ATtiny406
AVR® Microcontroller with Core Independent Peripherals
and picoPower® Technology
Introduction
®
The ATtiny406 microcontrollers are using the high-performance, low-power AVR RISC architecture, and
are capable of running at up to 20 MHz, with up to 4 KB Flash, 256 bytes of SRAM, and 128 bytes of
EEPROM in a 20-pin package.The series uses the latest technologies with a flexible and low-power
architecture including Event System and SleepWalking, accurate analog features, and advanced
peripherals.
Features
•
•
•
CPU:
®
– AVR 8-bit CPU
– Running at up to 20 MHz
– Single cycle I/O access
– Two-level interrupt controller
– Two-cycle hardware multiplier
Memories:
– 4 KB In-system self-programmable Flash memory
– 128B EEPROM
– 256B SRAM
– Write/Erase Cycles: 10,000 Flash/100,000 EEPROM
– Data Retention: 20 Years at 85°C
System:
– Power-on Reset (POR)
– Brown-out Detection (BOD)
– Clock Options:
• 16/20 MHz Low-Power Internal RC Oscillator with:
– ±3% Accuracy over full temperature and voltage range
– ±2% Drift over limited temperature and 1.8 ... 3.6V voltage range
• 32.768 kHz Ultra Low-Power (ULP) Internal RC Oscillator with ±10% Accuracy, ±2%
Calibration Step Size
• External Clock Input
– Single Pin Unified Program Debug Interface (UPDI)
– Three Sleep Modes:
• Idle with all peripherals running and mode for immediate wake-up time
© 2018 Microchip Technology Inc.
Datasheet Preliminary
DS40001976A-page 1
ATtiny406
•
•
•
•
•
Standby
– Configurable operation of selected peripherals
– SleepWalking peripherals
• Power-down with wake-up functionality
Peripherals:
– 3-channel Event System
– One 16-bit Timer/Counter Type A with Dedicated Period Register, Three Compare Channels
(TCA)
– One 16-bit Timer/Counter Type B with Input Capture (TCB)
– One 16-bit Real-Time Counter (RTC) running from Internal RC Oscillator
– One USART 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
• Standard mode (Sm, 100 kHz)
• Fast mode (Fm, 400 kHz)
• Fast mode Plus (Fm+, 1 MHz)
– Configurable Custom Logic (CCL) with Two Programmable Look-up Tables (LUT)
– Analog Comparator (AC)
– 10-bit 115 ksps Analog-to-Digital Converter (ADC)
– Five selectable internal voltage references: 0.55V, 1.1V, 1.5V, 2.5V, and 4.3V
– Automated CRC memory scan
– Watchdog Timer (WDT) with Window mode, with separate on-chip oscillator
– External interrupt on all general purpose pins
I/O and Packages:
– 18 Programmable I/O lines
– 20-pin VQFN and SOIC300
Temperature Ranges:
– -40°C to 105°C
– -40°C to 125°C Temperature graded device options available
Speed Grades:
– 0-5 MHz @ 1.8V – 5.5V
– 0-10 MHz @ 2.7V – 5.5V
– 0-20 MHz @ 4.5V – 5.5V
© 2018 Microchip Technology Inc.
Datasheet Preliminary
DS40001976A-page 2
Table of Contents
Introduction......................................................................................................................1
Features.......................................................................................................................... 1
®
1. tinyAVR 0-Series Overview......................................................................................9
1.1.
Configuration Summary................................................................................................................9
2. Ordering Information................................................................................................ 11
2.1.
ATtiny406....................................................................................................................................11
3. Block Diagram......................................................................................................... 12
4. Pinout...................................................................................................................... 13
4.1.
4.2.
20-Pin VQFN.............................................................................................................................. 13
20-Pin SOIC............................................................................................................................... 13
5. I/O Multiplexing and Considerations........................................................................15
5.1.
Multiplexed Signals.................................................................................................................... 15
6. Memories.................................................................................................................16
6.1.
6.2.
6.3.
6.4.
6.5.
6.6.
6.7.
6.8.
6.9.
6.10.
Overview.................................................................................................................................... 16
Memory Map.............................................................................................................................. 16
In-System Reprogrammable Flash Program Memory................................................................16
SRAM Data Memory.................................................................................................................. 17
EEPROM Data Memory............................................................................................................. 17
User Row....................................................................................................................................18
Signature Bytes.......................................................................................................................... 18
Memory Section Access from CPU and UPDI on Locked Device..............................................18
I/O Memory.................................................................................................................................19
Configuration and User Fuses (FUSE).......................................................................................22
7. Peripherals and Architecture................................................................................... 41
7.1.
7.2.
7.3.
Peripheral Module Address Map................................................................................................ 41
Interrupt Vector Mapping............................................................................................................ 42
System Configuration (SYSCFG)...............................................................................................43
8. AVR CPU................................................................................................................. 46
8.1.
8.2.
8.3.
8.4.
8.5.
8.6.
8.7.
Features..................................................................................................................................... 46
Overview.................................................................................................................................... 46
Architecture................................................................................................................................ 46
Arithmetic Logic Unit (ALU)........................................................................................................ 48
Functional Description................................................................................................................49
Register Summary - CPU...........................................................................................................54
Register Description................................................................................................................... 54
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Datasheet Preliminary
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ATtiny406
9. Nonvolatile Memory Controller (NVMCTRL)........................................................... 59
9.1.
9.2.
9.3.
9.4.
9.5.
Features..................................................................................................................................... 59
Overview.................................................................................................................................... 59
Functional Description................................................................................................................60
Register Summary - NVMCTRL................................................................................................. 67
Register Description................................................................................................................... 67
10. Clock Controller (CLKCTRL)................................................................................... 75
10.1.
10.2.
10.3.
10.4.
10.5.
Features..................................................................................................................................... 75
Overview.................................................................................................................................... 75
Functional Description................................................................................................................77
Register Summary - CLKCTRL.................................................................................................. 82
Register Description................................................................................................................... 82
11. Sleep Controller (SLPCTRL)................................................................................... 91
11.1.
11.2.
11.3.
11.4.
11.5.
Features..................................................................................................................................... 91
Overview.................................................................................................................................... 91
Functional Description................................................................................................................92
Register Summary - SLPCTRL.................................................................................................. 95
Register Description................................................................................................................... 95
12. Reset Controller (RSTCTRL)...................................................................................97
12.1.
12.2.
12.3.
12.4.
12.5.
Features..................................................................................................................................... 97
Overview.................................................................................................................................... 97
Functional Description................................................................................................................98
Register Summary - RSTCTRL................................................................................................101
Register Description................................................................................................................. 101
13. CPU Interrupt Controller (CPUINT)....................................................................... 104
13.1.
13.2.
13.3.
13.4.
13.5.
Features................................................................................................................................... 104
Overview.................................................................................................................................. 104
Functional Description..............................................................................................................106
Register Summary - CPUINT................................................................................................... 112
Register Description................................................................................................................. 112
14. Event System (EVSYS)......................................................................................... 117
14.1.
14.2.
14.3.
14.4.
14.5.
Features................................................................................................................................... 117
Overview...................................................................................................................................117
Functional Description..............................................................................................................120
Register Summary - EVSYS.................................................................................................... 122
Register Description................................................................................................................. 122
15. Port Multiplexer (PORTMUX)................................................................................ 131
15.1. Overview.................................................................................................................................. 131
15.2. Register Summary - PORTMUX.............................................................................................. 132
15.3. Register Description................................................................................................................. 132
16. I/O Pin Configuration (PORT)................................................................................137
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ATtiny406
16.1.
16.2.
16.3.
16.4.
16.5.
16.6.
16.7.
Features................................................................................................................................... 137
Overview.................................................................................................................................. 137
Functional Description..............................................................................................................139
Register Summary - PORT...................................................................................................... 143
Register Description - Ports..................................................................................................... 143
Register Summary - VPORT.................................................................................................... 155
Register Description - Virtual Ports.......................................................................................... 155
17. Brown-Out Detector (BOD)....................................................................................160
17.1.
17.2.
17.3.
17.4.
17.5.
Features................................................................................................................................... 160
Overview.................................................................................................................................. 160
Functional Description..............................................................................................................162
Register Summary - BOD.........................................................................................................164
Register Description................................................................................................................. 164
18. Voltage Reference (VREF).................................................................................... 171
18.1.
18.2.
18.3.
18.4.
18.5.
Features................................................................................................................................... 171
Overview.................................................................................................................................. 171
Functional Description..............................................................................................................171
Register Summary - VREF.......................................................................................................173
Register Description................................................................................................................. 173
19. Watchdog Timer (WDT).........................................................................................176
19.1.
19.2.
19.3.
19.4.
19.5.
Features................................................................................................................................... 176
Overview.................................................................................................................................. 176
Functional Description..............................................................................................................178
Register Summary - WDT........................................................................................................ 182
Register Description................................................................................................................. 182
20. 16-bit Timer/Counter Type A (TCA)....................................................................... 186
20.1.
20.2.
20.3.
20.4.
20.5.
20.6.
20.7.
Features................................................................................................................................... 186
Overview.................................................................................................................................. 186
Functional Description..............................................................................................................190
Register Summary - TCA in Normal Mode (CTRLD.SPLITM=0)............................................. 200
Register Description - Normal Mode........................................................................................ 201
Register Summary - TCA in Split Mode (CTRLD.SPLITM=1).................................................. 221
Register Description - Split Mode.............................................................................................221
21. 16-bit Timer/Counter Type B (TCB)....................................................................... 237
21.1.
21.2.
21.3.
21.4.
21.5.
Features................................................................................................................................... 237
Overview.................................................................................................................................. 237
Functional Description..............................................................................................................240
Register Summary - TCB......................................................................................................... 248
Register Description................................................................................................................. 248
22. Real-Time Counter (RTC)......................................................................................260
22.1. Features................................................................................................................................... 260
22.2. Overview.................................................................................................................................. 260
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ATtiny406
22.3. RTC Functional Description..................................................................................................... 262
22.4. PIT Functional Description....................................................................................................... 263
22.5. Events...................................................................................................................................... 265
22.6. Interrupts.................................................................................................................................. 266
22.7. Sleep Mode Operation............................................................................................................. 266
22.8. Synchronization........................................................................................................................267
22.9. Configuration Change Protection............................................................................................. 267
22.10. Register Summary - RTC.........................................................................................................268
22.11. Register Description................................................................................................................. 268
23. Universal Synchronous and Asynchronous Receiver and Transmitter (USART).. 284
23.1.
23.2.
23.3.
23.4.
23.5.
Features................................................................................................................................... 284
Overview.................................................................................................................................. 284
Functional Description..............................................................................................................288
Register Summary - USART.................................................................................................... 303
Register Description................................................................................................................. 303
24. Serial Peripheral Interface (SPI)............................................................................322
24.1.
24.2.
24.3.
24.4.
24.5.
Features................................................................................................................................... 322
Overview.................................................................................................................................. 322
Functional Description..............................................................................................................325
Register Summary - SPI...........................................................................................................333
Register Description................................................................................................................. 333
25. Two-Wire Interface (TWI)...................................................................................... 342
25.1.
25.2.
25.3.
25.4.
25.5.
Features................................................................................................................................... 342
Overview.................................................................................................................................. 342
Functional Description..............................................................................................................344
Register Summary - TWI..........................................................................................................357
Register Description................................................................................................................. 357
26. Cyclic Redundancy Check Memory Scan (CRCSCAN)........................................ 377
26.1.
26.2.
26.3.
26.4.
26.5.
Features................................................................................................................................... 377
Overview.................................................................................................................................. 377
Functional Description..............................................................................................................379
Register Summary - CRCSCAN...............................................................................................382
Register Description................................................................................................................. 382
27. Configurable Custom Logic (CCL).........................................................................386
27.1.
27.2.
27.3.
27.4.
27.5.
Features................................................................................................................................... 386
Overview.................................................................................................................................. 386
Functional Description..............................................................................................................388
Register Summary - CCL......................................................................................................... 397
Register Description................................................................................................................. 397
28. Analog Comparator (AC)....................................................................................... 405
28.1. Features................................................................................................................................... 405
28.2. Overview.................................................................................................................................. 405
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Datasheet Preliminary
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ATtiny406
28.3. Functional Description..............................................................................................................407
28.4. Register Summary - AC........................................................................................................... 409
28.5. Register Description................................................................................................................. 409
29. Analog-to-Digital Converter (ADC)........................................................................ 414
29.1.
29.2.
29.3.
29.4.
29.5.
Features................................................................................................................................... 414
Overview.................................................................................................................................. 414
Functional Description..............................................................................................................418
Register Summary - ADCn.......................................................................................................426
Register Description................................................................................................................. 426
30. Unified Program and Debug Interface (UPDI)....................................................... 444
30.1.
30.2.
30.3.
30.4.
30.5.
Features................................................................................................................................... 444
Overview.................................................................................................................................. 444
Functional Description..............................................................................................................447
Register Summary - UPDI........................................................................................................467
Register Description................................................................................................................. 467
31. Electrical Characteristics....................................................................................... 478
31.1. Disclaimer.................................................................................................................................478
31.2. Absolute Maximum Ratings .....................................................................................................478
31.3. General Operating Ratings ......................................................................................................479
31.4. Power Consumption for ATtiny406...........................................................................................480
31.5. Wake-Up Time..........................................................................................................................481
31.6. Power Consumption of Peripherals..........................................................................................482
31.7. BOD and POR Characteristics................................................................................................. 483
31.8. External Reset Characteristics................................................................................................. 483
31.9. Oscillators and Clocks..............................................................................................................484
31.10. I/O Pin Characteristics............................................................................................................. 485
31.11. USART..................................................................................................................................... 486
31.12. SPI........................................................................................................................................... 487
31.13. TWI...........................................................................................................................................488
31.14. VREF........................................................................................................................................490
31.15. ADC..........................................................................................................................................492
31.16. AC............................................................................................................................................ 494
31.17. UPDI Timing.............................................................................................................................495
31.18. Programming Time...................................................................................................................495
32. Typical Characteristics...........................................................................................496
32.1.
32.2.
32.3.
32.4.
32.5.
32.6.
32.7.
32.8.
Power Consumption................................................................................................................. 496
GPIO........................................................................................................................................ 503
VREF Characteristics............................................................................................................... 511
BOD Characteristics.................................................................................................................513
ADC Characteristics................................................................................................................. 516
AC Characteristics....................................................................................................................521
OSC20M Characteristics..........................................................................................................524
OSCULP32K Characteristics................................................................................................... 526
© 2018 Microchip Technology Inc.
Datasheet Preliminary
DS40001976A-page 7
ATtiny406
33. Errata.....................................................................................................................527
33.1. Errata - ATtiny406 ................................................................................................................... 527
34. Package Drawings.................................................................................................529
34.1. 20-Pin SOIC............................................................................................................................. 529
34.2. 20-Pin VQFN............................................................................................................................ 530
35. Thermal Considerations........................................................................................ 531
35.1. Thermal Resistance Data.........................................................................................................531
35.2. Junction Temperature...............................................................................................................531
36. Instruction Set Summary....................................................................................... 532
37. Conventions...........................................................................................................537
37.1.
37.2.
37.3.
37.4.
Numerical Notation...................................................................................................................537
Memory Size and Type.............................................................................................................537
Frequency and Time.................................................................................................................537
Registers and Bits.................................................................................................................... 538
38. Acronyms and Abbreviations.................................................................................539
39. Data Sheet Revision History..................................................................................542
39.1. Revision History....................................................................................................................... 542
The Microchip Web Site.............................................................................................. 543
Customer Change Notification Service........................................................................543
Customer Support....................................................................................................... 543
Microchip Devices Code Protection Feature............................................................... 543
Legal Notice.................................................................................................................544
Trademarks................................................................................................................. 544
Quality Management System Certified by DNV...........................................................545
Worldwide Sales and Service......................................................................................546
© 2018 Microchip Technology Inc.
Datasheet Preliminary
DS40001976A-page 8
ATtiny406
tinyAVR®
1.
0-Series Overview
tinyAVR® 0-Series Overview
The figure below shows the tinyAVR 0-series, laying out pin count variants and memory sizes:
•
•
Vertical migration can be done upwards without code modification since these devices are pin
compatible and provide the same or additional features. Downward migration may require code
modification due to fewer available instances of some peripherals.
Horizontal migration to the left reduces the pin count and therefore, the available features.
Figure 1-1. Device Family Overview
Flash
4KB
ATtiny402
ATtiny404
2KB
ATtiny202
ATtiny204
8
14
ATtiny406
Pins
20
The fully compatible variants of the ATtiny devices, that is the vertical migration option shown in the figure
above, come with both smaller and larger Flash memories.
Devices with different Flash memory size typically also have different SRAM and EEPROM.
The name of a device of the ATtiny family contains information as depicted below (not all options are
available):
Figure 1-2. Device Designations
AT tiny 406 - SFR
Package up to 20 pins
Flash size in KB
Feature set
Pin count
6=20 pins
4=14 pins
2= 8 pins
Configuration Summary
1.1.1
Peripheral Summary
Table 1-1. Peripheral Summary
R=Tape & Reel
Temperature Range
N=-40°C to +105°C
F=-40°C to +125°C
Package Type
M=VQFN
S=SOIC300
SS=SOIC150
ATtiny406
1.1
Carrier Type
Pins
20
SRAM
256B
Flash
4 KB
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 9
ATtiny406
0-Series Overview
ATtiny406
tinyAVR®
EEPROM
128B
Max. frequency (MHz)
20
16-bit Timer/Counter type A (TCA)
1
16-bit Timer/Counter type B (TCB)
1
12-bit Timer/Counter type D (TCD)
No
Real-Time Counter (RTC)
1
USART
1
SPI
1
TWI (I2C)
1
ADC
1
ADC channels
12
DAC
No
AC
1
AC inputs
2p/2n
Peripheral Touch Controller (PTC)
No
Custom Logic
1
Window Watchdog
1
Event System channels
3
General purpose I/O
18
External interrupts
18
CRCSCAN
1
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 10
ATtiny406
Ordering Information
2.
Ordering Information
2.1
ATtiny406
Table 2-1. ATtiny406 Ordering Codes
Ordering Code(1) Flash Package Type
(GPC)
Leads Power Supply Operational Range
ATtiny406-MNR
4 KB
VQFN (ZCL)
20
1.8V - 5.5V
Industrial (-40°C +105°C) Tape & Reel
ATtiny406-MFR
4 KB
VQFN (ZCL)
20
1.8V - 5.5V
Industrial (-40°C +125°C) Tape & Reel
ATtiny406-SNR
4 KB
SOIC300 (SRJ)
20
1.8V - 5.5V
Industrial (-40°C +105°C) Tape & Reel
ATtiny406-SFR
4 KB
SOIC300 (SRJ)
20
1.8V - 5.5V
Industrial (-40°C +125°C) Tape & Reel
1.
Carrier Type
Pb-free packaging complies with the European Directive for Restriction of Hazardous Substances
(RoHS directive). They are also Halide free and fully Green.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 11
ATtiny406
Block Diagram
3.
Block Diagram
Figure 3-1. Block Diagram
UPDI
UPDI / RESET
CRC
CPU
OCD
To
detectors
M
M
Flash
M
S
SRAM
BUS Matrix
S
EEPROM
S
S
AINP0
AINN0
OUT
NVMCTRL
PORTS
AC0
GPIOR
AIN[11:0]
ADC0
EVOUT[n:0]
EVSYS
LUTn-IN[2:0]
LUTn-OUT
CCL
WO[5:0]
WO
RXD
TXD
XCK
XDIR
TCA0
TCB0
USART0
E
V
E
N
T
R
O
U
T
I
N
G
N
E
T
W
O
R
K
D
A
T
A
B
U
S
CPUINT
System
management
RSTCTRL
I
N
/
O
U
T
D
A
T
A
B
U
S
PA[7:0]
PB[5:0]
PC[3:0]
Detectors/
references
RST/12V
POR
Bandgap
BOD/
VLM
CLKCTRL
SLPCTRL
Clock generation
CLKOUT
WDT
OSC20M
EXTCLK
OSC32K
MISO
MOSI
SCK
SS
SPI0
SDA
SCL
TWI0
© 2018 Microchip Technology Inc.
RTC
Datasheet Preliminary
40001976A-page 12
ATtiny406
Pinout
4.
Pinout
4.1
20-Pin VQFN
PA1
PA0/RESET/UPDI
PC3
PC2
PC1
20
19
18
17
16
Note:
For the most current package drawings, see the Microchip Packaging Specification located at http://
ww.microchip.com/packaging.
13
PB1
VDD
4
12
PB2
PA4
5
11
PB3
10
3
PB4
GND
9
PB0
PB5
14
8
2
PA7
EXTCLK /PA3
7
PC0
PA6
15
6
1
PA5
PA2
Input supply
Programming, Debug, Reset
Ground
Clock
GPIO VDD power domain
Digital function only
Analog function
4.2
20-Pin SOIC
Note:
For the most current package drawings, see the Microchip Packaging Specification located at http://
ww.microchip.com/packaging.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 13
ATtiny406
Pinout
VDD
1
20
GND
PA4
2
19
PA3/EXTCLK
PA5
3
18
PA2
PA6
4
17
PA1
PA7
5
16
PA0/RESET/UPDI
PB5
6
15
PC3
PB4
7
14
PC2
PB3
8
13
PC1
PB2
9
12
PC0
PB1
10
11
PB0
Input supply
Programming, Debug, Reset
Ground
Clock
GPIO VDD power domain
Digital function only
Analog function
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 14
ATtiny406
I/O Multiplexing and Considerations
5.
I/O Multiplexing and Considerations
5.1
Multiplexed Signals
VQFN 20-pin
SOIC 20-pin
Table 5-1. PORT Function Multiplexing
Pin Name (1,2)
19
16
PA0
20
17
PA1
AIN1
TXD
MOSI
SDA
1
18
PA2
EVOUT0
AIN2
RxD
MISO
SCL
2
19
PA3
EXTCLK
AIN3
XCK
SCK
WO3
3
20
GND
4
1
VDD
5
2
PA4
AIN4
XDIR
SS
WO4
6
3
PA5
AIN5
OUT
7
4
PA6
AIN6
AINN0
MOSI
8
5
PA7
AIN7
AINP0
MISO
9
6
PB5
AIN8
AINP1
10
7
PB4
AIN9
AINN1
11
8
PB3
12
9
PB2
13
10
PB1
AIN10
XCK
SDA
WO1
14
11
PB0
AIN11
XDIR
SCL
WO0
15
12
PC0
SCK
16
13
PC1
MISO
17
14
PC2
18
15
PC3
Other/Special
RESET/UPDI
CLKOUT
ADC0
AC0
USART0
SPI0
TWI0
TCB0
AIN0
EVOUT1
CCL
LUT0-IN0
LUT0-IN1
LUT0-IN2
WO5
LUT0-OUT
WO
LUT1-OUT
WO2
WO1
LUT0-OUT
WO0
RxD
EVOUT2
TCA0
TxD
WO2
W0
LUT1-OUT
MOSI
SS
WO3
LUT1-IN0
Note:
1. Pin names are of type Pxn, with x being the PORT instance (A, B) and n the pin number. Notation
for signals is PORTx_PINn. All pins can be used as event input.
