be sampled at the falling
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XCK clock edge. If inverted I/O is enabled (INVEN = 1), the falling XCK clock edge represents the start of a new data
bit, and the received data will be sampled at the rising XCK clock edge.
23.3.3.1.2 External Clock Limitations
When the USART is configured in Synchronous Slave mode, the XCK signal must be provided externally by the
master device. Since the clock is provided externally, configuring the BAUD register will have no impact on the
transfer speed. Successful clock recovery requires the clock signal to be sampled at least twice for each rising and
falling edge. The maximum XCK speed in Synchronous Operation mode, fSlave_XCK, is therefore limited by:
�Slave_XCK<
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4
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 to ensure that XCK is sampled a minimum of two times for each edge.
23.3.3.1.3 USART in Master SPI Mode
The USART may be configured to function with multiple different communication interfaces, and one of these is the
Serial Peripheral Interface (SPI) where it can function as the master device. The SPI is a four-wire interface that
enables a master device to communicate with one or multiple slaves.
Frame Formats
The serial frame for the USART in Master SPI mode always contains eight Data bits. The Data bits can be configured
to be transmitted with either the LSb or MSb first, by writing to the Data Order bit (UDORD) in the Control C register
(USARTn.CTRLC).
SPI does not use Start, Stop, or Parity bits, so the transmission frame can only consist of the Data bits.
Clock Generation
Being a master device in a synchronous communication interface, the USART in Master SPI mode must generate the
interface clock to be shared with the slave devices. The interface clock is generated using the fractional Baud Rate
Generator, which is described in 23.3.2.2.1 The Fractional Baud Rate Generator.
Each Data bit is transmitted by pulling the data line high or low for one full clock period. The receiver will sample bits
in the middle of the transmitter hold period as shown in the figure below. It also shows how the timing scheme can be
configured using the Inverted I/O Enable (INVEN) bit in the PORTx.PINnCTRL register and the USART Clock Phase
(UCPHA) bit in the USARTn.CTRLC register.
UCPHA = 1
UCPHA = 0
Figure 23-5. Data Transfer Timing Diagrams
INVEN = 0
INVEN = 1
XCK
XCK
Data transmit (TxD)
Data transmit (TxD)
Data sample (RxD)
Data sample (RxD)
XCK
XCK
Data transmit (TxD)
Data transmit (TxD)
Data sample (RxD)
Data sample (RxD)
The table below further explains the figure above.
Table 23-2. Functionality of INVEN and UCPHA Bits
INVEN
UCPHA
Leading Edge (1)
Trailing Edge (1)
0
0
Rising, sample
Falling, transmit
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...........continued
INVEN
UCPHA
Leading Edge (1)
Trailing Edge (1)
0
1
Rising, transmit
Falling, sample
1
0
Falling, sample
Rising, transmit
1
1
Falling, transmit
Rising, sample
Note:
1. The leading edge is the first clock edge of a clock cycle. The trailing edge is the last clock edge of a clock
cycle.
Data Transmission
Data transmission in Master SPI mode is functionally identical to general USART operation as described in the
Operation section. The transmitter interrupt flags and corresponding USART interrupts are also identical. See
23.3.2.3 Data Transmission for further description.
Data Reception
Data reception in Master SPI mode is identical in function to general USART operation as described in the Operation
section. The receiver interrupt flags and the corresponding USART interrupts are also identical, aside from the
receiver error flags that are not in use and always read as ‘0’. See 23.3.2.4 Data Reception for further description.
USART in Master SPI Mode vs. SPI
The USART in Master SPI mode is fully compatible with a stand-alone SPI peripheral. Their data frame and timing
configurations are identical. Some SPI specific special features are, however, not supported with the USART in
Master SPI mode:
• Write Collision Flag Protection
• Double-Speed mode
• Multi-Master support
A comparison of the pins used with USART in Master SPI mode and with SPI is shown in the table below.
Table 23-3. Comparison of USART in Master SPI Mode and SPI Pins
USART
SPI
Comment
TXD
MOSI
Master out
RXD
MISO
Master in
XCK
SCK
Functionally identical
-
SS
Not supported by USART in Master SPI mode(1)
Note:
1. For the stand-alone SPI peripheral, this pin is used with the Multi-Master function or as a dedicated Slave
Select pin. The Multi-Master function is not available with the USART in Master SPI mode, and no dedicated
Slave Select pin is available.
23.3.3.2 Asynchronous Operation
23.3.3.2.1 Clock Recovery
Since there is no common clock signal when using Asynchronous mode, each communicating device generates
separate clock signals. These clock signals must be configured to run at the same baud rate for the communication
to take place. The devices, therefore, run at the same speed, but their timing is skewed in relation to each other. To
accommodate this, the USART features a hardware clock recovery unit which synchronizes the incoming
asynchronous serial frames with the internally generated baud rate clock.
The figure below illustrates the sampling process for the Start bit of an incoming frame. It shows the timing scheme
for both Normal and Double-Speed mode (the RXMODE bits in the USARTn.CTRLB register configured respectively
to 0x00 and 0x01). The sample rate for Normal mode is 16 times the baud rate, while the sample rate for DoubleSpeed mode is eight times the baud rate (see 23.3.3.2.4 Double-Speed Operation for more details). The horizontal
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arrows show the maximum synchronization error. Note that the maximum synchronization error is larger in DoubleSpeed mode.
Figure 23-6. 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 falling edge from Idle (high) state to the Start bit (low), the Start bit detection
sequence is initiated. In the figure above, sample 1 denotes the first sample reading ‘0’. The clock recovery logic then
uses three subsequent samples (samples 8, 9, and 10 in Normal mode, and samples 4, 5, 6 in Double-Speed mode)
to decide if a valid Start bit is received. If two or three samples read ‘0’, the Start bit is accepted. The clock recovery
unit is synchronized, and the data recovery can begin. If less than two samples read ‘0’, the Start bit is rejected. This
process is repeated for each Start bit.
23.3.3.2.2 Data Recovery
As with clock recovery, the data recovery unit samples at a rate 8 or 16 times faster than the baud rate depending on
whether it is running in Double-Speed or Normal mode, respectively. The figure below shows the sampling process
for reading a bit in a received frame.
Figure 23-7. 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
A majority voting technique is, like with clock recovery, used on the three center samples for deciding the logic level
of the received bit. The process is repeated for each bit until a complete frame is received.
The data recovery unit will only receive the first Stop bit while ignoring the rest if there are more. If the sampled Stop
bit is read ‘0’, the Frame Error flag will be set. The figure below shows the sampling of a Stop bit. It also shows the
earliest possible beginning of the next frame's Start bit.
Figure 23-8. 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 the figure
above. For Double-Speed mode the first low level must be delayed to point (B), being the first sample after the
majority vote samples. Point (C) marks a Stop bit of full length at the nominal baud rate.
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23.3.3.2.3 Error Tolerance
The speed of the internally generated baud rate and the externally received data rate should ideally be identical, but
due to natural clock source error, this is normally not the case. The USART is tolerant of such error, and the limits of
this tolerance make up what is sometimes known as the Operational Range.
The following tables list the operational range of the USART, being the maximum receiver baud rate error that can be
tolerated. Note that Normal-Speed mode has higher toleration of baud rate variations than Double-Speed mode.
Table 23-4. Recommended Maximum Receiver Baud Rate Error for Normal Speed Mode
D
Rslow [%]
Rfast [%]
Maximum Total Error [%]
Recommended Max. Receiver Error [%]
5
93.20
106.67
-6.80/+6.67
±3.0
6
94.12
105.79
-5.88/+5.79
±2.5
7
94.81
105.11
-5.19/+5.11
±2.0
8
95.36
104.58
-4.54/+4.58
±2.0
9
95.81
104.14
-4.19/+4.14
±1.5
10
96.17
103.78
-3.83/+3.78
±1.5
Note:
• D: The sum of character size and parity size (D = 5 to 10 bits)
• RSLOW: The ratio of the slowest incoming data rate that can be accepted in relation to the receiver baud rate
• RFAST: The ratio of the fastest incoming data rate that can be accepted in relation to the receiver baud rate
Table 23-5. Recommended Maximum Receiver Baud Rate Error for Double Speed Mode
D
Rslow [%]
Rfast [%]
Maximum Total Error [%]
Recommended Max. Receiver Error [%]
5
94.12
105.66
-5.88/+5.66
±2.5
6
94.92
104.92
-5.08/+4.92
±2.0
7
95.52
104.35
-4.48/+4.35
±1.5
8
96.00
103.90
-4.00/+3.90
±1.5
9
96.39
103.53
-3.61/+3.53
±1.5
10
96.70
103.23
-3.30/+3.23
±1.0
Note:
• D: The sum of character size and parity size (D = 5 to 10 bits)
• RSLOW: The ratio of the slowest incoming data rate that can be accepted in relation to the receiver baud rate
• RFAST: The ratio of the fastest incoming data rate that can be accepted in relation to the receiver baud rate
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.
The following equations are used to calculate the maximum ratio of the incoming data rate and the internal receiver
baud rate.
����� =
•
•
•
� �+1
� � + 1 + �� − 1
����� =
� �+2
� � + 1 + ��
D: The sum of character size and parity size (D = 5 to 10 bits)
S: Samples per bit. S = 16 for Normal Speed mode and S = 8 for Double-Speed mode.
SF: First sample number used for majority voting. SF = 8 for Normal-Speed mode and SF = 4 for Double-Speed
mode.
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•
•
•
SM: Middle sample number used for majority voting. SM = 9 for Normal-Speed mode and SM = 5 for DoubleSpeed mode.
RSLOW: The ratio of the slowest incoming data rate that can be accepted in relation to the receiver baud rate
RFAST: The ratio of the fastest incoming data rate that can be accepted in relation to the receiver baud rate
23.3.3.2.4 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 bits in the Control B (USARTn.CTRLB) register
to 0x01.
When enabled, the baud rate for a given asynchronous baud rate setting will be doubled. This is shown in the
equations in 23.3.2.2.1 The Fractional Baud Rate Generator. 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 23.3.3.2.3 Error Tolerance for more details.
23.3.3.2.5 Auto-Baud
The auto-baud feature lets the USART configure its BAUD register based on input from a communication device.
This allows the device to communicate autonomously with multiple devices communicating with different baud rates.
The USART peripheral features two auto-baud modes: Generic Auto-Baud mode and LIN Constrained Auto-Baud
mode.
Both auto-baud modes must receive an auto-baud frame as seen in the figure below.
Figure 23-9. Auto-Baud Timing
Break Field
Sync Field
Tbit
8 Tbit
The break field is detected when 12 or more consecutive low cycles are sampled and notifies the USART that it is
about to receive the synchronization field. After the break field, when the Start bit of the synchronization field is
detected, a counter running at the peripheral clock speed is started. The counter is then incremented for the next
eight Tbit of the synchronization field. When all eight bits are sampled, the counter is stopped. The resulting counter
value is in effect the new BAUD register value.
When the USART Receive mode is set to GENAUTO (the RXMODE bits in the USARTn.CTRLB register), the
Generic Auto-Baud mode is enabled. In this mode, one can set the Wait For Break (WFB) bit in the USARTn.STATUS
register to enable detection of a break field of any length (that is, also shorter than 12 cycles). This makes it possible
to set an arbitrary new baud rate without knowing the current baud rate. If the measured sync field results in a valid
BAUD value (0x0064 - 0xFFFF), the BAUD register is updated.
When USART Receive mode is set to LINAUTO mode (the RXMODE bits in the USARTn.CTRLB register), it follows
the LIN format. The WFB functionality of the Generic Auto-Baud mode is not compatible with the LIN Constrained
Auto-Baud mode. This means that the received signal must be low for 12 peripheral clock cycles or more for a break
field to be valid. When a break field has been detected, the USART expects the following synchronization field
character to be 0x55. If the received synchronization field character is not 0x55, the Inconsistent Sync Field Error
Flag (the ISFIF bit in the USARTn.STATUS register) is set, and the baud rate is unchanged.
23.3.3.2.6 Half Duplex Operation
Half duplex is a type of communication where two or more devices may communicate with each other, but only one at
a time. The USART can be configured to operate in the following half duplex modes:
• One-Wire mode
• RS-485 mode
One-Wire Mode
One-Wire mode is enabled by setting the Loop-Back Mode Enable (LBME) bit in the USARTn.CTRLA register. This
will enable an internal connection between the TXD pin and the USART receiver, making the TXD pin a combined
TxD/RxD line. The RXD pin will be disconnected from the USART receiver and may be controlled by a different
peripheral.
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In One-Wire mode, multiple devices are able to manipulate the TxD/RxD line at the same time. In the case where one
device drives the pin to a logical high level (VCC), and another device pulls the line low (GND), a short will occur. To
accommodate this, the USART features an Open-Drain mode (the ODME bit in the USARTn.CTRLB register) which
prevents the transmitter from driving a pin to a logical high level, thereby constraining it to only be able to pull it low.
Combining this function with the internal pull-up feature (the PULLUPEN bit in the PORTx.PINnCTRL register) will let
the line be held high through a pull-up resistor, allowing any device to pull it low. When the line is pulled low the
current from VCC to GND will be limited by the pull-up resistor. The TXD pin is automatically set to output by hardware
when the Open-Drain mode is enabled.
When the USART is transmitting to the TxD/RxD line, it will also receive its own transmission. This can be used to
check for overlapping transmissions by checking if the received data are the same as the transmitted data as it
should be.
RS-485 Mode
RS-485 is a communication standard supported by the USART peripheral. It is a physical interface that defines the
setup of a communication circuit. Data are transmitted using differential signaling, making communication robust
against noise. RS-485 is enabled by writing to the RS485 bit field (USARTn.CTRLA).
The RS-485 mode supports external line driver devices that convert a single USART transmission into corresponding
differential pair signals. Writing RS485[0] to ‘1’ enables the automatic control of the XDIR pin that can be used to
enable transmission or reception for the line driver device. The USART automatically drives the XDIR pin high while
the USART is transmitting and pulls it low when the transmission is complete. An example of such a circuit is shown
in the figure below.
Figure 23-10. RS-485 Bus Connection
Line Driver
TXD
TX Driver
XDIR
Differential Bus
+
-
USART
RX Driver
RXD
The XDIR 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 XDIR pin will remain high for the complete frame including Stop bit(s).
Figure 23-11. XDIR Drive Timing
TxD
St
0
1
2
3
4
5
6
7
Sp1
XDIR
Guard
time
Stop
Writing RS485[1] to ‘1’ enables the RS-485 mode which automatically sets the TXD pin to output one clock cycle
before starting transmission and sets it back to input when the transmission is complete.
RS-485 mode is compatible with One-Wire mode. One-Wire mode enables an internal connection between the TXD
pin and the USART receiver, making the TXD pin a combined TxD/RxD line. The RXD pin will be disconnected from
the USART receiver and may be controlled by a different peripheral. An example of such a circuit is shown in the
figure below.
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Figure 23-12. RS-485 with Loop-Back Mode Connection
TXD
Line Driver
TX Driver
XDIR
Differential Bus
+
-
USART
RXD
RX Driver
23.3.3.2.7 IRCOM Mode of Operation
The USART peripheral can be configured in Infrared Communication mode (IRCOM) which is IrDA® 1.4 compatible
with baud rates up to 115.2 kbps. When enabled, the IRCOM mode enables infrared pulse encoding/decoding for the
USART.
Figure 23-13. Block Diagram
IRCOM
Event System
Events
Encoded RxD
Pulse
Decoding
Decoded RxD
USART
Pulse
Encoding
RXD
TXD
Decoded RxD
Encoded RxD
The USART is set in IRCOM mode by writing 0x02 to the CMODE bits in the USARTn.CTRLC register. The data on
the TXD/RXD pins are the inverted values of the transmitted/received infrared pulse. It is also possible to select an
event channel from the Event System as an input for the IRCOM receiver. This enables the IRCOM to receive input
from the I/O pins or sources other than the corresponding RXD pin. This will disable the RxD 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 the 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.
When IRCOM mode is enabled, Double-Speed mode cannot be used for the USART.
23.3.4
Additional Features
23.3.4.1 Parity
Parity bits can be used by the USART to check the validity of a data frame. The Parity bit is set by the transmitter
based on the number of bits with the value of ‘1’ in a transmission and controlled by the receiver upon reception. If
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the Parity bit is inconsistent with the transmission frame, the receiver may assume that the data frame has been
corrupted.
Even or odd parity can be selected for error checking by writing the Parity Mode (PMODE) bits in the
USARTn.CTRLC register. If even parity is selected, the Parity bit is set to ‘1’ if the number of Data bits with value ‘1’
is odd (making the total number of bits with value ‘1’ even). If odd parity is selected, the Parity bit is set to ‘1’ if the
number of data bits with value ‘1’ is even (making the total number of bits with value ‘1’ 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 (the PERR bit in the
USARTn.RXDATAH register) is set.
If LIN Constrained Auto-Baud mode is enabled (RXMODE = 0x03 in the USARTn.CTRLB register), a parity check is
only performed on the protected identifier field. A parity error is detected if one of the equations below is not true,
which sets the Parity Error flag.
�0 = ��0 XOR ��1 XOR ��2 XOR ��4
�1 = NOT ��1 XOR ��3 XOR ��4 XOR ��5
Figure 23-14. Protected Identifier Field and Mapping of Identifier and Parity Bits
Protected identifier field
St
ID0 ID1 ID2 ID3 ID4 ID5 P0
P1
Sp
23.3.4.2 Start-of-Frame Detection
The Start-of-Frame Detection feature enables the USART to wake up from Standby Sleep mode upon data reception.
When a high-to-low transition is detected on the RXD pin, the oscillator is powered up, and the USART peripheral
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. The 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 section.
If a false Start bit is detected, the device will, if another wake-up source has not been triggered, go back into the
Standby Sleep mode.
The Start-of-Frame detection works in Asynchronous mode only. It is enabled by writing the Start-of-Frame Detection
Enable (SFDEN) bit in the USARTn.CTRLB register. If a Start bit is detected while the device is in Standby Sleep
mode, the USART Receive Start Interrupt Flag (RXSIF) bit is set.
The USART Receive Complete Interrupt Flag (RXCIF) bit and the RXSIF bit share the same interrupt line, but each
has its dedicated interrupt settings. The table below shows the USART Start Frame Detection modes, depending on
the interrupt setting.
Table 23-6. 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
Disabled
Enabled
System/all clocks are awakened on Receive Complete interrupt.
1
Enabled
x
System/all clocks are awakened when a Start bit is detected.
Note: The SLEEP instruction will not shut down the oscillator if there is ongoing communication.
23.3.4.3 Multiprocessor Communication
The Multiprocessor Communication mode (MPCM) 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
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mode is enabled by writing a ‘1’ to the MPCM bit in the Control B register (USARTn.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 ‘1’, the frame contains an address. When the frame type bit is ‘0’, the frame is a data frame. If 5to 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.
23.3.4.3.1 Using Multiprocessor Communication
The following procedure should be used to exchange data in Multiprocessor Communication mode (MPCM):
1.
2.
3.
4.
All slave MCUs are in Multiprocessor Communication mode.
The master MCU sends an address frame, and all slaves receive and read this frame.
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.
5.
The process then repeats from step 2.
23.3.5
Events
The USART can generate the events described in the table below.
Table 23-7. Event Generators in USART
Generator Name
Description
Peripheral Event
USARTn
XCK
The clock signal in SPI Master
mode and Synchronous USART
Master mode
Event Type
Generating Clock
Domain
Length of Event
Pulse
CLK_PER
One XCK period
The table below describes the event user and its associated functionality.
Table 23-8. Event Users in USART
User Name
23.3.6
Peripheral
Input
USARTn
IREI
Description
USARTn IrDA event input
Input Detection
Async/Sync
Pulse
Sync
Interrupts
Table 23-9. Available Interrupt Vectors and Sources
Name Vector Description
Conditions
RXC
Receive Complete interrupt
DRE
Data Register Empty
interrupt
The transmit buffer is empty/ready to receive new data (DREIE)
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)
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•
•
•
There is unread data in the receive buffer (RXCIE)
Receive of Start-of-Frame detected (RXSIE)
Auto-Baud Error/ISFIF flag set (ABEIE)
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When an Interrupt condition occurs, the corresponding Interrupt flag is set in the STATUS register
(USARTn.STATUS).
An interrupt source is enabled or disabled by writing to the corresponding bit in the Control A register
(USARTn.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 USARTn.STATUS register for details
on how to clear Interrupt flags.
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23.4
Register Summary - USARTn
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x07
RXDATAL
RXDATAH
TXDATAL
TXDATAH
STATUS
CTRLA
CTRLB
CTRLC
CTRLC
0x08
BAUD
0x0A
0x0B
0x0C
0x0D
0x0E
CTRLD
DBGCTRL
EVCTRL
TXPLCTRL
RXPLCTRL
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
15:8
7:0
7:0
7:0
7:0
7:0
23.5
DATA[7:0]
RXCIF
BUFOVF
FERR
PERR
DATA[8]
DATA[7:0]
RXCIF
TXCIF
RXCIE
TXCIE
RXEN
TXEN
CMODE[1:0]
CMODE[1:0]
DREIF
DREIE
RXSIF
RXSIE
SFDEN
PMODE[1:0]
ISFIF
LBME
ODME
SBMODE
DATA[8]
BDF
WFB
ABEIE
RS485[1:0]
RXMODE[1:0]
MPCM
CHSIZE[2:0]
UDORD
UCPHA
BAUD[7:0]
BAUD[15:8]
ABW[1:0]
DBGRUN
IREI
TXPL[7:0]
RXPL[6:0]
Register Description
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23.5.1
Receiver Data Register Low Byte
Name:
Offset:
Reset:
Property:
RXDATAL
0x00
0x00
-
Reading the USARTn.RXDATAL register will return the contents of the eight least significant RXDATA bits.