2.
All pins can be used for external interrupt, where pins Px2 and Px6 of each port have full
asynchronous detection.
Tip: Signals on alternative pin locations are in typewriter font.
See PORTMUX chapter for selecting the altarnative pin locations.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 15
ATtiny406
Memories
6.
Memories
6.1
Overview
The main memories are SRAM data memory, EEPROM data memory, and Flash program memory. In
addition, the peripheral registers are located in the I/O memory space.
Table 6-1. Physical Properties of Flash Memory
Property
ATtiny406
Size
4 KB
Page size
64B
Number of pages
64
Start address
0x8000
Table 6-2. Physical Properties of SRAM
Property
ATtiny406
Size
256B
Start address
0x3F00
Table 6-3. Physical Properties of EEPROM
Property
ATtiny406
Size
128B
Page size
32B
Number of pages
4
Start address
0x1400
Related Links
I/O Memory
6.2
Memory Map
6.3
In-System Reprogrammable Flash Program Memory
The ATtiny406 contains 4 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 as 4K x 16. For write protection,
the Flash program memory space can be divided into three sections (see the illustration below):
Bootloader section, application code section, and application data section, with restricted access rights
among them.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 16
ATtiny406
Memories
The Program Counter (PC) is 11-bits wide 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.
The entire Flash memory is mapped in the memory space and is accessible with normal LD/ST
instructions as well as the LPM instruction. For LD/ST instructions, the Flash is mapped from address
0x8000. For the LPM instruction, the Flash start address is 0x0000.
The ATtiny406 also has a CRC peripheral that is a master on the bus.
Figure 6-1. Flash and the Three Sections
FLASHSTART: 0x8000
BO OT
BOOTEND>0: 0x8000+BOOTEND*256
FLASH
AP PL ICA TIO N
CO DE
APPEND>0: 0x8000+APPEND*256
AP PL ICA TIO N
DA TA
FLASHEND
Related Links
Configuration Summary
Nonvolatile Memory Controller (NVMCTRL)
6.4
SRAM Data Memory
The 256B SRAM is used for data storage and stack.
Related Links
AVR CPU
Stack and Stack Pointer
6.5
EEPROM Data Memory
The ATtiny406 has 128 bytes of EEPROM data memory, see Memory Map section. The EEPROM
memory supports single byte read and write. The EEPROM is controlled by the Nonvolatile Memory
Controller (NVMCTRL).
Related Links
Memory Map
Nonvolatile Memory Controller (NVMCTRL)
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 17
ATtiny406
Memories
6.6
User Row
In addition to the EEPROM, the ATtiny406 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 be written by the
UPDI when the part is locked. USERROW is not affected by a chip erase.
Related Links
Memory Map
Nonvolatile Memory Controller (NVMCTRL)
Unified Program and Debug Interface (UPDI)
6.7
Signature Bytes
All ATtiny microcontrollers have a 3-byte signature code that identifies the device. This code can be read
in both Serial and Parallel mode. The three bytes reside in a separate address space. For the device, the
signature bytes are given in the following table.
Note: When the device is locked, only the System Information Block (SIB) can be obtained.
Table 6-4. Device ID
Device Name
Signature Bytes Address
ATtiny406
0x00
0x01
0x02
0x1E
0x92
0x25
Related Links
System Information Block
6.8
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 non-valid value to the LOCKBIT bit field in FUSE.LOCKBIT.
Table 6-5. 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
No
Yes
Yes
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 18
ATtiny406
Memories
Memory Section
CPU Access
UPDI Access
Read
Write
Read
Write
USERROW
Yes
Yes
Yes
Yes
SIGROW
Yes
No
Yes
No
Other Fuses
Yes
No
Yes
Yes
Table 6-6. 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
No
No
No
USERROW
Yes
Yes
No
Yes(2)
SIGROW
Yes
No
Yes
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.
Related Links
Fuse Summary - FUSE
LOCKBIT
Unified Program and Debug Interface (UPDI)
Enabling of KEY Protected Interfaces
6.9
I/O Memory
All ATtiny406 I/Os and peripherals are located in the I/O memory 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 memory
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 memory space.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 19
ATtiny406
Memories
I/O registers within the address range 0x00 - 0x1F are directly bit accessible using the SBI and CBI
instructions. In these registers, the value of single bits can be checked by using the SBIS and SBIC
instructions. Refer to the Instruction Set section for more details.
For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O
memory addresses should never be written.
Some of the interrupt flags are cleared by writing a '1' to them. On ATtiny406 devices, the CBI and SBI
instructions will only operate on the specified bit, and can 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 ATtiny406 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.
Related Links
Memory Map
Peripheral Module Address Map
Instruction Set Summary
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 20
ATtiny406
Memories
6.9.1
Register Summary - GPIOR
Offset
Name
Bit Pos.
0x00
GPIOR0
7:0
GPIOR[7:0]
0x01
GPIOR1
7:0
GPIOR[7:0]
0x02
GPIOR2
7:0
GPIOR[7:0]
0x03
GPIOR3
7:0
GPIOR[7:0]
6.9.2
Register Description - GPIOR
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 21
ATtiny406
Memories
6.9.2.1
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
GPIOR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – GPIOR[7:0] GPIO Register byte
6.10
Configuration and User Fuses (FUSE)
Fuses are part of the nonvolatile memory and hold factory calibration data and device configuration. The
fuses are available from device power-up. The fuses can be read by the CPU or the UPDI, but can only
be programmed or cleared by the UPDI. The configuration and calibration values stored in the fuses are
written to their respective target registers at the end of the start-up sequence.
The content of the Signature Row fuses (SIGROW) is pre-programmed and cannot be altered. SIGROW
holds information such as device ID, serial number, and calibration values.
The fuses for peripheral configuration (FUSE) are pre-programmed but can be altered by the user.
Altered values in the configuration fuse will be effective only after a Reset.
Note: When writing the fuses write all reserved bits to ‘1’.
This device provides a User Row fuse area (USERROW) that can hold application data. The USERROW
can be programmed on a locked device by the UPDI. This can be used for final configuration without
having programming or debugging capabilities enabled.
Related Links
Signature Row Description
Fuse Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 22
ATtiny406
Memories
6.10.1
Signature Row Summary - SIGROW
Offset
Name
Bit Pos.
0x00
DEVICEID0
7:0
DEVICEID[7:0]
0x01
DEVICEID1
7:0
DEVICEID[7:0]
0x02
DEVICEID2
7:0
DEVICEID[7:0]
0x03
SERNUM0
7:0
SERNUM[7:0]
0x04
SERNUM1
7:0
SERNUM[7:0]
0x05
SERNUM2
7:0
SERNUM[7:0]
0x06
SERNUM3
7:0
SERNUM[7:0]
0x07
SERNUM4
7:0
SERNUM[7:0]
0x08
SERNUM5
7:0
SERNUM[7:0]
0x09
SERNUM6
7:0
SERNUM[7:0]
0x0A
SERNUM7
7:0
SERNUM[7:0]
0x0B
SERNUM8
7:0
SERNUM[7:0]
0x0C
SERNUM9
7:0
SERNUM[7:0]
0x0D
...
Reserved
0x1F
0x20
TEMPSENSE0
7:0
TEMPSENSE[7:0]
0x21
TEMPSENSE1
7:0
TEMPSENSE[7:0]
0x22
OSC16ERR3V
7:0
OSC16ERR3V[7:0]
0x23
OSC16ERR5V
7:0
OSC16ERR5V[7:0]
0x24
OSC20ERR3V
7:0
OSC20ERR3V[7:0]
0x25
OSC20ERR5V
7:0
OSC20ERR5V[7:0]
6.10.2
Signature Row Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 23
ATtiny406
Memories
6.10.2.1 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
4
3
2
1
0
Access
R
R
R
R
Reset
x
x
x
R
R
R
R
x
x
x
x
x
DEVICEID[7:0]
Bits 7:0 – DEVICEID[7:0] Byte n of the Device ID
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 24
ATtiny406
Memories
6.10.2.2 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
SERNUM[7:0]
Access
R
R
R
R
R
R
R
R
Reset
x
x
x
x
x
x
x
x
Bits 7:0 – SERNUM[7:0] Serial Number Byte n
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 25
ATtiny406
Memories
6.10.2.3 Temperature Sensor Calibration n
Name:
Offset:
Reset:
Property:
TEMPSENSEn
0x20 + n*0x01 [n=0..1]
[Temperature sensor calibration value]
-
These registers contain correction factors for temperature measurements by the ADC.
SIGROW.TEMPSENSE0 is a correction factor for the gain/slope (unsigned), SIGROW.TEMPSENSE1 is
a correction factor for the offset (signed).
Bit
7
6
5
4
Access
R
R
R
R
Reset
x
x
x
x
3
2
1
0
R
R
R
R
x
x
x
x
TEMPSENSE[7:0]
Bits 7:0 – TEMPSENSE[7:0] Temperature Sensor Calibration Byte n
Refer to Temperature Measurement for how to use the values and to the Signature Row Description
section for location of the values.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 26
ATtiny406
Memories
6.10.2.4 OSC16 Error at 3V
Name:
Offset:
Reset:
Property:
OSC16ERR3V
0x22
[Oscillator frequency error value]
-
Bit
7
6
5
4
Access
R
R
R
R
Reset
x
x
x
x
3
2
1
0
R
R
R
R
x
x
x
x
OSC16ERR3V[7:0]
Bits 7:0 – OSC16ERR3V[7:0] OSC16 Error at 3V
These registers contain the signed oscillator frequency error value when running at internal 16 MHz at 3V,
as measured during production.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 27
ATtiny406
Memories
6.10.2.5 OSC16 Error at 5V
Name:
Offset:
Reset:
Property:
OSC16ERR5V
0x23
[Oscillator frequency error value]
-
Bit
7
6
5
4
Access
R
R
R
R
Reset
x
x
x
x
3
2
1
0
R
R
R
R
x
x
x
x
OSC16ERR5V[7:0]
Bits 7:0 – OSC16ERR5V[7:0] OSC16 Error at 5V
These registers contain the signed oscillator frequency error value when running at internal 16 MHz at 5V,
as measured during production.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 28
ATtiny406
Memories
6.10.2.6 OSC20 Error at 3V
Name:
Offset:
Reset:
Property:
OSC20ERR3V
0x24
[Oscillator frequency error value]
-
Bit
7
6
5
4
Access
R
R
R
R
Reset
x
x
x
x
3
2
1
0
R
R
R
R
x
x
x
x
OSC20ERR3V[7:0]
Bits 7:0 – OSC20ERR3V[7:0] OSC20 Error at 3V
These registers contain the signed oscillator frequency error value when running at internal 20 MHz at 3V,
as measured during production.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 29
ATtiny406
Memories
6.10.2.7 OSC20 Error at 5V
Name:
Offset:
Reset:
Property:
OSC20ERR5V
0x25
[Oscillator frequency error value]
-
Bit
7
6
5
4
Access
R
R
R
R
Reset
x
x
x
x
3
2
1
0
R
R
R
R
x
x
x
x
OSC20ERR5V[7:0]
Bits 7:0 – OSC20ERR5V[7:0] OSC20 Error at 5V
These registers contain the signed oscillator frequency error value when running at internal 20 MHz at 5V,
as measured during production.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 30
ATtiny406
Memories
6.10.3
Fuse Summary - FUSE
Offset
Name
Bit Pos.
0x00
WDTCFG
7:0
0x01
BODCFG
7:0
0x02
OSCCFG
7:0
WINDOW[3:0]
LVL[2:0]
PERIOD[3:0]
SAMPFREQ
ACTIVE[1:0]
OSCLOCK
SLEEP[1:0]
FREQSEL[1:0]
0x03
...
Reserved
0x04
0x05
SYSCFG0
7:0
CRCSRC[1:0]
RSTPINCFG[1:0]
0x06
SYSCFG1
7:0
0x07
APPEND
7:0
APPEND[7:0]
0x08
BOOTEND
7:0
BOOTEND[7:0]
0x09
Reserved
0x0A
LOCKBIT
7:0
LOCKBIT[7:0]
6.10.4
EESAVE
SUT[2:0]
Fuse Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 31
ATtiny406
Memories
6.10.4.1 Watchdog Configuration
Name:
Offset:
Reset:
Property:
WDTCFG
0x00
-
Bit
7
6
5
4
3
2
Access
R
Reset
0
1
0
R
R
R
R
R
0
0
0
0
R
R
0
0
0
WINDOW[3:0]
PERIOD[3:0]
Bits 7:4 – WINDOW[3:0] Watchdog Window Time-out Period
This value is loaded into the WINDOW bit field of the Watchdog Control A register (WDT.CTRLA) during
Reset.
Bits 3:0 – PERIOD[3:0] Watchdog Time-out Period
This value is loaded into the PERIOD bit field of the Watchdog Control A register (WDT.CTRLA) during
Reset.
Related Links
Register Summary - WDT
Reset Controller (RSTCTRL)
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 32
ATtiny406
Memories
6.10.4.2 BOD Configuration
Name:
Offset:
Reset:
Property:
BODCFG
0x01
-
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
7
6
5
LVL[2:0]
4
3
SAMPFREQ
2
1
ACTIVE[1:0]
0
SLEEP[1:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 7:5 – LVL[2:0] BOD Level
This value is loaded into the LVL bit field of the BOD Control B register (BOD.CTRLB) during Reset.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
BODLEVEL0
BODLEVEL1
BODLEVEL2
BODLEVEL3
BODLEVEL4
BODLEVEL5
BODLEVEL6
BODLEVEL7
Description
1.8V
2.15V
2.60V
2.95V
3.30V
3.70V
4.00V
4.30V
Bit 4 – SAMPFREQ BOD Sample Frequency
This value is loaded into the SAMPFREQ bit of the BOD Control A register (BOD.CTRLA) during Reset.
Value
0x0
0x1
Description
Sample frequency is 1 kHz
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 register (BOD.CTRLA) during Reset.
Value
0x0
0x1
0x2
0x3
Description
Disabled
Enabled
Sampled
Enabled with wake-up halted until BOD is ready
Bits 1:0 – SLEEP[1:0] BOD Operation Mode in Sleep
This value is loaded into the SLEEP bit field of the BOD Control A register (BOD.CTRLA) during Reset.
Value
0x0
0x1
Description
Disabled
Enabled
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 33
ATtiny406
Memories
Value
0x2
0x3
Description
Sampled
Reserved
Related Links
Register Summary - BOD
Reset Controller (RSTCTRL)
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 34
ATtiny406
Memories
6.10.4.3 Oscillator Configuration
Name:
Offset:
Reset:
Property:
Bit
7
OSCCFG
0x02
-
6
5
4
3
2
1
OSCLOCK
0
FREQSEL[1:0]
Access
R
R
R
Reset
0
1
0
Bit 7 – OSCLOCK Oscillator Lock
This fuse bit is loaded to LOCK in CLKCTRL.OSC20MCALIBB during Reset.
Value
0
1
Description
Calibration registers of the 20 MHz oscillator are accessible
Calibration registers of the 20 MHz oscillator are locked
Bits 1:0 – FREQSEL[1:0] Frequency Select
These bits select the operation frequency of the 16/20 MHz internal oscillator (OSC20M), and determine
the respective factory calibration values to be written to CAL20M in CLKCTRL.OSC20MCALIBA and
TEMPCAL20M in CLKCTRL.OSC20MCALIBB.
Value
0x1
0x2
Other
Description
Run at 16 MHz with corresponding factory calibration
Run at 20 MHz with corresponding factory calibration
Reserved
Related Links
Register Summary - CLKCTRL
Reset Controller (RSTCTRL)
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 35
ATtiny406
Memories
6.10.4.4 System Configuration 0
Name:
Offset:
Reset:
Property:
SYSCFG0
0x05
0xC4
-
Bit
7
6
5
4
Access
R
R
R
R
R
Reset
1
1
0
1
0
CRCSRC[1:0]
3
2
1
0
RSTPINCFG[1:0]
EESAVE
Bits 7:6 – CRCSRC[1:0] CRC Source
See CRC description for more information about the functionality.
Value
00
01
10
11
Name
FLASH
BOOT
BOOTAPP
NOCRC
Description
CRC of full Flash (boot, application code and application data)
CRC of boot section
CRC of application code and boot sections
No CRC
Bits 3:2 – RSTPINCFG[1:0] Reset Pin Configuration
These bits select the Reset/UPDI pin configuration.
Value
0x0
0x1
0x2
0x3
Description
GPIO
UPDI
RESET
Reserved
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
0
1
Description
EEPROM erased during chip erase
EEPROM not erased under chip erase
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 36
ATtiny406
Memories
6.10.4.5 System Configuration 1
Name:
Offset:
Reset:
Property:
Bit
7
SYSCFG1
0x06
-
6
5
4
3
2
1
0
SUT[2:0]
Access
R
R
R
Reset
1
1
1
Bits 2:0 – SUT[2:0] Start-Up Time Setting
These bits select the start-up time between power-on and code execution.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Description
0 ms
1 ms
2 ms
4 ms
8 ms
16 ms
32 ms
64 ms
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 37
ATtiny406
Memories
6.10.4.6 Application Code End
Name:
Offset:
Reset:
Property:
APPEND
0x07
-
Bit
7
6
5
4
3
2
1
0
Access
R
R
R
R
Reset
0
0
0
R
R
R
R
0
0
0
0
0
APPEND[7:0]
Bits 7:0 – APPEND[7:0] Application Code Section End
These bits set the end of the application code section in blocks of 256 bytes. The end of the application
code section should be set as BOOT size plus application code size. The remaining Flash will be
application data. A value of 0x00 defines the Flash from BOOTEND*256 to end of Flash as application
code. When both FUSE.APPEND and FUSE.BOOTEND are 0x00, the entire Flash is BOOT section.
Related Links
Nonvolatile Memory Controller (NVMCTRL)
Flash
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 38
ATtiny406
Memories
6.10.4.7 Boot End
Name:
Offset:
Reset:
Property:
BOOTEND
0x08
-
Bit
7
6
5
4
Access
R
R
R
R
Reset
0
0
0
0
3
2
1
0
R
R
R
R
0
0
0
0
BOOTEND[7:0]
Bits 7:0 – BOOTEND[7:0] Boot Section End
These bits set the end of the boot section in blocks of 256 bytes. A value of 0x00 defines the whole Flash
as BOOT section. When both FUSE.APPEND and FUSE.BOOTEND are 0x00, the entire Flash is BOOT
section.
Related Links
Nonvolatile Memory Controller (NVMCTRL)
Flash
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 39
ATtiny406
Memories
6.10.4.8 Lockbits
Name:
Offset:
Reset:
Property:
Bit
LOCKBIT
0x0A
-
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
LOCKBIT[7:0]
Access
Reset
Bits 7:0 – LOCKBIT[7:0] Lockbits
When the part is locked, UPDI cannot access the system bus, so it cannot read out anything but CSspace.
Value
0xC5
other
Description
Valid key - the device is open
Invalid - The device is locked
Related Links
Memory Section Access from CPU and UPDI on Locked Device
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Datasheet Preliminary
40001976A-page 40
ATtiny406
Peripherals and Architecture
7.
Peripherals and Architecture
7.1
Peripheral Module Address Map
The address map shows the base address for each peripheral. For complete register description and
summary for each peripheral module, refer to the respective module chapters.
Table 7-1. Peripheral Module Address Map
Base Address
Name
Description
0x0000
VPORTA
Virtual Port A
0x0004
VPORTB
Virtual Port B
0x0008
VPORTC
Virtual Port C
0x001C
GPIO
General Purpose I/O registers
0x0030
CPU
CPU
0x0040
RSTCTRL
Reset Controller
0x0050
SLPCTRL
Sleep Controller
0x0060
CLKCTRL
Clock Controller
0x0080
BOD
Brown-Out Detector
0x00A0
VREF
Voltage Reference
0x0100
WDT
Watchdog Timer
0x0110
CPUINT
Interrupt Controller
0x0120
CRCSCAN
Cyclic Redundancy Check Memory Scan
0x0140
RTC
Real-Time Counter
0x0180
EVSYS
Event System
0x01C0
CCL
Configurable Custom Logic
0x0200
PORTMUX
Port Multiplexer
0x0400
PORTA
Port A Configuration
0x0420
PORTB
Port B Configuration
0x0440
PORTC
Port C Configuration
0x0600
ADC0
Analog-to-Digital Converter/Peripheral Touch Controller
0x0680
AC0
Analog Comparator 0
0x0800
USART0
Universal Synchronous Asynchronous Receiver Transmitter
0x0810
TWI0
Two-Wire Interface
0x0820
SPI0
Serial Peripheral Interface
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Datasheet Preliminary
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ATtiny406
Peripherals and Architecture
7.2
Base Address
Name
Description
0x0A00
TCA0
Timer/Counter Type A instance 0
0x0A40
TCB0
Timer/Counter Type B instance 0
0x0F00
SYSCFG
System Configuration
0x1000
NVMCTRL
Nonvolatile Memory Controller
0x1100
SIGROW
Signature Row
0x1280
FUSES
Device-specific fuses
0x1300
USERROW
User Row
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 Interrupt section in the Functional description
of the respective peripheral for more details on the available interrupt sources.
When the interrupt condition occurs, an Interrupt Flag (nameIF) is set in the Interrupt Flags register of the
peripheral (peripheral.INTFLAGS).
An interrupt is enabled or disabled by writing to the corresponding Interrupt Enable bit (nameIE) in the
peripheral's Interrupt Control register (peripheral.INTCTRL).
The naming of the registers may vary slightly in some peripherals.
An interrupt request is generated when the corresponding interrupt is enabled and the interrupt flag is set.
The interrupt request remains active until the interrupt flag is cleared. See the peripheral's INTFLAGS
register for details on how to clear interrupt flags.
Interrupts must be enabled globally for interrupt requests to be generated.
Table 7-2. Interrupt Vector Mapping
Vector Number Peripheral Source
Definition
0
RESET
RESET
1
CRCSCAN_NMI
NMI - Non-Maskable Interrupt from CRC
2
BOD_VLM
VLM - Voltage Level Monitor
3
PORTA_PORT
PORTA - Port A
4
PORTB_PORT
PORTB - Port B
5
PORTC_PORT
PORTC - Port C
6
RTC_CNT
RTC - Real-Time Counter
7
RTC_PIT
PIT - Periodic Interrupt Timer (in RTC peripheral)
8
TCA0_LUNF/TCA0_OVF
TCA0 - Timer Counter Type A, LUNF/OVF
9
TCA0_HUNF
TCA0, HUNF
10
TCA0_LCMP0/TCA0_CMP0 TCA0, LCMP0/CMP0
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Datasheet Preliminary
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ATtiny406
Peripherals and Architecture
Vector Number Peripheral Source
Definition
11
TCA0_LCMP1/TCA0_CMP1 TCA0, LCMP1/CMP1
12
TCA0_CMP2/TCA0_LCMP2 TCA0, LCMP2/CMP2
13
TCB0_INT
TCB0 - Timer Counter Type B
16
-
-
17
AC0_AC
AC0 – Analog Comparator
18
-
-
19
-
-
20
ADC0_RESRDY
ADC0 – Analog-to-Digital Converter, RESRDY
21
ADC0_WCOMP
ADC0, WCOMP
22
-
-
23
-
-
24
TWI0_TWIS
TWI0 - Two-Wire Interface/I2C, TWIS
25
TWI0_TWIM
TWI0, TWIM
26
SPI0_INT
SPI0 - Serial Peripheral Interface
27
USART0_RXC
USART0 - Universal Asynchronous ReceiverTransmitter, RXC
28
USART0_DRE
USART0, DRE
29
USART0_TXC
USART0, TXC
30
NVMCTRL_EE
NVM - Nonvolatile Memory
Related Links
Nonvolatile Memory Controller (NVMCTRL)
I/O Pin Configuration (PORT)
Real-Time Counter (RTC)
Serial Peripheral Interface (SPI)
Universal Synchronous and Asynchronous Receiver and Transmitter (USART)
Two-Wire Interface (TWI)
Cyclic Redundancy Check Memory Scan (CRCSCAN)
16-bit Timer/Counter Type A (TCA)
16-bit Timer/Counter Type B (TCB)
Analog Comparator (AC)
Analog-to-Digital Converter (ADC)
7.3
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.
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Datasheet Preliminary
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ATtiny406
Peripherals and Architecture
7.3.1
Register Summary - SYSCFG
Offset
Name
Bit Pos.
0x01
REVID
7:0
7.3.2
REVID[7:0]
Register Description - SYSCFG
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Peripherals and Architecture
7.3.2.1
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
R
R
R
R
Reset
Bits 7:0 – REVID[7:0] Revision ID
These bits contain the device revision. 0x00 = A, 0x01 = B, and so on.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
AVR CPU
8.
AVR CPU
8.1
Features
•
•
•
•
•
•
•
•
8.2
8-Bit, High-Performance AVR RISC CPU:
– 135 instructions
– Hardware multiplier
32 8-Bit Registers Directly Connected to the Arithmetic Logic Unit (ALU)
Stack in RAM
Stack Pointer Accessible in I/O Memory Space
Direct Addressing of up to 64 KB of Unified Memory:
– Entire Flash accessible with all LD/ST instructions
True 16-Bit Access to 16-Bit I/O Registers
Efficient Support for 8-, 16-, and 32-Bit Arithmetic
Configuration Change Protection for System Critical Features
Overview
All AVR devices use the 8-bit AVR CPU. The CPU is able to access memories, perform calculations,
control peripherals, and execute instructions in the program memory. Interrupt handling is described in a
separate section.
Related Links
Memories
Nonvolatile Memory Controller (NVMCTRL)
CPU Interrupt Controller (CPUINT)
8.3
Architecture
In order to maximize performance and parallelism, the AVR CPU uses a Harvard architecture with
separate buses for program and data. Instructions in the program memory are executed with single-level
pipelining. While one instruction is being executed, the next instruction is prefetched from the program
memory. This enables instructions to be executed on every clock cycle.
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Datasheet Preliminary
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ATtiny406
AVR CPU
Figure 8-1. AVR CPU Architecture
Register file
R31 (ZH)
R29 (YH)
R27 (XH)
R25
R23
R21
R19
R17
R15
R13
R11
R9
R7
R5
R3
R1
R30 (ZL)
R28 (YL)
R26 (XL)
R24
R22
R20
R18
R16
R14
R12
R10
R8
R6
R4
R2
R0
Program
Counter
Flash Program
Memory
Instruction
Register
Instruction
Decode
Data Memory
Stack
Pointer
STATUS
Register
ALU
The Arithmetic Logic Unit (ALU) supports arithmetic and logic operations between registers or between a
constant and a register. Also, single-register operations can be executed in the ALU. After an arithmetic
operation, the STATUS register is updated to reflect information about the result of the operation.
The ALU is directly connected to the fast-access register file. The 32 8-bit general purpose working
registers all have single clock cycle access time allowing single-cycle arithmetic logic unit operation
© 2018 Microchip Technology Inc.
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ATtiny406
AVR CPU
between registers or between a register and an immediate. Six of the 32 registers can be used as three
16-bit Address Pointers for program and data space addressing, enabling efficient address calculations.
The program memory bus is connected to Flash, and the first program memory Flash address is 0x0000.
The data memory space is divided into I/O registers, SRAM, EEPROM, and Flash.
All I/O Status and Control registers reside in the lowest 4 KB addresses of the data memory. This is
referred to as the I/O memory space. The lowest 64 addresses are accessed directly with single-cycle
IN/OUT instructions, or as the data space locations from 0x00 to 0x3F. These addresses can be accessed
using load (LD/LDS/LDD) and store (ST/STS/STD) instructions. The lowest 32 addresses can even be
accessed with single-cycle SBI/CBI instructions and SBIS/SBIC instructions. The rest is the extended
I/O memory space, ranging from 0x0040 to 0x0FFF. The I/O registers here must be accessed as data
space locations using load and store instructions.
Data addresses 0x1000 to 0x1800 are reserved for memory mapping of fuses, the NVM controller and
EEPROM. The addresses from 0x1800 to 0x7FFF are reserved for other memories, such as SRAM.
The Flash is mapped in the data space from 0x8000 and above. The Flash can be accessed with all load
and store instructions by using addresses above 0x8000. The LPM instruction accesses the Flash similar
to the code space, where the Flash starts at address 0x0000.
For a summary of all AVR instructions, refer to the Instruction Set Summary section. For details of all AVR
instructions, refer to http://www.microchip.com/design-centers/8-bit.
Related Links
Nonvolatile Memory Controller (NVMCTRL)
Memories
Instruction Set Summary
8.4
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 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.
8.4.1
Hardware Multiplier
The multiplier is capable of multiplying two 8-bit numbers into a 16-bit result. The hardware multiplier
supports different variations of signed and unsigned integer and fractional numbers:
•
•
•
•
Multiplication of signed/unsigned integers
Multiplication of signed/unsigned fractional numbers
Multiplication of a signed integer with an unsigned integer
Multiplication of a signed fractional number with an unsigned one
A multiplication takes two CPU clock cycles.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
AVR CPU
8.5
Functional Description
8.5.1
Program Flow
After Reset, the CPU will execute instructions from the lowest address in the Flash program memory,
0x0000. The Program Counter (PC) 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.
8.5.2
Instruction Execution Timing
The AVR CPU is clocked by the CPU clock: CLK_CPU. No internal clock division is applied. The figure
below shows the parallel instruction fetches and instruction executions enabled by the Harvard
architecture and the fast-access register file concept. This is the basic pipelining concept enabling up to 1
MIPS/MHz performance with high efficiency.
Figure 8-2. The Parallel Instruction Fetches and Instruction Executions
T1
T2
T3
T4
clkCPU
1st Instruction Fetch
1st Instruction Execute
2nd Instruction Fetch
2nd Instruction Execute
3rd Instruction Fetch
3rd Instruction Execute
4th Instruction Fetch
The following figure shows the internal timing concept for the register file. In a single clock cycle, an ALU
operation using two register operands is executed and the result is stored in the destination register.
Figure 8-3. Single Cycle ALU Operation
T1
T2
T3
T4
clkCPU
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
8.5.3
Status Register
The Status register (CPU.SREG) contains information about the result of the most recently executed
arithmetic or logic instruction. This information can be used for altering program flow in order to perform
conditional operations.
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ATtiny406
AVR CPU
CPU.SREG is updated after all ALU operations, as specified in the Instruction Set Summary. This will in
many cases remove the need for using the dedicated compare instructions, resulting in faster and more
compact code. CPU.SREG is not automatically stored/restored when entering/returning from an Interrupt
Service Routine. Maintaining the Status register between context switches must, therefore, be handled by
user-defined software. CPU.SREG is accessible in the I/O memory space.
Related Links
Instruction Set Summary
8.5.4
Stack and Stack Pointer
The stack is used for storing return addresses after interrupts and subroutine calls. 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 is pushed and popped from the stack using the PUSH and POP instructions. The stack grows from
higher to lower memory locations. This implies that pushing data onto the stack decreases the SP, and
popping data off the stack increases the SP. The Stack Pointer is automatically set to the highest address
of the internal SRAM after Reset. If the stack is changed, it must be set to point above address 0x2000,
and it must be defined before any subroutine calls are executed and before interrupts are enabled.
During interrupts or subroutine calls the return address is automatically pushed on the stack as a Word
Pointer and the SP is decremented by '2'. The return address consists of two bytes and the Least
Significant Byte is pushed on the stack first (at the higher address). As an example, a Byte Pointer return
address of 0x0006 is saved on the stack as 0x0003 (shifted one bit to the right), pointing to the fourth 16bit instruction word in the program memory. The return address is popped off the stack with RETI (when
returning from interrupts) and RET (when returning from subroutine calls) and the SP is incremented by
two.
The SP is decremented by '1' when data is pushed on the stack with the PUSH instruction, and
incremented by '1' when data is popped off the stack using the POP instruction.
To prevent corruption when updating the Stack Pointer from software, a write to SPL will automatically
disable interrupts for up to four instructions or until the next I/O memory write.
8.5.5
Register File
The register file consists of 32 8-bit general purpose working registers with single clock cycle access time.
The register file supports the following input/output schemes:
•
•
•
•
One 8-bit output operand and one 8-bit result input
Two 8-bit output operands and one 8-bit result input
Two 8-bit output operands and one 16-bit result input
One 16-bit output operand and one 16-bit result input
Six of the 32 registers can be used as three 16-bit Address Register Pointers for data space addressing,
enabling efficient address calculations.
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Datasheet Preliminary
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ATtiny406
AVR CPU
Figure 8-4. AVR CPU General Purpose Working Registers
R0
R1
R2
Addr.
0x00
0x01
0x02
R13
R14
R15
R16
R17
0x0D
0x0E
0x0F
0x10
0x11
R26
R27
R28
R29
R30
R31
0x1A
0x1B
0x1C
0x1D
0x1E
0x1F
0
7
...
...
X-register Low Byte
X-register High Byte
Y-register Low Byte
Y-register High Byte
Z-register Low Byte
Z-register High Byte
The register file is located in a separate address space and is, therefore, not accessible through
instructions operation on data memory.
8.5.5.1
The X-, Y-, and Z-Registers
Registers R26...R31 have added functions besides their general purpose usage.
These registers can form 16-bit Address Pointers for addressing data memory. These three address
registers are called the X-register, Y-register, and Z-register. Load and store instructions can use all X-,
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 Zregisters are used.
Figure 8-5. The X-, Y-, and Z-Registers
Bit (individually)
7
X-register
15
Bit (individually)
7
Y-register
Bit (individually)
R29
7
7
R31
8
7
0
7
8
7
0
0
7
8
7
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
0
The lowest register address holds the Least Significant Byte (LSB), and the highest register address
holds the Most Significant Byte (MSB). In the different addressing modes, these address registers
function as fixed displacement, automatic increment, and automatic decrement.
Related Links
Instruction Set Summary
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
AVR CPU
8.5.6
Accessing 16-Bit Registers
The AVR data bus is 8-bits wide, and so accessing 16-bit registers requires atomic operations. These
registers must be byte accessed using two read or write operations. 16-bit registers are connected to the
8-bit bus and a temporary register using a 16-bit bus.
For a write operation, the low byte of the 16-bit register must be written before the high byte. The low byte
is then written into the temporary register. When the high byte of the 16-bit register is written, the
temporary register is copied into the low byte of the 16-bit register in the same clock cycle.
For a read operation, the low byte of the 16-bit register must be read before the high byte. When the low
byte register is read by the CPU, the high byte of the 16-bit register is copied into the temporary register
in the same clock cycle as the low byte is read. When the high byte is read, it is then read from the
temporary register.
This ensures that the low and high bytes of 16-bit registers are always accessed simultaneously when
reading or writing the register.
Interrupts can corrupt the timed sequence if an interrupt is triggered and accesses the same 16-bit
register during an atomic 16-bit read/write operation. To prevent this, interrupts can be disabled when
writing or reading 16-bit registers.
The temporary registers can be read and written directly from user software.
8.5.7
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 the protected selfprogramming.
Related Links
CCP
8.5.7.1
Sequence for Write Operation to Configuration Change Protected I/O Registers
In order to write to registers protected by CCP, these steps are required:
1.
2.
The software writes the signature that enables change of protected I/O registers to the CCP bit field
in the CPU.CCP register.
Within four instructions, the software must write the appropriate data to the protected register.
Most protected registers also contain a write enable/change enable/lock bit. This bit must be written
to '1' in the same operation as the data are written.
The protected change is immediately disabled if the CPU performs write operations to the I/O
register or data memory, if load or store accesses to Flash, NVMCTRL, EEPROM are conducted,
or if the SLEEP instruction is executed.
8.5.7.2
Sequence for Execution of Self-Programming
In order to execute self-programming (the execution of writes to the NVM controller's command register),
the following steps are required:
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Datasheet Preliminary
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ATtiny406
AVR CPU
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.
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Datasheet Preliminary
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ATtiny406
AVR CPU
8.6
Register Summary - CPU
Offset
Name
Bit Pos.
0x04
CCP
7:0
CCP[7:0]
0x05
...
Reserved
0x0C
0x0D
SP
0x0F
SREG
8.7
7:0
SP[7:0]
15:8
SP[15:8]
7:0
I
T
H
S
V
N
Z
C
Register Description
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Datasheet Preliminary
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ATtiny406
AVR CPU
8.7.1
Configuration Change Protection
Name:
Offset:
Reset:
Property:
Bit
7
CCP
0x04
0x00
-
6
5
4
3
2
1
0
CCP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – CCP[7:0] Configuration Change Protection
Writing the correct signature to this bit field allows changing protected I/O registers or executing protected
instructions within the next four CPU instructions executed.
All interrupts are ignored during these cycles. After these cycles, interrupts will automatically be handled
again by the CPU, and any pending interrupts will be executed according to their level and priority.
When the protected I/O register signature is written, CCP[0] will read as '1' as long as the CCP feature is
enabled.
When the protected self-programming signature is written, CCP[1] will read as '1' as long as the CCP
feature is enabled.
CCP[7:2] will always read as zero.
Value
0x9D
0xD8
Name
SPM
IOREG
© 2018 Microchip Technology Inc.
Description
Allow Self-Programming
Un-protect protected I/O registers
Datasheet Preliminary
40001976A-page 55
ATtiny406
AVR CPU
8.7.2
Stack Pointer
Name:
Offset:
Reset:
Property:
SP
0x0D
0xxxxx
-
The CPU.SP holds the Stack Pointer (SP) that points to the top of the stack. After Reset, the Stack
Pointer points to the highest internal SRAM address.
Only the number of bits required to address the available data memory including external memory (up to
64 KB) is implemented for each device. Unused bits will always read as zero.
The CPU.SPL and CPU.SPH register pair represents the 16-bit value, CPU.SP. The low byte [7:0] (suffix
L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset + 0x01. For
more details on reading and writing 16-bit registers, refer to Accessing 16-Bit Registers.
To prevent corruption when updating the 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.
Bit
15
14
13
12
11
10
9
8
SP[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
x
x
x
x
x
x
x
x
Bit
7
6
5
4
3
2
1
0
SP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
x
x
x
x
x
x
x
x
Bits 15:8 – SP[15:8] Stack Pointer High Byte
These bits hold the MSB of the 16-bit register.
Bits 7:0 – SP[7:0] Stack Pointer Low Byte
These bits hold the LSB of the 16-bit register.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
AVR CPU
8.7.3
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 affected by the different
instructions, see the Instruction Set Summary.
Bit
Access
Reset
7
6
5
4
3
2
1
0
I
T
H
S
V
N
Z
C
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 – I Global Interrupt Enable
Writing a '1' to this bit 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.
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AVR CPU
Bit 0 – C Carry Flag
The carry flag (C) indicates a carry in an arithmetic or logic operation.
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Nonvolatile Memory Controller (NVMCTRL)
9.
Nonvolatile Memory Controller (NVMCTRL)
9.1
Features
•
•
•
•
•
•
9.2
Unified Memory
In-System Programmable
Self-Programming and Boot Loader Support
Configurable Sections for Write Protection:
– Boot section for boot loader code or application code
– Application code section for application code
– Application data section for application code or data storage
Signature Row for Factory-Programmed Data:
– ID for each device type
– Serial number for each device
– Calibration bytes for factory calibrated peripherals
User Row for Application Data:
– 32 bytes in size
– Can be read and written from software
– Can be written from UPDI on locked device
– Content is kept after chip erase
Overview
The NVM Controller (NVMCTRL) is the interface between the device, the Flash, and the EEPROM. The
Flash and EEPROM are reprogrammable memory blocks that retain their values even when not powered.
The Flash is mainly used for program storage, 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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Nonvolatile Memory Controller (NVMCTRL)
9.2.2
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 9-1. NVMCTRL System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
Yes
CPUINT
Events
No
-
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
Interrupts
9.2.2.1
Clocks
This peripheral always runs on the CPU clock (CLK_CPU). It will request this clock also in sleep modes if
a write/erase is ongoing.
Related Links
Clock Controller (CLKCTRL)
9.2.2.2
I/O Lines and Connections
Not applicable.
9.2.2.3
Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
9.2.2.4
Events
Not applicable.
9.2.2.5
Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in Debugging
mode will halt normal operation of the peripheral.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
Unified Program and Debug Interface (UPDI)
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.
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Nonvolatile Memory Controller (NVMCTRL)
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: 0x8000
BO OT
BOOTEND>0: 0x8000+BOOTEND*256
AP PL ICA TIO N
CO DE
APPEND>0: 0x8000+APPEND*256
AP PL ICA TIO N
DA TA
Section Sizes
The sizes of these sections are set by the Boot Section End fuse (FUSE.BOOTEND) and Application
Code Section End fuse (FUSE.APPEND).
The fuses select the section sizes in blocks of 256 bytes. As shown in Figure 9-2, the BOOT section
stretches from the start of the Flash until BOOTEND. The APPCODE section runs from BOOTEND until
APPEND. The remaining area is the APPDATA section. If APPEND is written to 0, the APPCODE section
runs from BOOTEND to the end of Flash (removing the APPDATA section). If BOOTEND and APPEND
are written to 0, the entire Flash is regarded as BOOT section. APPEND should either be set to 0 or a
value greater or equal than BOOTEND.
Table 9-2. Setting Up Flash Sections
BOOTEND APPEND
BOOT Section
APPCODE Section
APPDATA Section
0
0
0 to FLASHEND
-
-
>0
0
0 to 256*BOOTEND
256*BOOTEND to
FLASHEND
-
>0
==
BOOTEND
0 to 256*BOOTEND
-
256*BOOTEND to
FLASHEND
>0
>
BOOTEND
0 to 256*BOOTEND
256*BOOTEND to
256*APPEND
256*APPEND to
FLASHEND
Note:
•
See also the BOOTEND and APPEND descriptions.
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Nonvolatile Memory Controller (NVMCTRL)
•
Interrupt vectors are by default located after the BOOT section. This can be changed in the
interrupt controller. Refer to Interrupt Vector Locations.
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 one
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.
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Nonvolatile Memory Controller (NVMCTRL)
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 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:
•
Fill the page buffer
•
Write the page buffer to Flash with the Erase/Write Page command
Alternative 2:
•
Write to a location in the page to set up the address
•
Perform a Erase Page command
•
Fill the page buffer
•
Perform a Write Page command
The NVM command set supports both a single erase and write operation, and split Page Erase and Page
Write commands. This split commands enable shorter programming time for each command, and the
erase operations can be done during non-time-critical programming execution.
The EEPROM programming is similar, but only the bytes updated in the page buffer will be written or
erased in the EEPROM.
9.3.2.4
Commands
Reading of the Flash/EEPROM and writing of the page buffer is handled with normal load/store
instructions. Other operations, such as writing and erasing the memory arrays, are handled by commands
in the NVM.
To execute a command in the NVM:
1. 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.
Write Command
The Write command of the Flash controller writes the content of the page buffer to the Flash or EEPROM.
If the write is to the Flash, the CPU will stop executing code as long as the Flash is busy with the write
operation. If the write is to the EEPROM, the CPU can continue executing code while the operation is
ongoing.
The page buffer will be automatically cleared after the operation is finished.
Erase Command
The Erase command erases the current page. There must be one byte written in the page buffer for the
Erase command to take effect.
For erasing the Flash, first, write to one address in the desired page, then execute the command. The
whole page in the Flash will then be erased. The CPU will be halted while the erase is ongoing.
For the EEPROM, only the bytes written in the page buffer will be erased when the command is
executed. To erase a specific byte, write to its corresponding address before executing the command. To
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Nonvolatile Memory Controller (NVMCTRL)
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 be automatically cleared after the operation is finished.
Erase-Write Operation
The Erase/Write command is a combination of the Erase and Write command, but without clearing the
page buffer after the Erase command: The erase/write operation first erases the selected page, then it
writes the content of the page buffer to the same page.
When executed on the Flash, the CPU will be halted when the operations are ongoing. When executed
on EEPROM, the CPU can continue executing code.
The page buffer will be automatically cleared after the operation is finished.
Page Buffer Clear Command
The Page Buffer Clear command clears the page buffer. The contents of the page buffer will be all ones
after the operation. The CPU will be halted when the operation executes (seven CPU cycles).
Chip Erase Command
The Chip Erase command erases the Flash and the EEPROM. The EEPROM is unaltered if the
EEPROM Save During Chip Erase (EESAVE) fuse in FUSE.SYSCFG0 is set. The 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 ones after the operation.
EEPROM Erase Command
The EEPROM Erase command erases the EEPROM. The EEPROM will be all ones after the operation.
The CPU will be halted while the EEPROM is being erased.
Fuse Write Command
The Fuse Write command writes the fuses. It can only be used by the UPDI, the CPU cannot start this
command.