The receive buffer consists of a two-level buffer. The data buffer and the corresponding flags in the high byte of
RXDATA will change state whenever the receive buffer is accessed (read). If the CHSIZE bits in the USARTn.CTRLC
register are set to 9BIT Low byte first, read the USARTn.RXDATAL register before the USARTn.RXDATAH register.
Otherwise, always read the USARTn.RXDATAH register before the USARTn.RXDATAL register in order to get the
correct flags.
Bit
7
6
5
4
3
2
1
0
R
0
R
0
R
0
R
0
DATA[7:0]
Access
Reset
R
0
R
0
R
0
R
0
Bits 7:0 – DATA[7:0] Receiver Data Register
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23.5.2
Receiver Data Register High Byte
Name:
Offset:
Reset:
Property:
RXDATAH
0x01
0x00
-
Reading the USARTn.RXDATAH register location will return the contents of the ninth RXDATA bit plus Status bits.
The receive buffer consists of a two-level buffer. The data buffer and the corresponding flags in the high byte of
USARTn.RXDATAH will change state whenever the receive buffer is accessed (read). If the CHSIZE bits in the
USARTn.CTRLC register are set to 9BIT Low byte first, read the USARTn.RXDATAL register before the
USARTn.RXDATAH register. Otherwise, always read the USARTn.RXDATAH register before the USARTn.RXDATAL
register in order to get the correct flags.
Bit
Access
Reset
7
RXCIF
R
0
6
BUFOVF
R
0
5
4
3
2
FERR
R
0
1
PERR
R
0
0
DATA[8]
R
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 (that is,
does not contain any unread data). When the receiver is disabled the receive buffer will be flushed and,
consequently, the RXCIF bit will become ‘0’.
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
(USARTn.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. This bit
is set if the received character had a frame error, that is, when the first Stop bit was ‘0’ and cleared when the Stop bit
of the received data is ‘1’. This bit is valid until the receive buffer (USARTn.RXDATAL) is read. The FERR bit is not
affected by the SBMODE bit in the USARTn.CTRLC register 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 bit will always be read as ‘0’. This bit is valid until the receive buffer
(USARTn.RXDATAL) is read. For details on parity calculation refer to 23.3.4.1 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 the DATA[8] bit in the
USARTn.RXDATAH register reads low.
This flag is not used in Master SPI mode of operation.
Bit 0 – DATA[8] Receiver Data Register
When the USART receiver is configured to LINAUTO mode, this bit indicates if the received data are within the
response space of a LIN frame. If the received data are in the protected identifier field, this bit will be read as ‘0’.
Otherwise, the bit will be read as ‘1’. For a receiver mode other than LINAUTO mode, the DATA[8] bit holds the ninth
data bit in the received character when operating with serial frames with nine data bits.
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23.5.3
Transmit Data Register Low Byte
Name:
Offset:
Reset:
Property:
TXDATAL
0x02
0x00
-
The Transmit Data Buffer (TXB) register will be the destination for data written to the USARTn.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 USARTn.STATUS register is set. Data written to
the DATA bits when the DREIF flag is not set will be ignored by the USART transmitter. When data are 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 are then transmitted on the TXD pin.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
DATA[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – DATA[7:0] Transmit Data Register
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23.5.4
Transmit Data Register High Byte
Name:
Offset:
Reset:
Property:
TXDATAH
0x03
0x00
-
The USARTn.TXDATAH register 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 the USARTn.TXDATAL register
except if the CHSIZE bits in the USARTn.CTRLC register are is set to 9BIT low byte first, where the
USARTn.TXDATAL register should be written first.
This bit is unused in Master SPI mode of operation.
Bit
7
6
5
4
3
Access
Reset
2
1
0
DATA[8]
W
0
Bit 0 – DATA[8] Transmit Data Register
This bit is used when CHSIZE=9BIT in the USARTn.CTRLC register.
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23.5.5
USART Status Register
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
RXCIF
R
0
STATUS
0x04
0x00
-
6
TXCIF
R/W
0
5
DREIF
R
1
4
RXSIF
R/W
0
3
ISFIF
R/W
0
2
1
BDF
R/W
0
0
WFB
R/W
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
(that is, does not contain any unread data). When the receiver is disabled the receive buffer will be flushed and,
consequently, the RXCIF bit will become ‘0’.
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
This flag 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 but has not yet been
moved into the Shift register. The DREIF bit 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
This flag indicates a valid Start condition on the RxD line. The flag is set when the system is in Standby Sleep mode
and a high (IDLE) to low (START) valid transition is detected on the RxD line. If the start detection is not enabled, the
RXSIF bit will always read ‘0’. This flag can only be cleared by writing a ‘1’ to its bit location. This flag is not used in
the Master SPI mode operation.
Bit 3 – ISFIF Inconsistent Sync Field Interrupt Flag
This flag is set when the auto-baud is enabled and the Sync Field bit time is 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 flag is intended for USART configured to LINAUTO Receive mode. 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 the next data are received. The bit will behave identically when the 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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Bit 0 – WFB Wait For Break
Writing this bit to ‘1’ will register the next low and high transition on the 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 allows the
user to set any BAUD rate through BREAK and SYNC as long as it falls within the valid range of the USARTn.BAUD
register. This bit will always read ‘0’.
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23.5.6
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
RXCIE
R/W
0
CTRLA
0x05
0x00
-
6
TXCIE
R/W
0
5
DREIE
R/W
0
4
RXSIE
R/W
0
3
LBME
R/W
0
2
ABEIE
R/W
0
1
0
RS485[1:0]
R/W
0
R/W
0
Bit 7 – RXCIE Receive Complete Interrupt Enable
This bit enables the Receive Complete interrupt (interrupt vector RXC). The enabled interrupt will be triggered when
the RXCIF bit in the USARTn.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 bit in the USARTn.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 bit 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 a ‘1’ to this bit enables an internal connection between the TXD pin and the USART receiver and disables
input from the RXD pin to the USART receiver.
Bit 2 – ABEIE Auto-baud Error Interrupt Enable
Writing a ‘1’ to this bit enables the auto-baud error interrupt on interrupt vector RXC. The enabled interrupt will trigger
for conditions where the ISFIF flag is set.
Bits 1:0 – RS485[1:0] RS-485 Mode
These bits enable the RS-485 and select the operation mode. Writing RS485[0] to ‘1’ enables the RS-485 mode
which automatically drives the XDIR pin high one clock cycle before starting transmission and pulls it low again when
the transmission is complete. Writing RS485[1] to ‘1’ enables the RS-485 mode which automatically sets the TXD pin
to output one clock cycle before starting transmission and sets it back to input when the transmission is complete.
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23.5.7
Control B
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
RXEN
R/W
0
CTRLB
0x06
0x00
-
6
TXEN
R/W
0
5
4
SFDEN
R/W
0
3
ODME
R/W
0
2
1
RXMODE[1:0]
R/W
R/W
0
0
0
MPCM
R/W
0
Bit 7 – RXEN Receiver Enable
Writing this bit to ‘1’ enables the USART receiver. 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 auto-baud
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 the TXEN bit to ‘0’) will not become effective until ongoing and
pending transmissions are completed (that is, when the Transmit Shift register and Transmit Buffer register does not
contain data to be transmitted). When the transmitter is disabled, it will no longer override the TXD pin, and the pin
direction is automatically set as input by hardware, even if it was configured as output by the user.
Bit 4 – SFDEN Start-of-Frame Detection Enable
Writing this bit to ‘1’ enables the USART Start-of-Frame Detection mode. The Start-of-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’ gives the TXD pin open-drain functionality. Internal Pull-up should be enabled for the TXD pin
(the PULLUPEN bit in the PORTx.PINnCTRL register) to prevent the line from floating when a logic ‘1’ is output to
the TXD pin.
Bits 2:1 – RXMODE[1:0] Receiver Mode
Writing these bits select the receiver mode of the USART. In the 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 the RXMODE bits should always be written to 0x00.
RXMODE must be 0x00 when the USART Communication mode is configured to IRCOM. Setting RXMODE to
GENAUTO enables generic auto-baud where the SYNC character is valid when eight bits alternating between ‘0’ and
‘1’ have 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 every two bits falls within 32 ±6 baud samples
of the internal baud rate and match data value 0x55. The GENAUTO and LINAUTO modes are only supported for
USART operated in Asynchronous Slave mode.
Value
Name
Description
0x00
NORMAL
Normal USART mode, standard transmission speed
0x01
CLK2X
Normal USART mode, double transmission speed
0x02
GENAUTO
Generic Auto-Baud mode
0x03
LINAUTO
LIN Constrained Auto-Baud mode
Bit 0 – MPCM Multi-Processor Communication Mode
Writing a ‘1’ to this bit enables the Multi-Processor Communication mode: The USART receiver ignores all incoming
frames that do not contain address information. The transmitter is unaffected by the MPCM setting. For more
information see 23.3.4.3 Multiprocessor Communication.
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23.5.8
Control C - Asynchronous Mode
Name:
Offset:
Reset:
Property:
CTRLC
0x07
0x03
-
This register description is valid for all modes except the Master SPI mode. When the USART Communication Mode
bits (CMODE) in this register are written to ‘MSPI’, see CTRLC - Master SPI mode for the correct description.
Bit
Access
Reset
7
6
CMODE[1:0]
R/W
R/W
0
0
5
4
PMODE[1:0]
R/W
R/W
0
0
3
SBMODE
R/W
0
2
R/W
0
1
CHSIZE[2:0]
R/W
1
0
R/W
1
Bits 7:6 – CMODE[1:0] USART Communication Mode
Writing these bits select the Communication mode of the USART.
Writing a 0x03 to these bits alters the available bit fields in this register, see CTRLC - Master SPI mode.
Value
Name
Description
0x00
ASYNCHRONOUS
Asynchronous USART
0x01
SYNCHRONOUS
Synchronous USART
0x02
IRCOM
Infrared Communication
0x03
MSPI
Master SPI
Bits 5:4 – PMODE[1:0] Parity Mode
Writing these bits enable and select 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 (PERR) flag in the STATUS (USARTn.STATUS) register if a mismatch is detected.
Value
Name
Description
0x0
DISABLED
Disabled
0x1
Reserved
0x2
EVEN
Enabled, even parity
0x3
ODD
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.
Value
Description
0
1 Stop bit
1
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
Name
Description
0x00
5BIT
5-bit
0x01
6BIT
6-bit
0x02
7BIT
7-bit
0x03
8BIT
8-bit
0x04
Reserved
0x05
Reserved
0x06
9BITL
9-bit (Low byte first)
0x07
9BITH
9-bit (High byte first)
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23.5.9
Control C - Master SPI Mode
Name:
Offset:
Reset:
Property:
CTRLC
0x07
0x00
-
This register description is valid only when the USART is in Master SPI mode (CMODE written to MSPI). For other
CMODE values, see CTRLC - Asynchronous mode.
See 23.3.3.1.3 USART in Master SPI Mode for a full description of the Master SPI mode operation.
Bit
Access
Reset
7
6
CMODE[1:0]
R/W
R/W
0
0
5
4
3
2
UDORD
R/W
0
1
UCPHA
R/W
0
0
Bits 7:6 – CMODE[1:0] USART Communication Mode
Writing these bits select the communication mode of the USART.
Writing a value different than 0x03 to these bits alters the available bit fields in this register, see CTRLC Asynchronous mode.
Value
Name
Description
0x00
ASYNCHRONOUS
Asynchronous USART
0x01
SYNCHRONOUS
Synchronous USART
0x02
IRCOM
Infrared Communication
0x03
MSPI
Master SPI
Bit 2 – UDORD USART Data Order
Writing this bit selects the frame format.
The receiver and transmitter use the same setting. Changing the setting of the UDORD bit will corrupt all ongoing
communication for both the receiver and the transmitter.
Value
Description
0
MSb of the data word is transmitted first
1
LSb of the data word is transmitted first
Bit 1 – UCPHA USART Clock Phase
The UCPHA bit setting determines if data are sampled on the leading (first) edge or tailing (last) edge of XCKn. Refer
to Clock Generation for details.
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23.5.10 Baud Register
Name:
Offset:
Reset:
Property:
BAUD
0x08
0x00
-
The USARTn.BAUDL and USARTn.BAUDH register pair represents the 16-bit value, USARTn.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.
Ongoing transmissions of the transmitter and receiver will be corrupted if the baud rate is changed. Writing to this
register will trigger an immediate update of the baud rate prescaler. For more information on how to set the baud rate,
see Table 23-1, Equations for Calculating Baud Rate Register Setting.
Bit
15
14
13
12
11
10
9
8
R/W
0
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
BAUD[15:8]
Access
Reset
Bit
R/W
0
R/W
0
R/W
0
R/W
0
7
6
5
4
BAUD[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
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.
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23.5.11 Control D
Name:
Offset:
Reset:
Property:
Bit
CTRLD
0x0a
0x00
-
7
6
5
4
3
2
1
0
ABW[1:0]
Access
Reset
R/W
0
R/W
0
Bits 7:6 – ABW[1:0] Auto-baud Window Size
These bits set the window size for which the SYNC character bits are validated.
Value
Name
Description
0x00
WDW0
18% tolerance
0x01
WDW1
15% tolerance
0x02
WDW2
21% tolerance
0x03
WDW3
25% tolerance
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23.5.12 Debug Control Register
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x0B
0x00
-
6
5
4
3
2
Access
Reset
1
0
DBGRUN
R/W
0
Bit 0 – DBGRUN Debug Run
Value
Description
0
The peripheral is halted in Break Debug mode and ignores events
1
The peripheral will continue to run in Break Debug mode when the CPU is halted
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23.5.13 IrDA Control Register
Name:
Offset:
Reset:
Property:
Bit
7
EVCTRL
0x0C
0x00
-
6
5
4
3
Access
Reset
2
1
0
IREI
R/W
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 RXD pin is automatically disabled.
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23.5.14 IRCOM Transmitter Pulse Length Control Register
Name:
Offset:
Reset:
Property:
Bit
7
TXPLCTRL
0x0D
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
TXPL[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – TXPL[7:0] Transmitter Pulse Length
This 8-bit value sets the pulse modulation scheme for the transmitter. Setting this register will have effect only if
IRCOM mode is selected by the USART, and it must be configured before the USART transmitter is enabled (TXEN).
Value
Description
0x00
3/16 of the baud rate period pulse modulation is used.
0x01-0xF Fixed pulse length coding is used. The 8-bit value sets the number of system clock periods for the
E
pulse. The start of the pulse will be synchronized with the rising edge of the baud rate clock.
0xFF
Pulse coding disabled. 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.
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23.5.15 IRCOM Receiver Pulse Length Control Register
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
RXPLCTRL
0x0E
0x00
-
6
5
4
R/W
0
R/W
0
R/W
0
3
RXPL[6:0]
R/W
0
2
1
0
R/W
0
R/W
0
R/W
0
Bits 6:0 – RXPL[6:0] Receiver Pulse Length
This 7-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, and it must be configured before the USART receiver is enabled (RXEN).
Value
Description
0x00
Filtering disabled.
0x01-0x7 Filtering enabled. The value of RXPL+1 represents the number of samples required for a received
F
pulse to be accepted.
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SPI - Serial Peripheral Interface
24.
SPI - Serial Peripheral Interface
24.1
Features
•
•
•
•
•
•
•
•
24.2
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 full duplex communication between an AVR device and peripheral devices or between several
microcontrollers. The SPI peripheral can be configured as either 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
desired slave's slave select (SS) signal low. Master and slave prepare the data to be sent to 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.
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SPI - Serial Peripheral Interface
24.2.1
Block Diagram
Figure 24-1. SPI Block Diagram
MASTER
SLAVE
Transmit Data Register
(DATA)
Transmit Data Register
(DATA)
Transmit Buffer
Register
Transmit Buffer
Register
LSb
MSb
MISO
MISO
MOSI
MOSI
SCK
SCK
SS
SS
8-bit Shift Register
MSb
LSb
8-bit Shift Register
SPI CLOCK
GENERATOR
First Receive Buffer
Register
First Receive Buffer
Register
Receive Buffer
Register
Second Receive Buffer
Register
Receive Data Register
(DATA)
Receive Data Register
(DATA)
The SPI is built around an 8-bit Shift register that will shift data out and in at the same time. The Transmit Data
register and the Receive Data register are not physical registers but are mapped to other registers when written or
read: Writing the Transmit Data register (SPIn.DATA) will write the Shift register in Normal mode and the Transmit
Buffer register in Buffer mode. Reading the Receive Data register (SPIn.DATA) will read the First Receive Buffer
register in normal mode and the Second Receive Data register in Buffer mode.
In Master mode, the SPI has a clock generator to generate the SCK clock. In Slave mode, the received SCK clock is
synchronized and sampled to trigger the shifting of data in the Shift register.
24.2.2
Signal Description
Table 24-1. Signals in Master and Slave Mode
Signal
Description
Pin Configuration
Master Mode
Slave Mode
MOSI
Master Out Slave In
User defined
Input
MISO
Master In Slave Out
Input
User defined
SCK
Slave clock
User defined
Input
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SPI - Serial Peripheral Interface
...........continued
Signal
SS
Description
Slave select
Pin Configuration
Master Mode
Slave Mode
User defined
Input
When the SPI module is enabled, the data direction of the MOSI, MISO, SCK, and SS pins is overridden according to
Table 24-1.
The data direction of the pins with "User defined" pin configuration is not controlled by the SPI: The data direction is
controlled by the application software configuring the port peripheral. If these pins are configured with data direction
as input, they can be used as regular I/O pin inputs. If these pins are configured with data direction as output, their
output value is controlled by the SPI. The MISO pin has a special behavior: When the SPI is in Slave mode and the
MISO pin is configured as an output, the SS pin controls the output buffer of the pin: If SS is low, the output buffer
drives the pin, if SS is high, the pin is tri-stated.
The data direction of the pins with "Input" pin configuration is controlled by the SPI hardware.
24.3
Functional Description
24.3.1
Initialization
Initialize the SPI to a basic functional state by following these steps:
1. Configure the SS pin in the port peripheral.
2. Select SPI Master/Slave operation by writing the Master/Slave Select bit (MASTER) in the Control A register
(SPIn.CTRLA).
3. In Master mode, select the clock speed by writing the Prescaler bits (PRESC) and the Clock Double bit
(CLK2X) in SPIn.CTRLA.
4. Optional: Select the Data Transfer mode by writing to the MODE bits in the Control B register (SPIn.CTRLB).
5. Optional: Write the Data Order bit (DORD) in SPIn.CTRLA.
6. Optional: Setup Buffer mode by writing BUFEN and BUFWR bits in the Control B register (SPIn.CTRLB).
7. Optional: To disable the multi-master support in Master mode, write ‘1’ to the Slave Select Disable bit (SSD) in
SPIn.CTRLB.
8. Enable the SPI by writing a ‘1’ to the ENABLE bit in SPIn.CTRLA.
24.3.2
Operation
24.3.2.1 Master Mode Operation
When the SPI is configured in Master mode, a write to the SPIn.DATA register will start a new transfer. The SPI clock
generator starts and the hardware shifts the eight bits into the selected slave. After the byte is shifted out the interrupt
flag is set (IF flag in SPIn.INTFLAGS). The SPI master can operate in two modes, Normal and Buffered, as explained
below.
24.3.2.1.1 SS Pin Functionality in Master Mode - Multi-Master Support
In Master mode, the Slave Select Disable bit in Control Register B (SSD bit in SPIn.CTRLB) controls how the SPI
uses the SS line.
•
•
If SSD in SPIn.CTRLB is ‘0’, the SPI can use the SS pin to transition from Master to Slave mode. This allows
multiple SPI masters on the same SPI bus.
If SSD in SPIn.CTRLB is ‘1’, the SPI does not use the SS pin, and it can be used as a regular I/O pin, or by
other peripheral modules.
If SSD in SPIn.CTRLB is ‘0’ and the SS is configured as an output pin, it can be used as a regular I/O pin or by other
peripheral modules, and will not affect the SPI system.
If the SSD bit in SPIn.CTRLB is ‘0’ and the SS is configured as an input pin, the SS pin must be held high to ensure
master SPI operation. A low level will be interpreted as another master is trying to take control of the bus. This will
switch the SPI into Slave mode and the hardware of the SPI will perform the following actions:
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SPI - Serial Peripheral Interface
1.
2.
The master bit in the SPI Control A Register (MASTER in SPIn.CTRLA) is cleared and the SPI system
becomes a slave. The direction of the pins will be switched according to Table 24-2.
The interrupt flag in the Interrupt Flags register (IF in SPIn.INTFLAGS) will be set. If the interrupt is enabled
and the global interrupts are enabled the interrupt routine will be executed.
Table 24-2. Overview of the SS Pin Functionality when the SSD Bit in SPIn.CTRLB is Zero
SS Configuration
SS Pin-Level
Description
Input
High
Master activated (selected)
Low
Master deactivated, switched to
Slave mode
High
Master activated (selected)
Output
Low
Note:
If the AVR device is configured for Master mode and it cannot be ensured that the SS pin will stay high between two
transmissions, the status of the Master bit (the MASTER bit in SPIn.CTRLA) has to be checked before a new byte is
written. After the Master bit has been cleared by a low level on the SS line, it must be set by the application to reenable the SPI Master mode.
24.3.2.1.2 Normal Mode
In Normal mode, the system is single-buffered in the transmit direction and double-buffered in the receive direction.
This influences the data handling in the following ways:
1. New bytes to be sent cannot be written to the Data register (SPIn.DATA) before the entire transfer has
completed. A premature write will cause corruption of the transmitted data, and the hardware will set the Write
Collision Flag (WRCOL in SPIn.INTFLAGS).
2. Received bytes are written to the First Receive Buffer register immediately after the transmission is completed.
3. The First Receive Buffer register has to be read before the next transmission is completed or data will be lost.
This register is read by reading SPIn.DATA.
4. The Transmit Buffer register and Second Receive Buffer register are not used in Normal mode.
After a transfer has completed, the Interrupt Flag will be set in the Interrupt Flags register (IF in SPI.INTFLAGS). This
will cause the corresponding interrupt to be executed if this interrupt and the global interrupts are enabled. Setting the
Interrupt Enable (IE) bit in the Interrupt Control register (SPIn.INTCTRL) will enable the interrupt.
24.3.2.1.3 Buffer Mode
The Buffer mode is enabled by setting the BUFEN bit in SPIn.CTRLB. The BUFWR bit in SPIn.CTRLB has no effect
in Master mode. In Buffer mode, the system is double-buffered in the transmit direction and triple-buffered in the
receive direction. This influences the data handling the following ways:
1. New bytes to be sent can be written to the Data register (SPIn.DATA) as long as the Data Register Empty
Interrupt Flag (DREIF) in the Interrupt Flag Register (SPIn.INTFLAGS) is set. The first write will be transmitted
right away and the following write will go to the Transmit Buffer register.
2. A received byte is placed in a two-entry RX FIFO comprised of the First and Second Receive Buffer registers
immediately after the transmission is completed.
3. The Data register is used to read from the RX FIFO. The RX FIFO must be read at least every second transfer
to avoid any loss of data.
If both the Shift register and the Transmit Buffer register becomes empty, the Transfer Complete Interrupt Flag
(TXCIF) in the Interrupt Flags register (SPIn.INTFLAGS) will be set. This will cause the corresponding interrupt to be
executed if this interrupt and the global interrupts are enabled. Setting the Transfer Complete Interrupt Enable
(TXCIE) in the Interrupt Control register (SPIn.INTCTRL) enables the Transfer Complete Interrupt.
24.3.2.2 Slave Mode
In Slave mode, the SPI peripheral receives SPI clock and Slave Select from a Master. Slave mode supports three
operational modes: One unbuffered mode and two buffered modes. In 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 peripheral clock cycles.
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Preliminary Datasheet
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ATmega3208/3209
SPI - Serial Peripheral Interface
24.3.2.2.1 SS Pin Functionality in Slave Mode
The Slave Select (SS) pin plays a central role in the operation of the SPI. Depending on the mode the SPI is in and
the configuration of this pin, it can be used to activate or deactivate devices. The SS pin is used as a Chip Select pin.
In Slave mode, SS, MOSI, and SCK are always inputs. The behavior of the MISO pin depends on the configured data
direction of the pin in the port peripheral and the value of SS: When SS is driven low, the SPI is activated and will
respond to received SCK pulses by clocking data out on MISO if the user has configured the data direction of the
MISO pin as an output. When SS is driven high the SPI is deactivated, meaning that it will not receive incoming data.
If the MISO pin data direction is configured as an output, the MISO pin will be tristated. The following table shows an
overview of the SS pin functionality.
Table 24-3. Overview of the SS Pin Functionality
SS Configuration
SS Pin-Level
Always Input
Description
MISO Pin Mode
Port Direction =
Output
Port Direction =
Input
High
Slave deactivated
(deselected)
Tri-stated
Input
Low
Slave activated
(selected)
Output
Input
Note:
In Slave mode, the SPI state machine will be reset when the SS pin is brought high. If the SS is brought high during a
transmission, the SPI will stop sending and receiving immediately and both data received and data sent must be
considered as 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.
24.3.2.2.2 Normal Mode
In Normal mode, the SPI peripheral will remain idle as long as the SS pin is driven high. In this state, the software
may update the contents of the SPIn.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 SPIn.INTFLAGS is set.
The user application may continue placing new data to be sent into the SPIn.DATA register before reading the
incoming data. New bytes to be sent cannot be written to SPIn.DATA before the entire transfer has completed. A
premature write will be ignored, and the hardware will set the Write Collision Flag (WRCOL in SPIn.INTFLAGS).
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.
Figure 24-2. SPI Timing Diagram in Normal Mode (Buffer Mode Not Enabled)
SS
SCK
Write DATA
Write value
0x43
0x44
0x45
0x46
WRCOL
IF
Shift Register
Data sent
0x43
0x43
0x44
0x44
0x46
0x46
The figure above shows three transfers and one write to the DATA register while the SPI is busy with a transfer. This
write will be ignored and the Write Collision Flag (WRCOL in SPIn.INTFLAGS) is set.
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Preliminary Datasheet
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ATmega3208/3209
SPI - Serial Peripheral Interface
24.3.2.2.3 Buffer Mode
To avoid data collisions, the SPI peripheral can be configured in buffered mode by writing a ‘1’ to the Buffer Mode
Enable bit in the Control B register (BUFEN in SPIn.CTRLB). In this mode, the SPI has additional interrupt flags and
extra buffers. The extra buffers are shown in Figure 24-1. There are two different modes for the Buffer mode,
selected with the Buffer mode Wait for Receive bit (BUFWR). The two different modes are described below with
timing diagrams.
Figure 24-3. SPI Timing Diagram in Buffer Mode with BUFWR in SPIn.CTRLB Written to ‘0’
SS
SCK
Write DATA
Write value
0x43
0x44
0x45
0x46
DREIF
TXCIF
RXCIF
Transmit Buffer
Shift Register
Data sent
0x43
Dummy
Dummy
0x46
0x44
0x44
0x43
0x43
0x44
0x46
0x46
All writes to the Data register goes to the Transmit Buffer register. The figure above shows that the value 0x43 is
written to the Data register, but it is not immediately transferred to the shift register so the first byte sent will be a
dummy byte. The value of the dummy byte is whatever was in the shift register at the time, usually the last received
byte. After the first dummy transfer is completed the value 0x43 is transferred to the Shift register. Then 0x44 is
written to the Data register and goes to the Transmit Buffer register. A new transfer is started and 0x43 will be sent.
The value 0x45 is written to the Data register, but the Transmit Buffer register is not updated since it is already full
containing 0x44 and the Data Register Empty Interrupt Flag (DREIF in SPIn.INTFLAGS) is low. The value 0x45 will
be lost. After the transfer, the value 0x44 is moved to the Shift register. During the next transfer, 0x46 is written to the
Data register and 0x44 is sent out. After the transfer is complete, 0x46 is copied into the Shift register and sent out in
the next transfer.
The Data Register Empty Interrupt Flag (DREIF in SPIn.INTFLAGS) goes low every time the Transmit Buffer register
is written and goes high after a transfer when the previous value in the Transmit Buffer register is copied into the Shift
register. The Receive Complete Interrupt Flag (RXCIF in SPIn.INTFLAGS) is set one cycle after the Data Register
Empty Interrupt Flag goes high. The Transfer Complete Interrupt Flag is set one cycle after the Receive Complete
Interrupt Flag is set when both the value in the shift register and the Transmit Buffer register have been sent.
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Preliminary Datasheet
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ATmega3208/3209
SPI - Serial Peripheral Interface
Figure 24-4. SPI Timing Diagram in Buffer Mode with CTRLB.BUFWR Written to ‘1’
SS
SCK
Write DATA
Write value
0x43
0x44
0x45
0x46
DREIF
TXCIF
RXCIF
Transmit Buffer
Shift Register
Data sent
0x46
0x44
0x43
0x43
0x46
0x44
0x43
0x44
0x46
All writes to the Data register goes to the transmit buffer. The figure above shows that the value 0x43 is written to the
Data register and since the Slave Select pin is high it is copied to the Shift register the next cycle. Then the next write
(0x44) will go to the Transmit Buffer register. During the first transfer, the value 0x43 will be shifted out. In the figure
above, the value 0x45 is written to the Data register, but the Transmit Buffer register is not updated since the Data
Register Empty Interrupt Flag is low. After the transfer is completed, the value 0x44 from the Transmit Buffer register
is copied to the Shift register. The value 0x46 is written to the Transmit Buffer register. During the next two transfers,
0x44 and 0x46 are shifted out. The flags behave the same as with Buffer mode Wait for Receive Bit (BUFWR in
SPIn.CTRLB) set to ‘0’.
24.3.2.3 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 (SPIn.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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Preliminary Datasheet
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ATmega3208/3209
SPI - Serial Peripheral Interface
Figure 24-5. SPI Data Transfer Modes
1
2
3
4
5
6
7
8
MISO
1
2
3
4
5
6
7
8
MOSI
1
2
3
4
5
6
7
8
SPI Mode 0
Cycle #
SS
SCK
sampling
SPI Mode 1
Cycle #
1
2
3
4
5
6
7
8
MISO
1
2
3
4
5
6
7
8
MOSI
1
2
3
4
5
6
7
8
SS
SCK
sampling
SPI Mode 2
Cycle #
1
2
3
4
5
6
7
8
MISO
1
2
3
4
5
6
7
8
MOSI
1
2
3
4
5
6
7
8
SS
SCK
sampling
SPI Mode 3
Cycle #
1
2
3
4
5
6
7
8
MISO
1
2
3
4
5
6
7
8
MOSI
1
2
3
4
5
6
7
8
SS
SCK
sampling
24.3.2.4 Events
The event system output from SPI is SPI SCK value generated by the SPI. The SCK toggles only when the SPI is
enabled, in master mode and transmitting. Otherwise, the SCK is not toggling. Refer to the SPI transfer modes as
configured in SPIn.CTRLB for the idle state of SCK.
SPI has no event inputs.
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Preliminary Datasheet
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ATmega3208/3209
SPI - Serial Peripheral Interface
24.3.2.5 Interrupts
Table 24-4. Available Interrupt Vectors and Sources
Name
Vector Description
SPI
SPI interrupt
Conditions
•
•
•
•
SSI: Slave Select Trigger Interrupt
DRE: Data Register Empty Interrupt
TXC: Transfer Complete Interrupt
RXC: Receive Complete Interrupt
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 (peripheral.INTCTRL) register.
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.
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ATmega3208/3209
SPI - Serial Peripheral Interface
24.4
Register Summary - SPIn
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x03
0x04
CTRLA
CTRLB
INTCTRL
INTFLAGS
INTFLAGS
DATA
7:0
7:0
7:0
7:0
7:0
7:0
24.5
BUFEN
RXCIE
IF
RXCIF
DORD
BUFWR
TXCIE
WRCOL
TXCIF
MASTER
CLK2X
DREIE
SSIE
DREIF
SSIF
DATA[7:0]
PRESC[1:0]
SSD
ENABLE
MODE[1:0]
IE
BUFOVF
Register Description
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ATmega3208/3209
SPI - Serial Peripheral Interface
24.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CTRLA
0x00
0x00
-
6
DORD
R/W
0
5
MASTER
R/W
0
4
CLK2X
R/W
0
3
2
1
PRESC[1:0]
R/W
R/W
0
0
0
ENABLE
R/W
0
Bit 6 – DORD Data Order
Value
Description
0
The MSb of the data word is transmitted first
1
The LSb of the data word is transmitted first
Bit 5 – MASTER Master/Slave Select
This bit selects the desired SPI mode.
If SS is configured as input and driven low while this bit is ‘1’, this bit is cleared, and the IF flag in SPIn.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 SPIn.CTRLB.
Value
Description
0
SPI Slave mode selected
1
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
Description
0
SPI speed (SCK frequency) is not doubled
1
SPI speed (SCK frequency) is doubled in Master mode
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
Name
Description
0x0
DIV4
CLK_PER/4
0x1
DIV16
CLK_PER/16
0x2
DIV64
CLK_PER/64
0x3
DIV128
CLK_PER/128
Bit 0 – ENABLE SPI Enable
Value
Description
0
SPI is disabled
1
SPI is enabled
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Preliminary Datasheet
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ATmega3208/3209
SPI - Serial Peripheral Interface
24.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
BUFEN
R/W
0
CTRLB
0x01
0x00
-
6
BUFWR
R/W
0
5
4
3
2
SSD
R/W
0
1
0
MODE[1:0]
R/W
0
R/W
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
Description
0
One SPI transfer must be completed before the data is copied into the Shift register.
1
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 SPIn.CTRLA), SS does not disable Master
mode.
Value
Description
0
Enable the Slave Select line when operating as SPI Master
1
Disable the Slave Select line when operating as SPI Master
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
Name
Description
0x0
0
Leading edge: Rising, sample
Trailing edge: Falling, setup
0x1
1
Leading edge: Rising, setup
Trailing edge: Falling, sample
0x2
2
Leading edge: Falling, sample
Trailing edge: Rising, setup
0x3
3
Leading edge: Falling, setup
Trailing edge: Rising, sample
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Preliminary Datasheet
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ATmega3208/3209
SPI - Serial Peripheral Interface
24.5.3
Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
RXCIE
R/W
0
INTCTRL
0x02
0x00
-
6
TXCIE
R/W
0
5
DREIE
R/W
0
4
SSIE
R/W
0
3
2
1
0
IE
R/W
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 SPIn.INTFLAGS register is set. In the Non-Buffer mode, this bit is ‘0’.
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 SPIn.INTFLAGS register is set. In the Non-Buffer mode, this bit is ‘0’.
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 SPIn.INTFLAGS register is set. In the Non-Buffer mode, this bit is ‘0’.
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 SPIn.INTFLAGS register is set. In the Non-Buffer mode, this bit is ‘0’.
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 SPIn.INTFLAGS register.
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Preliminary Datasheet
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ATmega3208/3209
SPI - Serial Peripheral Interface
24.5.4
Interrupt Flags - Normal Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
IF
R/W
0
INTFLAGS
0x03
0x00
-
6
WRCOL
R/W
0
5
4
3
2
1
0
Bit 7 – IF Receive Complete Interrupt Flag/Interrupt Flag
This flag is set when a serial transfer is complete and one byte is completely shifted in/out of the SPIn.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 SPIn.INTFLAGS register when IF is set, and then accessing the SPIn.DATA register.
Bit 6 – WRCOL Transfer Complete Interrupt Flag/Write Collision Flag
The WRCOL flag is set if the SPIn.DATA register is written to before a complete byte has been shifted out. This flag is
cleared by first reading the SPIn.INTFLAGS register when WRCOL is set, and then accessing the SPIn.DATA
register.
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ATmega3208/3209
SPI - Serial Peripheral Interface
24.5.5
Interrupt Flags - Buffer Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
RXCIF
R/W
0
INTFLAGS
0x03
0x00
-
6
TXCIF
R/W
0
5
DREIF
R/W
0
4
SSIF
R/W
0
3
2
1
0
BUFOVF
R/W
0
Bit 7 – RXCIF Receive Complete Interrupt Flag
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).
When interrupt-driven data reception is used, the receive complete interrupt routine must read the received data from
SPIn.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 ‘1’ to its bit location.
Bit 6 – TXCIF Transfer Complete Interrupt Flag/Write Collision Flag
This flag is set when all the data in the transmit shift register has been shifted out and there is no new data in the
transmit buffer (SPIn.DATA). The flag is cleared by writing a ‘1’ to its bit location.
Bit 5 – DREIF Data Register Empty Interrupt Flag
This flag indicates whether the transmit buffer (SPIn.DATA) is ready to receive new data. The flag is ‘1’ when the
transmit buffer is empty and ‘0’ when the transmit buffer contains data to be transmitted that has not yet been moved
into the Shift register. DREIF is cleared after a Reset to indicate that the transmitter is ready.
DREIF is cleared by writing SPIn.DATA. When interrupt-driven data transmission is used, the Data register empty
interrupt routine must either write new data to SPIn.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.
Bit 4 – SSIF Slave Select Trigger Interrupt Flag
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 ‘1’ to its bit location.
Bit 0 – BUFOVF Buffer Overflow
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 (SPIn.DATA) is read. Always write this bit location to ‘0’ when writing
the SPIn.INTFLAGS register.
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Preliminary Datasheet
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ATmega3208/3209
SPI - Serial Peripheral Interface
24.5.6
Data
Name:
Offset:
Reset:
Property:
Bit
7
DATA
0x04
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
DATA[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – DATA[7:0] SPI Data
The SPIn.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 this register in Buffer mode will read the second receive buffer and the contents of the first receive buffer will
be moved to the second receive buffer.
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Preliminary Datasheet
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ATmega3208/3209
TWI - Two-Wire Interface
25.
TWI - Two-Wire Interface
25.1
Features
•
•
•
•
•
•
25.2
Bidirectional, two-wire communication interface
Philips I2C compatible
– Standard mode (Sm/100 kHz with slew-rate limited output)
– Fast mode (Fm/400 kHz with slew-rate limited output)
– Fast mode plus (Fm+/1 MHz with ×10 output drive strength)
System Management Bus (SMBus) 2.0 compatible (100 kHz with slew-rate limited output)
– Support arbitration between Start/Repeated Start and data bit
– Slave arbitration allows support for the Address Resolution Protocol (ARP)
– Configurable SMBus Layer 1 time-outs in hardware
– Independent time-outs for Dual mode
Independent Master and Slave operation
– Combined (same pins) or Dual mode (separate pins)
– Single or multi-master bus operation with full arbitration support
Flexible slave address match hardware operating in all sleep modes, including Power-Down
– 7-bit and general call address recognition
– 10-bit addressing support in collaboration with software
– Address mask register allows address range masking, alternatively it can be used as a secondary address
match
– Optional software address recognition for unlimited number of addresses
Input filter for bus noise suppression
Overview
The Two-Wire Interface (TWI) peripheral is a bidirectional, two-wire communication interface peripheral. The only
external hardware needed to implement the bus are two pull-up resistors, one for each bus line.
Any device connected to the TWI bus can act as a master, a slave, or both. The master generates the serial clock
(SCL) and initiates data transactions by addressing one slave and telling whether it wants to transmit or receive data.
One TWI bus connects many slaves to one or several masters. An arbitration scheme handles the case where more
than one master tries to transmit data at the same time. The mechanisms for resolving bus contention are inherent in
the protocol standards.
The TWI peripheral supports concurrent master and slave functionality, which are implemented as independent units
with separate enabling and configuration. The master module supports multi-master bus operation and arbitration. It
also generates the serial clock (SCL) by using a baud rate generator capable of generating the standard (Sm) and
fast (Fm, Fm+) bus frequencies from 100 kHz up to 1 MHz. A “smart mode” is added that can be enabled to autotrigger operations and thus reduce software complexity.
The slave module implements a 7-bit address match and general address call recognition in hardware. 10-bit
addressing is also supported. It also incorporates an address mask register that can be used as a second address
match register or as a register for address range masking. The address recognition hardware continues to operate in
all sleep modes, including Power Down mode. This enables the slave to wake up the device even from the deepest
sleep modes where all oscillators are turned OFF when it detects address match. Address matching can optionally be
fully handled by software.
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.
It is also possible to enable the Dual mode. In this case, the slave I/O pins are selected from an alternative port,
enabling fully independent and simultaneous master and slave operation.
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Preliminary Datasheet
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ATmega3208/3209
TWI - Two-Wire Interface
25.2.1
Block Diagram
Figure 25-1. TWI Block Diagram
Master
BAUD
TxDATA
0
baud rate generator
Slave
TxDATA
SCL
SCL hold low
0
SCL hold low
shift register
shift register
0
SDA
0
RxDATA
25.2.2
ADDR/ADDRMASK
RxDATA
==
Signal Description
Signal
Description
Type
SCL
Serial clock line
Digital I/O
SDA
Serial data line
Digital I/O
25.3
Functional Description
25.3.1
Initialization
Before enabling the master or the slave unit, ensure that the correct settings for SDASETUP, SDAHOLD, and, if
used, Fast-mode plus (FMPEN) are stored in TWI.CTRLA. If alternate pins are to be used for the slave, this must be
specified in the TWIn.DUALCTRL register as well. Note that for dual mode the master enables the primary SCL/SDA
pins, while the ENABLE bit in TWIn.DUALCTRL enables the secondary pins.
Master Operation
It is recommended to write the Master Baud Rate register (TWIn.BAUD) before enabling the TWI master since
TIMEOUT is dependent on the baud rate setting. To start the TWI master, write a ‘1’ to the ENABLE bit and configure
an appropriate TIMEOUT if using the TWI in an SMBus environment. The ENABLE and TIMEOUT bits are all located
in the Master Control A register (TWIn.MCTRLA). If no TIMEOUT value is set, which is the case for I²C operation, the
bus state must be manually set to IDLE by writing 0x1 to BUSSTATE in TWIn.MSTATUS at a “safe” point in time.
Note that unlike the SMBus specification, the I²C specification does not specify when it is safe to assume that the bus
is IDLE in a multi-master system. The application can solve this by ensuring that after all masters connected to the
bus are enabled, one supervising master performs a transfer before any of the other masters. The stop condition of
this initial transfer will indicate to the Bus State Monitor logic that the bus is IDLE and ready.
Slave Operation
To start the TWI slave, write the Slave Address (TWIn.SADDR), and write a '1' to the ENABLE bit in the Slave Control
A register (TWIn.SCTRLA). The TWI peripheral will wait to receive a byte addressed to it.
25.3.2
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 a slave, where the master controls the bus and all communication.
Figure 25-2 illustrates the TWI bus topology.
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Figure 25-2. 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
A 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 25-3 shows a TWI transaction.
Figure 25-3. 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.
25.3.2.1 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 the SCL line is kept high.
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Figure 25-4. 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).
25.3.2.2 Bit Transfer
As illustrated by Figure 25-5, 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 25-5. Data Validity
SDA
SCL
DATA
Valid
Change
Allowed
Combining bit transfers result 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.
25.3.2.3 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.
25.3.2.4 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 one Acknowledge bit. The direction bit in the previous address packet determines the direction in which
the data is transferred.
25.3.2.5 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 25-6 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 ‘0’ (ADDRESS+W).
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Figure 25-6. 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 25-7 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 ‘1’ (ADDRESS+R). The addressed slave must
acknowledge the address for the master to be allowed to continue the transaction.