Follow this procedure to use this command:
•
Write the address of the fuse to the Address register (NVMCTRL.ADDR)
•
Write the data to be written to the fuse to the Data register (NVMCTRL.DATA)
•
Execute the Fuse Write command.
•
After the fuse is written, a Reset is required for the updated value to take effect.
For reading fuses, use a regular read on the memory location.
9.3.3
Preventing Flash/EEPROM Corruption
During periods of low VDD, the Flash program or EEPROM data can be corrupted if the supply voltage is
too low for the CPU and the Flash/EEPROM to operate properly. These issues are the same as for board
level systems using Flash/EEPROM, and the same design solutions should be applied.
A Flash/EEPROM corruption can be caused by two situations when the voltage is too low: First, a regular
write sequence to the Flash requires a minimum voltage to operate correctly. Also, the CPU itself can
execute instructions incorrectly when the supply voltage is too low. See the Electrical Characteristics
chapter for Maximum Frequency vs. VDD.
Flash/EEPROM corruption can be avoided by these measures:
Keep the device in Reset during periods of insufficient power supply voltage. This can be done by
enabling the internal Brown-Out Detector (BOD).
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Nonvolatile Memory Controller (NVMCTRL)
The voltage level monitor in the BOD can be used to prevent starting a write to the EEPROM close to the
BOD level.
If the detection levels of the internal BOD does not match the required detection level, an external low
VDD Reset protection circuit can be used. If a Reset occurs while a write operation is ongoing, the write
operation will be aborted.
Related Links
General Operating Ratings
Brown-Out Detector (BOD)
9.3.4
Interrupts
Table 9-3. Available Interrupt Vectors and Sources
Offset Name
Vector Description
Conditions
0x00
NVM
The EEPROM is ready for new write/erase operations.
EEREADY
When an interrupt condition occurs, the corresponding interrupt flag is set in the Interrupt Flags register of
the peripheral (NVMCTRL.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding bit in the peripheral's Interrupt
Enable register (NVMCTRL.INTEN).
An interrupt request is generated when the corresponding interrupt source is enabled and the interrupt
flag is set. The interrupt request remains active until the interrupt flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear interrupt flags.
9.3.5
Sleep Mode Operation
If there is no ongoing write operation, the NVMCTRL will enter sleep mode when the system enters sleep
mode.
If a write operation is ongoing when the system enters a sleep mode, the NVM block, the NVM Controller,
and the system clock will remain on until the write is finished. This is valid for all sleep modes, including
Power-Down Sleep mode.
The EEPROM Ready interrupt will wake-up the device only from Idle Sleep mode.
The page buffer is cleared when waking up from Sleep.
9.3.6
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
Table 9-4. NVMCTRL - Registers under Configuration Change Protection
Register
Key
NVMCTRL.CTRLA
SPM
Related Links
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ATtiny406
Nonvolatile Memory Controller (NVMCTRL)
Sequence for Execution of Self-Programming
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Nonvolatile Memory Controller (NVMCTRL)
9.4
Register Summary - NVMCTRL
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
STATUS
7:0
0x03
INTCTRL
7:0
EEREADY
0x04
INTFLAGS
7:0
EEREADY
0x05
Reserved
0x06
DATA
0x08
ADDR
9.5
CMD[2:0]
WRERROR
7:0
DATA[7:0]
15:8
DATA[15:8]
7:0
ADDR[7:0]
15:8
ADDR[15:8]
BOOTLOCK
APCWP
EEBUSY
FBUSY
Register Description
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Nonvolatile Memory Controller (NVMCTRL)
9.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
CTRLA
0x00
0x00
Configuration Change Protection
7
6
5
4
3
2
1
0
CMD[2:0]
Access
Reset
R/W
R/W
R/W
0
0
0
Bits 2:0 – CMD[2:0] Command
Write this bit field to issue a command. The Configuration Change Protection key for self-programming
(SPM) has to be written within four instructions before this write.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
WP
ER
ERWP
PBC
CHER
EEER
WFU
Description
No command
Write page buffer to memory (NVMCTRL.ADDR selects which memory)
Erase page (NVMCTRL.ADDR selects which memory)
Erase and write page (NVMCTRL.ADDR selects which memory)
Page buffer clear
Chip erase: erase Flash and EEPROM (unless EESAVE in FUSE.SYSCFG is '1')
EEPROM Erase
Write fuse (only accessible through UPDI)
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9.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
7
CTRLB
0x01
0x00
-
6
5
4
3
2
Access
Reset
1
0
BOOTLOCK
APCWP
R/W
R/W
0
0
Bit 1 – BOOTLOCK Boot Section Lock
Writing a '1' to this bit locks the boot section from read and instruction fetch.
If this bit is '1', a read from the boot section will return '0'. A fetch from the boot section will also return 0
as instruction.
This bit can 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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9.5.3
Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x02
0x00
-
6
5
4
3
2
1
0
WRERROR
EEBUSY
FBUSY
Access
R
R
R
Reset
0
0
0
Bit 2 – WRERROR Write Error
This bit will read '1' when a write error has happened. A write error could be writing to different sections
before doing a page write or writing to a protected area. This bit is valid for the last operation.
Bit 1 – EEBUSY EEPROM Busy
This bit will read '1' when the EEPROM is busy with a command.
Bit 0 – FBUSY Flash Busy
This bit will read '1' when the Flash is busy with a command.
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Nonvolatile Memory Controller (NVMCTRL)
9.5.4
Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x03
0x00
-
6
5
4
3
2
1
0
EEREADY
Access
R/W
Reset
0
Bit 0 – EEREADY EEPROM Ready Interrupt
Writing a '1' to this bit enables the interrupt, which indicates that the EEPROM is ready for new write/
erase operations.
This is a level interrupt that will be triggered only when the EEREADY flag in the INTFLAGS register is set
to zero. Thus, the interrupt should not be enabled before triggering an NVM command, as the EEREADY
flag will not be set before the NVM command issued. The interrupt should be disabled in the interrupt
handler.
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Nonvolatile Memory Controller (NVMCTRL)
9.5.5
Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x04
0x00
-
6
5
4
3
2
1
0
EEREADY
Access
R/W
Reset
0
Bit 0 – EEREADY EEREADY Interrupt Flag
Interrupt flag for the EEPROM interrupt. This bit is cleared by writing a '1' to it. When this interrupt is
enabled, it will immediately request an interrupt, and it will continue to request interrupts - even if no
EEPROM writes are initiated.
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Nonvolatile Memory Controller (NVMCTRL)
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. For more details on reading and writing 16-bit registers, refer
to Accessing 16-Bit Registers.
Bit
15
14
13
12
11
10
9
8
DATA[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
DATA[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:0 – DATA[15:0] Data Register
This register is used by the UPDI for fuse write operations.
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Nonvolatile Memory Controller (NVMCTRL)
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. For more details on reading and writing 16-bit registers, refer
to Accessing 16-Bit Registers.
Bit
15
14
13
12
11
10
9
8
ADDR[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
ADDR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:0 – ADDR[15:0] Address
The Address register contains the address to the last memory location that has been updated.
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Clock Controller (CLKCTRL)
10.
Clock Controller (CLKCTRL)
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:
– 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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Clock Controller (CLKCTRL)
10.2.1
Block Diagram - CLKCTRL
Figure 10-1. CLKCTRL Block Diagram
NVM
RAM
CPU
CLK_CPU
CLK_PER
CLKOUT
RTC
Other
Peripherals
WDT
INT
BOD
PRESCALER
CLK_RTC
CLK_WDT
CLK_BOD
Main Clock Prescaler
CLK_MAIN
RTC
CLKSEL
Main Clock Switch
DIV32
OSCULP32K
OSC20M
OSC20M
int. Oscillator
32 KHz ULP
Int. Oscillator
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.
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Clock Controller (CLKCTRL)
–
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.
10.2.2
Signal Description
Signal
Type
Description
CLKOUT
Digital output
CLK_PER output
Related Links
I/O Multiplexing and Considerations
10.3
Functional Description
10.3.1
Sleep Mode Operation
When a clock source is not used/requested it will turn off. It is possible to request 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 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 77
ATtiny406
Clock Controller (CLKCTRL)
Figure 10-2. Main Clock and Prescaler
OSC20M
32kHz Osc.
CLK_MAIN
Main Clock Prescaler
(Div 1, 2, 4, 8, 16, 32,
64, 6, 10, 24, 48)
External clock
CLK_PER
The Main Clock and Prescaler configuration registers (CLKCTRL.MCLKCTRLA,
CLKCTRL.MCLKCTRLB) are protected by the Configuration Change Protection Mechanism, employing a
timed write procedure for changing these registers.
Related Links
Configuration Change Protection (CCP)
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. Since the actual frequency of the OSC20M is determined by the Frequency Select
bits (FREQSEL) of the Oscillator Configuration fuse (FUSE.OSCCFG), these frequencies are possible
after Reset:
Table 10-1. Peripheral Clock Frequencies After Reset
CLK_MAIN
as Per FREQSEL in FUSE.OSCCFG
Resulting CLK_PER
16 MHz
2.66 MHz
20 MHz
3.3 MHz
See the OSC20M description for further details.
Related Links
16/20 MHz Oscillator (OSC20M)
10.3.4
Clock Sources
All internal clock sources are enabled automatically when they are requested by a peripheral.
The respective Oscillator Status bits in the Main Clock Status register (CLKCTRL.MCLKSTATUS) indicate
whether the clock source is running and stable.
Related Links
Configuration and User Fuses (FUSE)
Configuration Change Protection (CCP)
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.
Related Links
Electrical Characteristics
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). The center frequencies are:
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 78
ATtiny406
Clock Controller (CLKCTRL)
•
•
16 MHz
20 MHz
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 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.
The start-up time of this oscillator is analog start-up time plus four oscillator cycles. Refer to the Electrical
Characteristics section for the start-up time.
When changing the oscillator calibration value, the frequency may overshoot. If the oscillator is used as
the main clock (CLK_MAIN) it is recommended to change the main clock prescaler so that the main clock
frequency does not exceed ¼ of the maximum operation main clock frequency as described in the
General Operating Ratings section. The system clock prescaler can be changed back after the oscillator
calibration value has been updated.
Related Links
Electrical Characteristics
Configuration and User Fuses (FUSE)
Configuration Change Protection
General Operating Ratings
Main Clock After Reset
Oscillators and Clocks
OSC20M Stored Frequency Error Compensation
This oscillator can operate at multiple frequencies, selected by the value of the Frequency Select bits
(FREQSEL) in the Oscillator Configuration fuse (FUSE.OSCCFG) at Reset. As previously mentioned
appropriate calibration values are loaded to adjust to center frequency (OSC20M), and temperature drift
compensation (TEMPCAL20M), meeting the specifications defined in the internal oscillator
characteristics. For applications requiring wider operating range, the relative factory stored frequency
error after calibrations can be used. The 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
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 79
ATtiny406
Clock Controller (CLKCTRL)
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 LSBs the lower bits of the Q.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
*/
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
Related Links
Oscillators and Clocks
32 KHz Oscillator (OSCULP32K)
The 32 KHz oscillator is optimized for Ultra Low-Power (ULP) operation.
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.
Related Links
Electrical Characteristics
Brown-Out Detector (BOD)
Watchdog Timer (WDT)
Real-Time Counter (RTC)
10.3.4.2 External Clock Sources
This external clock source is available:
•
External Clock from pin. (EXTCLK).
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). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 80
ATtiny406
Clock Controller (CLKCTRL)
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
Table 10-2. CLKCTRL - Registers Under Configuration Change Protection
Register
Key
CLKCTRL.MCLKCTRLB
IOREG
CLKCTRL.MCLKLOCK
IOREG
CLKCTRL.MCLKCTRLA
IOREG
CLKCTRL.OSC20MCTRLA
IOREG
CLKCTRL.OSC20MCALIBA
IOREG
CLKCTRL.OSC20MCALIBB
IOREG
CLKCTRL.OSC32KCTRLA
IOREG
Related Links
Sequence for Write Operation to Configuration Change Protected I/O Registers
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 81
ATtiny406
Clock Controller (CLKCTRL)
10.4
Register Summary - CLKCTRL
Offset
Name
Bit Pos.
0x00
MCLKCTRLA
7:0
0x01
MCLKCTRLB
7:0
0x02
MCLKLOCK
7:0
0x03
MCLKSTATUS
7:0
CLKOUT
CLKSEL[1:0]
PDIV[3:0]
PEN
LOCKEN
EXTS
OSC32KS
OSC20MS
SOSC
0x04
...
Reserved
0x0F
0x10
OSC20MCTRLA
7:0
0x11
OSC20MCALIBA
7:0
0x12
OSC20MCALIBB
7:0
RUNSTDBY
CAL20M[5:0]
LOCK
TEMPCAL20M[3:0]
0x13
...
Reserved
0x17
0x18
10.5
OSC32KCTRLA
7:0
RUNSTDBY
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 82
ATtiny406
Clock Controller (CLKCTRL)
10.5.1
Main Clock Control A
Name:
Offset:
Reset:
Property:
Bit
7
MCLKCTRLA
0x00
0x00
Configuration Change Protection
6
5
4
3
2
1
CLKOUT
Access
Reset
0
CLKSEL[1:0]
R/W
R
R
R
R
R
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 – CLKOUT System Clock Out
When this bit is written to '1', the system clock is output to CLKOUT pin.
When the device is in a Sleep mode, there is no clock output unless a peripheral is using the system
clock.
Bits 1:0 – CLKSEL[1:0] Clock Select
This bit field selects the source for the Main Clock (CLK_MAIN).
Value
0x0
0x1
0x2
0x3
Name
OSC20M
OSCULP32K
Reserved
EXTCLK
© 2018 Microchip Technology Inc.
Description
16/20 MHz internal oscillator
32 KHz internal ultra low-power oscillator
Reserved
External clock
Datasheet Preliminary
40001976A-page 83
ATtiny406
Clock Controller (CLKCTRL)
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
0
PDIV[3:0]
PEN
Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
1
0
0
0
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.
User software must ensure a correct configuration of input frequency (CLK_MAIN) and prescaler settings,
such that the resulting frequency of CLK_PER never exceeds the allowed maximum (see Electrical
Characteristics).
Value
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x8
0x9
0xA
0xB
0xC
other
Description
Division
2
4
8
16
32
64
6
10
12
24
48
Reserved
Bit 0 – PEN Prescaler Enable
This bit must be written '1' to enable the prescaler. When enabled, the division ratio is selected by the
PDIV bit field.
When this bit is written to '0', the main clock will pass through undivided (CLK_PER=CLK_MAIN),
regardless of the value of PDIV.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 84
ATtiny406
Clock Controller (CLKCTRL)
10.5.3
Main Clock Lock
Name:
Offset:
Reset:
Property:
Bit
7
MCLKLOCK
0x02
0x00
Configuration Change Protection
6
5
4
3
2
1
0
LOCKEN
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
x
Bit 0 – LOCKEN Lock Enable
Writing this bit to '1' will lock the CLKCTRL.MCLKCTRLA and CLKCTRL.MCLKCTRLB registers, and, if
applicable, the calibration settings for the current main clock source from further software updates. Once
locked, the CLKCTRL.MCLKLOCK registers cannot be accessed until the next hardware Reset.
This provides protection for the CLKCTRL.MCLKCTRLA and CLKCTRL.MCLKCTRLB registers and
calibration settings for the main clock source from unintentional modification by software.
Related Links
Configuration and User Fuses (FUSE)
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 85
ATtiny406
Clock Controller (CLKCTRL)
10.5.4
Main Clock Status
Name:
Offset:
Reset:
Property:
Bit
7
MCLKSTATUS
0x03
0x00
-
5
4
EXTS
6
OSC32KS
OSC20MS
3
2
1
0
Access
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
SOSC
Bit 7 – EXTS External Clock Status
Value
0
1
Description
EXTCLK has not started
EXTCLK has started
Bit 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
0
1
Description
OSCULP32K is not stable
OSCULP32K is stable
Bit 4 – OSC20MS OSC20M Status
The Status bit will only be available if the source is requested as the main clock or by another module. If
the oscillator RUNSTDBY bit is set but the oscillator is unused/not requested, this bit will be 0.
Value
0
1
Description
OSC20M is not stable
OSC20M is stable
Bit 0 – SOSC Main Clock Oscillator Changing
Value
0
1
Description
The clock source for CLK_MAIN is not undergoing a switch
The clock source for CLK_MAIN is undergoing a switch, and will change as soon as the new
source is stable.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 86
ATtiny406
Clock Controller (CLKCTRL)
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
2
1
0
RUNSTDBY
Access
R
R
R
R
R
R
R/W
R
Reset
0
0
0
0
0
0
0
0
Bit 1 – RUNSTDBY Run Standby
This bit 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 87
ATtiny406
Clock Controller (CLKCTRL)
10.5.6
16/20 MHz Oscillator Calibration A
Name:
Offset:
Reset:
Property:
Bit
7
OSC20MCALIBA
0x11
Based on FREQSEL in FUSE.OSCCFG
Configuration Change Protection
6
5
4
3
2
1
0
CAL20M[5:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
x
x
x
x
x
x
Bits 5:0 – CAL20M[5:0] Calibration
These bits change the frequency around the current center frequency of the OSC20M for fine-tuning.
At Reset, the factory calibrated values are loaded based on the FREQSEL bits in FUSE.OSCCFG.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 88
ATtiny406
Clock Controller (CLKCTRL)
10.5.7
16/20 MHz Oscillator Calibration B
Name:
Offset:
Reset:
Property:
Bit
7
OSC20MCALIBB
0x12
Based on FUSE.OSCCFG
Configuration Change Protection
6
5
4
3
LOCK
2
1
0
TEMPCAL20M[3:0]
Access
R
R/W
R/W
R/W
R/W
Reset
x
x
x
x
x
Bit 7 – LOCK Oscillator Calibration Locked by Fuse
When this bit is set, the calibration settings in CLKCTRL.OSC20MCALIBA and
CLKCTRL.OSC20MCALIBB cannot be changed.
The Reset, the 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 89
ATtiny406
Clock Controller (CLKCTRL)
10.5.8
32 KHz Oscillator Control A
Name:
Offset:
Reset:
Property:
Bit
7
OSC32KCTRLA
0x18
0x00
Configuration Change Protection
6
5
4
3
2
1
0
RUNSTDBY
Access
R/W
Reset
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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 90
ATtiny406
Sleep Controller (SLPCTRL)
11.
Sleep Controller (SLPCTRL)
11.1
Features
•
•
11.2
Three sleep modes:
– Idle
– Standby
– Power-Down
Configurable Standby Sleep mode where peripherals can be configured as ON or OFF.
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.
When the device enters a sleep mode, program execution is stopped, and depending on the entered
sleep mode, different peripherals and clock domains are turned off.
To enter a sleep mode, the SLPCTRL must be enabled and the desired sleep mode must be stated. The
software decides when to enter that sleep mode by using a dedicated SLEEP instruction.
Interrupts are used to wake-up the device from sleep. The available interrupt wake-up sources depend on
the configured sleep mode. When an interrupt occurs, the device will wake-up and execute the interrupt
service routine before continuing normal program execution from the first instruction after the SLEEP
instruction. Any Reset will 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-up, 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
11.2.2
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 91
ATtiny406
Sleep Controller (SLPCTRL)
Table 11-1. SLPCTRL System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
No
-
Events
No
-
Debug
Yes
UPDI
11.2.2.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
Clock Controller (CLKCTRL)
11.2.2.2 I/O Lines and Connections
Not applicable.
11.2.2.3 Interrupts
Not applicable.
11.2.2.4 Events
Not applicable.
11.2.2.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. The SLPCTRL is only affected
by a break in debug operation: If the SLPCTRL is in a sleep mode when a break occurs, the device will
wake-up and the SLPCTRL will go to Active mode, even if there are no pending interrupt requests.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
11.3
Functional Description
11.3.1
Initialization
To put the device into a sleep mode, follow these steps:
•
Configure and enable the interrupts that should wake-up the device from sleep. Also enable global
interrupts.
WARNING
•
If there are no interrupts enabled when going to sleep, the device cannot wake-up again.
Only a Reset will allow the device to continue operation.
Select the sleep mode to be entered and enable the Sleep Controller by writing to the Sleep Mode
bits (SMODE) and the Enable bit (SEN) in the Control A register (SLPCTRL.CTRLA). A SLEEP
instruction must be run to make the device actually go to sleep.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 92
ATtiny406
Sleep Controller (SLPCTRL)
11.3.2
Operation
11.3.2.1 Sleep Modes
In addition to Active mode, there are three different sleep modes, with decreasing power consumption
and functionality.
Idle
The CPU stops executing code, no peripherals are disabled.
All interrupt sources can wake-up the device.
Standby
The user can configure peripherals to be enabled or not, using the respective RUNSTBY bit.
This means that the power consumption is highly dependent on what functionality is enabled,
and thus may vary between the Idle and Power-Down levels.
SleepWalking is available for the ADC module.
The wake-up sources are pin interrupts, TWI address match, UART Start-of-Frame interrupt
(if USART is enabled to run in Standby), RTC interrupt (if RTC enabled to run in Standby),
and TCB interrupt.
Only the WDT and the PIT (a component of the RTC) are active.
The only wake-up sources are the pin change interrupt and TWI address match.
PowerDown
Table 11-2. Sleep Mode Activity Overview
Group
Peripheral
Active in Sleep Mode
Clock
Active Clock
Domain
Oscillators
Wake-Up
Sources
Idle
Standby
Power-Down
CPU
CLK_CPU
Peripherals
CLK_PER
X
RTC
CLK_RTC
X
X*
ADC
CLK_PER
X
X*
PIT (RTC)
CLK_RTC
X
X
X
WDT
CLK_WDT
X
X
X
Main Clock Source
X
X*
RTC Clock Source
X
X*
WDT Oscillator
X
X
X
INTn and Pin Change
X
X
X
TWI Address Match
X
X
X
Periodic Interrupt Timer
X
X
X
UART Start-of-Frame
X
X*
ADC Window
X
X*
RTC Interrupt
X
X*
All other Interrupts
X
Note:
•
X means active. X* indicates that the RUNSTBY bit of the corresponding peripheral must be set to
enter the active state.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Sleep Controller (SLPCTRL)
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 11-3. Sleep Modes and Start-Up Time
Sleep Mode
Start-Up Time
IDLE
6 CLK
Standby
6 CLK + OSC start-up
Power-Down
6 CLK + OSC start-up
The start-up time for the different clock sources is described in the Clock Controller (CLKCTRL) section.