Figure 25-7. Master Read Transaction
Transaction
Data Packet
Address Packet
S
R
ADDRESS
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 25-8 illustrates a combined transaction. A combined transaction consists of several read and write
transactions separated by Repeated Start conditions (Sr).
Figure 25-8. 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
25.3.2.6 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 25-9.
Figure 25-9. 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.
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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.
25.3.2.7 Arbitration
A master can start a bus transaction only if it has detected that the bus is idle. As the TWI bus is a multi-master 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 25-10. TWI Arbitration
DEVICE1 Loses arbitration
DEVICE1_SDA
DEVICE2_SDA
SDA
(wired-AND)
bit 7
bit 6
bit 5
bit 4
SCL
S
Figure 25-10 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.
25.3.2.8 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 25-11 shows 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.
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Figure 25-11. 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.
25.3.3
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 time-out detection,
and a bit counter. These are used to determine the bus state. The 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 25-12. The values of the Bus State bits according to
state, are shown in binary in the figure below.
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Figure 25-12. Bus State, State Diagram
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)
After a system reset and/or TWI master enable, the bus state is unknown. The bus state machine can be forced to
enter the idle state 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 time-out is enabled, the bus
state will change to idle on the occurrence of a time-out. 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 time-out is enabled, the bus state will change from busy to idle on the occurrence of a time-out.
If a Start condition is generated internally while in an 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 issuing 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).
25.3.4
Operation
25.3.4.1 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 time-out period should be
set in TWI Master mode. Refer to 25.3.4.2 TWI Master Operation for more details.
25.3.4.2 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.
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 25-13 shows the TWI master operation. The diamondshaped symbols (SW) indicate where software interaction is required. Clearing the interrupt flags releases the SCL
line.
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Figure 25-13. 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
BUSY
A
P
A
Sr
Bus state
Mn
Diagram connections
IDLE
M4
M2
M3
A
R
A
DATA
The number of interrupts generated is kept to a minimum by an automatic handling of most conditions.
25.3.4.2.1 Clock Generation
The TWIn.MBAUD register must be set to a value that results in a TWI bus clock frequency (fSCL) equal or less than
100 kHz/400 kHz/1 MHz, 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 (TWIn.MBAUD), 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.
Figure 25-14. 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
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•
•
•
•
TSU;STA – Set-up time for repeated start condition
THIGH is timed using the SCL high time count from TWIn.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 BAUD field in TWIn.MBAUD value is used to time both SCL high and SCL low which gives the following formula
of SCL frequency:
25.3.4.2.2 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, both the Master Write Interrupt Flag (WIF in
TWIn.MSTATUS) and Arbitration Lost Flag (ARBLOST in TWIn.MSTATUS) are 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
TWIn.MSTATUS) is set in addition to the write interrupt and arbitration lost flags.
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 TWIn.MSTATUS) and the Master
Received Acknowledge Flag (RXACK in TWIn.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 TWIn.MSTATUS) is set and the
Master Received Acknowledge Flag (RXACK in TWIn.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 TWIn.MSTATUS) is set and the Master
Received Acknowledge Flag (RXACK in TWIn.MSTATUS) is cleared. The clock hold is active at this point, preventing
further activity on the bus.
25.3.4.2.3 Transmitting Data Packets
Assuming the above M3 case, the master can start transmitting data by writing to the Master Data (TWIn.MDATA)
register, which will also clear the Write Interrupt Flag (WIF). During data transfer, the master is continuously
monitoring the bus for collisions and errors. The WIF will be set anew after the full data packet transfer has been
completed, the arbitration is lost (ARBLOST), or if a bus error (BUSERR) occur during the transfer.
The WIF, ARBLOST, and BUSERR flags together with the value of the last acknowledge bit (RXACK) are all located
in the Master Status (TWIn.MSTATUS) register. The RXACK status is only valid if WIF is set and not valid if
ARBLOST or BUSERR is set, so the software driver must check this first. The RXACK will be zero if the slave
responds to the data with an ACK, which indicates that the slave is ready for more data (if any). A NACK received
from the slave indicates that the slave is not able to or does not need to receive more data after the last byte. The
master must then either issue a Repeated Start (Sr) (write a new value to TWIn.MADDR) or complete the transaction
by issuing a Stop condition (MCMD field in TWIn.MCTRLB = MCMD_STOP).
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In I²C slaves, the use of Repeated Start conditions (Sr) entirely depends on how each slave interprets the protocol. In
SMBus slaves, interpretation of a Repeated Start condition is defined by higher levels of the protocol specification.
25.3.4.2.4 Receiving Data Packets
Assuming case M4 above, the master has already received one byte from the slave. The master read interrupt flag is
set, and the master must prepare to receive new data. The master must respond to each byte with ACK or NACK. A
NACK response might not be successfully executed, as arbitration can be lost during the transmission. If a collision is
detected, the master loses arbitration and the arbitration lost flag is set.
25.3.4.2.5 Quick Command Mode
With Quick Command enabled (QCEN in TWIn.MCTRLA), the R/W# bit of the slave address denotes the command.
This is an 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 TWIn.MSTATUS will be set
depending on the 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 TWIn.MCTRLB.
Figure 25-15. Quick Command Frame Format
S
Address
R/W
A
P
25.3.4.3 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 25-16 shows the TWI slave operation. The diamond-shaped
symbols (SW) indicate where software interaction is required.
Figure 25-16. 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
Driver software
The master provides data
on the bus
Slave provides data on
the bus
Sn
S1
A
A
SW
SLAVE DATA INTERRUPT
W
SW
Interrupt on STOP
Condition Enabled
SW
A/A
DATA
SW
A/A
Diagram connections
The number of interrupts generated is kept to a minimum by automatic handling of most conditions. The 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.
25.3.4.3.1 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
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address and store the address in the TWIn.DATA register. If the received address is not a match, the slave will not
acknowledge and store the address, but 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.
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.
25.3.4.3.2 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.
25.3.4.3.3 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.
25.3.4.4 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 TWIn.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 TWIn.SCTRLA), DIF (Data Interrupt Flag) will automatically be
cleared if Data register (TWIn.SDATA) is read or written.
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25.3.5
Interrupts
Table 25-1. Available Interrupt Vectors and Sources
Name
Vector Description
Conditions
Slave
TWI Slave interrupt
•
•
DIF: Data Interrupt Flag in TWIn.SSTATUS set
APIF: Address or Stop Interrupt Flag in TWIn.SSTATUS set
Master
TWI Master interrupt
•
•
RIF: Read Interrupt Flag in TWIn.MSTATUS set
WIF: Write Interrupt Flag in TWIn.MSTATUS set
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Master register (TWIn.MSTATUS) or
Slave Status register (TWIn.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.
25.3.6
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. The master will stop operation in all Sleep modes.
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TWI - Two-Wire Interface
25.4
Register Summary - TWIn
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x0C
0x0D
0x0E
CTRLA
DUALCTRL
DBGCTRL
MCTRLA
MCTRLB
MSTATUS
MBAUD
MADDR
MDATA
SCTRLA
SCTRLB
SSTATUS
SADDR
SDATA
SADDRMASK
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
25.5
SDASETUP
RIEN
WIEN
RIF
WIF
DIEN
APIEN
DIF
APIF
QCEN
SDAHOLD[1:0]
SDAHOLD[1:0]
TIMEOUT[1:0]
FLUSH
ACKACT
CLKHOLD
RXACK
ARBLOST
BUSERR
BAUD[7:0]
ADDR[7:0]
DATA[7:0]
PIEN
PMEN
ACKACT
CLKHOLD
RXACK
COLL
BUSERR
ADDR[7:0]
DATA[7:0]
ADDRMASK[6:0]
FMPEN
FMPEN
ENABLE
DBGRUN
SMEN
ENABLE
MCMD[1:0]
BUSSTATE[1:0]
SMEN
ENABLE
SCMD[1:0]
DIR
AP
ADDREN
Register Description
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TWI - Two-Wire Interface
25.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
-
6
5
4
SDASETUP
R/W
0
Access
Reset
3
2
SDAHOLD[1:0]
R/W
R/W
0
0
1
FMPEN
R/W
0
0
Bit 4 – SDASETUP SDA Setup Time
By default, there are four clock cycles of setup time on SDA out signal while reading from the slave part of the TWI
module. Writing this bit to '1' will change the setup time to eight clocks.
Value
Name
Description
0
4CYC
SDA setup time is four clock cycles
1
8CYC
SDA setup time is eight clock cycle
Bits 3:2 – SDAHOLD[1:0] SDA Hold Time
Writing these bits selects the SDA hold time.
Table 25-2. SDA Hold Time
SDAHOLD[1:0] Nominal Hold Time Hold Time Range Across All
Corners [ns]
Description
0x0
OFF
0
Hold time OFF.
0x1
50 ns
36 - 131
Backward compatible setting.
0x2
300 ns
180 - 630
Meets SMBus specification under
typical conditions.
0x3
500 ns
300 - 1050
Meets SMBus specification across all
corners.
Bit 1 – FMPEN FM Plus Enable
Writing these bits selects the 1 MHz bus speed (Fast mode plus, Fm+) for the TWI in default configuration or for TWI
Master in dual mode configuration.
Value
Description
0
Fm+ disabled
1
Fm+ enabled
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TWI - Two-Wire Interface
25.5.2
Dual Mode Control Configuration
Name:
Offset:
Reset:
Property:
Bit
DUALCTRL
0x01
0x00
-
7
6
5
4
Access
Reset
3
2
SDAHOLD[1:0]
R/W
R/W
0
0
1
FMPEN
R/W
0
0
ENABLE
R/W
0
Bits 3:2 – SDAHOLD[1:0] SDA Hold Time
These bits select the SDA hold time for the TWI Slave.
This bit field is ignored when the dual control is disabled.
Table 25-3. SDA Hold Time
SDAHOLD[1:0] Nominal Hold Time
[ns]
Hold Time Range Across all
Corners [ns]
Description
0x0
0
0
Hold time OFF.
0x1
50
36 - 131
Backward compatible setting.
0x2
300
180 - 630
Meets SMBus specification under
typical conditions.
0x3
500
300 - 1050
Meets SMBus specification across all
corners.
Bit 1 – FMPEN FM Plus Enable
This bit selects the 1 MHz bus speed for the TWI Slave. This bit is ignored when dual control is disabled.
Bit 0 – ENABLE Dual Control Enable
Writing this bit to ‘1’ enables the TWI dual control.
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TWI - Two-Wire Interface
25.5.3
Debug Control
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x02
0x00
-
6
5
4
3
2
Access
Reset
1
0
DBGRUN
R/W
0
Bit 0 – DBGRUN Debug Run
Value
Description
0
The peripheral is halted in Break Debug mode and ignores events
1
The peripheral will continue to run in Break Debug mode when the CPU is halted
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TWI - Two-Wire Interface
25.5.4
Master Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
RIEN
R/W
0
MCTRLA
0x03
0x00
-
6
WIEN
R/W
0
5
4
QCEN
R/W
0
3
2
TIMEOUT[1:0]
R/W
R/W
0
0
1
SMEN
R/W
0
0
ENABLE
R/W
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
(TWIn.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
(TWIn.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
(TWIn.MCTRLB) or the Master Address register (TWIn.MADDR).
Bits 3:2 – TIMEOUT[1:0] Inactive Bus Time-Out
Setting the inactive bus time-out (TIMEOUT) bits to a non-zero value will enable the inactive bus time-out supervisor.
If the bus is inactive for longer than the TIMEOUT setting, the bus state logic will enter the Idle state.
Value
Name
Description
0x0
DISABLED
Bus time-out disabled. I2C.
0x1
50US
50 µs - SMBus (assume baud is set to 100 kHz)
0x2
100US
100 µs (assume baud is set to 100 kHz)
0x3
200US
200 µs (assume baud is set to 100 kHz)
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 (TWIn.MDATA) register.
Bit 0 – ENABLE Enable TWI Master
Writing this bit to '1' enables the TWI as master.
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TWI - Two-Wire Interface
25.5.5
Master Control B
Name:
Offset:
Reset:
Property:
Bit
MCTRLB
0x04
0x00
-
7
6
5
Access
Reset
4
3
FLUSH
R/W
0
2
ACKACT
R/W
0
1
0
MCMD[1:0]
R/W
0
R/W
0
Bit 3 – FLUSH Flush
Writing a '1' to this bit generates a strobe for one clock cycle disabling and then enabling the master.
Writing '0' has no effect.
The purpose is to clear the internal state of the master: For TWI master to transmit successfully, it is recommended to
write the Master Address register (TWIn.MADDR) first and then the Master Data register (TWIn.MDATA).
The peripheral will transmit invalid data if TWIn.MDATA is written before TWIn.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
Description
0
Send ACK
1
Send NACK
Bits 1:0 – MCMD[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 25-4. Command Settings
MCMD[1:0]
DIR
Description
0x0
X
NOACT - No action
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
(TWIn.MDATA).
The acknowledge action bits and command bits can be written at the same time.
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TWI - Two-Wire Interface
25.5.6
Master Status
Name:
Offset:
Reset:
Property:
MSTATUS
0x05
0x00
-
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 (TWIn.MADDR), Master Data register
(TWIn.MDATA), or the Command bits (CMD) in the Master Control B register (TWIn.MCTRLB).
Bit
Access
Reset
7
RIF
R/W
0
6
WIF
R/W
0
5
CLKHOLD
R/W
0
4
RXACK
R
0
3
ARBLOST
R/W
0
2
BUSERR
R/W
0
1
0
BUSSTATE[1:0]
R/W
R/W
0
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 TWIn.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 TWIn.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. Writing a ‘1’ to it.
2. Writing to the TWIn.MADDR register.
3. Writing to the TWIn.MDATA register.
4. Reading the TWIn.DATA register while the ACKACT control bits in TWIn.MCTRLB are set to either send ACK
or NACK.
5. Writing a valid command to the TWIn.MCTRLB register.
Bit 4 – RXACK Received Acknowledge
This bit is read-only and contains the most recently received Acknowledge bit from the slave. When read as ‘0’, the
most recent acknowledge bit from the slave was ACK. When read as ‘1’, the most recent acknowledge bit was
NACK.
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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TWI - Two-Wire Interface
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 the operation or
resend the data packet. Either way, the next required software interaction is in both cases to write to the
TWIn.MADDR register. A write access to the TWIn.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
TWIn.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 re-enabling, 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
Name
Description
0x0
UNKNOWN
Unknown bus state
0x1
IDLE
Bus is idle
0x2
OWNER
This TWI controls the bus
0x3
BUSY
The bus is busy
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TWI - Two-Wire Interface
25.5.7
Master Baud Rate
Name:
Offset:
Reset:
Property:
Bit
7
MBAUD
0x06
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
BAUD[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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 TWIn.MCTRLA is '0').
For more information on how to calculate the frequency, see the Clock Generation section.
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25.5.8
Master Address
Name:
Offset:
Reset:
Property:
Bit
7
MADDR
0x07
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
ADDR[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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 (TWIn.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 (TWIn.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 (TWIn.MSETUP)
is set accordingly. Completing the operation sets the WIF in the Master Status register (TWIn.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 (TWIn.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 TWIn.MADDR register as the bus protocol’s Read/Write flag (R/W).
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25.5.9
Master DATA
Name:
Offset:
Reset:
Property:
Bit
7
MDATA
0x08
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
DATA[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – DATA[7:0] Data
The bit field gives direct access to the master's 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. Built-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 (TWIn.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 TWIn.MSTATUS and type of register access (read or
write).
A write access to this register will, independent of ACKACT in TWIn.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 TWIn.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 TWIn.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 TWIn.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 TWIn.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 mutually 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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TWI - Two-Wire Interface
25.5.10 Slave Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
DIEN
R/W
0
SCTRLA
0x09
0x00
-
6
APIEN
R/W
0
5
PIEN
R/W
0
4
3
2
PMEN
R/W
0
1
SMEN
R/W
0
0
ENABLE
R/W
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
(TWIn.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
(TWIn.SSTATUS). A TWI slave Address or Stop interrupt will be generated only if this bit, APIF, and the Global
Interrupt Flag (I) in CPU.SREG are all ‘1’.
The slave stop interrupt shares the interrupt flag and vector with the slave address interrupt. The
TWIn.SCTRAL.PIEN must be written to ‘1’ in order for the APIF to be set on a stop condition and when the interrupt
occurs the TWIn.SSTATUS.AP bit will determine whether an address match or a stop condition 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 (TWIn.SADDR) to determine which
address to recognize as the slave’s own address.
Bit 1 – SMEN Smart Mode Enable
Writing this bit to ‘1’ enables the slave Smart mode. When the Smart mode is enabled, issuing a command with CMD
or reading/writing DATA resets the interrupt and operation continues. If the 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.
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TWI - Two-Wire Interface
25.5.11 Slave Control B
Name:
Offset:
Reset:
Property:
Bit
SCTRLB
0x0A
0x00
-
7
6
5
4
3
Access
Reset
2
ACKACT
R/W
0
1
0
SCMD[1:0]
R/W
0
R/W
0
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 TWIn.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
Name
Description
0
ACK
Send ACK
1
NACK
Send NACK
Bits 1:0 – SCMD[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 25-5. Command Settings
SCMD[1:0]
DIR Description
0x0
X
NOACT - 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.
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TWI - Two-Wire Interface
25.5.12 Slave Status
Name:
Offset:
Reset:
Property:
SSTATUS
0x0B
0x00
-
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 (TWIn.SDATA) register or the
CMD bits in the Slave Control B register (TWIn.SCTRLB).
Bit
Access
Reset
7
DIF
R/W
0
6
APIF
R/W
0
5
CLKHOLD
R
0
4
RXACK
R
0
3
COLL
R/W
0
2
BUSERR
R/W
0
1
DIR
R
0
0
AP
R
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 the 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. Writing to the Slave DATA register.
2. Reading the Slave DATA register.
3. Writing a valid command to the CTRLB register.
The DIF flag can be used to generate a slave data interrupt (see the description of the DIEN control bit in
TWIn.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 the same software interactions as described for the DIF
flag.
The APIF flag can be used to generate a slave address or stop interrupt (see the description of the AIEN control bit in
TWIn.CTRLA). Take special note of that the slave stop interrupt shares the interrupt vector with the 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 the most recently received Acknowledge bit from the master. When read as ‘0’, the
most recent acknowledge bit from the master was ACK. When read as ‘1’, the most recent acknowledge bit was
NACK.
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). The DIF flag will be set to ‘1’ at the end as a result of the internal completion of an unsuccessful
transaction. Similarly, when a collision occurs because the slave has not been able to transmit a NACK bit, it means
the address match already happened and the APIF flag is set as a result. APIF/DIF flags can only generate interrupts
whose handlers can be used to check for the collision. Writing 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 the 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.
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ATmega3208/3209
TWI - Two-Wire Interface
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 will restart by waiting
for a new Start condition (S). The TWI bus error detector is part of the TWI Master circuitry. For bus errors to be
detected, the TWI Master must be enabled (ENABLE bit in TWIn.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
Name
Description
0
STOP
A Stop condition generated the interrupt on APIF
1
ADR
Address detection generated the interrupt on APIF
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ATmega3208/3209
TWI - Two-Wire Interface
25.5.13 Slave Address
Name:
Offset:
Reset:
Property:
Bit
7
SADDR
0x0C
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
ADDR[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – ADDR[7:0] Address
The Slave Address register in combination with the Slave Address Mask register (TWIn.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 ‘1’ 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 seven 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 TWI slave address
match logic only supports 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.
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ATmega3208/3209
TWI - Two-Wire Interface
25.5.14 Slave Data
Name:
Offset:
Reset:
Property:
Bit
7
SDATA
0x0D
0x00
-
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
DATA[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
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).
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ATmega3208/3209
TWI - Two-Wire Interface
25.5.15 Slave Address Mask
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
SADDRMASK
0x0E
0x00
-
7
6
5
R/W
0
R/W
0
R/W
0
4
ADDRMASK[6:0]
R/W
0
3
2
1
R/W
0
R/W
0
R/W
0
0
ADDREN
R/W
0
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 the
TWIn.SADDRMASK register can mask (disable) the corresponding address bits in the TWI slave Address Register
(TWIn.SADDR). 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 TWIn.SADDR register. In other words, masked bits will
always match.
If ADDREN is written to '1', the TWIn.SADDRMASK can be loaded with a second slave address in addition to the
TWIn.SADDR register. In this mode, the slave will match on two unique addresses, one in TWIn.SADDR and the
other in TWIn.SADDRMASK.
Bit 0 – ADDREN Address Mask Enable
If this bit is written to '1', the slave address match logic responds to the two unique addresses in slave TWIn.SADDR
and TWIn.SADDRMASK.
If this bit is '0', the TWIn.SADDRMASK register acts as a mask to the TWIn.SADDR register.
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Preliminary Datasheet
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ATmega3208/3209
CRCSCAN - Cyclic Redundancy Check Memory Sca...
26.
CRCSCAN - Cyclic Redundancy Check Memory Scan
26.1
Features
•
•
•
•
26.2
CRC-16-CCITT
Check of the entire Flash section, application code, and/or boot section
Selectable NMI trigger on failure
User configurable check during internal reset initialization
Overview
A Cyclic Redundancy Check (CRC) takes a data stream of bytes from the NVM (either the entire Flash, only the Boot
section, or both application code and Boot section) and generates a checksum. The CRC peripheral (CRCSCAN) can
be used to detect errors in the 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 a shift register as depicted below, starting with the
most significant bit. If the last bytes in the section contain the correct checksum, the CRC will pass. See 26.3.2.1
Checksum for how to place the checksum. The initial value of the checksum register is 0xFFFF.
Figure 26-1. 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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ATmega3208/3209
CRCSCAN - Cyclic Redundancy Check Memory Sca...