In addition to the normal wake-up time it is possible to make the device wait until the BOD is ready before
executing code. This is done by writing 0x3 to the BOD Operation mode in Active and Idle bits (ACTIVE)
in the BOD Configuration fuse (FUSE.BODCFG). If the BOD is ready before the normal wake-up time, the
net wake-up time will be the same. If the BOD takes longer than the normal wake-up time, the wake-up
time will be extended until the BOD is ready. This ensures correct supply voltage whenever code is
executed.
11.3.3
Configuration Change Protection
Not applicable.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 94
ATtiny406
Sleep Controller (SLPCTRL)
11.4
Register Summary - SLPCTRL
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
11.5
SMODE[1:0]
SEN
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 95
ATtiny406
Sleep Controller (SLPCTRL)
11.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
-
6
5
4
3
2
1
SMODE[1:0]
0
SEN
Access
R
R
R
R
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 2:1 – SMODE[1:0] Sleep Mode
Writing these bits selects the sleep mode entered when the Sleep Enable bit (SEN) is written to '1' and
the SLEEP instruction is executed.
Value
0x0
0x1
0x2
other
Name
IDLE
STANDBY
PDOWN
-
Description
Idle Sleep mode enabled
Standby Sleep mode enabled
Power-Down Sleep mode enabled
Reserved
Bit 0 – SEN Sleep Enable
This bit must be written to '1' before the SLEEP instruction is executed to make the MCU enter the
selected sleep mode.
© 2018 Microchip Technology Inc.
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ATtiny406
Reset Controller (RSTCTRL)
12.
Reset Controller (RSTCTRL)
12.1
Features
•
•
•
Reset the device and set it to an initial state.
Reset Flag register for identifying the Reset source in software.
Multiple Reset sources:
–
–
12.2
Power supply Reset sources: Brown-out Detect (BOD), Power-on Reset (POR)
User Reset sources: External Reset pin (RESET), Watchdog Reset (WDT), Software Reset
(SW), and UPDI Reset.
Overview
The Reset Controller (RSTCTRL) manages the Reset of the device. It issues a device Reset, sets the
device to its initial state, and allows the Reset source to be identified by software.
12.2.1
Block Diagram
Figure 12-1. Reset System Overview
RESET SOURCES
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
© 2018 Microchip Technology Inc.
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ATtiny406
Reset Controller (RSTCTRL)
12.3
Functional Description
12.3.1
Initialization
The Reset Controller (RSTCTRL) is always enabled, but some of the Reset sources must be enabled
(either by fuses or by software) before they can request a Reset.
After any Reset, the Reset source that caused the Reset is found in the Reset Flag register
(RSTCTRL.RSTFR).
After a Power-on Reset, only the POR flag will be set.
The flags are kept until they are cleared by writing a '1' to them.
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).
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.
All volatile logic is reset on POR. All fuses are reloaded after the Reset is released.
Brown-Out Detector (BOD) Reset Source
The on-chip Brown-out Detection circuit will monitor the VDD level during operation by comparing it to a
fixed trigger level. The trigger level for the BOD can be selected by fuses. If BOD is unused in the
application it is forced to a minimum level in order to ensure a safe operation during internal Reset and
chip erase.
All logic is reset on BOD Reset, except the BOD configuration. All fuses are reloaded after the Reset is
released.
Related Links
Brown-Out Detector (BOD)
Software Reset
The software Reset makes it possible to issue a system Reset from software. The Reset is generated by
writing a '1' to the Software Reset Enable bit (SWRE) in the Software Reset register (RSTCTRL.SWRR).
The Reset will take place immediately after the bit is written and the device will be kept in reset until the
Reset sequence is completed. All logic is reset on software Reset, except UPDI and BOD configuration.
All fuses are reloaded after the Reset is released.
External Reset
The external Reset is enabled by fuse (see fuse map).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Reset Controller (RSTCTRL)
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. All logic is reset on external reset, except UPDI and BOD
configuration. All fuses are reloaded after the Reset is released.
Related Links
Configuration and User Fuses (FUSE)
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.
All logic is reset on WDT Reset, except UPDI and BOD configuration. All fuses are reloaded after the
Reset is released.
Related Links
Watchdog Timer (WDT)
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. All logic
is reset on UPDI Reset, except the UPDI itself and BOD configuration. All fuses are reloaded after the
Reset is released. See UPDI chapter on how to generate a UPDI Reset request.
Related Links
Unified Program and Debug Interface (UPDI)
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 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 CRC source is set up to run (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). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Reset Controller (RSTCTRL)
Table 12-1. RSTCTRL - Registers Under Configuration Change Protection
Register
Key
RSTCTRL.SWRR
IOREG
Related Links
Sequence for Write Operation to Configuration Change Protected I/O Registers
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 100
ATtiny406
Reset Controller (RSTCTRL)
12.4
Register Summary - RSTCTRL
Offset
Name
Bit Pos.
0x00
RSTFR
7:0
0x01
SWRR
7:0
12.5
UPDIRF
SWRF
WDRF
EXTRF
BORF
PORF
SWRE
Register Description
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Datasheet Preliminary
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ATtiny406
Reset Controller (RSTCTRL)
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
R
R
Reset
0
0
5
4
3
2
1
0
UPDIRF
SWRF
WDRF
EXTRF
BORF
PORF
R/W
R/W
R/W
R/W
R/W
R/W
x
x
x
x
x
x
Bit 5 – UPDIRF UPDI Reset Flag
This bit is set if a UPDI Reset occurs.
Bit 4 – SWRF Software Reset Flag
This bit is set if a Software Reset occurs.
Bit 3 – WDRF Watchdog Reset Flag
This bit is set if a Watchdog Reset occurs.
Bit 2 – EXTRF External Reset Flag
This bit is set if an External Reset occurs.
Bit 1 – BORF Brown-Out Reset Flag
This bit is set if a Brown-out 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 other flags are cleared. No other flags can be set before a
full system boot is run after the POR.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Reset Controller (RSTCTRL)
12.5.2
Software Reset Register
Name:
Offset:
Reset:
Property:
Bit
7
SWRR
0x01
0x00
Configuration Change Protection
6
5
4
3
2
1
0
SWRE
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
Bit 0 – SWRE Software Reset Enable
When this bit is written to '1', a software Reset will occur.
This bit will always read as '0'.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
CPU Interrupt Controller (CPUINT)
13.
CPU Interrupt Controller (CPUINT)
13.1
Features
•
•
•
•
•
•
•
•
•
13.2
Short and Predictable Interrupt Response Time
Separate Interrupt Configuration and Vector Address for Each Interrupt
Interrupt Prioritizing by Level and Vector Address
Two Interrupt Priority Levels: 0 (normal) and 1 (high)
Higher Priority for One Interrupt
Optional Round Robin Priority Scheme for Priority Level 0 Interrupts
Non-Maskable Interrupts (NMI) for Critical Functions
Interrupt Vectors Optionally Placed in the Application Section or the Boot Loader Section
Selectable Compact Vector Table
Overview
An interrupt request signals a change of state inside a peripheral, and can be used to alter program
execution. Peripherals can have one or more interrupts, and all are individually enabled and configured.
When an interrupt is enabled and configured, it will generate an interrupt request when the interrupt
condition occurs.
The CPU Interrupt Controller (CPUINT) handles and prioritizes interrupt requests. When an interrupt is
enabled and the interrupt condition occurs, the CPUINT will receive the interrupt request. Based on the
interrupt's priority level and the priority level of any ongoing interrupts, the interrupt request is either
acknowledged or kept pending until it has priority. When an interrupt request is acknowledged by the
CPUINT, the Program Counter is set to point to the interrupt vector. The interrupt vector is normally a
jump to the interrupt handler (i.e., the software routine that handles the interrupt). After returning from the
interrupt handler, program execution continues from where it was before the interrupt occurred. One
instruction is always executed before any pending interrupt is served.
The CPUINT Status register (CPUINT.STATUS) contains state information that ensures that the CPUINT
returns to the correct interrupt level when the RETI (interrupt return) instruction is executed at the end of
an interrupt handler. Returning from an interrupt will return the CPUINT to the state it had before entering
the interrupt. CPUINT.STATUS is not saved automatically upon an interrupt request.
By default, all peripherals are priority level 0. It is possible to set one single interrupt vector to the higher
priority level 1. Interrupts are prioritized according to their priority level and their interrupt vector address.
Priority level 1 interrupts will interrupt level 0 interrupt handlers. Among priority level 0 interrupts, the
priority is determined from the interrupt vector address, where the lowest interrupt vector address has the
highest interrupt priority.
Optionally, a round robin scheduling scheme can be enabled for priority level 0 interrupts. This ensures
that all interrupts are serviced within a certain amount of time.
Interrupt generation must be globally enabled by writing a '1' to the Global Interrupt Enable bit (I) in the
CPU Status register (CPU.SREG). This bit is not cleared when an interrupt is acknowledged.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 104
ATtiny406
CPU Interrupt Controller (CPUINT)
13.2.1
Block Diagram
Figure 13-1. CPUINT Block Diagram
Interrupt Controller
Priority
Decoder
Peripheral 1
INT REQ
CPU "RETI"
CPU INT ACK
CPU
INT LEVEL
Peripheral
n
INT REQ
CPU INT REQ
INT REQ
INT ACK
STATUS
LVL0PRI
LVL1VEC
Global
Interrupt
Enable
Wake-up
CPU.SREG
Sleep
Controller
13.2.2
Signal Description
Not applicable.
13.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 13-1. CPUINT System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
No
-
Events
No
-
Debug
Yes
UPDI
Related Links
Debug Operation
Clocks
13.2.3.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
Clock Controller (CLKCTRL)
13.2.3.2 I/O Lines and Connections
Not applicable.
13.2.3.3 Interrupts
Not applicable.
13.2.3.4 Events
Not applicable.
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Datasheet Preliminary
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ATtiny406
CPU Interrupt Controller (CPUINT)
13.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in Debugging
mode will halt normal operation of the peripheral.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
Unified Program and Debug Interface (UPDI)
13.3
Functional Description
13.3.1
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 table below shows Reset addresses and Interrupt vector placement, dependent on the value of
Interrupt Vector Select bit (IVSEL) in the Control A register (CPUINT.CTRLA).
If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular program
code can be placed at these locations.
Table 13-2. Reset and Interrupt Vector Placement
IVSEL
Reset Address
Interrupt Vectors Start Address
0
0x0000
Application start address +
Interrupt vector offset address
1
0x0000
Interrupt vector offset address
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Datasheet Preliminary
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ATtiny406
CPU Interrupt Controller (CPUINT)
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
the figure below, 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 the figure below,
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.
A return from an interrupt handling routine takes four to five clock cycles, depending on the size of the
Program Counter. During these clock cycles, the Program Counter is popped from the stack and the
Stack Pointer is incremented. See the figure above, third diagram.
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Datasheet Preliminary
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ATtiny406
CPU Interrupt Controller (CPUINT)
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 8kB of Flash or less use RJMP instead of JMP, which takes only two clock cycles.
13.3.2.4 Interrupt Level
The interrupt level is default on level 0 (normal) for all interrupt sources. It is possible to select one
interrupt source to level 1 (high) by writing interrupt address to CPUINT.LVL1VEC register. This source
will have higher priority than normal level interrupts.
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ATtiny406
CPU Interrupt Controller (CPUINT)
An interrupt request from a level 1 source will interrupt any ongoing interrupt handler from a level 0
interrupt. When returning from the level 1 interrupt handler, the execution of the level 0 interrupt handler
will continue.
13.3.2.5 Interrupt Priority
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.
Related Links
Interrupt Vector Mapping
Static Priority
Interrupt Vectors (IVEC) are located at fixed addresses. For static priority, the interrupt vector address
decides the priority within normal interrupt level, where the lowest interrupt vector address has the
highest priority. Refer to the Interrupt Vector Mapping of the device for available interrupt lines and their
base address offset.
Figure 13-3. Static Priority
Lowest Address
IVEC 0
Highest Priority
:
:
:
IVEC x
IVEC x+1
:
:
:
Highest Address
IVEC n
Lowest Priority
Related Links
Interrupt Vector Mapping
Round Robin Scheduling
To avoid "starvation" for priority level 0 (LVL0) interrupt requests with static priority (i.e. some interrupts
might never be served), the CPUINT offers round robin scheduling for LVL0 interrupts.
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).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
CPU Interrupt Controller (CPUINT)
When round robin scheduling is enabled, the interrupt vector address for the last acknowledged LVL0
interrupt will have the lowest priority the next time one or more LVL0 interrupts are requested, as
illustrated in the figure below.
Figure 13-4. Round Robin Scheduling
IVEC x last acknowledge
interrupt
IVEC x+1 last acknowledge
interrupt
IVEC 0
IVEC 0
:
:
:
:
:
:
IVEC x
Lowest Priority
IVEC x
IVEC x+1
Highest Priority
IVEC x+1
Lowest Priority
IVEC x+2
Highest Priority
:
:
:
IVEC n
:
:
:
IVEC n
Compact Vector Table
The Compact Vector Table (CVT) is a feature to allow writing of compact code.
When CVT is enabled by writing a '1' to the CVT bit in the Control A register (CPUINT.CTRLA), the vector
table contains these three interrupt vectors:
1. The non-maskable interrupts (NMI) at vector address 1.
2. The priority level 1 (LVL1) interrupt at vector address 2.
3. All priority level 0 (LVL0) interrupts share vector address 3.
This feature is most suitable for applications using a small number of interrupt generators.
13.3.3
Events
Not applicable.
13.3.4
Sleep Mode Operation
Not applicable.
13.3.5
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
CPU Interrupt Controller (CPUINT)
Table 13-3. INTCTRL - Registers under Configuration Change Protection
Register
Key
IVSEL in CPUINT.CTRLA
IOREG
CVT in CPUINT.CTRLA
IOREG
Related Links
Sequence for Write Operation to Configuration Change Protected I/O Registers
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 111
ATtiny406
CPU Interrupt Controller (CPUINT)
13.4
Register Summary - CPUINT
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
IVSEL
CVT
LVL0RR
0x01
STATUS
7:0
0x02
LVL0PRI
7:0
LVL0PRI[7:0]
0x03
LVL1VEC
7:0
LVL1VEC[7:0]
13.5
NMIEX
LVL1EX
LVL0EX
Register Description
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ATtiny406
CPU Interrupt Controller (CPUINT)
13.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
Access
Reset
CTRLA
0x00
0x00
Configuration Change Protection
6
5
IVSEL
CVT
4
3
2
1
LVL0RR
0
R/W
R/W
R/W
0
0
0
Bit 6 – IVSEL Interrupt Vector Select
If 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
0
1
Description
Interrupt vectors are placed at the start of the application section of the Flash
Interrupt vectors are placed at the start of the boot section of the Flash
Bit 5 – CVT Compact Vector Table
This bit is protected by the Configuration Change Protection mechanism.
Value
0
1
Description
Compact Vector Table function is disabled
Compact Vector Table function is enabled
Bit 0 – LVL0RR Round Robin Priority Enable
This bit is not protected by the Configuration Change Protection mechanism.
Value
0
1
Description
Priority is fixed for priority level 0 interrupt requests: The lowest interrupt vector address has
highest priority.
Round Robin priority scheme is enabled for priority level 0 interrupt requests
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ATtiny406
CPU Interrupt Controller (CPUINT)
13.5.2
Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x01
0x00
-
1
0
NMIEX
6
5
4
3
2
LVL1EX
LVL0EX
Access
R
R
R
Reset
0
0
0
Bit 7 – NMIEX Non-Maskable Interrupt Executing
This flag is set if a non-maskable interrupt is executing. The flag is cleared when returning (RETI) from
the interrupt handler.
Bit 1 – LVL1EX Level 1 Interrupt Executing
This flag is set when a priority level 1 interrupt is executing, or when the interrupt handler has been
interrupted by an NMI. The flag is cleared when returning (RETI) from the interrupt handler.
Bit 0 – LVL0EX Level 0 Interrupt Executing
This flag is set when a priority level 0 interrupt is executing, or when the interrupt handler has been
interrupted by a priority level 1 interrupt or an NMI. The flag is cleared when returning (RETI) from the
interrupt handler.
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ATtiny406
CPU Interrupt Controller (CPUINT)
13.5.3
Interrupt Priority Level 0
Name:
Offset:
Reset:
Property:
Bit
7
LVL0PRI
0x02
0x00
-
6
5
4
3
2
1
0
LVL0PRI[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – LVL0PRI[7:0] Interrupt Priority Level 0
When Round Robin is enabled (LVL0RR bit in CPUINT.CTRLA is '1'), this bit field stores the vector of the
last acknowledged priority level 0 (LVL0) interrupt. The stored vector will have the lowest priority next time
one or more LVL0 interrupts are pending.
If Round Robin is disabled (LVL0RR in CPUINT.CTRLA is '0'), the vector address-based priority scheme
(lowest address has the highest priority) is governing the priorities of LVL0 interrupt requests.
If a system Reset is asserted, the lowest interrupt vector address will have the highest priority within the
LVL0.
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ATtiny406
CPU Interrupt Controller (CPUINT)
13.5.4
Interrupt Vector with Priority Level 1
Name:
Offset:
Reset:
Property:
Bit
7
LVL1VEC
0x03
0x00
-
6
5
4
3
2
1
0
LVL1VEC[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – LVL1VEC[7:0] Interrupt Vector with Priority Level 1
This bit field contains the address of the single vector with increased priority level 1 (LVL1).
If this bit field has the value 0x00, no vector has LVL1. Consequently, the LVL1 interrupt is disabled.
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ATtiny406
Event System (EVSYS)
14.
Event System (EVSYS)
14.1
Features
•
•
•
•
•
•
•
•
14.2
System for Direct Peripheral-to-Peripheral Signaling
Peripherals can Directly Produce, Use, and React to Peripheral Events
Short Response Time
Up to Three Parallel Event Channels Available; Two Asynchronous and One Synchronous
Channels can be Configured to Have One Triggering Peripheral Action and Multiple Peripheral
Users
Peripherals can Directly Trigger and React to Events from Other Peripherals
Events can be Sent and/or Received by Most Peripherals, and by Software
Works in Active mode and Standby Sleep mode
Overview
The Event System (EVSYS) enables direct peripheral-to-peripheral signaling. It allows a change in one
peripheral (the event generator) to trigger actions in other peripherals (the event users) through event
channels, without using the CPU. It is designed to provide short and predictable response times between
peripherals, allowing for autonomous peripheral control and interaction, and also for the synchronized
timing of actions in several peripheral modules. It is thus a powerful tool for reducing the complexity, size,
and the execution time of the software.
A change of the event generator's state is referred to as an event and usually corresponds to one of the
peripheral's interrupt conditions. Events can be directly forwarded to other peripherals using the
dedicated event routing network. The routing of each channel is configured in software, including event
generation and use.
Only one trigger from an event generator peripheral can be routed on each channel, but multiple
channels can use the same generator source. Multiple peripherals can use events from the same
channel.
A channel path can be either asynchronous or synchronous to the main clock. The mode must be
selected based on the requirements of the application.
The Event System can directly connect analog and digital converters, analog comparators, I/O port pins,
the real-time counter, timer/counters, and the configurable custom logic peripheral. Events can also be
generated from software and the peripheral clock.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 117
ATtiny406
Event System (EVSYS)
14.2.1
Block Diagram
Figure 14-1. Block Diagram
Sync user x
Sync event channel ”k”
Sync event channel 0
Sync source 0
Sync source 1
Sync user 0
Sync source n
SYNCCH
SYNCSTROBE
..
.
..
.
..
.
Async source m
ASYNCCH
SYNCUSER
Async user y
Async user 0
Async event channel ”l”
Async event channel 0
Async source 0
Async source 1
To sync user
..
.
..
.
ASYNCSTROBE
To async user
ASYNCUSER
Figure 14-2. Example of Event Source, Generator, User, and Action
Event Generator
Event User
Timer/Counter
ADC
Compare Match
Over-/Underflow
|
Event
Routing
Network
Error
Channel Sweep
Single
Conversion
Event Action Selection
Event Source
Event Action
Note:
1. For an overview of peripherals supporting events, refer the block diagram of the device.
2. For a list of event generators, refer to the Channel n Generator Selection registers
(EVSYS.SYNCCH and EVSYS.ASYNCCH).
3. For a list of event users, refer to the User Channel n Input Selection registers (EVSYS.SYNCUSER
and EVSYS.ASYNCUSER).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 118
ATtiny406
Event System (EVSYS)
14.2.2
Signal Description
Internal Event Signaling
The event signaling can happen either synchronously or asynchronously to the main clock (CLK_MAIN).
Depending on the underlying event, the event signal can be a pulse with a duration of one clock cycle, or
a level signal (similar to a status flag).
Event Output to Pin
Signal
Type
Description
EVOUT[2:0]
Digital Output
Event Output
Related Links
I/O Lines
Block Diagram - CLKCTRL
14.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 14-1. EVSYS System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORTMUX
Interrupts
No
-
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
14.2.3.1 Clocks
The EVSYS uses the peripheral clock for I/O registers and software events. When set up correctly, the
routing network can also be used in sleep modes without any clock. Software events will not work in
sleep modes where the peripheral clock is halted.
Related Links
Clock Controller (CLKCTRL)
14.2.3.2 I/O Lines
The EVSYS can output three event channels asynchronously on pins. The output signals are called
EVOUT[2:0].
1. Configure which event channel (one of SYNCCH[1:0] or ASYNCCH[3:0]) is output on which
EVOUTn bit by writing to EVSYS.ASYNCUSER10, EVSYS.ASYNCUSER9, or
EVSYS.ASYNCUSER8, respectively.
2. Optional: configure the pin properties using the port peripheral.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 119
ATtiny406
Event System (EVSYS)
3.
Enable the pin output by writing '1' to the respective EVOUTn bit in the Control A register of the
PORTMUX peripheral (PORTMUX.CTRLA).
Related Links
Port Multiplexer (PORTMUX)
I/O Pin Configuration (PORT)
14.3
Functional Description
14.3.1
Initialization
Before enabling events within the device, the event users multiplexer and event channels must be
configured.
Related Links
Event User Multiplexer Setup
Event System Channel
14.3.2
Operation
14.3.2.1 Event User Multiplexer Setup
The event user multiplexer selects the channel for an event user. Each event user has one dedicated
event user multiplexer. Each multiplexer is connected to the supported event channel outputs and can be
configured to select one of these channels.
Event users which support asynchronous events also support synchronous events. There are also event
users that support only synchronous events.
The event user multiplexers are configured by writing to the corresponding registers:
•
Event users supporting both synchronous and asynchronous events are configured by writing to the
respective asynchronous User Channel Input Selection n register (EVSYS.ASYNCUSERn).
•
The users of synchronous-only events are configured by writing to the respective Synchronous
User Channel Input Selection n register (EVSYS.SYNCUSERn).
The default setup of all user multiplexers is OFF.
14.3.2.2 Event System Channel
An event channel can be connected to one of the event generators. Event channels support either
asynchronous generators or synchronous generators.
The source for each asynchronous event channel is configured by writing to the respective Asynchronous
Channel n Input Selection register (EVSYS.ASYNCCHn).
The source for each synchronous event channel is configured by writing to the respective Synchronous
Channel n Input Selection register (EVSYS.SYNCCHn).
14.3.2.3 Event Generators
Each event channel can receive the events from several event generators. For details on event
generation, refer to the documentation of the corresponding peripheral.
For each event channel, there are several possible event generators, only one of which can be selected
at a time. The event generator trigger is selected for each channel by writing to the respective channel
registers (EVSYS.ASYNCCHn, EVSYS.SYNCCHn). By default, the channels are not connected to any
event generator.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 120
ATtiny406
Event System (EVSYS)
14.3.2.4 Software Event
In a software event, the CPU will “strobe” an event channel by inverting the current value for one system
clock cycle.
A software event is triggered on a channel by writing a '1' to the respective Strobe bit in the appropriate
Channel Strobe register:
•
Software events on asynchronous channel l are initiated by writing a '1' to the ASYNCSTROBE[l]
bit in the Asynchronous Channel Strobe register (EVSYS.ASYNCSTROBE).
•
Software events on synchronous channel k are initiated by writing a '1' to the SYNCSTROBE[k] bit
in the Synchronous Channel Strobe register (EVSYS.SYNCSTROBE).
Software events are no different to those produced by event generator peripherals with respect to event
users: when the bit is written to '1', an event will be generated on the respective channel, and received
and processed by the event user.
14.3.3
Interrupts
Not applicable.
14.3.4
Sleep Mode Operation
When configured, the Event System will work in all sleep modes. One exception is software events that
require a system clock.
14.3.5
Debug Operation
This peripheral is unaffected by entering Debug mode.
Related Links
Unified Program and Debug Interface (UPDI)
14.3.6
Synchronization
Asynchronous events are synchronized and handled by the compatible event users. Event user
peripherals not compatible with asynchronous events can only be configured to listen to synchronous
event channels.
14.3.7
Configuration Change Protection
Not applicable.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 121
ATtiny406
Event System (EVSYS)
14.4
Register Summary - EVSYS
Offset
Name
Bit Pos.
0x00
ASYNCSTROBE
7:0
ASYNCSTROBE[7:0]
0x01
SYNCSTROBE
7:0
SYNCSTROBE[7:0]
0x02
ASYNCCH0
7:0
ASYNCCH[7:0]
0x03
ASYNCCH1
7:0
ASYNCCH[7:0]
7:0
SYNCCH[7:0]
0x04
...
Reserved
0x09
0x0A
SYNCCH0
0x0B
...
Reserved
0x11
0x12
ASYNCUSER0
7:0
ASYNCUSER[7:0]
0x13
ASYNCUSER1
7:0
ASYNCUSER[7:0]
0x14
ASYNCUSER2
7:0
ASYNCUSER[7:0]
0x15
ASYNCUSER3
7:0
ASYNCUSER[7:0]
0x16
ASYNCUSER4
7:0
ASYNCUSER[7:0]
0x17
ASYNCUSER5
7:0
ASYNCUSER[7:0]
0x18
ASYNCUSER6
7:0
ASYNCUSER[7:0]
0x19
ASYNCUSER7
7:0
ASYNCUSER[7:0]
0x1A
ASYNCUSER8
7:0
ASYNCUSER[7:0]
0x1B
ASYNCUSER9
7:0
ASYNCUSER[7:0]
0x1C
ASYNCUSER10
7:0
ASYNCUSER[7:0]
0x1D
...
Reserved
0x21
0x22
SYNCUSER0
7:0
SYNCUSER[7:0]
0x23
SYNCUSER1
7:0
SYNCUSER[7:0]
14.5
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 122
ATtiny406
Event System (EVSYS)
14.5.1
Asynchronous Channel Strobe
Name:
Offset:
Reset:
Property:
Bit
7
ASYNCSTROBE
0x00
0x00
-
6
5
4
3
2
1
0
ASYNCSTROBE[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – ASYNCSTROBE[7:0] Asynchronous Channel Strobe
If the Strobe register location is written, each event channel will be inverted for one system clock cycle
(i.e., a single event is generated).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 123
ATtiny406
Event System (EVSYS)
14.5.2
Synchronous Channel Strobe
Name:
Offset:
Reset:
Property:
Bit
7
SYNCSTROBE
0x01
0x00
-
6
5
4
3
2
1
0
SYNCSTROBE[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – SYNCSTROBE[7:0] Synchronous Channel Strobe
If the Strobe register location is written, each event channel will be inverted for one system clock cycle
(i.e., a single event is generated).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 124
ATtiny406
Event System (EVSYS)
14.5.3
Asynchronous Channel n Generator Selection
Name:
Offset:
Reset:
Property:
Bit
7
ASYNCCH
0x02 + n*0x01 [n=0..1]
0x00
-
6
5
4
3
2
1
0
ASYNCCH[7:0]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Reset
Bits 7:0 – ASYNCCH[7:0] Asynchronous Channel Generator Selection
Table 14-2. ASYNCCH0
Value
Description
0x00
OFF
0x01
CCL_LUT0
0x02
CCL_LUT1
0x03
AC0_OUT
0x04
Reserved
0x05
Reserved
0x06
Reserved
0x07
Reserved
0x08
RTC_OVF
0x09
RTC_CMP
0x0A
PORTA0
0x0B
PORTA1
0x0C
PORTA2
0x0D
PORTA3
0x0E
PORTA4
0x0F
PORTA5
0x10
PORTA6
0x11
PORTA7
0x12
UPDI
Other
Reserved
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 125
ATtiny406
Event System (EVSYS)
Table 14-3. ASYNCCH1
Value
Description
0x00
OFF
0x01
CCL_LUT0
0x02
CCL_LUT1
0x03
AC0_OUT
0x04
Reserved
0x05
Reserved
0x06
Reserved
0x07
Reserved
0x08
RTC_OVF
0x09
RTC_CMP
0x0A
PORTB0
0x0B
PORTB1
0x0C
PORTB2
0x0D
PORTB3
0x0E
PORTB4
0x0F
PORTB5
0x10
PORTB6
0x11
PORTB7
Other
Reserved
Note: Not all pins of a port are actually available on devices with low pin counts. Check the Pinout
Diagram and/or the I/O Multiplexing table for details.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 126
ATtiny406
Event System (EVSYS)
14.5.4
Synchronous Channel n Generator Selection
Name:
Offset:
Reset:
Property:
Bit
7
SYNCCH
0x0A
0x00
-
6
5
4
3
2
1
0
SYNCCH[7:0]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Reset
Bits 7:0 – SYNCCH[7:0] Synchronous Channel Generator Selection
Table 14-4. SYNCCH0
Value
Description
0x00
OFF
0x01
TCB0
0x02
TCA0_OVF_LUNF
0x03
TCA0_HUNF
0x04
TCA0_CMP0
0x05
TCA0_CMP1
0x06
TCA0_CMP2
0x07
PORTC0
0x08
PORTC1
0x09
PORTC2
0x0A
PORTC3
0x0B
PORTC4
0x0C
PORTC5
0x0D
PORTA0
0x0E
PORTA1
0x0F
PORTA2
0x10
PORTA3
0x11
PORTA4
0x12
PORTA5
0x13
PORTA6
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 127
ATtiny406
Event System (EVSYS)
Value
Description
0x14
PORTA7
Other
Reserved
Note: Not all pins of a port are actually available on devices with low pin counts. Check the Pinout
Diagram and/or the I/O Multiplexing table for details.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 128
ATtiny406
Event System (EVSYS)
14.5.5
Asynchronous User Channel n Input Selection
Name:
Offset:
Reset:
Property:
Bit
7
ASYNCUSER
0x12 + n*0x01 [n=0..10]
0x00
-
6
5
4
3
2
1
0
ASYNCUSER[7:0]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Reset
Bits 7:0 – ASYNCUSER[7:0] Asynchronous User Channel Selection
Table 14-5. User Multiplexer Numbers
USERn
User Multiplexer
Description
n=0
TCB0
Timer/Counter B 0
n=1
ADC0
ADC 0
n=2
CCL_LUT0EV0
CCL LUT0 Event 0
n=3
CCL_LUT1EV0
CCL LUT1 Event 0
n=4
CCL_LUT0EV1
CCL LUT0 Event 1
n=5
CCL_LUT1EV1
CCL LUT1 Event 1
n=6,7
Reserved
Reserved
n=8
EVOUT0
Event OUT 0
n=9
EVOUT1
Event OUT 1
n=10
EVOUT2
Event OUT 2
Value
0x0
0x1
0x3
0x4
Description
OFF
SYNCCH0
ASYNCCH0
ASYNCCH1
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 129
ATtiny406
Event System (EVSYS)
14.5.6
Synchronous User Channel n Input Selection
Name:
Offset:
Reset:
Property:
Bit
7
SYNCUSER
0x22 + n*0x01 [n=0..1]
0x00
-
6
5
4
3
2
1
0
SYNCUSER[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – SYNCUSER[7:0] Synchronous User Channel Selection
Table 14-6. User Multiplexer Numbers
USERn
User Multiplexer
Description
n=0
TCA0
Timer/Counter A
n=1
USART0
USART
Value
0x0
0x1
Name
OFF
SYNCCH0
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 130
ATtiny406
Port Multiplexer (PORTMUX)
15.
15.1
Port Multiplexer (PORTMUX)
Overview
The Port Multiplexer (PORTMUX) can either enable or disable functionality of pins, or change between
default and alternative pin positions. This depends on the actual pin and property and is described in
detail in the PORTMUX register map.
For available pins and functionalities, refer to the Multiplexed Signals table.
Related Links
I/O Multiplexing and Considerations
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 131
ATtiny406
Port Multiplexer (PORTMUX)
15.2
Register Summary - PORTMUX
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
CTRLC
7:0
0x03
CTRLD
7:0
15.3
LUT1
LUT0
TCA05
TCA04
EVOUT2
EVOUT1
SPI0
TCA03
TCA02
EVOUT0
USART0
TCA01
TCA00
TCB0
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 132
ATtiny406
Port Multiplexer (PORTMUX)
15.3.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
-
6
Access
Reset
5
4
2
1
0
LUT1
LUT0
3
EVOUT2
EVOUT1
EVOUT0
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 5 – LUT1 CCL LUT 1 output
Write this bit to '1' to select alternative pin location for CCL LUT 1.
Bit 4 – LUT0 CCL LUT 0 output
Write this bit to '1' to select alternative pin location for CCL LUT 0.
Bit 2 – EVOUT2 Event Output 2
Write this bit to '1' to enable event output 2.
Bit 1 – EVOUT1 Event Output 1
Write this bit to '1' to enable event output 1.
Bit 0 – EVOUT0 Event Output 0
Write this bit to '1' to enable event output 0.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 133
ATtiny406
Port Multiplexer (PORTMUX)
15.3.2
Control B
Name:
Offset:
Reset:
Property:
Bit
7
CTRLB
0x01
0x00
-
6
5
4
3
Access
Reset
2
1
0
SPI0
USART0
R/W
R/W
0
0
Bit 2 – SPI0 SPI 0 communication
Write this bit to '1' to select alternative communication pins for SPI 0.
Bit 0 – USART0 USART 0 communication
Write this bit to '1' to select alternative communication pins for USART 0.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 134
ATtiny406
Port Multiplexer (PORTMUX)
15.3.3
Control C
Name:
Offset:
Reset:
Property:
Bit
7
CTRLC
0x02
0x00
-
6
Access
Reset
5
4
3
2
1
0
TCA05
TCA04
TCA03
TCA02
TCA01
TCA00
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit 5 – TCA05 TCA0 Waveform output 5
Write this bit to '1' to select alternative output pin for TCA0 waveform output 5 in Split mode.
Not applicable when TCA in normal mode.
Bit 4 – TCA04 TCA0 Waveform output 4
Write this bit to '1' to select alternative output pin for TCA0 waveform output 4 in Split mode.
Not applicable when TCA in normal mode.
Bit 3 – TCA03 TCA0 Waveform output 3
Write this bit to '1' to select alternative output pin for TCA0 waveform output 3 in Split mode.
Not applicable when TCA in normal mode.
Bit 2 – TCA02 TCA0 Waveform output 2
Write this bit to '1' to select alternative output pin for TCA0 waveform output 2.
In Split Mode, this bit controls output from low byte compare channel 2.
Bit 1 – TCA01 TCA0 Waveform output 1
Write this bit to '1' to select alternative output pin for TCA0 waveform output 1.
In Split mode, this bit controls output from low byte compare channel 1.
Bit 0 – TCA00 TCA0 Waveform output 0
Write this bit to '1' to select alternative output pin for TCA0 waveform output 0.
In Split mode, this bit controls output from low byte compare channel 0.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 135
ATtiny406
Port Multiplexer (PORTMUX)
15.3.4
Control D
Name:
Offset:
Reset:
Property:
Bit
7
CTRLD
0x03
0x00
-
6
5
4
3
2
1
0
TCB0
Access
R/W
Reset
0
Bit 0 – TCB0 TCB0 output
Write this bit to '1' to select alternative output pin for 16-bit timer/counter B 0.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
16.
I/O Pin Configuration (PORT)
16.1
Features
•
•
•
•
•
16.2
General Purpose Input and Output Pins with Individual Configuration
Output Driver with Configurable Inverted I/O and Pullup
Input with Interrupts and Events:
– Sense both edges
– Sense rising edges
– Sense falling edges
– Sense low level
Asynchronous Pin Change Sensing That Can Wake the Device From all Sleep Modes
Efficient and Safe Access to Port Pins
– Hardware read-modify-write through dedicated toggle/clear/set registers
– Mapping of often-used PORT registers into bit-accessible I/O memory space (virtual ports)
Overview
The I/O pins of the device are controlled by instances of the port peripheral registers. This device has the
following instances of the I/O pin configuration (PORT): PORTA, PORTB, and PORTC.
Refer to the I/O Multiplexing table to see which pins are controlled by what instance of port. The offsets of
the port instances and of the corresponding virtual port instances are listed in the Peripherals and
Architecture section.
Each of the port pins has a corresponding bit in the Data Direction (PORT.DIR) and Data Output Value
(PORT.OUT) registers to enable that pin as an output and to define the output state. For example, pin
PA3 is controlled by DIR[3] and OUT[3] of the PORTA instance.
The Data Input Value (PORT.IN) is set as the input value of a port pin with resynchronization to the main
clock. To reduce power consumption, these input synchronizers are not clocked if the Input Sense
Configuration bit field (ISC) in PORT.PINnCTRL is INPUT_DISABLE. The value of the pin can always be
read, whether the pin is configured as input or output.
The port also supports synchronous and asynchronous input sensing with interrupts for selectable pin
change conditions. Asynchronous pin-change sensing means that a pin change can wake the device
from all sleep modes, including the modes where no clocks are running.
All pin functions are configurable individually per pin. The pins have hardware read-modify-write (RMW)
functionality for 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.
Related Links
I/O Multiplexing and Considerations
Peripherals and Architecture
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 137
ATtiny406
I/O Pin Configuration (PORT)
16.2.1
Block Diagram
Figure 16-1. PORT Block Diagram
Pullup enable
Invert Enable
OUTn
Q
D
Pxn
OUT Override
R
DIRn
Q
D
DIR
Override
R
Input Disable
Input
Disable
Override
Synchronizer
INn
Synchronized
input
Q
D Q
R
D
R
Digital Input /
Asynchronous event
Analog input/output
16.2.2
Signal Description
Signal
Type
Description
EXTINT
Digital input
External interrupt - available on all I/O pins
Related Links
I/O Multiplexing and Considerations
16.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
Table 16-1. PORT System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
No
-
Related Links
Events
Clocks
Interrupts
16.2.3.1 Clocks
This peripheral depends on the peripheral clock.
16.2.3.2 I/O Lines and Connections
Not applicable.
16.2.3.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
Related Links
CPU Interrupt Controller (CPUINT)
Interrupts
SREG
16.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
Event System (EVSYS)
16.2.3.5 Debug Operation
This peripheral is unaffected by entering Debug mode.
16.3
Functional Description
16.3.1
Initialization
After Reset, all standard function device I/O pads are connected to the port with outputs tri-stated and
input buffers enabled, even if there is no clock running.
For best power consumption, disable the input of unused pins and pins that are used as analog inputs or
outputs.
Specific pins, such as those used for connecting a debugger, may be configured differently, as required
by their special function.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
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 Virtual Ports
The Virtual PORT registers map the most frequently used regular PORT registers into the bit-accessible
I/O space. Writing to the Virtual PORT registers has the same effect as writing to the regular registers, but
allows for memory-specific instructions, such as bit-manipulation instructions, which are not valid for the
extended I/O memory space where the regular PORT registers reside.
Table 16-2. Virtual Port Mapping
Regular PORT Register
Mapped to Virtual PORT Register
PORT.DIR
VPORT.DIR
PORT.OUT
VPORT.OUT
PORT.IN
VPORT.IN
PORT.INTFLAG
VPORT.INTFLAG
Related Links
Register Summary - VPORT
I/O Multiplexing and Considerations
Peripherals and Architecture
16.3.2.3 Pin Configuration
The Pin n Configuration register (PORT.PINnCTRL) is used to configure inverted I/O, pullup, and input
sensing of a pin.
All input and output on the respective pin n can be inverted by writing a '1' to the Inverted I/O Enable bit
(INVEN) in PORT.PINnCTRL.
Toggling the INVEN bit causes an edge on the pin, which can be detected by all peripherals using this
pin, and is seen by interrupts or events if enabled.
Pullup of pin n is enabled by writing a '1' to the Pullup Enable bit (PULLUPEN) in PORT.PINnCTRL.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
Changes of the signal on a pin can trigger an interrupt. The exact conditions are defined by writing to the
Input/Sense bit field (ISC) in PORT.PINnCTRL.
When setting or changing interrupt settings, take these points into account:
•
If an INVEN bit is toggled in the same cycle as the interrupt setting, the edge caused by the
inversion toggling may not cause an interrupt request.
•
If an input is disabled while synchronizing an interrupt, that interrupt may be requested on reenabling the input, even if it is re-enabled with a different interrupt setting.
•
If the interrupt setting is changed while synchronizing an interrupt, that interrupt may not be
accepted.
•
Only 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
Related Links
I/O Multiplexing and Considerations
16.3.3
Interrupts
Table 16-3. Available Interrupt Vectors and Sources
Offset Name
0x00
Vector Description
Conditions
PORTx PORT A, B, C interrupt INTn in PORT.INTFLAGS is raised as configured by ISC bit in
PORT.PINnCTRL.
Each port pin n can be configured as an interrupt source. Each interrupt can be individually enabled or
disabled by writing to ISC in PORT.PINCTRL.
When an interrupt condition occurs, the corresponding interrupt flag is set in the Interrupt Flags register of
the peripheral (peripheral.INTFLAGS).
An interrupt request is generated when the corresponding interrupt is enabled and the interrupt flag is set.
The interrupt request remains active until the interrupt flag is cleared. See the peripheral's INTFLAGS
register for details on how to clear interrupt flags.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
Asynchronous Sensing Pin Properties
Table 16-4. Behavior Comparison of Fully/Partly Asynchronous Sense Pin
Property
Synchronous or Partly Asynchronous Sense
Support
Minimum pulse-width Minimum one system clock cycle
to trigger interrupt
Full Asynchronous Sense
Support
Less than a system clock
cycle
Waking the device
from sleep
From all interrupt sense configurations from sleep From all interrupt sense
modes with main clock running. Only from
configurations from all sleep
BOTHEDGES or LEVEL interrupt sense
modes
configuration from sleep modes with main clock
stopped.
Interrupt "dead time"
No new interrupt for three cycles after the
previous
No limitation
Minimum wake-up
pulse length
Value on pad must be kept until the system clock
has restarted
No limitation
Related Links
AVR CPU
SREG
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 the
Sleep mode. Peripherals connected to the ports can be affected by Sleep modes, described in the
respective peripherals' documentation.
The port peripheral will always use the main clock. Input synchronization will halt when this clock stops.
16.3.6
Synchronization
Not applicable.
16.3.7
Configuration Change Protection
Not applicable.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
16.4
Register Summary - PORT
Offset
Name
Bit Pos.
0x00
DIR
7:0
0x01
DIRSET
7:0
DIRSET[7:0]
0x02
DIRCLR
7:0
DIRCLR[7:0]
0x03
DIRTGL
7:0
DIRTGL[7:0]
0x04
OUT
7:0
OUT[7:0]
0x05
OUTSET
7:0
OUTSET[7:0]
0x06
OUTCLR
7:0
OUTCLR[7:0]
0x07
OUTTGL
7:0
OUTTGL[7:0]
0x08
IN
7:0
IN[7:0]
0x09
INTFLAGS
7:0
INT[7:0]
DIR[7:0]
0x0A
...
Reserved
0x0F
0x10
PIN0CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x11
PIN1CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x12
PIN2CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x13
PIN3CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x14
PIN4CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x15
PIN5CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x16
PIN6CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
0x17
PIN7CTRL
7:0
INVEN
PULLUPEN
ISC[2:0]
16.5
Register Description - Ports
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
16.5.1
Data Direction
Name:
Offset:
Reset:
Property:
Bit
7
DIR
0x00
0x00
-
6
5
4
3
2
1
0
DIR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DIR[7:0] Data Direction
This bit field selects the data direction for the individual pins n of the port.
Writing a '1' to PORT.DIR[n] configures and enables pin n as an output pin.
Writing a '0' to PORT.DIR[n] configures pin n as an input pin. It can be configured by writing to the ISC bit
in PORT.PINnCTRL.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
16.5.2
Data Direction Set
Name:
Offset:
Reset:
Property:
Bit
7
DIRSET
0x01
0x00
-
6
5
4
3
2
1
0
DIRSET[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DIRSET[7:0] Data Direction Set
This bit field can be used instead of a read-modify-write to set individual pins as output.
Writing a '1' to DIRSET[n] will set the corresponding PORT.DIR[n] bit.
Reading this bit field will always return the value of PORT.DIR.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
16.5.3
Data Direction Clear
Name:
Offset:
Reset:
Property:
Bit
7
DIRCLR
0x02
0x00
-
6
5
4
3
2
1
0
DIRCLR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DIRCLR[7:0] Data Direction Clear
This register can be used instead of a read-modify-write to configure individual pins as input.
Writing a '1' to DIRCLR[n] will clear the corresponding bit in PORT.DIR.
Reading this bit field will always return the value of PORT.DIR.
© 2018 Microchip Technology Inc.