26.2.1
Block Diagram
Figure 26-2. Cyclic Redundancy Check Block Diagram
Memory
(Boot, App,
Flash)
CTRLB
CTRLA
Source
Enable,
Reset
CRC
calculation
BUSY
STATUS
CRC OK
CHECKSUM
26.3
Functional Description
26.3.1
Initialization
NMI Req
To enable a CRC in software (or via the debugger):
1. Write the Source (SRC) bit field 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).
3. The CRC will start after three cycles. The CPU will continue executing during these three cycles.
The CRCSCAN can be configured to perform a code memory scan before the device leaves reset. If this check fails,
the CPU is not allowed to start normal code execution. This feature is enabled and controlled by the CRCSRC field in
FUSE.SYSCFG0, see the “Fuses” chapter for more information.
If this feature is enabled, a successful CRC check will have the following outcome:
• Normal code execution starts
• The ENABLE bit in CRCSCAN.CTRLA will be ‘1’
• The SRC bit field in CRCSCAN.CTRLB will reflect the checked section(s)
• The OK flag in CRCSCAN.STATUS will be ‘1’
If this feature is enabled, a non-successful CRC check will have the following outcome:
• Normal code execution does not start, the CPU will hang executing no code
• The ENABLE bit in CRCSCAN.CTRLA will be ‘1’
• The SRC bit field in CRCSCAN.CTRLB will reflect the checked section(s)
• The OK flag in CRCSCAN.STATUS will be ‘0’
• This condition can be observed using the debug interface
26.3.2
Operation
The CRC is operating in Priority mode: the CRC peripheral has priority access to the Flash and will stall the CPU until
completed.
In Priority mode, the CRC fetches a new word (16-bit) on every third main clock cycle, or when the CRC peripheral is
configured to do a scan from startup.
26.3.2.1 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 checksum must be saved in the last bytes of the BOOT section, and similarly for
APPLICATION and entire Flash. Table 26-1 shows explicitly how the checksum should be stored for the different
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Preliminary Datasheet
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ATmega3208/3209
CRCSCAN - Cyclic Redundancy Check Memory Sca...
sections. Also, see the CRCSCAN.CTRLB register description for how to configure which section to check and the
device fuse description for how to configure the BOOTEND and APPEND fuses.
Table 26-1. Placement the Pre-Calculated Checksum in Flash
26.3.3
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 26-2. Available Interrupt Vectors and Sources
Name
Vector Description
Conditions
NMI
Non-Maskable Interrupt
Generated on CRC failure
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
cannot be disabled.
A non-maskable interrupt can be triggered even if interrupts are not globally enabled.
26.3.4
Sleep Mode Operation
CTCSCAN is halted in all sleep modes. In all CPU Sleep modes, the CRCSCAN peripheral is halted and will resume
operation when the CPU wakes up.
The CRCSCAN starts operation three cycles after writing the EN bit in CRCSCAN.CTRLA. During these three cycles,
it is possible to enter Sleep mode. In this case:
1. The CRCSCAN will not start until the CPU is woken up.
2. Any interrupt handler will execute after CRCSCAN has finished.
26.3.5
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 Non-Maskable Interrupt
Enable bit (NMIEN) in the Control A register (CRCSCAN.CTRLA) cannot be altered.
OK bit in CRCSCAN.STATUS:
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CRCSCAN - Cyclic Redundancy Check Memory Sca...
– 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.
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ATmega3208/3209
CRCSCAN - Cyclic Redundancy Check Memory Sca...
26.4
Register Summary - CRCSCAN
Offset
Name
Bit Pos.
0x00
0x01
0x02
CTRLA
CTRLB
STATUS
7:0
7:0
7:0
26.5
RESET
NMIEN
ENABLE
SRC[1:0]
OK
BUSY
Register Description
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CRCSCAN - Cyclic Redundancy Check Memory Sca...
26.5.1
Control A
Name:
Offset:
Reset:
Property:
CTRLA
0x00
0x00
-
If an NMI has been triggered, this register is not writable.
Bit
Access
Reset
7
RESET
R/W
0
6
5
4
3
2
1
NMIEN
R/W
0
0
ENABLE
R/W
0
Bit 7 – RESET Reset CRCSCAN
Writing this bit to ’1’ resets the CRCSCAN peripheral: The CRCSCAN Control registers and Status register
(CRCSCAN.CTRLA, CRCSCAN.CTRLB, CRCSCAN.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 (the BUSY bit in CRCSCAN.STATUS is ’1’) and
not busy (the BUSY bit is ’0’) and will take effect immediately.
If NMIEN is ’1’, this bit is only writable when the CRCSCAN is not busy (the 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 (the 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 configured to run a scan during the MCU startup sequence to verify Flash sections before
letting the CPU start normal code execution (see the “Initialization” section). If this feature is enabled, 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).
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CRCSCAN - Cyclic Redundancy Check Memory Sca...
26.5.2
Control B
Name:
Offset:
Reset:
Property:
CTRLB
0x01
0x00
-
The CRCSCAN.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.
Bit
7
6
5
4
3
2
1
0
SRC[1:0]
Access
Reset
R/W
0
R/W
0
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, refer to
the fuse description.
The CRC can be enabled during internal reset initialization to verify Flash sections before letting the CPU start (see
the “Fuses” chapter). 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).
Value
Name
Description
0x0
FLASH
The CRC is performed on the entire Flash (boot, application code, and application data
sections).
0x1
BOOTAPP The CRC is performed on the boot and application code sections of Flash.
0x2
BOOT
The CRC is performed on the boot section of Flash.
0x3
Reserved.
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CRCSCAN - Cyclic Redundancy Check Memory Sca...
26.5.3
Status
Name:
Offset:
Reset:
Property:
STATUS
0x02
0x02
-
The status register contains the busy and OK information. It is not writable, only readable.
Bit
7
6
5
4
3
Access
Reset
2
1
OK
R
1
0
BUSY
R
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 the CRCSCAN. As long as the CRC module is busy, it will 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 is limited.
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ATmega3208/3209
CCL – Configurable Custom Logic
27.
CCL – Configurable Custom Logic
27.1
Features
•
•
•
•
•
•
•
•
•
27.2
Glue Logic for General Purpose PCB Design
4 Programmable Look-Up Tables (LUTs)
Combinatorial Logic Functions: Any Logic Expression which is a Function of up to Three Inputs.
Sequencer Logic Functions:
– Gated D flip-flop
– JK flip-flop
– Gated D latch
– RS latch
Flexible LUT Input Selection:
– I/Os
– Events
– Subsequent LUT output
– Internal peripherals such as:
• Analog comparator
• Timers/Counters
• USART
• SPI
Clocked by a System Clock or other Peripherals
Output can be Connected to I/O Pins or an Event System
Optional Synchronizer, Filter, or Edge Detector Available on Each LUT Output
Optional Interrupt Generation from Each LUT Output:
– Rising edge
– Falling edge
– Both edges
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 constraints by combining Core Independent Peripherals (CIPs) to handle the most time-critical
parts of the application independent of the CPU.
The CCL peripheral provides a number of Look-up Tables (LUTs). Each LUT consists of three inputs, a truth table, a
synchronizer/filter, and an edge detector. Each LUT can generate an output as a user programmable logic expression
with three inputs. The output is generated from the inputs using the combinatorial logic and can be filtered to remove
spikes. The CCL can be configured to generate an interrupt request on changes in the LUT outputs.
Neighboring LUTs can be combined to perform specific operations. A sequencer can be used for generating complex
waveforms.
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ATmega3208/3209
CCL – Configurable Custom Logic
27.2.1
Block Diagram
Figure 27-1. Configurable Custom Logic
Even LUT n
INSEL
Internal
Events
I/O
Peripherals
FILTSEL
LUTn-IN[2:0]
Filter/
Synch
TRUTH
CLKSRC
Edge
Detector
LUTn-OUT
CLK_LUTn
Clock Sources
LUTn-IN[2]
Sequencer
Odd LUT n+1
INSEL
Internal
Events
I/O
Peripherals
CLKSRC
Clock Sources
LUTn+1-IN[2]
SEQSEL
EDGEDET
FILTSEL
LUTn+1-IN[2:0]
Filter/
Synch
TRUTH
EDGEDET
LUTn+1-OUT
Edge
Detector
CLK_LUTn+1
Table 27-2. Sequencer and LUT Connection
27.2.2
Sequencer
Even and Odd LUT
SEQ0
LUT0 and LUT1
SEQ1
LUT2 and LUT3
Signal Description
Name
Type
Description
LUTn-OUT
Digital output
Output from the look-up table
LUTn-IN[2:0]
Digital input
Input to the look-up table. LUTn-IN[2] can serve as CLK_LUTn.
Refer to I/O Multiplexing and Considerations for details on the pin mapping for this peripheral. One signal can be
mapped to several pins.
27.2.2.1 CCL Input Selection MUX
The following peripherals outputs are available as inputs into the CCL LUT.
Value
Input Source
0x00
MASK
None
0x01
FEEDBACK
LUTn
0x02
LINK
0x03
EVENTA
Event input source A
0x04
EVENTB
Event input source B
0x05
IO
0x06
AC
0x07
-
© 2020 Microchip Technology Inc.
INSEL0
INSEL1
INSEL2
LUT(n+1)
IN0
IN1
IN2
AC0 OUT
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CCL – Configurable Custom Logic
...........continued
Value
Input Source
0x08
USART
0x09
SPI
0x0A
TCA0
0x0B
-
0x0C
TCB
Other
-
INSEL0
INSEL1
INSEL2
USART0 TXD
USART1 TXD
USART2 TXD
SPI0 MOSI
SPI0 MOSI
SPI0 SCK
WO0
WO1
WO2
TCB0 WO
TCB1 WO
TCB2 WO
Note:
• SPI connections to the CCL work only in master SPI mode
• USART connections to the CCL work only in asynchronous/synchronous USART master mode.
27.3
Functional Description
27.3.1
Operation
27.3.1.1 Enable-Protected Configuration
The configuration of the LUTs and sequencers is enable-protected, meaning that they can only be configured when
the corresponding even LUT is disabled (ENABLE=0 in the LUT n Control A register, CCL.LUTnCTRLA). This is a
mechanism to suppress the undesired output from the CCL under (re-)configuration.
The following bits and registers are enable-protected:
•
•
Sequencer Selection (SEQSEL) in the Sequencer Control n register (CCL.SEQCTRLn)
LUT n Control x registers (CCL.LUTnCTRLx), except the ENABLE bit in CCL.LUTnCTRLA
The enable-protected bits in the CCL.LUTnCTRLx registers can be written at the same time as ENABLE in
CCL.LUTnCTRLA is written to ‘1’, but not at the same time as ENABLE is written to ‘0’.
The enable protection is denoted by the enable-protected property in the register description.
27.3.1.2 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.
27.3.1.3 Truth Table Logic
The truth table in each LUT unit can generate a combinational logic output as a function of up to three inputs
(IN[2:0]). The unused inputs can be turned off (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 below.
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Preliminary Datasheet
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ATmega3208/3209
CCL – Configurable Custom Logic
Figure 27-2. Truth Table Output Value Selection of a LUT
TRUTH[0]
TRUTH[1]
TRUTH[2]
TRUTH[3]
TRUTH[4]
TRUTH[5]
TRUTH[6]
TRUTH[7]
OUT
IN[2:0]
Table 27-3. Truth Table of a 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]
27.3.1.4 Truth Table Inputs Selection
Input Overview
The inputs can be individually:
•
•
•
•
•
OFF
Driven by peripherals
Driven by internal events from the Event System
Driven by I/O pin inputs
Driven by other LUTs
The input for each LUT is configured by writing the Input Source Selection bits in the LUT Control registers:
• INSEL0 in CCL.LUTnCTRLB
• INSEL1 in CCL.LUTnCTRLB
• INSEL2 in CCL.LUTnCTRLC
Internal Feedback Inputs (FEEDBACK)
The output from a sequencer can be used as an input source for the two LUTs it is connected to.
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Preliminary Datasheet
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ATmega3208/3209
CCL – Configurable Custom Logic
Figure 27-3. Feedback Input Selection
Even LUT
Sequencer
Odd LUT
When selected (INSELy=FEEDBACK in LUTnCTRLx), the sequencer (SEQ) output is used as input for the
corresponding LUTs.
Linked LUT (LINK)
When selecting the LINK input option, the next LUT’s direct output is used as LUT input. In general, LUT[n+1] is
linked to the input of LUT[n]. LUT0 is linked to the input of the last LUT.
Example 27-1. Linking all LUTs on a Device with Four LUTs
•
•
•
•
LUT1 is the input for LUT0
LUT2 is the input for LUT1
LUT3 is the input for LUT2
LUT0 is the input for LUT3 (wrap-around)
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
CCL – Configurable Custom Logic
Figure 27-4. Linked LUT Input Selection
LUT0
SEQ0
LUT1
LUT2
SEQ1
LUT3
Event Input Selection (EVENTx)
Events from the Event System can be used as inputs to the LUTs by writing to the INSELn bit groups in the LUT n
Control A and B registers.
I/O Pin Inputs (IO)
When selecting the IO option, the LUT input will be connected to its corresponding I/O pin. Refer to the I/O
Multiplexing section in the data sheet for more details about where the LUTnINy pins are located.
Peripherals
The different peripherals on the three input lines of each LUT are selected by writing to the Input Select (INSEL) bits
in the LUT Control registers (LUTnCTRLB and LUTnCTRLC).
27.3.1.5 Filter
By default, the LUT output is a combinational function of the LUT inputs. This may cause some short glitches when
the inputs change the value. These glitches can be removed by clocking through filters if demanded by application
needs.
The Filter Selection bits (FILTSEL) in the LUT n Control A registers (CCL.LUTnCTRLA) define the digital filter
options.
When FILTSEL=SYNCH, the output is synchronized with CLK_LUTn. The output will be delayed by two positive
CLK_LUTn edges.
When FILTSEL=FILTER, only the input that is persistent for more than two positive CLK_LUTn edges will pass
through the gated flip-flop to the output. The output will be delayed by four positive CLK_LUTn edges.
One clock cycle later, after the corresponding LUT is disabled, all internal filter logic is cleared.
© 2020 Microchip Technology Inc.
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CCL – Configurable Custom Logic
Figure 27-5. Filter
FILTSEL
DISABLE
Input
SYNCH
OUT
Q
D
R
Q
D
R
Q
D
R
D
EN
Q
FILTER
R
CLK_LUTn
CLR
27.3.1.6 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 can be programmed to provide inverted output.
The edge detector is enabled by writing ‘1’ to the Edge Detection bit (EDGEDET) in the LUT n Control A register
(CCL.LUTnCTRLA). In order to avoid unpredictable behavior, a valid filter option must be enabled.
The 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 27-6. Edge Detector
EDGEDET
CLK_LUTn
27.3.1.7 Sequencer Logic
Each LUT pair can be connected to a sequencer. The sequencer can function as either D flip-flop, JK flip-flop, gated
D latch, or RS latch. The function is selected by writing the Sequencer Selection (SEQSEL) bit group in the
Sequencer Control register (CCL.SEQCTRLn).
The sequencer receives its input from either the LUT, filter or edge detector, depending on the configuration.
A sequencer is clocked by the same clock as the corresponding even LUT. The clock source is selected by the Clock
Source (CLKSRC) bit group in the LUT n Control A register (CCL.LUTnCTRLA).
The flip-flop output (OUT) is refreshed on the rising edge of the clock. When the even LUT is disabled, the latch is
cleared asynchronously. The flip-flop Reset signal (R) is kept enabled for one clock cycle.
Gated D Flip-Flop (DFF)
The D input is driven by the even LUT output, and the G input is driven by the odd LUT output.
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CCL – Configurable Custom Logic
Figure 27-7. D Flip-Flop
Even LUT
CLK_LUTn
Odd LUT
Table 27-4. DFF Characteristics
R
G
D
OUT
1
X
X
Clear
0
1
1
Set
0
1
0
Clear
0
0
X
Hold state (no change)
JK Flip-Flop (JK)
The J input is driven by the even LUT output, and the K input is driven by the odd LUT output.
Figure 27-8. JK Flip-Flop
Even LUT
CLK_LUTn
Odd LUT
Table 27-5. 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
Gated D Latch (DLATCH)
The D input is driven by the even LUT output, and the G input is driven by the odd LUT output.
Figure 27-9. D Latch
Even LUT
D
Odd LUT
G
Q
OUT
Table 27-6. D Latch Characteristics
G
D
OUT
0
X
Hold state (no change)
1
0
Clear
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CCL – Configurable Custom Logic
...........continued
G
D
OUT
1
1
Set
RS Latch (RS)
The S input is driven by the even LUT output, and the R input is driven by the odd LUT output.
Figure 27-10. RS Latch
Even LUT
S
Odd LUT
R
Q
OUT
Table 27-7. RS Latch Characteristics
S
R
OUT
0
0
Hold state (no change)
0
1
Clear
1
0
Set
1
1
Forbidden state
27.3.1.8 Clock Source Settings
The filter, edge detector, and sequencer are, by default, clocked by the system clock (CLK_PER). It is also possible
to use other clock inputs (CLK_LUTn) to clock these blocks. This is configured by writing the Clock Source
(CLKSRC) bits in the LUT Control A register.
Figure 27-11. Clock Source Settings
Edge
detector
CLK_PER
IN[2]
OSC20M
OSCULP32K
OSCULP1K
Filter
Sequential
logic
CLKSRC
LUTn
When the Clock Source (CLKSRC) bit is written to 0x1, IN[2] is used to clock the corresponding filter and edge
detector (CLK_LUTn). The sequencer is clocked by the CLK_LUTn of the even LUT in the pair. When CLKSRC is
written to 0x1, IN[2] is treated as OFF (low) in the TRUTH table.
The CCL peripheral must be disabled while changing the clock source to avoid undefined outputs from the peripheral.
27.3.2
Interrupts
Table 27-8. Available Interrupt Vectors and Sources
Name Vector Description Conditions
CCL
CCL interrupt
© 2020 Microchip Technology Inc.
INTn in INTFLAG is raised as configured by the INTMODEn bits in the
CCL.INTCTRLn register
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CCL – Configurable Custom Logic
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 (peripheral.INTCTRL) register.
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.
27.3.3
Events
The CCL can generate the events shown in the table below.
Table 27-9. Event Generators in the CCL
Generator Name
Description
Event Type Generating Clock Domain Length of Event
Peripheral Event
CCL
LUTn
LUT output level Level
Asynchronous
Depends on the CCL
configuration
The CCL has the event users below for detecting and acting upon input events.
Table 27-10. Event Users in the CCL
User Name
Peripheral
Input
CCL
LUTnx
Description
Input Detection
Async/Sync
LUTn input x or clock signal
No detection
Async
The event signals are passed directly to the LUTs without synchronization or input detection logic.
Two event users are available for each LUT. They can be selected as LUTn inputs by writing to the INSELn bit groups
in the LUT n Control B and Control C registers (CCL.LUTnCTRLB or LUTnCTRLC).
Refer to the Event System (EVSYS) section for more details regarding the event types and the EVSYS configuration.
27.3.4
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, and/or
sequencer are enabled, the LUT output will be forced to ‘0’ in Standby Sleep mode. In Idle Sleep mode, the TRUTH
table decoder will continue the operation and the LUT output will be refreshed accordingly, regardless of the
RUNSTDBY bit.
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 sequencer. The availability of the IN[2] clock in sleep modes will
depend on the sleep settings of the peripheral used.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
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ATmega3208/3209
CCL – Configurable Custom Logic
27.4
Register Summary - CCL
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
...
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x0C
0x0D
0x0E
0x0F
0x10
0x11
0x12
0x13
0x14
0x15
0x16
0x17
CTRLA
SEQCTRL0
SEQCTRL1
7:0
7:0
7:0
27.5
RUNSTDBY
ENABLE
SEQSEL0[3:0]
SEQSEL1[3:0]
Reserved
INTCTRL0
Reserved
INTFLAGS
LUT0CTRLA
LUT0CTRLB
LUT0CTRLC
TRUTH0
LUT1CTRLA
LUT1CTRLB
LUT1CTRLC
TRUTH1
LUT2CTRLA
LUT2CTRLB
LUT2CTRLC
TRUTH2
LUT3CTRLA
LUT3CTRLB
LUT3CTRLC
TRUTH3
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
7:0
INTMODE3[1:0]
INTMODE2[1:0]
INTMODE1[1:0]
INT3
EDGEDET
OUTEN
INSEL1[3:0]
FILTSEL[1:0]
EDGEDET
OUTEN
INSEL1[3:0]
FILTSEL[1:0]
EDGEDET
OUTEN
INSEL1[3:0]
FILTSEL[1:0]
EDGEDET
OUTEN
INSEL1[3:0]
FILTSEL[1:0]
INTMODE0[1:0]
INT2
INT1
CLKSRC[2:0]
INSEL0[3:0]
INSEL2[3:0]
INT0
ENABLE
CLKSRC[2:0]
INSEL0[3:0]
INSEL2[3:0]
ENABLE
CLKSRC[2:0]
INSEL0[3:0]
INSEL2[3:0]
ENABLE
CLKSRC[2:0]
INSEL0[3:0]
INSEL2[3:0]
ENABLE
TRUTH[7:0]
TRUTH[7:0]
TRUTH[7:0]
TRUTH[7:0]
Register Description
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Preliminary Datasheet
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CCL – Configurable Custom Logic
27.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CTRLA
0x00
0x00
-
6
RUNSTDBY
R/W
0
5
4
3
2
1
0
ENABLE
R/W
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.
Value
Description
0
The system clock is not required in Standby Sleep mode
1
The system clock is required in Standby Sleep mode
Bit 0 – ENABLE Enable
Value
Description
0
The peripheral is disabled
1
The peripheral is enabled
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ATmega3208/3209
CCL – Configurable Custom Logic
27.5.2
Sequencer Control 0
Name:
Offset:
Reset:
Property:
Bit
7
SEQCTRL0
0x01
0x00
Enable-Protected
6
Access
Reset
5
4
3
R/W
0
2
1
SEQSEL0[3:0]
R/W
R/W
0
0
0
R/W
0
Bits 3:0 – SEQSEL0[3:0] Sequencer Selection
This bit group selects the sequencer configuration for LUT0 and LUT1.