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ATtiny406
I/O Pin Configuration (PORT)
16.5.4
Data Direction Toggle
Name:
Offset:
Reset:
Property:
Bit
7
DIRTGL
0x03
0x00
-
6
5
4
3
2
1
0
DIRTGL[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DIRTGL[7:0] Data Direction Toggle
This bit field can be used instead of a read-modify-write to toggle the direction of individual pins.
Writing a '1' to DIRTGL[n] will toggle the corresponding bit in PORT.DIR.
Reading this bit field will always return the value of PORT.DIR.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
16.5.5
Output Value
Name:
Offset:
Reset:
Property:
Bit
7
OUT
0x04
0x00
-
6
5
4
3
2
1
0
OUT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – OUT[7:0] Output Value
This bit field defines the data output value for the individual pins n of the port.
If OUT[n] is written to '1', pin n is driven high.
If OUT[n] is written to '0', pin n is driven low.
In order to have any effect, the pin direction must be configured as output.
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ATtiny406
I/O Pin Configuration (PORT)
16.5.6
Output Value Set
Name:
Offset:
Reset:
Property:
Bit
7
OUTSET
0x05
0x00
-
6
5
4
3
2
1
0
OUTSET[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – OUTSET[7:0] Output Value Set
This bit field can be used instead of a read-modify-write to set the output value of individual pins to '1'.
Writing a '1' to OUTSET[n] will set the corresponding bit in PORT.OUT.
Reading this bit field will always return the value of PORT.OUT.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
16.5.7
Output Value Clear
Name:
Offset:
Reset:
Property:
Bit
7
OUTCLR
0x06
0x00
-
6
5
4
3
2
1
0
OUTCLR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – OUTCLR[7:0] Output Value Clear
This register can be used instead of a read-modify-write to clear the output value of individual pins to '0'.
Writing a '1' to OUTCLR[n] will clear the corresponding bit in PORT.OUT.
Reading this bit field will always return the value of PORT.OUT.
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Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
16.5.8
Output Value Toggle
Name:
Offset:
Reset:
Property:
Bit
7
OUTTGL
0x07
0x00
-
6
5
4
3
2
1
0
OUTTGL[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – OUTTGL[7:0] Output Value Toggle
This register can be used instead of a read-modify-write to toggle the output value of individual pins.
Writing a '1' to OUTTGL[n] will toggle the corresponding bit in PORT.OUT.
Reading this bit field will always return the value of PORT.OUT.
© 2018 Microchip Technology Inc.
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ATtiny406
I/O Pin Configuration (PORT)
16.5.9
Input Value
Name:
Offset:
Reset:
Property:
Bit
7
IN
0x08
0x00
-
6
5
4
3
2
1
0
IN[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – IN[7:0] Input Value
This register shows the value present on the pins if the digital input driver is enabled. IN[n] shows the
value of pin n of the port. The input is not sampled and cannot be read if the digital input buffers are
disabled.
Writing to a bit of PORT.IN will toggle the corresponding bit in PORT.OUT.
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ATtiny406
I/O Pin Configuration (PORT)
16.5.10 Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x09
0x00
-
6
5
4
3
2
1
0
INT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – INT[7:0] Interrupt Pin Flag
The INT Flag is set when a pin change/state matches the pin's input sense configuration.
Writing a '1' to a flag's bit location will clear the flag.
For enabling and executing the interrupt, refer to ISC bit description in PORT.PINnCTRL.
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ATtiny406
I/O Pin Configuration (PORT)
16.5.11 Pin n Control
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
PINCTRL
0x10 + n*0x01 [n=0..7]
0x00
-
6
5
4
3
2
1
0
INVEN
PULLUPEN
ISC[2:0]
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 7 – INVEN Inverted I/O Enable
Value
0
1
Description
I/O on pin n not inverted
I/O on pin n inverted
Bit 3 – PULLUPEN Pullup Enable
Value
0
1
Description
Pullup disabled for pin n
Pullup enabled for pin n
Bits 2:0 – ISC[2:0] Input/Sense Configuration
These bits configure the input and sense configuration of pin n. The sense configuration determines how
a port interrupt can be triggered. If the input buffer is disabled, the input cannot be read in the IN register.
Value
0x0
0x1
0x2
0x3
0x4
0x5
other
Name
INTDISABLE
BOTHEDGES
RISING
FALLING
INPUT_DISABLE
LEVEL
-
© 2018 Microchip Technology Inc.
Description
Interrupt disabled but input buffer enabled
Sense both edges
Sense rising edge
Sense falling edge
Digital input buffer disabled
Sense low level
Reserved
Datasheet Preliminary
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ATtiny406
I/O Pin Configuration (PORT)
16.6
Register Summary - VPORT
Offset
Name
Bit Pos.
0x00
DIR
7:0
DIR[7:0]
0x01
OUT
7:0
OUT[7:0]
0x02
IN
7:0
IN[7:0]
0x03
INTFLAGS
7:0
INT[7:0]
16.7
Register Description - Virtual Ports
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ATtiny406
I/O Pin Configuration (PORT)
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
memory-specific instructions, such as bit-manipulation instructions, which are not valid for the extended
I/O memory space where the regular PORT registers reside.
Bit
7
6
5
4
3
2
1
0
DIR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DIR[7:0] Data Direction
This bit field selects the data direction for the individual pins in the port.
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ATtiny406
I/O Pin Configuration (PORT)
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
memory-specific instructions, such as bit-manipulation instructions, which are not valid for the extended
I/O memory space where the regular PORT registers reside.
Bit
7
6
5
4
3
2
1
0
OUT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – OUT[7:0] Output Value
This bit field selects the data output value for the individual pins in the port.
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ATtiny406
I/O Pin Configuration (PORT)
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
memory-specific instructions, such as bit-manipulation instructions, which are not valid for the extended
I/O memory space where the regular PORT registers reside.
Bit
7
6
5
4
3
2
1
0
IN[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – 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 VPORT.IN will toggle the corresponding bit in VPORT.OUT.
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ATtiny406
I/O Pin Configuration (PORT)
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
memory-specific instructions, such as bit-manipulation instructions, which are not valid for the extended
I/O memory space where the regular PORT registers reside.
Bit
7
6
5
4
3
2
1
0
INT[7:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bits 7:0 – INT[7:0] Interrupt Pin Flag
The INT flag is set when a pin change/state matches the pin's input sense configuration, and the pin is
configured as source for port interrupt.
Writing a '1' to this flag's bit location will clear the flag.
For enabling and executing the interrupt, refer to PORT_PINnCTRL.ISC.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Brown-Out Detector (BOD)
17.
Brown-Out Detector (BOD)
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 brown-out 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Brown-Out Detector (BOD)
17.2.1
Block Diagram
Figure 17-1. BOD Block Diagram
VDD
BOD Level
and
Calibration
-
Brown-out
Detection
+
Bandgap
VLM Interrupt Level
Bandgap
17.2.2
+
VLM Interrupt
Detection
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 17-1. BOD System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
Interrupts
Events
17.2.2.1 Clocks
The BOD uses the 32 KHz oscillator (OSCULP32K) as clock source for CLK_BOD.
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Datasheet Preliminary
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ATtiny406
Brown-Out Detector (BOD)
17.2.2.2 I/O Lines and Connections
Not applicable.
17.2.2.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
Related Links
CPU Interrupt Controller (CPUINT)
SREG
Interrupts
17.2.2.4 Events
Not applicable.
17.2.2.5 Debug Operation
This peripheral is unaffected by entering Debug mode.
The VLM interrupt will not be executed if the CPU is halted in Debug mode.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
17.3
Functional Description
17.3.1
Initialization
The BOD settings are loaded from fuses during Reset. The BOD level and operating mode in Active and
Idle Sleep mode are set by fuses and cannot be changed by the CPU. The operating mode in Standby
and Power-Down Sleep mode is loaded from fuses 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).
If the BOD/VLM is enabled in Sampled mode, only VLMCFG=0x1 (crossing threshold from above) in
BOD.INTCTRL will trigger an interrupt.
17.3.2
Interrupts
Table 17-2. Available Interrupt Vectors and Sources
Offset Name Vector Description
0x00
VLM
Conditions
Voltage Level Monitor Supply voltage crossing the VLM threshold as configured by
VLMCFG in BOD.INTCTRL
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 162
ATtiny406
Brown-Out Detector (BOD)
When an interrupt condition occurs, the corresponding interrupt flag is set in the Interrupt Flags register of
the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the interrupt
flag is set. The interrupt request remains active until the interrupt flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear interrupt flags.
Related Links
AVR CPU
SREG
17.3.3
Sleep Mode Operation
There are two separate fuses defining the BOD configuration in different sleep modes; One fuse defines
the mode used in Active mode and Idle Sleep mode (ACTIVE in FUSE.BODCFG), and is written to the
ACTIVE bits in the Control A register (BOD.CTRLA). The second fuse (SLEEP in FUSE.BODCFG)
selects the mode used in Standby Sleep mode and Power-Down Sleep mode, and is loaded into the
SLEEP bits in the Control A register (BOD.CTRLA).
The operating mode in Active mode and Idle Sleep mode (i.e., ACTIVE in BOD.CTRLA) cannot be
altered by software. The operating mode in Standby Sleep mode and Power-Down Sleep mode can be
altered by writing to the SLEEP bits in the Control A register (BOD.CTRLA).
When the device is going into Standby Sleep mode or Power-Down Sleep mode, the BOD will change
operation mode as defined by SLEEP in BOD.CTRLA. When the device is waking up from Standby or
Power-Down Sleep mode, the BOD will operate in the mode defined by the ACTIVE bit field in
BOD.CTRLA.
17.3.4
Synchronization
Not applicable.
17.3.5
Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
Table 17-3. Registers Under Configuration Change Protection
Register
Key
SLEEP in BOD.CTRLA
IOREG
Related Links
Sequence for Write Operation to Configuration Change Protected I/O Registers
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 163
ATtiny406
Brown-Out Detector (BOD)
17.4
Register Summary - BOD
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
SAMPFREQ
ACTIVE[1:0]
SLEEP[1:0]
LVL[2:0]
0x02
...
Reserved
0x07
0x08
VLMCTRLA
7:0
0x09
INTCTRL
7:0
0x0A
INTFLAGS
7:0
VLMIF
0x0B
STATUS
7:0
VLMS
17.5
VLMLVL[1:0]
VLMCFG[1:0]
VLMIE
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 164
ATtiny406
Brown-Out Detector (BOD)
17.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
Loaded from fuse
Configuration Change Protection
6
5
4
3
SAMPFREQ
2
1
ACTIVE[1:0]
0
SLEEP[1:0]
Access
R
R
R
R
R
R
R/W
R/W
Reset
0
0
0
x
x
x
x
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
0x0
0x1
Description
Sample frequency is 1 kHz
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
0x0
0x1
0x2
0x3
Description
Disabled
Enabled
Sampled
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
0x0
0x1
0x2
0x3
Description
Disabled
Enabled
Sampled
Reserved
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 165
ATtiny406
Brown-Out Detector (BOD)
17.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
7
CTRLB
0x01
Loaded from fuse
-
6
5
4
3
2
1
0
LVL[2:0]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
x
x
x
Bits 2:0 – LVL[2:0] BOD Level
These bits select the BOD threshold level.
The Reset value is loaded from the BOD Level bits (LVL) in the BOD Configuration Fuse
(FUSE.BODCFG).
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
BODLEVEL0
BODLEVEL1
BODLEVEL2
BODLEVEL3
BODLEVEL4
BODLEVEL5
BODLEVEL6
BODLEVEL7
© 2018 Microchip Technology Inc.
Description
1.8V
2.15V
2.60V
2.95V
3.30V
3.70V
4.00V
4.30V
Datasheet Preliminary
40001976A-page 166
ATtiny406
Brown-Out Detector (BOD)
17.5.3
VLM Control A
Name:
Offset:
Reset:
Property:
Bit
7
VLMCTRLA
0x08
0x00
-
6
5
4
3
2
1
0
VLMLVL[1:0]
Access
R
R
R
R
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 1:0 – VLMLVL[1:0] VLM Level
These bits select the VLM threshold relative to the BOD threshold (LVL in BOD.CTRLB).
Value
0x0
0x1
0x2
other
Description
VLM threshold 5% above BOD threshold
VLM threshold 15% above BOD threshold
VLM threshold 25% above BOD threshold
Reserved
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 167
ATtiny406
Brown-Out Detector (BOD)
17.5.4
Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x09
0x00
-
6
5
4
3
2
1
VLMCFG[1:0]
0
VLMIE
Access
R
R
R
R
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 2:1 – VLMCFG[1:0] VLM Configuration
These bits select which incidents will trigger a VLM interrupt.
Value
0x0
0x1
0x2
Other
Description
Voltage crosses VLM threshold from above
Voltage crosses VLM threshold from below
Either direction is triggering an interrupt request
Reserved
Bit 0 – VLMIE VLM Interrupt Enable
Writing a '1' to this bit enables the VLM interrupt.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 168
ATtiny406
Brown-Out Detector (BOD)
17.5.5
VLM Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x0A
0x00
-
6
5
4
3
2
1
0
VLMIF
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
Bit 0 – VLMIF VLM Interrupt Flag
This flag is set when a trigger from the VLM is given, as configured by the VLMCFG bit in the
BOD.INTCTRL register. The flag is only updated when the BOD is enabled.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 169
ATtiny406
Brown-Out Detector (BOD)
17.5.6
VLM Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x0B
0x00
-
6
5
4
3
2
1
0
VLMS
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bit 0 – VLMS VLM Status
This bit is only valid when the BOD is enabled.
Value
0
1
Description
The voltage is above the VLM threshold level
The voltage is below the VLM threshold level
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 170
ATtiny406
Voltage Reference (VREF)
18.
Voltage Reference (VREF)
18.1
Features
18.2
•
Programmable Voltage Reference Sources:
– One for each ADC peripheral
– One for each AC peripheral
•
Each Reference Source Supports Five Different Voltages:
– 0.55V
– 1.1V
– 1.5V
– 2.5V
– 4.3V
Overview
The Voltage Reference (VREF) peripheral provides control registers for the voltage reference sources
used by several peripherals. The user can select the reference voltages for the ADC0 by writing to the
ADC0 Reference Select bit field (ADC0REFSEL) in the Control A register (VREF.CTRLA), and for AC0 by
writing to the AC0 Reference Select bit field DAC0REFSEL in VREF.CTRLA.
A voltage reference source is enabled automatically when requested by a peripheral. The user can
enable the reference voltage sources (and thus, override the automatic disabling of unused sources) by
writing to the respective Force Enable bit (ADC0REFEN) in the Control B register (VREF.CTRLB). This
may be desirable to decrease start-up time, at the cost of increased power consumption.
18.2.1
Block Diagram
Figure 18-1. VREF Block Diagram
Reference reque st
Reference enable
Reference se lect
Bandgap
Reference
Gen erator
Ban dgap
ena ble
18.3
Functional Description
18.3.1
Initialization
0.55V
1.1V
1.5V
2.5V
4.3V
BUF
Inte rnal
Reference
The default configuration will enable the respective source when the ADC0, AC0 is requesting a
reference voltage. The default reference voltages are 0.55V but can be configured by writing to the
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 171
ATtiny406
Voltage Reference (VREF)
respective Reference Select bit field (ADC0REFSEL, DAC0REFSEL) in the Control A register
(VREF.CTRLA).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 172
ATtiny406
Voltage Reference (VREF)
18.4
Register Summary - VREF
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
18.5
ADC0REFSEL[2:0]
DAC0REFSEL[2:0]
ADC0REFEN DAC0REFEN
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 173
ATtiny406
Voltage Reference (VREF)
18.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
-
6
5
4
3
2
ADC0REFSEL[2:0]
Access
Reset
1
0
DAC0REFSEL[2:0]
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bits 6:4 – ADC0REFSEL[2:0] ADC0 Reference Select
These bits select the reference voltage for the ADC0.
Value
0x0
0x1
0x2
0x3
0x4
other
Description
0.55V
1.1V
2.5V
4.3V
1.5V
Reserved
Bits 2:0 – DAC0REFSEL[2:0] AC0 Reference Select
These bits select the reference voltage for the AC0.
Value
0x0
0x1
0x2
0x3
0x4
other
Description
0.55V
1.1V
2.5V
4.3V
1.5V
Reserved
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 174
ATtiny406
Voltage Reference (VREF)
18.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
7
CTRLB
0x01
0x00
-
6
5
4
3
Access
Reset
2
1
0
ADC0REFEN
DAC0REFEN
R/W
R/W
0
0
Bit 1 – ADC0REFEN ADC0 Reference Force Enable
Writing a '1' to this bit forces the voltage reference for the ADC0 to be running, even if it is not requested.
Writing a '0' to this bit allows automatic enable/disable of the reference source by the peripheral.
Bit 0 – DAC0REFEN AC0 Reference Force Enable
Writing a '1' to this bit forces the voltage reference for the AC0 to be running, even if it is not requested.
Writing a '0' to this bit allows automatic enable/disable of the reference source by the peripheral.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 175
ATtiny406
Watchdog Timer (WDT)
19.
Watchdog Timer (WDT)
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.
Related Links
Configuration Change Protection (CCP)
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 176
ATtiny406
Watchdog Timer (WDT)
19.2.1
Block Diagram
Figure 19-1. WDT Block Diagram
"Inside closed window"
CTRLA
WINDOW
CLK_WDT
"Enable
open window
and clear count"
=
COUNT
=
PERIOD
System
Reset
CTRLA
WDR
(instruction)
19.2.2
Signal Description
Not applicable.
19.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 19-1. WDT System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
No
-
Events
No
-
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
19.2.3.1 Clocks
A 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 WDT Control register will require synchronization between the clock domains.
Related Links
Electrical Characteristics
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 177
ATtiny406
Watchdog Timer (WDT)
19.2.3.2 I/O Lines and Connections
Not applicable.
19.2.3.3 Interrupts
Not applicable.
19.2.3.4 Events
Not applicable.
19.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in Debugging
mode will halt normal operation of the peripheral.
When halting the CPU in Debug mode, the WDT counter is reset.
When starting the CPU again and the WDT was operating in Window mode, the first closed window timeout period will be disabled, and a Normal mode time-out period is executed.
Related Links
Window Mode
19.3
Functional Description
19.3.1
Initialization
•
•
The WDT is enabled when a non-zero value is written to the Period bits (PERIOD) in the Control A
register (WDT.CTRLA).
Optional: Write a non-zero value to the Window bits (WINDOW) in WDT.CTRLA to enable Window
mode operation.
All bits in the Control A register and the Lock bit (LOCK) in the STATUS register (WDT.STATUS) are write
protected by the Configuration Change Protection mechanism.
The Reset value of WDT.CTRLA is defined by a fuse (FUSE.WDTCFG), so the WDT can be enabled at
boot time. If this is the case, the LOCK bit in WDT.STATUS is set at boot time.
Related Links
Register Summary - WDT
19.3.2
Operation
19.3.2.1 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).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 178
ATtiny406
Watchdog Timer (WDT)
Figure 19-2. Normal Mode Operation
WDT Count
Timely WDT Reset (WDR)
WDT Timeout
System Reset
Here:
TO WDT = 16ms
5
10
15
20
25
30
TOWDT
35
t [ms]
Normal mode is enabled as long as the WINDOW bit field in the Control A register (WDT.CTRLA) is 0x0.
Related Links
Register Summary - WDT
19.3.2.2 Window Mode
In Window mode operation, the WDT uses two different 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 = 8ms
5
10
15
20
TOWDTW
25
30
TOWDT
35
t [ms]
The Window mode is enabled by writing a non-zero value to the WINDOW bit field in the Control A
register (WDT.CTRLA), and disabled by writing WINDOW=0x0.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 179
ATtiny406
Watchdog Timer (WDT)
19.3.2.3 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.
LOCK in WDT.STATUS can only be written to '1'. It can only be cleared in Debug mode.
If the WDT configuration is loaded from fuses, LOCK is automatically set in WDT.STATUS.
Related Links
Configuration Change Protection (CCP)
19.3.3
Events
Not applicable.
19.3.4
Interrupts
Not applicable.
19.3.5
Sleep Mode Operation
The WDT will continue to operate in any sleep mode where the source clock is active.
19.3.6
Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domain, the Control A
register (WDT.CTRLA) is synchronized when written. The Synchronization Busy flag (SYNCBUSY) in the
STATUS register (WDT.STATUS) indicates if there is an ongoing synchronization.
Writing to WDT.CTRLA while SYNCBUSY=1 is not allowed.
The following registers are synchronized when written:
•
PERIOD bits in Control A register (WDT.CTRLA)
•
Window Period bits (WINDOW) in WDT.CTRLA
The WDR instruction will need 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). In order to write to
these, a certain key must be written to the CPU.CCP register first, followed by a write access to the
protected bits within four CPU instructions.
It is possible to try writing to these registers any time, but the values are not altered.
The following registers are under CCP:
Table 19-2. WDT - Registers Under Configuration Change Protection
Register
Key
WDT.CTRLA
IOREG
LOCK bit in WDT.STATUS
IOREG
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 180
ATtiny406
Watchdog Timer (WDT)
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)
Related Links
Configuration Change Protection (CCP)
Sequence for Write Operation to Configuration Change Protected I/O Registers
CCP
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 181
ATtiny406
Watchdog Timer (WDT)
19.4
Register Summary - WDT
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
STATUS
7:0
19.5
WINDOW[3:0]
LOCK
PERIOD[3:0]
SYNCBUSY
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 182
ATtiny406
Watchdog Timer (WDT)
19.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
CTRLA
0x00
From FUSE.WDTCFG
Configuration Change Protection
7
6
5
4
3
2
WINDOW[3:0]
Access
Reset
1
0
PERIOD[3:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
x
x
x
x
x
x
x
x
Bits 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
Name
OFF
8CLK
16CLK
32CLK
© 2018 Microchip Technology Inc.
Description
0.008s
0.016s
0.032s
Datasheet Preliminary
40001976A-page 183
ATtiny406
Watchdog Timer (WDT)
Value
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
other
Name
64CLK
128CLK
256CLK
512CLK
1KCLK
2KCLK
4KCLK
8KCLK
-
© 2018 Microchip Technology Inc.
Description
0.064s
0.128s
0.256s
0.512s
1.0s
2.0s
4.1s
8.2s
Reserved
Datasheet Preliminary
40001976A-page 184
ATtiny406
Watchdog Timer (WDT)
19.5.2
Status
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
STATUS
0x01
0x00
Configuration Change Protection
6
5
4
3
2
1
0
LOCK
SYNCBUSY
R/W
R
0
0
Bit 7 – LOCK Lock
Writing this bit to '1' write protects the WDT.CTRLA register.
It is only possible to write this bit to '1'. This bit can only be cleared in Debug mode.