Value
Name
Description
0x0
DISABLE
The sequencer is disabled
0x1
DFF
D flip-flop
0x2
JK
JK flip-flop
0x3
LATCH
D latch
0x4
RS
RS latch
Other
Reserved
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ATmega3208/3209
CCL – Configurable Custom Logic
27.5.3
Sequencer Control 1
Name:
Offset:
Reset:
Property:
Bit
7
SEQCTRL1
0x02
0x00
Enable-Protected
6
Access
Reset
5
4
3
R/W
0
2
1
SEQSEL1[3:0]
R/W
R/W
0
0
0
R/W
0
Bits 3:0 – SEQSEL1[3:0] Sequencer Selection
This bit group selects the sequencer configuration for LUT2 and LUT3.
Value
Name
Description
0x0
DISABLE
The sequencer is disabled
0x1
DFF
D flip-flop
0x2
JK
JK flip-flop
0x3
LATCH
D latch
0x4
RS
RS latch
Other
Reserved
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ATmega3208/3209
CCL – Configurable Custom Logic
27.5.4
Interrupt Control 0
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
INTCTRL0
0x05
0x00
-
7
6
INTMODE3[1:0]
R/W
R/W
0
0
5
4
INTMODE2[1:0]
R/W
R/W
0
0
3
2
INTMODE1[1:0]
R/W
R/W
0
0
1
0
INTMODE0[1:0]
R/W
R/W
0
0
Bits 0:1, 2:3, 4:5, 6:7 – INTMODE
The bits in INTMODEn select the interrupt sense configuration for LUTn-OUT.
Value
Name
Description
0x0
INTDISABLE
Interrupt disabled
0x1
RISING
Sense rising edge
0x2
FALLING
Sense falling edge
0x3
BOTH
Sense both edges
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ATmega3208/3209
CCL – Configurable Custom Logic
27.5.5
Interrupt Flag
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x07
0x00
-
6
Access
Reset
5
4
3
INT3
R/W
0
2
INT2
R/W
0
1
INT1
R/W
0
0
INT0
R/W
0
Bits 0, 1, 2, 3 – INT Interrupt Flag
The INTn flag is set when the LUTn output change matches the Interrupt Sense mode as defined in CCL.INTCTRLn.
Writing a ‘1’ to this flag’s bit location will clear the flag.
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CCL – Configurable Custom Logic
27.5.6
LUT n Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
LUTnCTRLA
0x08 + n*0x04 [n=0..3]
0x00
Enable-Protected
7
EDGEDET
R/W
0
6
OUTEN
R/W
0
5
4
FILTSEL[1:0]
R/W
R/W
0
0
3
R/W
0
2
CLKSRC[2:0]
R/W
0
1
R/W
0
0
ENABLE
R/W
0
Bit 7 – EDGEDET Edge Detection
Value
Description
0
Edge detector is disabled
1
Edge detector is enabled
Bit 6 – OUTEN Output Enable
This bit enables the LUT output to the LUTn OUT pin. When written to ‘1’, the pin configuration of the PORT I/OController is overridden.
Value
Description
0
Output to pin disabled
1
Output to pin enabled
Bits 5:4 – FILTSEL[1:0] Filter Selection
These bits select the LUT output filter options.
Value
Name
0x0
DISABLE
0x1
SYNCH
0x2
FILTER
0x3
-
Description
Filter disabled
Synchronizer enabled
Filter enabled
Reserved
Bits 3:1 – CLKSRC[2:0] Clock Source Selection
This bit selects between various clock sources to be used as the clock (CLK_LUTn) for a LUT.
The CLK_LUTn of the even LUT is used for clocking the sequencer of a LUT pair.
Value
Name
Description
0x0
CLKPER
CLK_PER is clocking the LUT
0x1
IN2
LUT input 2 is clocking the LUT
0x2
-
Reserved
0x3
-
Reserved
0x4
OSC20M
16/20 MHz oscillator before prescaler is clocking the LUT
0x5
OSCULP32K
32.768 kHz internal oscillator is clocking the LUT
0x6
OSCULP1K
1.024 kHz (OSCKULP32K after DIV32) is clocking the LUT
0x7
-
Reserved
Bit 0 – ENABLE LUT Enable
Value
Description
0
The LUT is disabled
1
The LUT is enabled
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Preliminary Datasheet
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ATmega3208/3209
CCL – Configurable Custom Logic
27.5.7
LUT n Control B
Name:
Offset:
Reset:
Property:
LUTnCTRLB
0x09 + n*0x04 [n=0..3]
0x00
Enable-Protected
Note:
1. SPI connections to the CCL work in master SPI mode only.
2. USART connections to the CCL work only when the USART is in one of the following modes:
– Asynchronous USART
– Synchronous USART master
Bit
7
Access
Reset
6
5
INSEL1[3:0]
R/W
R/W
0
0
R/W
0
4
3
R/W
0
R/W
0
2
1
INSEL0[3:0]
R/W
R/W
0
0
0
R/W
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
Name
Description
0x0
MASK
None (masked)
0x1
FEEDBACK
Feedback input
0x2
LINK
Output from LUTn+1
0x3
EVENTA
Event input source A
0x4
EVENTB
Event input source B
0x5
IO
I/O-pin LUTn-IN1
0x6
AC0
AC0 out
0x7
-
Reserved
0x8
USART1
USART1 TXD
0x9
SPI0
SPI0 MOSI
0xA
TCA0
TCA0 WO1
0xB
-
Reserved
0xC
TCB1
TCB1 WO
Other
-
Reserved
Bits 3:0 – INSEL0[3:0] LUT n Input 0 Source Selection
These bits select the source for input 0 of LUT n.
Value
Name
Description
0x0
MASK
None (masked)
0x1
FEEDBACK
Feedback input
0x2
LINK
Output from LUTn+1
0x3
EVENTA
Event input source A
0x4
EVENTB
Event input source B
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Preliminary Datasheet
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ATmega3208/3209
CCL – Configurable Custom Logic
...........continued
Value
Name
Description
0x5
IO
I/O-pin LUTn-IN0
0x6
AC0
AC0 out
0x7
-
Reserved
0x8
USART0
USART0 TXD
0x9
SPI0
SPI0 MOSI
0xA
TCA0
TCA0 WO0
0xB
-
Reserved
0xC
TCB0
TCB0 WO
Other
-
Reserved
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CCL – Configurable Custom Logic
27.5.8
LUT n Control C
Name:
Offset:
Reset:
Property:
Bit
LUTnCTRLC
0x0A + n*0x04 [n=0..3]
0x00
Enable-Protected
7
6
5
4
Access
Reset
3
R/W
0
2
1
INSEL2[3:0]
R/W
R/W
0
0
0
R/W
0
Bits 3:0 – INSEL2[3:0] LUT n Input 2 Source Selection
These bits select the source for input 2 of LUT n.
Value
Name
Description
0x0
MASK
None (masked)
0x1
FEEDBACK
Feedback input
0x2
LINK
Output from LUTn+1
0x3
EVENTA
Event input source A
0x4
EVENTB
Event input source B
0x5
IO
I/O-pin LUTn-IN2
0x6
AC0
AC0 out
0x7
-
Reserved
0x8
USART2
USART2 TXD
0x9
SPI0
SPI0 SCK
0xA
TCA0
TCA0 WO2
0xB
-
Reserved
0xC
TCB2
TCB2 WO
Other
-
Reserved
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ATmega3208/3209
CCL – Configurable Custom Logic
27.5.9
TRUTHn
Name:
Offset:
Reset:
Property:
Bit
7
TRUTHn
0x0B + n*0x04 [n=0..3]
0x00
Enable-Protected
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
TRUTH[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
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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ATmega3208/3209
AC - Analog Comparator
28.
AC - Analog Comparator
28.1
Features
•
•
•
•
•
•
•
28.2
Selectable response time
Selectable hysteresis
Analog comparator output available on pin
Comparator output inversion available
Flexible input selection:
– Four Positive pins
– Three Negative pins
– Internal reference voltage generator (DACREF)
Interrupt generation on:
– Rising edge
– Falling edge
– Both edges
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 and internally generated inputs. The analog comparator output state
can also be output on a pin for use by external devices.
An AC has one positive input and one negative input. The digital output from the comparator is '1' when the
difference between the positive and the negative input voltage is positive, and '0' otherwise.
Block Diagram
Figure 28-1. Analog Comparator
AINP0
.
.
.
+
AINPn
VREF
.
..
Voltage
divider
-
Controller
logic
Invert
AINNn
AC
Hysteresis
AINN0
Enable
28.2.1
CMP
(Int. Req)
OUT
Event out
CTRLA
DACREF
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ATmega3208/3209
AC - Analog Comparator
28.2.2
Signal Description
Signal
Description
Type
AINNn
Negative Input n
Analog
AINPn
Positive Input n
Analog
OUT
Comparator Output for AC
Digital
28.3
Functional Description
28.3.1
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)
• 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 2.5 µs. If an internal reference is used, the reference start-up time is
normally longer than the AC start-up time.
To avoid the pin being tri-stated when the AC is disabled, the OUT pin must be configured as output in PORTx.DIR
28.3.2
Operation
28.3.2.1 Input Hysteresis
Applying an input hysteresis helps to prevent 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 (ACn.CTRLA).
28.3.2.2 Input Sources
An 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 (ACn.MUXTRLA).
28.3.2.2.1 Pin Inputs
The following Analog input pins on the port can be selected as input to the analog comparator:
•
•
•
•
•
•
•
AINN0
AINN1
AINN2
AINP0
AINP1
AINP2
AINP3
28.3.2.2.2 Internal Inputs
The DAC has the following internal inputs:
•
Internal reference voltage generator (DACREF)
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AC - Analog Comparator
28.3.2.3 Power Modes
For power sensitive applications, the AC provides multiple power modes with balance power consumption and
propagation delay. A mode is selected by writing to the Mode bits (MODE) in the Control A register (ACn.CTRLA).
28.3.2.4 Signal Compare and Interrupt
After successful initialization of the AC, and after configuring the desired properties, the result of the comparison is
continuously updated and available for application software, the Event system, or on a pin.
The AC can generate a comparator Interrupt, COMP. The AC can request this interrupt on either rising, falling, or
both edges of the toggling comparator output. This is configured by writing to the Interrupt Modes bit field in the
Control A register (INTMODE bits in ACn.CTRLA).
The Interrupt is enabled by writing a ‘1’ to the Analog Comparator Interrupt Enable bit in the Interrupt Control register
(COMP bit in ACn.INTCTRL).
28.3.3
Events
The AC will generate the following event automatically when the AC is enabled:
•
The digital output from the AC (OUT in the block diagram) is available as an Event System source. The events
from the AC are asynchronous to any clocks in the device.
The AC has no event inputs.
28.3.4
Interrupts
Table 28-1. Available Interrupt Vectors and Sources
Name
Vector Description
Conditions
COMP
Analog comparator interrupt
AC output is toggling as configured by INTMODE in ACn.CTRLA
When an interrupt condition occurs, the corresponding Interrupt Flag is set in the Status register (ACn.STATUS).
An interrupt source is enabled or disabled by writing to the corresponding bit in the peripheral's Interrupt Control
register (ACn.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 ACn.STATUS register description for
details on how to clear Interrupt Flags.
28.3.5
Sleep Mode Operation
In Idle sleep mode, the AC will continue to operate as normal.
In Standby sleep mode, the AC is disabled by default. If the Run in Standby Sleep Mode bit (RUNSTDBY) in the
Control A register (ACn.CTRLA) is written to '1', the AC will continue to operate as normal with Event, Interrupt, and
AC output on pad even if the CLK_PER is not running in Standby sleep mode.
In Power Down sleep mode, the AC and the output to the pad are disabled.
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Preliminary Datasheet
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ATmega3208/3209
AC - Analog Comparator
28.4
Register Summary - AC
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
CTRLA
Reserved
MUXCTRL
Reserved
DACREF
Reserved
INTCTRL
STATUS
7:0
RUNSTDBY
7:0
INVERT
28.5
7:0
7:0
7:0
OUTEN
INTMODE[1:0]
LPMODE
MUXPOS[1:0]
HYSMODE[1:0]
ENABLE
MUXNEG[1:0]
DACREF[7:0]
STATE
CMP
CMP
Register Description
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AC - Analog Comparator
28.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
RUNSTDBY
R/W
0
CTRLA
0x00
0x00
-
6
OUTEN
R/W
0
5
4
INTMODE[1:0]
R/W
R/W
0
0
3
LPMODE
R/W
0
2
1
HYSMODE[1:0]
R/W
R/W
0
0
0
ENABLE
R/W
0
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
Description
0
In Standby sleep mode, the peripheral is halted
1
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 edges of the AC output triggers an interrupt request.
Value
Name
Description
0x0
BOTHEDGE
Both negative and positive edge
0x1
Reserved
0x2
NEGEDGE
Negative edge
0x3
POSEDGE
Positive edge
Bit 3 – LPMODE Low-Power Mode
Writing a '1' to this bit reduces the current through the comparator. This reduces the power consumption but
increases the reaction time of the AC.
Value
Description
0
Low-Power mode disabled
1
Low-Power mode enabled
Bits 2:1 – HYSMODE[1:0] Hysteresis Mode Select
Writing these bits select the hysteresis mode for the AC input.
Value
Name
Description
0x0
NONE
No hysteresis
0x1
SMALL
Small hysteresis
0x2
MEDIUM
Medium hysteresis
0x3
LARGE
Large hysteresis
Bit 0 – ENABLE Enable AC
Writing this bit to '1' enables the AC.
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AC - Analog Comparator
28.5.2
Mux Control
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
MUXCTRL
0x02
0x00
-
7
INVERT
R/W
0
6
5
4
3
MUXPOS[1:0]
R/W
R/W
0
0
2
1
0
MUXNEG[1:0]
R/W
R/W
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
Name
Description
0x0
AINP0
Positive pin 0
0x1
AINP1
Positive pin 1
0x2
AINP2
Positive pin 2
0x3
AINP3
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
Name
Description
0x0
AINN0
Negative pin 0
0x1
AINN1
Negative pin 1
0x2
AINN2
Negative pin 2
0x3
DACREF
Internal DAC reference
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ATmega3208/3209
AC - Analog Comparator
28.5.3
DAC Voltage Reference
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
DACREF
0x04
0xFF
R/W
7
6
5
R/W
1
R/W
1
R/W
1
4
3
DACREF[7:0]
R/W
R/W
1
1
2
1
0
R/W
1
R/W
1
R/W
1
Bits 7:0 – DACREF[7:0] DACREF Data Value
These bits define the output voltage from the internal voltage divider. The DAC reference is divided from on the
selections in the VREF module and the output voltage is defined by:
DACREF
�DACREF =
× �REF
256
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AC - Analog Comparator
28.5.4
Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x06
0x00
-
6
5
4
3
Access
Reset
2
1
0
CMP
R/W
0
Bit 0 – CMP Analog Comparator Interrupt Enable
Writing this bit to '1' enables Analog Comparator Interrupt.
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AC - Analog Comparator
28.5.5
Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x07
0x00
-
6
Access
Reset
5
4
STATE
R
0
3
2
1
0
CMP
R/W
0
Bit 4 – STATE Analog Comparator State
This shows the current status of the OUT signal from the AC. This will have a synchronizer delay to get updated in
the I/O register (three 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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ADC - Analog-to-Digital Converter
29.
ADC - Analog-to-Digital Converter
29.1
Features
•
•
•
•
•
•
•
•
•
•
•
29.2
10-Bit Resolution
0V to VDD Input Voltage Range
Multiple Internal ADC Reference Voltages
External Reference Input
Free-running and Single Conversion mode
Interrupt Available on Conversion Complete
Optional Interrupt on Conversion Results
Temperature Sensor Input Channel
Optional Event triggered conversion
Window Comparator Function for accurate monitoring or defined Thresholds
Accumulation up to 64 Samples per Conversion
Overview
The Analog-to-Digital Converter (ADC) peripheral produces 10-bit results. The ADC input can either be internal (e.g.
a voltage reference) or external through the analog input pins. The ADC is connected to an analog multiplexer, which
allows selection of multiple single-ended voltage inputs. The single-ended voltage inputs refer to 0V (GND).
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.
The ADC input signal is fed through a sample-and-hold circuit that ensures that the input voltage to the ADC is held
at a constant level during sampling.
Selectable voltage references from the internal Voltage Reference (VREF) peripheral, VDD supply voltage, or external
VREF pin (VREFA).
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.
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ADC - Analog-to-Digital Converter
29.2.1
Block Diagram
Figure 29-1. Block Diagram
AVDD
VREFA
Internal reference
.
.
.
ADC
AINn
MUXPOS
"convert"
Temp.Sense
"enable"
DACREF0
ACC
"accumulate"
AIN0
AIN1
VREF
Control logic
RES
>
<
WCOMP
(Int. Req.)
WINLT
WINHT
RESRDY
(Int. Req.)
The analog input channel is selected by writing to the MUXPOS bits in the MUXPOS register (ADCn.MUXPOS). Any
of the ADC input pins, GND, internal Voltage Reference (VREF), or temperature sensor, can be selected as singleended input to the ADC. The ADC is enabled by writing a ‘1’ to the ADC ENABLE bit in the Control A register
(ADCn.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 ADCn.CTRLA is ‘0’.
The ADC generates a 10-bit result that can be read from the Result Register (ADCn.RES). The result is presented
right adjusted.
29.2.2
Signal Description
Pin Name
Type
Description
AIN[n:0]
Analog input
Analog input pin
VREFA
Analog input
External voltage reference pin
29.2.2.1 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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ADC - Analog-to-Digital Converter
Figure 29-2. 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 29-3. 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.
Figure 29-4. Integral Non-Linearity
Output Code
INL
Ideal ADC
Actual ADC
VREF
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ADC - Analog-to-Digital Converter
Differential NonLinearity (DNL)
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 29-5. 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.
29.3
Functional Description
29.3.1
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
(ADCn.CTRLA).
2. Optional: Enable the Free-Running mode by writing a ‘1’ to the Free-Running bit (FREERUN) in
ADCn.CTRLA.
3. 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 (ADCn.CTRLB).
4. Configure a voltage reference by writing to the Reference Selection bit (REFSEL) in the Control C register
(ADCn.CTRLC). The default is the internal voltage reference of the device (VREF, as configured there).
5. Configure the CLK_ADC by writing to the Prescaler bit field (PRESC) in the Control C register (ADCn.CTRLC).
6. Configure an input by writing to the MUXPOS bit field in the MUXPOS register (ADCn.MUXPOS).
7. Optional: Enable Start Event input by writing a ‘1’ to the Start Event Input bit (STARTEI) in the Event Control
register (ADCn.EVCTRL). Configure the Event System accordingly.
8. Enable the ADC by writing a ‘1’ to the ENABLE bit in ADCn.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 (ADCn.COMMAND).
29.3.1.1 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 peripheral.
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ADC - Analog-to-Digital Converter
29.3.2
Operation
29.3.2.1 Starting a Conversion
Once the input channel is selected by writing to the MUXPOS register (ADCn.MUXPOS), a conversion is triggered by
writing a ‘1’ to the ADC Start Conversion bit (STCONV) in the Command register (ADCn.COMMAND). This bit is ‘1’
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 (ADCn.INTFLAG) is set. The corresponding interrupt vector is executed if the Result Ready Interrupt
Enable bit (RESRDY) in the Interrupt Control register (ADCn.INTCTRL) is ‘1’ and the Global Interrupt Enable bit is ‘1’.
A single conversion can be started by writing a ‘1’ to the STCONV bit in ADCn.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 ADCn.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 (ADCn.EVCTRL). Any incoming event routed to the ADC through 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 ADCn.COMMAND is set. STCONV will
be cleared when the conversion is complete.
In Free-Running mode, the first conversion is started by writing the STCONV bit to ‘1’ in ADCn.COMMAND. A new
conversion cycle is started immediately after the previous conversion cycle has completed. A conversion complete
will set the RESRDY flag in ADCn.INTFLAGS.
29.3.2.2 Clock Generation
Figure 29-6. 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 50 kHz and 1.5 MHz for maximum resolution. If a lower
resolution than 10 bits is selected, the input clock frequency to the ADC can be higher than 1.5 MHz 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 100 kHz. The prescaling is selected by writing to the Prescaler bits (PRESC) in the Control C register
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ADC - Analog-to-Digital Converter
(ADCn.CTRLC). The prescaler starts counting from the moment the ADC is switched on by writing a ‘1’ to the
ENABLE bit in ADCn.CTRLA. The prescaler keeps running as long as the ENABLE bit is ‘1’. The prescaler counter is
reset to zero when the ENABLE bit is ‘0’.
When initiating a conversion by writing a ‘1’ to the Start Conversion bit (STCONV) in the Command register
(ADCn.COMMAND) or from an 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:
StartDelay =
PRESCfactor
+2
2
Figure 29-7. Start Conversion and Clock Generation
CLK_PER
STCONV
CLK_PER/2
CLK_PER/4
CLK_PER/8
29.3.2.3 Conversion Timing
A normal conversion takes 13 CLK_ADC cycles. The actual sample-and-hold takes place two CLK_ADC cycles after
the start of a conversion. Start of conversion is initiated by writing a ‘1’ to the STCONV bit in ADCn.COMMAND.
When a conversion is complete, the result is available in the Result register (ADCn.RES), and the Result Ready
interrupt flag is set (RESRDY in ADCn.INTFLAG). The interrupt flag will be cleared when the result is read from the
Result registers, or by writing a ‘1’ to the RESRDY bit in ADCn.INTFLAG.
Figure 29-8. ADC Timing Diagram - Single Conversion
Cycle Number
1
2
3
4
5
6
7
8
9
10
11
12
13
CLK_ADC
ENABLE
STCONV
RESRDY
RES
Result
conversion
complete
Both sampling time and sampling length can be adjusted using the Sample Delay bit field in Control D
(ADCn.CTRLD) and sampling Sample Length bit field in the Sample Control register (ADCn.SAMPCTRL). Both of
these control the ADC sampling time in a number of CLK_ADC cycles. This allows sampling high-impedance sources
without relaxing conversion speed. See the register description for further information. Total sampling time is given
by:
sample
SampleTime =
2 + SAMPDLY + SAMPLEN
�CLK_ADC
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ADC - Analog-to-Digital Converter
Figure 29-9. 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)
In Free-Running mode, a new conversion will be started immediately after the conversion completes, while the
STCONV bit is ‘1’. The sampling rate RS in free-running mode is calculated by:
�S =
�CLK_ADC
13 + SAMPDLY + SAMPLEN
Figure 29-10. ADC Timing Diagram - Free-Running Conversion
2
3
4
6
5
7
1
Cycle Number
8
9
10
11
12
13
1
2
CLK_ADC
ENABLE
STCONV
RESRDY
RES
Result
sample
conversion
complete
29.3.2.4 Changing Channel or Reference Selection
The MUXPOS bits in the ADCn.MUXPOS register and the REFSEL bits in the ADCn.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
ADCn.INTFLAGS is set). The conversion starts on the following rising CLK_ADC clock edge after the STCONV bit is
written to ‘1’.
29.3.2.4.1 ADC Input Channels
When changing channel selection, the user should observe the following guidelines to ensure that the correct
channel is selected:
In Single Conversion mode: 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.
In Free-Running mode: The channel should be selected before starting the first conversion. The channel selection
may be changed one ADC clock cycle after writing ‘1’ to the STCONV bit. Since the next conversion has already
started automatically, the next result will reflect the previous channel selection. Subsequent conversions will reflect
the new channel selection.
The ADC requires a settling time after switching the input channel - refer to the Electrical Characteristics section for
details.
29.3.2.4.2 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 value is 0x3FF.
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VREF can be selected by writing the Reference Selection bits (REFSEL) in the Control C register (ADCn.CTRLC) as
either VDD, external reference VREFA, or an internal reference from the VREF peripheral. VDD is connected to the ADC
through a passive switch.
When using the external reference voltage VREFA, configure ADCnREFSEL[0:2] in the corresponding VREF.CTRLn
register to the value that is closest, but above the 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.
29.3.2.4.3 Analog Input Circuitry
The analog input circuitry is illustrated in Figure 29-11. 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 10 kΩ or less. If such a source is
used, the sampling time will be negligible. If a source with a 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 29-11. Analog Input Schematic
IIH
ADCn
Rin
Cin
IIL
VDD/2
29.3.2.5 ADC Conversion Result
After the conversion is complete (RESRDY is ‘1’), the conversion result RES is available in the ADC Result Register
(ADCn.RES). The result for a 10-bit conversion is given as:
1023 × �IN
�REF
where VIN is the voltage on the selected input pin and VREF the selected voltage reference (see description for
REFSEL in ADCn.CTRLC and ADCn.MUXPOS).
RES =
29.3.2.6 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 by configuring the VREF peripheral.
2. Select the internal voltage reference by writing the REFSEL bits in ADCn.CTRLC to 0x0.
3. Select the ADC temperature sensor channel by configuring the MUXPOS register (ADCn.MUXPOS). This
enables the temperature sensor.
4. In ADCn.CTRLD select INITDLY ≥ 32 µs × �CLK_ADC
5.
6.
7.
8.
In ADCn.SAMPCTRL select SAMPLEN ≥ 32 µs × �CLK_ADC
In ADCn.CTRLC select SAMPCAP = 1
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 a gain/slope correction
• SIGROW.TEMPSENSE1 is an offset correction
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ADC - Analog-to-Digital Converter
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 bytes of the Result register (ADCn.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;
29.3.2.7 Window Comparator Mode
The ADC can raise the WCOMP flag in the Interrupt and Flag register (ADCn.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 (ADCn.WINLT and
ADCn.WINHT). Writing to the Window Comparator mode bit field (WINCM) in the Control E register (ADCn.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:
1. Choose which Window Comparator to use (see the WINCM description in ADCn.CTRLE), and set the required
threshold(s) by writing to ADCn.WINLT and/or ADCn.WINHT.
2. Optional: enable the interrupt request by writing a ‘1’ to the Window Comparator Interrupt Enable bit (WCOMP)
in the Interrupt Control register (ADCn.INTCTRL).
3. Enable the Window Comparator and select a mode by writing a non-zero value to the WINCM bit field in
ADCn.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 raised only once, after taking the last sample of the accumulation.
29.3.3
Events
An ADC conversion can be triggered automatically by an event input if the Start Event Input bit (STARTEI) in the
Event Control register (ADCn.EVCTRL) is written to ‘1’.
When a new result can be read from the Result register (ADCn.RES), the ADC will generate a result ready event.
The event is a pulse of length one clock period and handled by the Event System (EVSYS). The ADC result ready
event is always generated when the ADC is enabled.
See also the description of the Asynchronous User Channel n Input Selection in the Event System
(EVSYS.ASYNCUSERn).
29.3.4
Interrupts
Table 29-1. Available Interrupt Vectors and Sources
Name
Vector Description
Conditions
RESRDY Result Ready interrupt
The conversion result is available in the Result register (ADCn.RES).
WCOMP
As defined by WINCM in ADCn.CTRLE.
Window Comparator interrupt
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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 (peripheral.INTCTRL) register.
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.
29.3.5
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 (ADCn.CTRLA) is written to ‘1’.
When the device is entering Standby Sleep mode when RUNSTDBY is ‘1’, 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), or the ADC must be in
free-running mode with the first conversion triggered by software before entering sleep. 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 (ADCn.COMMAND) is set, and the conversion will start. When the conversion is completed, the
Result Ready Flag (RESRDY) in the Interrupt Flags register (ADCn.INTFLAGS) is set and the STCONV bit in
ADCn.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 (ADCn.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 the end of conversion, the Result Ready Flag (RESRDY) will be set, but the content of
the result registers (ADCn.RES) is invalid since the ADC was halted in the middle of a conversion.
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29.4
Register Summary - ADCn
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x0C
0x0D
0x0E
...
0x0F
CTRLA
CTRLB
CTRLC
CTRLD
CTRLE
SAMPCTRL
MUXPOS
Reserved
COMMAND
EVCTRL
INTCTRL
INTFLAGS
DBGCTRL
TEMP
7:0
7:0
7:0
7:0
7:0
7:0
7:0
0x10
RES
0x12
WINLT
0x14
WINHT
0x16
CALIB
29.5
RUNSTBY
7:0
7:0
7:0
7:0
7:0
7:0
RESSEL
SAMPCAP
INITDLY[2:0]
REFSEL[1:0]
ASDV
FREERUN
SAMPNUM[2:0]
PRESC[2:0]
SAMPDLY[3:0]
WINCM[2:0]
SAMPLEN[4:0]
MUXPOS[4:0]
WCOMP
WCOMP
ENABLE
STCONV
STARTEI
RESRDY
RESRDY
DBGRUN
TEMP[7:0]
Reserved
7:0
15:8
7:0
15:8
7:0
15:8
7:0
RES[7:0]
RES[15:8]
WINLT[7:0]
WINLT[15:8]
WINHT[7:0]
WINHT[15:8]
DUTYCYC
Register Description
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29.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
RUNSTBY
R/W
0
CTRLA
0x00
0x00
-
6
5
4
3
2
RESSEL
R/W
0
1
FREERUN
R/W
0
0
ENABLE
R/W
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.
Value
Description
0
Full 10-bit resolution. The 10-bit ADC results are accumulated or stored in the ADC Result register
(ADC.RES).
1
8-bit resolution. The conversion results are truncated to eight bits (MSbs) before they are accumulated
or stored in the ADC Result register (ADC.RES). The two Least Significant bits are discarded.
Bit 1 – FREERUN Free-Running
Writing a ‘1’ to this bit will enable the Free-Running mode for the data acquisition. The first conversion is started by
writing the STCONV bit in ADC.COMMAND high. In the Free-Running mode, a new conversion cycle is started
immediately after or as soon as the previous conversion cycle has completed. This is signaled by the RESRDY flag in
ADCn.INTFLAGS.
Bit 0 – ENABLE ADC Enable
Value
Description
0
ADC is disabled
1
ADC is enabled
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29.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
7
CTRLB
0x01
0x00
-
6
5
4
3
Access
Reset
2
R/W
0
1
SAMPNUM[2:0]
R/W
0
0
R/W
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 (ADC.RES) in one complete conversion.
Value
Name
Description
0x0
NONE
No accumulation.
0x1
ACC2
2 results accumulated.
0x2
ACC4
4 results accumulated.
0x3
ACC8
8 results accumulated.
0x4
ACC16
16 results accumulated.
0x5
ACC32
32 results accumulated.
0x6
ACC64
64 results accumulated.
0x7
Reserved.
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29.5.3
Control C
Name:
Offset:
Reset:
Property:
Bit
7
Access
Reset
R
0
CTRLC
0x02
0x00
-
6
SAMPCAP
R/W
0
5
4
REFSEL[1:0]
R/W
R/W
0
0
3
2
R
0
R/W
0
1
PRESC[2:0]
R/W
0
0
R/W
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
Description
0
Recommended for reference voltage values below 1V.
1
Reduced size of sampling capacitance. Recommended for higher reference voltages.
Bits 5:4 – REFSEL[1:0] Reference Selection
These bits select the voltage reference for the ADC.
Value
Name
Description
0x0
INTERNAL
Internal reference
0x1
VDD
VDD
0x2
VREFA
External reference VREFA
Other
Reserved.
Bits 2:0 – PRESC[2:0] Prescaler
These bits define the division factor from the peripheral clock (CLK_PER) to the ADC clock (CLK_ADC).
Value
Name
Description
0x0
DIV2
CLK_PER divided by 2
0x1
DIV4
CLK_PER divided by 4
0x2
DIV8
CLK_PER divided by 8
0x3
DIV16
CLK_PER divided by 16
0x4
DIV32
CLK_PER divided by 32
0x5
DIV64
CLK_PER divided by 64
0x6
DIV128
CLK_PER divided by 128
0x7
DIV256
CLK_PER divided by 256
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29.5.4
Control D
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
R/W
0
CTRLD
0x03
0x00
-
6
INITDLY[2:0]
R/W
0
5
R/W
0
4
ASDV
R/W
0
3
R/W
0
2
1
SAMPDLY[3:0]
R/W
R/W
0
0
0
R/W
0
Bits 7:5 – INITDLY[2:0] Initialization Delay
These bits define the initialization/start-up delay before the first sample when enabling the ADC or changing to an
internal reference voltage. Setting this delay will ensure that the reference, MUXes, etc. are 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
Name
Description
0x0
DLY0
Delay 0 CLK_ADC cycles.
0x1
DLY16
Delay 16 CLK_ADC cycles.
0x2
DLY32
Delay 32 CLK_ADC cycles.
0x3
DLY64
Delay 64 CLK_ADC cycles.
0x4
DLY128
Delay 128 CLK_ADC cycles.
0x5
DLY256
Delay 256 CLK_ADC cycles.
Other
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 the
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
Name
Description
0
ASVOFF
The Automatic Sampling Delay Variation is disabled.
1
ASVON
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 also be modified automatically from one sampling cycle to another, by setting
the ASDV bit. The delay is expressed as CLK_ADC cycles and is given directly by the bit field setting. The sampling
cap is kept open during the delay.
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29.5.5
Control E
Name:
Offset:
Reset:
Property:
Bit
7
CTRLE
0x4
0x00
-
6
5
4
3
Access
Reset
2
R/W
0
1
WINCM[2:0]
R/W
0
0
R/W
0
Bits 2:0 – WINCM[2:0] Window Comparator Mode
This field enables and defines 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.
Value
Name
Description
0x0
NONE
No Window Comparison (default)
0x1
BELOW
RESULT < WINLT
0x2
ABOVE
RESULT > WINHT
0x3
INSIDE
WINLT < RESULT < WINHT
0x4
OUTSIDE
RESULT < WINLT or RESULT >WINHT)
Other
Reserved
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29.5.6
Sample Control
Name:
Offset:
Reset:
Property:
Bit
7
SAMPCTRL
0x5
0x00
-
6
Access
Reset
5
4
3
R/W
0
R/W
0
2
SAMPLEN[4:0]
R/W
0
1
0
R/W
0
R/W
0
Bits 4:0 – SAMPLEN[4:0] Sample Length
These bits extend the ADC sampling length in a 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 increases with the selected sampling length.
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29.5.7
MUXPOS
Name:
Offset:
Reset:
Property:
Bit
7
MUXPOS
0x06
0x00
-
6
5
Access
Reset
4
3
R/W
0
R/W
0
2
MUXPOS[4:0]
R/W
0
1
0
R/W
0
R/W
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.
MUXPOS
Name
Input
0x00-0x0F
AIN0-AIN15
ADC input pin 0 - 15
0x10-0x1B
-
Reserved
0x1C
DACREF0
DAC reference in AC0
0x1D
-
Reserved
0x1E
TEMPSENSE
Temperature sensor
0x1F
GND
GND
Other
-
Reserved
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29.5.8
Command
Name:
Offset:
Reset:
Property:
Bit
7
COMMAND
0x08
0x00
-
6
5
4
3
Access
Reset
2
1
0
STCONV
R/W
0
Bit 0 – STCONV Start Conversion
Writing a ‘1’ to this bit will start a single measurement. If in Free-Running mode this will start the first conversion.
STCONV will read as ‘1’ as long as a conversion is in progress. When the conversion is complete, this bit is
automatically cleared.
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29.5.9
Event Control
Name:
Offset:
Reset:
Property:
Bit
7
EVCTRL
0x09
0x00
-
6
5
4
3
Access
Reset
2
1
0
STARTEI
R/W
0
Bit 0 – STARTEI Start Event Input
This bit enables using the event input as trigger for starting a conversion.
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29.5.10 Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x0A
0x00
-
6
5
4
3
Access
Reset
2
1
WCOMP
R/W
0
0
RESRDY
R/W
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.
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29.5.11 Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x0B
0x00
-
6
5
4
3
Access
Reset
2
1
WCOMP
R/W
0
0
RESRDY
R/W
0
Bit 1 – WCOMP Window Comparator Interrupt Flag
This window comparator flag is set when the measurement is complete and if the result matches the selected
Window Comparator mode defined by WINCM (ADCn.CTRLE). The comparison is done at the end of the 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.
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29.5.12 Debug Run
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x0C
0x00
-
6
5
4
3
2
Access
Reset
1
0
DBGRUN
R/W
0
Bit 0 – DBGRUN Debug Run
Value
Description
0
The peripheral is halted in Break Debug mode and ignores events
1
The peripheral will continue to run in Break Debug mode when the CPU is halted
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29.5.13 Temporary
Name:
Offset:
Reset:
Property:
TEMP
0x0D
0x00
-
The Temporary register is used by the CPU for single-cycle, 16-bit access to the 16-bit registers of this peripheral. It
can be read and written by software. Refer to 16-bit access in the AVR CPU chapter. There is one common
Temporary register for all the 16-bit registers of this peripheral.
Bit
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
TEMP[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 7:0 – TEMP[7:0] Temporary
Temporary register for read/write operations in 16-bit registers.
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29.5.14 Result
Name:
Offset:
Reset:
Property:
RES
0x10
0x00
-
The ADCn.RESL and ADCn.RESH register pair represents the 16-bit value, ADCn.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.
If the analog input is higher than the reference level of the ADC, the 10-bit ADC result will be equal the maximum
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 the maximum allowed 64
accumulations.
Bit
15
14
13
12
11
10
9
8
R
0
R
0
R
0
R
0
3
2
1
0
R
0
R
0
R
0
R
0
RES[15:8]
Access
Reset
R
0
R
0
R
0
R
0
Bit
7
6
5
4
RES[7:0]
Access
Reset
R
0
R
0
R
0
R
0
Bits 15:8 – RES[15:8] Result high byte
These bits constitute the MSB of the ADCn.RES register, where the MSb is RES[15]. The ADC itself has a 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 represents the largest number (full scale).
Bits 7:0 – RES[7:0] Result low byte
These bits constitute the LSB of ADC/Accumulator Result, (ADCn.RES) register. The data format in ADC and Digital
Accumulation is 1’s complement, where 0x0000 represents the zero and 0xFFFF represents the largest number (full
scale).
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ADC - Analog-to-Digital Converter
29.5.15 Window Comparator Low Threshold
Name:
Offset:
Reset:
Property:
WINLT
0x12
0x00
-
This register is the 16-bit low threshold for the digital comparator monitoring the ADCn.RES register. The ADC itself
has a 10-bit output, RES[9:0], where the MSb is RES[9]. The data format in ADC and Digital Accumulation is 1’s
complement, where 0x0000 represents the zero and 0xFFFF represents the largest number (full scale).
The ADCn.WINLTH and ADCn.WINLTL register pair represents the 16-bit value, ADCn.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.
When accumulating samples, the window comparator thresholds are applied to the accumulated value and not on
each sample.
Bit
Access
Reset
Bit
15
14
13
R/W
0
R/W
0
R/W
0
7
6
5
12
11
WINLT[15:8]
R/W
R/W
0
0
4
10
9
8
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
WINLT[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bits 15:8 – WINLT[15:8] Window Comparator Low Threshold High Byte
These bits hold the MSB of the 16-bit register.
Bits 7:0 – WINLT[7:0] Window Comparator Low Threshold Low Byte
These bits hold the LSB of the 16-bit register.
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ADC - Analog-to-Digital Converter
29.5.16 Window Comparator High Threshold
Name:
Offset:
Reset:
Property:
WINHT
0x14
0x00
-
This register is the 16-bit high threshold for the digital comparator monitoring the ADCn.RES register. The ADC itself
has a 10-bit output, RES[9:0], where the MSb is RES[9]. The data format in ADC and Digital Accumulation is 1’s
complement, where 0x0000 represents the zero and 0xFFFF represents the largest number (full scale).
The ADCn.WINHTH and ADCn.WINHTL register pair represents the 16-bit value, ADCn.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.
Bit
Access
Reset
Bit
15
14
13
R/W
0
R/W
0
R/W
0
7
6
5
12
11
WINHT[15:8]
R/W
R/W
0
0
4
10
9
8
R/W
0
R/W
0
R/W
0
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
WINHT[7:0]
Access
Reset
R/W
0
R/W
0
R/W
0
R/W
0
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.
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ADC - Analog-to-Digital Converter
29.5.17 Calibration
Name:
Offset:
Reset:
Property:
Bit
7
CALIB
0x16
0x01
-
6
5
4
3
2
Access
Reset
1
0
DUTYCYC
R/W
1
Bit 0 – DUTYCYC Duty Cycle
This bit determines the duty cycle of the ADC clock.
ADCclk > 1.5 MHz requires a minimum operating voltage of 2.7V.
Value
Description
0
50% Duty Cycle must be used if ADCclk > 1.5 MHz
1
25% Duty Cycle (high 25% and low 75%) must be used for ADCclk ≤ 1.5 MHz
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ATmega3208/3209
UPDI - Unified Program and Debug Interface
30.
UPDI - Unified Program and Debug Interface
30.1
Features
•
•
•
30.2
Programming:
– External programming through UPDI one-wire (1W) interface
• Uses a dedicated pin of the device for programming
• No GPIO pins occupied during operation
• Asynchronous Half-Duplex UART protocol towards the programmer with the programming time up to
0.9 Mbps.
Debugging:
– Memory mapped access to device address space (NVM, RAM, I/O)
– No limitation on device clock frequency
– Unlimited number of user program breakpoints
– Two hardware breakpoints
– Run-time readout of CPU Program Counter (PC), Stack Pointer (SP), and Status register (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 a 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 are done through the UPDI Physical interface (UPDI PHY), which is a one-wire UARTbased half duplex interface using a dedicated pin for data reception and transmission. Clocking of UPDI PHY is done
by the internal oscillator. The UPDI access layer grants access to the bus matrix, with memory mapped access to
system blocks such as memories, NVM, and peripherals.
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.
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UPDI - Unified Program and Debug Interface
30.2.1
Block Diagram
Figure 30-1. UPDI Block Diagram
ASI
Memories
UPDI PAD
(RX/TX Data)
UPDI
Physical
layer
UPDI
Access
layer
Bus Matrix
UPDI Controller
NVM
Peripherals
ASI Access
ASI Internal Interfaces
OCD
NVM
Controller
System
Management
30.2.2
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 the 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 the 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 4 MHz after enabling the UPDI. The UPDI clock frequency is
changed by writing the UPDI Clock Select (UPDICLKSEL) bits in the ASI_CTRLA register.
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UPDI - Unified Program and Debug Interface
Figure 30-2. UPDI Clock Domains
ASI
SYNCH
UPDI Controller
UPDI
Physical
layer
Clock
Controller
Clk_sys
Clk_sys
UPDI
CLKSEL
~
30.3.1
Clock
Controller
Clk_UPDI
UPDI clk
source
30.3
UPDI
Access
layer
~
Functional Description
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 30-3.
Figure 30-3. 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
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UPDI - Unified Program and Debug Interface
Data
Frame
IDLE
Frame
BREAK
SYNCH
ACK
Data frame consists of one Start bit (always low), eight data bits, one parity bit (even parity), and two
Stop bits (always high). If the 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 Parity Disable
(PARD) bit in UPDI.CTRLA, in which case the parity generation from the debugger can be ignored.
Special frame that consists of 12 high bits. This is the same as keeping the transmission line in an Idle
state.
Special frame that consists 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 an 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.
30.3.1.1 UPDI UART
All transmission and reception of serial data on the UPDI is achieved using the UPDI frames presented in Figure
30-3. Communication is initiated from the master (debugger/programmer) 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 30.3.3 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 performing a majority vote on the middle samples.
The transmission baud rate of the PDI PHY is related to the selected UPDI clock, which can be adjusted by UPDI
Clock Select (UPDICLKSEL) bit in UPDI.ASI_CTRLA. See Table 30-1 for recommended maximum and minimum
baud rate settings. The receive and transmit baud rates are always the same within the accuracy of the auto-baud.
Table 30-1. Recommended UART Baud Rate Based on UPDICLKSEL Setting
UPDICLKSEL[1:0]
Max. Recommended Baud Rate
Min. Recommended Baud Rate
0x1 (16 MHz)
0.9 Mbps
0.300 kbps
0x2 (8 MHz)
450 kbps
0.150 kbps
0x3 (4 MHz) - Default
225 kbps
0.075 kbps
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 30-2. 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
30.3.1.2 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 a communication error, or when the synchronization between the debugger and the UPDI
is lost.
To ensure that a BREAK is successfully received by the UPDI in all cases, the debugger should send two
consecutive BREAK characters. If a single BREAK is sent while the UPDI is receiving or transmitting (possibly at a
very low baud rate), the UPDI will not detect it. However, this will cause a frame error (RX) or contention error (TX),
and abort the ongoing operation. Then, the UPDI will detect the next BREAK. The first BREAK will be detected if the
UPDI is idle.
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 with the last baud rate setting and be derived from the last valid
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UPDI - Unified Program and Debug Interface
SYNCH character. If the communication error was caused by an incorrect sampling of the SYNCH character, the
device will not know the baud rate. To ensure that the BREAK will be detected in all cases, the recommended BREAK
duration should be 12-bit times the bit duration at the lowest possible baud rate (8192 times the CLK_PER) as shown
in Table 30-3).
Table 30-3. Recommended BREAK Character Duration
30.3.2
UPDICLKSEL[1:0]
Recommended BREAK Character Duration
0x1 (16 MHz)
6.15 ms
0x2 (8 MHz)
12.30 ms
0x3 (4 MHz) - Default
24.60 ms
Operation
The UPDI must be enabled before the UART communication can start.
30.3.2.1 UPDI Enable
The dedicated UPDI pad is configured as an input with pull-up.When the pull-up is detected by a connected
debugger, the UPDI enable sequence, as depicted below, is started.
Figure 30-4. UPDI Enable Sequence
1
Drive low from debugger to request UPDI clock
2
UPDI clock ready; Communication channel ready.
1
UPDIPAD
St
D0
D1
D2
UPDI.txd
D4
D5
D6
D7
Sp
SYNC (0x55)
(Autobaud)
Handshake / BREAK
TRES
UPDI.rxd
D3
(Ignore)
2
Hi-Z
Hi-Z
UPDI.txd = 0
TUPDI
debugger.
UPDI.txd
Hi-Z
Hi-Z
Debugger.txd = 0
TDeb0
Debugger.txd = z.
TDebZ
Table 30-4. Timing in the Figure
Timing Label
Max.
Min.
TRES
200 µs
10 µs
TUPDI
200 µs
10 µs
TDeb0
1 µs
200 ns
TDebZ
14 ms
200 µs
When the pull-up is detected, the debugger initiates the enable sequence by driving the line low for a duration of
TDeb0.
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UPDI - Unified Program and Debug Interface
The negative edge is detected by the UPDI, which starts 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 TUPDI will vary, depending on the status of the
oscillator when the UPDI is enabled. 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 transmitted to
synchronize the UPDI communication data rate. If the Start bit of the SYNCH character is not sent within maximum
TDebZ, the UPDI will disable itself, and the UPDI enabling sequence must be re-initiated. The UPDI is disabled if the
timing is violated to avoid the UPDI being enabled unintentionally.
After successful SYNCH character transmission, the first instruction frame can be transmitted.
30.3.2.2 UPDI Disable
Any programming or debug session should be terminated by writing the UPDI Disable (UPDIDIS) bit in UPDI.CTRLB.
Writing this bit will reset the UPDI including any decoded KEYs (see the KEY instruction section) and disable the
oscillator request for the module. If the disable operation is not performed, the UPDI and the oscillators request will
remain enabled. This causes power consumption increased for the application.
During the enable sequence the UPDI can disable itself in case of a faulty enable sequence. There are two cases
that will cause an automatic disable:
• A SYNCH character is not sent within 13.5 ms after the initial enable pulse described in 30.3.2.1 UPDI Enable.
• The first SYNCH character after an initiated enable is too short or too long to be detected as a valid SYNCH
character. See Table 30-1 for recommended baud rate operating ranges.
30.3.2.3 UPDI Communication Error Handling
The UPDI contains a comprehensive error detection system that provides information to the debugger when
recovering from an error scenario. The error detection consists of detecting physical transmission errors like parity
error, contention error, and frame error, to more high-level errors like access timeout error. See the UPDI Error
Signature (PESIG) bits in UPDI.STATUSB register for an overview of the available error signatures.
Whenever the UPDI detects an error, it will immediately enter 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 30.3.1.2 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 4 MHz default UPDI clock selection. This affects the baud
rate range of the UPDI according to Table 30-1.
• Execute a Load Control Status (LDCS) instruction to read the UPDI Error Signature (PESIG) bit in the
UPDI.STATUSB register and get the information about the occurred error. The error signature in the
STATUSB.PESIG will be cleared when the register is read.
• The UPDI is now recovered from the error state and ready to receive the next SYNCH character and instruction.
30.3.2.4 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 the Guard Time
Value (GTVAL) bit in the UPDI.CTRLA register. The duration of each IDLE bit is given by the baud rate used by the
current transmission.
Do not set CTRLA.GTVAL to 0x7 without IDLE bits.
Figure 30-5. 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
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
P
S1
S2
Data from UPDI to
debugger
The UPDI Guard Time is the minimum IDLE time (see CTRLA.GTVAL) that the connected debugger will experience
when waiting for data from the UPDI. The Maximum is the same as timeout (for example, 65536 UPDI clock cycles).
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UPDI - Unified Program and Debug Interface
The IDLE time before a transmission will be more than the expected Guard Time when the synchronization time plus
the data bus accessing time is longer than the Guard Time. For example, the system is running on a slow clock.
30.3.3
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
30.3.1.1 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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UPDI - Unified Program and Debug Interface
Figure 30-6. 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 .
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UPDI - Unified Program and Debug Interface
30.3.3.1 LDS - Load Data from Data Space Using Direct Addressing
The LDS instruction is used to load data from the bus matrix and into the serial shift register for serial readout. 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 bits. LDS instruction supports repeated
memory access when combined with the REPEAT instruction.
As shown in Figure 30-7, after issuing the SYNCH character followed by the LDS instruction, the number of desired
address bytes, as indicated by the Size A field in the instruction, must be transmitted. The output data size is selected
by the Size B 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 30-7. 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
30.3.3.2 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. The
maximum size for both address and data is 16 bits.
STS supports repeated memory access when combined with the REPEAT instruction.
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UPDI - Unified Program and Debug Interface
Figure 30-8. 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.
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.
4.
A new ACK is received after the data has been successfully transferred.
30.3.3.3 LD - Load Data from Data Space Using Indirect Addressing
The LD instruction is used to load data from the bus matrix and into the serial shift register for serial readout. 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 an LD of the UPDI Pointer register. The maximum supported
size for address and data load is 16 bits.
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Figure 30-9. 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.
30.3.3.4 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. The
maximum supported size for storing address and data is 16 bits.
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UPDI - Unified Program and Debug Interface
Figure 30-10. 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 Size A to the desired address size
After issuing the ST instruction, send Size A 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 Size B field of the instruction after the write is executed
• Set the Size B field in the instruction to the desired data size
• After sending the ST instruction, send Size B bytes of address data
•
Wait for the ACK character which signifies a successful write to the bus matrix
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UPDI - Unified Program and Debug Interface
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 the Pointer Post Increment register to automatically increase the address for each repeat cycle.
When using REPEAT, the data frame of Size B data bytes can be sent after each received ACK.
30.3.3.5 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 bytes and can only
access the internal UPDI register space. This instruction only supports byte access and the data size is not
configurable.
Figure 30-11. 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.
30.3.3.6 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 bytes, 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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Figure 30-12. 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 30-12 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.
30.3.3.7 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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Figure 30-13. 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 an 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).
30.3.3.8 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 30-5 for an overview of functions that are activated by KEYs. For the KEY instruction, only
64-bit 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 128 bits.
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Figure 30-14. 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 being 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.
30.3.4
System Clock Measurement with UPDI
It is possible to use the UPDI to get an 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 TCBn.CTRLB with setting CNTMODE=0x3, Input Capture Frequency Measurement mode.
• Write CAPTEI=1 in TCBn.EVCTRL to enable Event Interrupt. Keep EDGE = 0 in TCBn.EVCTRL.
• Configure the Event System as described in 30.3.8 Events.
• For the SYNCH character used to generate the UPDI events, it is recommended to use a slow baud rate in the
range of 10 kbps - 50 kbps 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 on the input event should be used for the
measurement. See the figure below for an example using 10 kbps UPDI SYNCH character pulses, giving a
capture window of 200 µs for the timer.
• It is possible to read out the captured value directly after the SYNCH character by reading the TCBn.CCMP
register or the value can be written to memory by the CPU once the capture is done.
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Figure 30-15. UPDI System Clock Measurement Events
Ignore first
capture event
200us
UPDI_
Input
TCB_CCMP
30.3.5
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 are 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 a 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 30-16. Interbyte Delay Example with LD and RPT
Too fast transm ission, no interbyte delay
RX
Debugger
Data
TX
RPT
CNT
LD*(ptr)
S
D0
GT
Debugger
Processing
B
D1
S
B
D1lots
D0
D2
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 30-16, GT denotes the Guard Time insertion, SB is for Stop Bit and IB is the inserted interbyte delay. The
rest of the frames are data and instructions.
30.3.6
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
30.3.3.8 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. The KEY size field should be set to 16 bytes when reading out the complete
SIB, and an 8-byte size can be used to read out only the Family_ID. See Figure 30-17 for SIB format description, and
which data is available at different readout sizes.
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Figure 30-17. System Information Block Format
16 8
30.3.7
[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 30-5
describes the available KEYs, and the condition required when doing the operation with the KEY active. There is no
requirement when shifting in the KEY, but you would, for instance, normally run a Chip Erase before enabling the
NVMPROG KEY to unlock the device for debugging. But if the NVMPROGKEY is shifted in first, it will not be reset by
shifting in the Chip Erase KEY afterwards.
Table 30-5. KEY Activation Overview
KEY Name
Description
Requirements for
Operation
Reset
Chip Erase
Start NVM Chip erase.
Clear Lockbits
None
UPDI Disable/UPDI Reset
NVMPROG
Activate NVM
Programming
Lockbits Cleared.
ASI_SYS_STATUS.NVMP
ROG set.
Programming Done/UPDI
Reset
USERROW-Write
Program User Row on
Locked part
Lockbits Set.
ASI_SYS_STATUS.UROW
PROG set.
Write to KEY status bit/
UPDI Reset
Table 30-6 gives an overview of the available KEY signatures that must be shifted in to activate the interfaces.
Table 30-6. KEY Activation Signatures
KEY Name
KEY Signature (LSB Written First)
Size
Chip Erase
0x4E564D4572617365
64 bits
NVMPROG
0x4E564D50726F6720
64 bits
USERROW-Write
0x4E564D5573267465
64 bits
30.3.7.1 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 30-6 for the CHIPERASE signature.
2.
3.
4.
5.
6.
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.
Write the Reset signature into the UPDI.ASI_RESET_REQ register. This will issue a System Reset.
Write 0x00 to the ASI Reset Request register (UPDI.ASI_RESET_REQ) to clear the System Reset.
Read the Lock Status bit in the ASI System Status register (LOCKSTATUS in UPDI.ASI_SYS_STATUS).
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.
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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.
30.3.7.2 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.
2.
Follow the Chip erase procedure as described in Chip Erase. If the part is already unlocked, this point can be
skipped.
Enter the NVMPROG KEY by using the KEY instruction. See Table 30-6 for the NVMPROG signature.
3.
4.
5.
6.
7.
Optional: Read the NVMPROG field in the KEY_STATUS register to see that the KEY has been activated.
Write the Reset signature into the ASI_RESET_REQ register. This will issue a System Reset.
Write 0x00 to the Reset signature in the ASI_RESET_REQ register to clear the System Reset.
Read NVMPROG in ASI_SYS_STATUS.
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.
30.3.7.3 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.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Enter the USERROW-Write KEY located in Table 30-6 by using the KEY instruction. See Table 30-6 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 (64 bytes), and it is only possible to write User Row data
to the first 64 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 64 bytes of the SRAM is
allowed.
30.3.8
Events
The UPDI is connected to the Event System (EVSYS) as described in the Event System (EVSYS) section.
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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 30.3.4 System Clock Measurement with UPDI provides the details on how
to set up the system for this operation.
30.3.9
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 the CPU clock OFF,
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 it is possible for the UPDI
to access the system bus and read the peripheral registers even in the deepest Sleep modes.
CLKREQ in UPDI.ASI_SYS_CTRL is by default ‘1’, which means that the default operation is keeping the system
clock on during Sleep modes.
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30.4
Register Summary
Offset
Name
Bit Pos.
0x00
0x01
0x02
0x03
0x04
...
0x06
0x07
0x08
0x09
STATUSA
STATUSB
CTRLA
CTRLB
7:0
7:0
7:0
7:0
ASI_KEY_STATUS
ASI_RESET_REQ
ASI_CTRLA
7:0
7:0
7:0
0x0A
ASI_SYS_CTRLA
7:0
0x0B
0x0C
ASI_SYS_STATUS
ASI_CRC_STATUS
7:0
7:0
30.5
UPDIREV[3:0]
IBDLY
PARD
DTD
NACKDIS
RSD
CCDETDIS
PESIG[2:0]
GTVAL[2:0]
UPDIDIS
Reserved
UROWWRITE NVMPROG CHIPERASE
RSTREQ[7:0]
RSTSYS
INSLEEP
UPDICLKSEL[1:0]
UROWWRITE
CLKREQ
_FINAL
NVMPROG UROWPROG
LOCKSTATUS
CRC_STATUS[2:0]
Register Description
These registers are readable only 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.
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30.5.1
Status A
Name:
Offset:
Reset:
Property:
Bit
7
STATUSA
0x00
0x10
-
6
5
4
R
0
R
1
3
2
1
0
UPDIREV[3:0]
Access
Reset
R
0
R
0
Bits 7:4 – UPDIREV[3:0] UPDI Revision
These bits are read-only and contain the revision of the current UPDI implementation.
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30.5.2
Status B
Name:
Offset:
Reset:
Property:
Bit
STATUSB
0x01
0x00
-
7
6
5
4
3
Access
Reset
2
R
0
1
PESIG[2:0]
R
0
0
R
0
Bits 2:0 – PESIG[2:0] UPDI Error Signature
These bits describe the UPDI Error Signature and are set when an internal UPDI error condition occurs. The PESIG
field is cleared on a read from the debugger.
Table 30-7. Valid Error Signatures
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 Time-out 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
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 443
ATmega3208/3209
UPDI - Unified Program and Debug Interface
30.5.3
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
IBDLY
R/W
0
CTRLA
0x02
0x00
-
6
5
PARD
R/W
0
4
DTD
R/W
0
3
RSD
R/W
0
2
R/W
0
1
GTVAL[2:0]
R/W
0
0
R/W
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, the regular GT delay used
for direction change will be used.
Bit 5 – PARD Parity Disable
Writing this bit to ‘1’ will disable parity detection in the UPDI by ignoring the Parity bit. This feature is recommended
only during testing.
Bit 4 – DTD Disable Time-out Detection
Setting this bit disables the time-out 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.
Value
Description
0x0
UPDI Guard Time: 128 cycles (default)
0x1
UPDI Guard Time: 64 cycles
0x2
UPDI Guard Time: 32 cycles
0x3
UPDI Guard Time: 16 cycles
0x4
UPDI Guard Time: 8 cycles
0x5
UPDI Guard Time: 4 cycles
0x6
UPDI Guard Time: 2 cycles
0x7
GT off (no extra Idle bits inserted)
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 444
ATmega3208/3209
UPDI - Unified Program and Debug Interface
30.5.4
Control B
Name:
Offset:
Reset:
Property:
Bit
7
CTRLB
0x03
0x00
-
6
Access
Reset
5
4
NACKDIS
R
0
3
CCDETDIS
R
0
2
UPDIDIS
R
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 ‘1’, contention detection is disabled.
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.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 445
ATmega3208/3209
UPDI - Unified Program and Debug Interface
30.5.5
ASI Key Status
Name:
Offset:
Reset:
Property:
Bit
7
ASI_KEY_STATUS
0x07
0x00
-
6
Access
Reset
5
UROWWRITE
R/W
0
4
NVMPROG
R
0
3
CHIPERASE
R
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 ‘0’.
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 ‘0’.
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 ‘0’.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 446
ATmega3208/3209
UPDI - Unified Program and Debug Interface
30.5.6
ASI Reset Request
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
ASI_RESET_REQ
0x08
0x00
-
7
6
5
R/W
0
R/W
0
R/W
0
4
3
RSTREQ[7:0]
R/W
R/W
0
0
2
1
0
R/W
0
R/W
0
R/W
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.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 447
ATmega3208/3209
UPDI - Unified Program and Debug Interface
30.5.7
ASI Control A
Name:
Offset:
Reset:
Property:
Bit
7
ASI_CTRLA
0x09
0x02
-
6
5
4
3
Access
Reset
2
1
0
UPDICLKSEL[1:0]
R/W
R/W
1
1
Bits 1:0 – UPDICLKSEL[1:0] UPDI Clock Select
Writing these bits select the UPDI clock output frequency. Default setting after Reset and enable is 4 MHz. Any other
clock output selection is only recommended when the BOD is at the highest level. For all other BOD settings, the
default 4 MHz selection is recommended.
Value
Description
0x0
Reserved
0x1
16 MHz UPDI clock
0x2
8 MHz UPDI clock
0x3
4 MHz UPDI clock (Default Setting)
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 448
ATmega3208/3209
UPDI - Unified Program and Debug Interface
30.5.8
ASI System Control A
Name:
Offset:
Reset:
Property:
ASI_SYS_CTRLA
0x0A
0x00
-
Bit
7
6
5
4
3
2
Access
Reset
R
0
R
0
R
0
R
0
R
0
R
0
1
UROWWRITE_
FINAL
R/W
0
0
CLKREQ
R/W
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 User Row-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 ‘0’ 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.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 449
ATmega3208/3209
UPDI - Unified Program and Debug Interface
30.5.9
ASI System Status
Name:
Offset:
Reset:
Property:
Bit
7
ASI_SYS_STATUS
0x0B
0x01
-
6
Access
Reset
5
RSTSYS
R
0
4
INSLEEP
R
0
3
NVMPROG
R
0
2
UROWPROG
R
0
1
0
LOCKSTATUS
R
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 Chip Erase is done, and the Lockbits are cleared, this bit will read as ‘0’.
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 450
ATmega3208/3209
UPDI - Unified Program and Debug Interface
30.5.10 ASI CRC Status
Name:
Offset:
Reset:
Property:
Bit
7
ASI_CRC_STATUS
0x0C
0x00
-
6
5
4
3
Access
Reset
2
R
0
1
CRC_STATUS[2:0]
R
0
0
R
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
Description
0x0
Not enabled
0x1
CRC enabled, busy
0x2
CRC enabled, done with OK signature
0x4
CRC enabled, done with FAILED signature
Other
Reserved
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 451
ATmega3208/3209
Instruction Set Summary
31.
Instruction Set Summary
Table 31-1. Status Register (SREG)
Terminology
Meaning
SREG
Status register
C
Carry flag in status register
Z
Zero flag in status register
N
Negative flag in status register
V
Two’s complement overflow indicator
S
N⊕V, for signed tests
H
Half Carry flag in status register
T
Transfer bit used by BLD and BST instructions
I
Global interrupt enable/disable flag
Table 31-2. Registers and Operands
Operand
Meaning
Rd
Destination (and source) register in the register file
Rr
Source register in the register file
R
Result after instruction is executed
K
Constant literal or byte data (8-bit)
k
Constant address data for program counter
b
Bit in the register file (3-bit)
s
Bit in the status register (3-bit)
X,Y,Z
Indirect address register (X=R27:R26, Y=R29:R28 and
Z=R31:R30)
P
I/O port address
q
Displacement for direct addressing (6-bit)
UU
Unsigned × Unsigned operands
SS
Signed × Signed operands
SU
Signed × Unsigned operands
Table 31-3. Stack
Terminology
Meaning
STACK
Stack for return address and pushed registers
SP
Stack Pointer to STACK
© 2020 Microchip Technology Inc.
Preliminary Datasheet
DS40002174A-page 452
ATmega3208/3209
Instruction Set Summary
Table 31-4. Memory Space Identifiers
Terminology
Meaning
DS(X)
X-pointer points to address in Data Space
DS(Y)
Y-pointer points to address in Data Space
DS(Z)
Z-pointer points to address in Data Space
DS(k)
Constant k points to address in Data Space
PS(Z)
Z-pointer points to address in Program Space
I/O(A)
A is an address in I/O Space
Table 31-5. Operator
Operator
Meaning
×
Arithmetic multiplication
+
Arithmetic addition
-
Arithmetic subtraction
∧
Logical AND
∨
Logical OR
⊕
Logical XOR
>>
Shift right
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