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.
Related Links
Synchronization
Configuration Change Protection
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 185
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.
16-bit Timer/Counter Type A (TCA)
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. In Split mode each compare channel only
supports single-slope PWM waveform generation.
A block diagram of the 16-bit timer/counter with closely related peripheral modules (in grey) is shown in
the figure below.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 186
ATtiny406
16-bit Timer/Counter Type A (TCA)
Figure 20-1. 16-bit Timer/Counter and Closely Related Peripherals
Timer/Counter
Base Counter
Counter
Control Logic
Compare Channel 0
Compare Channel 1
Compare Channel 2
Comparator
Buffer
Waveform
Generation
CLK_PER
Event
System
PORTS
Timer Period
Prescaler
This device provides one instance of the TCA peripheral, TCA0.
20.2.1
Block Diagram
The figure below shows a detailed block diagram of the timer/counter.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 187
ATtiny406
16-bit Timer/Counter Type A (TCA)
Figure 20-2. Timer/Counter Block Diagram
Base Coun ter
PERB
CTRLA
PER
EVCTRL
Clock Select
Event
Select
"count"
"clear"
"load"
"direction"
Counter
CNT
=
=0
TOP
BOTTOM
OVF/UNF
(INT Req.)
Control Logi c
"ev"
UPDATE
BV
Compare
(Unit x = {A,B,C})
BV
CMPnBUF
Control Logi c
CMPn
=
Wav efo rm
Generation
"match"
WOn Out
CMPn
(INT Req.)
The counter register (TCAn.CNT), period registers with buffer (TCAn.PER and TCAn.PERBUF), and
compare registers with buffers (TCAn.CMPx and TCAn.CMPBUFx) are 16-bit registers. All buffer
registers have a buffer valid (BV) flag that indicates when the buffer contains a new value.
During normal operation, the counter value is continuously compared to zero and the period (PER) value
to determine whether the counter has reached TOP or BOTTOM.
The counter value is also compared to the TCAn.CMPx registers. These comparisons can be used to
generate interrupt requests. The Waveform Generator modes use these comparisons to set the waveform
period or pulse width.
A prescaled peripheral clock and events from the event system can be used to control the counter.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 188
ATtiny406
16-bit Timer/Counter Type A (TCA)
Figure 20-3. Timer/Counter Clock Logic
CLK_PER
Prescaler
Event System
event
CKSEL
EVACT
(Encoding)
CLK_TCA
CNT
CNTEI
20.2.2
20.2.3
Signal Description
Signal
Description
Type
WO[2:0]
Digital output
Waveform output
WO[5:3]
Digital output
Waveform output - Split Mode only
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 20-1. TCA System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
WO[5:0]
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
Interrupts
Events
20.2.3.1 Clocks
This peripheral uses the system clock CLK_PER, and has its own prescaler.
Related Links
Clock Controller (CLKCTRL)
20.2.3.2 I/O Lines and Connections
Using the I/O lines of the peripheral requires configuration of the I/O pins.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 189
ATtiny406
16-bit Timer/Counter Type A (TCA)
Related Links
I/O Multiplexing and Considerations
I/O Pin Configuration (PORT)
20.2.3.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
Related Links
CPU Interrupt Controller (CPUINT)
SREG
Interrupts
20.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
Event System (EVSYS)
20.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in Debugging
mode will halt normal operation of the peripheral.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
Related Links
Unified Program and Debug Interface (UPDI)
20.3
Functional Description
20.3.1
Definitions
The following definitions are used throughout the documentation:
Table 20-2. Timer/Counter Definitions
Name
Description
BOTTOM The counter reaches BOTTOM when it becomes zero.
MAX
The counter reaches MAXimum when it becomes all ones.
TOP
The counter reaches TOP when it becomes equal to the highest value in the count
sequence.
UPDATE The update condition is met when the timer/counter reaches BOTTOM or TOP, depending on
the Waveform Generator mode.
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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 190
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.3.2
Initialization
To start using the timer/counter in a basic mode, follow these steps:
•
Write a TOP value to the Period register (TCAn.PER)
•
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.
•
Optional: By writing a '1' to the Enable Count on Event Input bit (CNTEI) in the Event Control
register (TCAn.EVCTRL), event inputs are counted instead of clock ticks.
•
The counter value can be read from the Counter bit field (CNT) in the Counter register
(TCAn.CNT).
20.3.3
Operation
20.3.3.1 Normal Operation
In normal operation, the counter is counting clock ticks in the direction selected by the Direction bit (DIR)
in the Control E register (TCAn.CTRLE), until it reaches TOP or BOTTOM. The clock ticks are from the
peripheral clock CLK_PER, optionally prescaled, depending on the Clock Select bit field (CLKSEL) in the
Control A register (TCAn.CTRLA).
When up-counting and TOP are reached, the counter will wrap to zero at the next clock tick. When downcounting, 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 (i.e., new, value that can be copied into the
corresponding Period or Compare register). When the Period register and Compare n registers are used
for a compare operation, the BV flag is set when data is written to the buffer register and cleared on an
UPDATE condition. This is shown for a Compare register below.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 191
ATtiny406
16-bit Timer/Counter Type A (TCA)
Figure 20-5. Period and Compare Double Buffering
"write enable"
"data write"
EN
CMPnBUF
BV
EN
UPDATE
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.
Figure 20-6. Changing the Period Without Buffering
Counter wraparound
MAX
"update"
"write"
CNT
BOTTOM
New TOP written to
PER that is higher
than current CNT.
New TOP written to
PER that is lower
than current CNT.
A counter wrap-around can occur in any mode of operation when up-counting without buffering. This is
due to the fact that the registers TCAn.CNT and TCAn.PER are continuously compared: if a new TOP
value is written to TCAn.PER that is lower than current TCAn.CNT, the counter will wrap first, before a
compare match happens.
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.
© 2018 Microchip Technology Inc.
New TOP written to
PER that is lower
than current CNT.
Datasheet Preliminary
40001976A-page 192
ATtiny406
16-bit Timer/Counter Type A (TCA)
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 wrap-around and the generation of odd waveforms.
Figure 20-8. Changing the Period Using Buffering
MAX
"update"
"write"
CNT
BOTTOM
New Period written to
PERB that is higher
than current CNT.
New Period written to
PERB that is lower
than current CNT.
New PER is updated
with PERB value.
20.3.3.4 Compare Channel
Each Compare Channel n continuously compares the counter value (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.
Waveform Generation
The compare channels can be used for waveform generation on the corresponding port pins. To make
the waveform visible on the connected port pin, the following requirements must be met:
1.
2.
3.
4.
5.
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).
The compare channels used must be enabled (CMPnEN=1 in TCAn.CTRLB). This will override the
corresponding port pin output register. An alternative pin can be selected by writing to the
respective TCA Waveform Output n bit (TCA0n) in the Control C register of the Port Multiplexer
(PORTMUX.CTRLC).
The direction for the associated port pin n must be configured as an output (PORTx.DIR[n]=1).
Optional: Enable inverted waveform output for the associated port pin n (INVEN=1 in PORTx.PINn).
Frequency (FRQ) Waveform Generation
For frequency generation, the period time (T) is controlled by a TCAn.CMPn register instead of the Period
register (TCAn.PER). The waveform generation output WG is toggled on each compare match between
the TCAn.CNT and TCAn.CMPn registers.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 193
ATtiny406
16-bit Timer/Counter Type A (TCA)
Figure 20-9. Frequency Waveform Generation
Period (T)
Direction change
CNT written
MAX
"update"
CNT
TOP
BOTTOM
WG Output
The waveform frequency (fFRQ) is defined by the following equation:
�FRQ =
f CLK_PER
2� CMPn+1
where N represents the prescaler divider used (CLKSEL in TCAn.CTRLA), and fCLK_PER is the system
clock for the peripherals.
The maximum frequency of the waveform generated is half of the peripheral clock frequency (fCLK_PER/2)
when TCAn.CMPn is written to zero (0x0000) and no prescaling is used (N=1, CLKSEL=0x0 in
TCAn.CTRLA).
Single-Slope PWM Generation
For single-slope Pulse-Width Modulation (PWM) generation, the period (T) is controlled by TCAn.PER,
while the values of TCAn.CMPn control the duty cycle of the WG output. The figure below shows how the
counter counts from BOTTOM to TOP and then restarts from BOTTOM. The waveform generator (WO)
output is set at TOP and cleared on the compare match between the TCAn.CNT and TCAn.CMPn
registers.
Figure 20-10. Single-Slope Pulse-Width Modulation
Period (T)
CMPn=BOTTOM
CMPn=TOP
MAX
TOP
"update"
"match"
CNT
CMPn
BOTTOM
Output WOn
The TCAn.PER register defines the PWM resolution. The minimum resolution is 2 bits
(TCA.PER=0x0003), and the maximum resolution is 16 bits (TCA.PER=MAX).
The following equation calculates the exact resolution for single-slope PWM (RPWM_SS):
�PWM_SS =
log PER+1
log 2
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.:
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 194
ATtiny406
16-bit Timer/Counter Type A (TCA)
�PWM_SS =
�CLK_PER
� PER+1
Dual-Slope PWM
For dual-slope PWM generation, the period (T) is controlled by TCAn.PER, while the values of
TCAn.CMPn control the duty cycle of the WG output.
The figure below shows how for dual-slope PWM the counter counts repeatedly from BOTTOM to TOP
and then from TOP to BOTTOM. The waveform generator output is set on BOTTOM, cleared on compare
match when up-counting, and set on compare match when down-counting.
Figure 20-11. Dual-Slope Pulse-Width Modulation
Period (T)
CMPn=BOTTOM
CMPn=TOP
"update"
"match"
MAX
CMPn
TOP
CNT
BOTTOM
Waveform Output WOn
Using dual-slope PWM results in a lower maximum operation frequency compared to the single-slope
PWM operation.
The period register (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 for dual-slope PWM (RPWM_DS):
�PWM_DS =
log PER+1
log 2
�PWM_DS =
�CLK_PER
2� ⋅ PER
The PWM frequency depends on the period setting (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.
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
© 2018 Microchip Technology Inc.
INVEN
Datasheet Preliminary
40001976A-page 195
ATtiny406
16-bit Timer/Counter Type A (TCA)
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 zero.
A Reset command will set all timer/counter registers to their initial values. A Reset can be issued only
when the timer/counter is not running (ENABLE=0 in 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. Split mode
does not support event action controlled operation.
Split Mode Differences to Normal Mode
•
Count;
– Down-count only
– Timer/counter counter high and low byte are independent (TCAn.LCNT, TCAn.HCNT)
•
Waveform Generation:
– Single-slope PWM only (WGMODE=SINGLESLOPE in TCAn.CTRLB)
•
Interrupt:
– No change for low byte Timer/Counter (TCAn.LCNT)
– Underflow interrupt for high byte Timer/Counter (TCAn.HCNT)
– No compare interrupt or flag for High-byte Compare n registers (TCAn.HCMPn)
•
Event Actions: Not Compatible
•
Buffer registers and Buffer Valid Flags: Unused
•
Register Access: Byte Access to all registers
•
Temp register: Unused, 16-bit register of the Normal mode are Accessed as 8-bit 'TCA_H' and
'TCA_L', Respectively
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 196
ATtiny406
16-bit Timer/Counter Type A (TCA)
Block Diagram
Figure 20-13. Timer/Counter Block Diagram Split Mode
Base Counter
HPER
LPER
"count high"
"load high"
"count low"
"load low"
Counter
HCNT
Clock Select
CTRLA
LCNT
HUNF
Control Logic
(INT Req.)
LUNF
(INT Req.)
=0
BOTTOML
BOTTOMH
=0
Compare
(Unit n = {0,1,2})
LCMPn
Waveform
Generation
"match"
=
WOn Out
LCMPn
(INT Req.)
Compare
(Unit n = {0,1,2})
HCMPn
=
Waveform
Generation
WO[n+3] Out
"match"
Split Mode Initialization
When shifting between Normal mode and Split mode, the functionality of some registers and bits change,
but their values do not. For this reason, disabling the peripheral (ENABLE=0 in 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:
•
Enable Split mode by writing a '1' to the Split mode enable bit in the Control D register (SPLITM in
TCAn.CTRLD)
•
Write a TOP value to the Period registers (TCAn.PER)
•
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.
•
The counter values can be read from the Counter bit field in the Counter registers (TCAn.CNT)
Activating Split mode results in changes to the functionality of some registers and register bits. The
modifications are described in a separate register map.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 197
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.3.4
Events
The TCA is an event generator. The following events will generate a one-cycle strobe on the event
channel outputs:
•
Timer overflow
•
Timer underflow in Split mode
•
Compare match channel 0
•
Compare match channel 1
•
Compare match channel 2
The peripheral can take the following actions on an input event:
•
•
•
•
The counter counts positive edges of the event signal.
The counter counts both positive and negative edges of the event signal.
The counter counts prescaled clock cycles as long as the event signal is high.
The counter counts prescaled clock cycles. The event signal controls the direction of counting. Upcounting when the event signal is low and down-counting when the event signal is high.
The specific action is selected by writing to the Event Action bits (EVACT) in the Event Control register
(TCAn.EVCTRL). Events as input are enabled by writing a '1' to the Enable Count on Event Input bit
(CNTEI in TCAn.EVCTRL).
Event controlled inputs are not used in Split mode.
20.3.5
Interrupts
Table 20-3. Available Interrupt Vectors and Sources in Normal Mode
Offset Name Vector Description
Conditions
0x00
OVF
The counter has reached its top value and wrapped to
zero.
0x04
CMP0 Compare channel 0 interrupt
Match between the counter value and the Compare 0
register.
0x06
CMP1 Compare channel 1 interrupt
Match between the counter value and the Compare 1
register.
0x08
CMP2 Compare channel 2 interrupt
Match between the counter value and the Compare 2
register.
Overflow and compare match
interrupt
Table 20-4. Available Interrupt Vectors and Sources in Split Mode
Offset Name
Vector Description
0x00
LUNF
Low byte underflow interrupt Low byte timer reaches BOTTOM.
0x02
HUNF
High byte underflow interrupt High byte timer reaches BOTTOM.
0x04
LCMP0 Compare channel 0 interrupt Match between the counter value and the low byte of
Compare 0 register.
© 2018 Microchip Technology Inc.
Conditions
Datasheet Preliminary
40001976A-page 198
ATtiny406
16-bit Timer/Counter Type A (TCA)
Offset Name
Vector Description
Conditions
0x06
LCMP1 Compare channel 1 interrupt Match between the counter value and the low byte of
Compare 1 register.
0x08
LCMP2 Compare channel 2 interrupt Match between the counter value and the low byte of the
Compare 2 register.
When an interrupt condition occurs, the corresponding interrupt flag is set in the Interrupt Flags register of
the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the interrupt
flag is set. The interrupt request remains active until the interrupt flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear interrupt flags.
Related Links
AVR CPU
SREG
20.3.6
Sleep Mode Operation
The timer/counter will continue operation in Idle Sleep mode.
20.3.7
Configuration Change Protection
Not applicable.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 199
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.4
Register Summary - TCA in Normal Mode (CTRLD.SPLITM=0)
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
CTRLC
7:0
0x03
CTRLD
7:0
0x04
CTRLECLR
7:0
CMD[1:0]
LUPD
DIR
0x05
CTRLESET
7:0
CMD[1:0]
LUPD
DIR
0x06
CTRLFCLR
7:0
CMP2BV
CMP1BV
CMP0BV
PERBV
0x07
CTRLFSET
7:0
CMP2BV
CMP1BV
CMP0BV
PERBV
0x08
Reserved
CLKSEL[2:0]
CMP2EN
CMP1EN
CMP0EN
ALUPD
ENABLE
WGMODE[2:0]
CMP2OV
CMP1OV
CMP0OV
SPLITM
0x09
EVCTRL
7:0
0x0A
INTCTRL
7:0
CMP2
CMP1
CMP0
EVACT[1:0]
CNTEI
OVF
0x0B
INTFLAGS
7:0
CMP2
CMP1
CMP0
OVF
0x0C
...
Reserved
0x0D
0x0E
DBGCTRL
7:0
0x0F
TEMP
7:0
TEMP[7:0]
DBGRUN
7:0
CNT[7:0]
15:8
CNT[15:8]
0x10
...
Reserved
0x1F
0x20
CNT
0x22
...
Reserved
0x25
0x26
PER
0x28
CMP0
0x2A
CMP1
0x2C
CMP2
7:0
PER[7:0]
15:8
PER[15:8]
7:0
CMP[7:0]
15:8
CMP[15:8]
7:0
CMP[7:0]
15:8
CMP[15:8]
7:0
CMP[7:0]
15:8
CMP[15:8]
0x2E
...
Reserved
0x35
0x36
PERBUF
0x38
CMP0nBUF
0x3A
CMP1nBUF
0x3C
CMP2nBUF
7:0
PERBUF[7:0]
15:8
PERBUF[15:8]
7:0
CMPBUF[7:0]
15:8
CMPBUF[15:8]
7:0
CMPBUF[7:0]
15:8
CMPBUF[15:8]
7:0
CMPBUF[7:0]
15:8
CMPBUF[15:8]
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 200
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5
Register Description - Normal Mode
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 201
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
-
6
5
4
3
2
1
CLKSEL[2:0]
Access
0
ENABLE
R/W
R/W
R/W
R/W
0
0
0
0
Reset
Bits 3:1 – CLKSEL[2:0] Clock Select
These bits select the clock frequency for the timer/counter.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
DIV1
DIV2
DIV4
DIV8
DIV16
DIV64
DIV256
DIV1024
Description
fTCA = fCLK_PER/1
fTCA = fCLK_PER/2
fTCA = fCLK_PER/4
fTCA = fCLK_PER/8
fTCA = fCLK_PER/16
fTCA = fCLK_PER/64
fTCA = fCLK_PER/256
fTCA = fCLK_PER/1024
Bit 0 – ENABLE Enable
Value
0
1
Description
The peripheral is disabled
The peripheral is enabled
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 202
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.2
Control B - Normal Mode
Name:
Offset:
Reset:
Property:
Bit
CTRLB
0x01
0x00
-
7
6
5
4
3
CMP2EN
CMP1EN
CMP0EN
ALUPD
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
Access
Reset
2
1
0
WGMODE[2:0]
Bits 4, 5, 6 – CMPEN Compare n Enable
In the FRQ or PWM Waveform Generation mode, these bits will override the PORT output register for the
corresponding pin.
Value
0
1
Description
Port output settings for the pin with WOn output respected
Port output settings for pin with WOn output overridden in FRQ or PWM Waveform
Generation mode
Bit 3 – ALUPD Auto-Lock Update
The Auto-Lock Update feature controls the Lock Update (LUPD) bit in the 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 CMPnBUF register values are not
transferred to the CMPn registers until all enabled compare buffers are written.
Value
0
1
Description
LUPD in TCA.CTRLE not altered by system
LUPD in TCA.CTRLE set and cleared automatically
Bits 2:0 – WGMODE[2:0] Waveform Generation Mode
These bits select the Waveform Generation mode and control the counting sequence of the counter, TOP
value, UPDATE condition, interrupt condition, and type of waveform that is generated.
No waveform generation is performed in the Normal mode of operation. For all other modes, the result
from the waveform generator will only be directed to the port pins if the corresponding CMPnEN bit has
been set to enable this. The port pin direction must be set as output.
Table 20-5. Timer Waveform Generation Mode
WGMODE[2:0]
Group Configuration Mode of Operation
Top
Update
OVF
Normal
PER
TOP
TOP
000
NORMAL
001
FRQ
Frequency
CMP0 TOP
TOP
010
-
Reserved
-
-
-
011
SINGLESLOPE
Single-slope PWM
PER
BOTTOM BOTTOM
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 203
ATtiny406
16-bit Timer/Counter Type A (TCA)
WGMODE[2:0]
Value
0x0
0x1
0x3
0x5
0x6
0x7
Other
Group Configuration Mode of Operation
Top
Update
OVF
Reserved
-
-
-
100
-
101
DSTOP
Dual-slope PWM
PER
BOTTOM TOP
110
DSBOTH
Dual-slope PWM
PER
BOTTOM TOP and BOTTOM
111
DSBOTTOM
Dual-slope PWM
PER
BOTTOM BOTTOM
Name
NORMAL
FRQ
SINGLESLOPE
DSTOP
DSBOTH
DSBOTTOM
-
© 2018 Microchip Technology Inc.
Description
Normal operation mode
Frequency mode
Single-slope PWM mode
Dual-slope PWM mode
Dual-slope PWM mode
Dual-slope PWM mode
Reserved
Datasheet Preliminary
40001976A-page 204
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.3
Control C - Normal Mode
Name:
Offset:
Reset:
Property:
Bit
7
CTRLC
0x02
0x00
-
6
5
4
3
Access
Reset
2
1
0
CMP2OV
CMP1OV
CMP0OV
R/W
R/W
R/W
0
0
0
Bit 2 – CMP2OV Compare Output Value 2
See CMP0OV.
Bit 1 – CMP1OV Compare Output Value 1
See CMP0OV.
Bit 0 – CMP0OV Compare Output Value 0
The CMPnOV bits allow direct access to the waveform generator's output compare value when the timer/
counter is not enabled. This is used to set or clear the WG output value when the timer/counter is not
running.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 205
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.4
Control D
Name:
Offset:
Reset:
Property:
Bit
7
CTRLD
0x03
0x00
-
6
5
4
3
2
1
0
SPLITM
Access
R/W
Reset
0
Bit 0 – SPLITM Enable Split Mode
This bit sets the timer/counter in Split mode operation. It will then work as two 8-bit timer/counters. The
register map will change compared to normal 16-bit mode.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 206
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.5
Control Register E Clear - Normal Mode
Name:
Offset:
Reset:
Property:
CTRLECLR
0x04
0x00
-
The individual Status bit can be cleared by writing a one to its bit location. This allows each bit to be
cleared without the use of a read-modify-write operation on a single register.
Each Status bit can be read out either by reading TCAn.CTRLESET or TCAn.CTRLECLR.
Bit
7
6
5
4
3
2
CMD[1:0]
Access
Reset
1
0
LUPD
DIR
R/W
R/W
R/W
R/W
0
0
0
0
Bits 3:2 – CMD[1:0] Command
These bits are used for software control of update, restart, and reset of the timer/counter. The command
bits are always read as zero.
Value
0x0
0x1
0x2
0x3
Name
NONE
UPDATE
RESTART
RESET
Description
No command
Force update
Force restart
Force hard Reset (ignored if TC is enabled)
Bit 1 – LUPD Lock Update
Lock update can be used to ensure that all buffers are valid before an update is performed.
Value
0
1
Description
The buffered registers are updated as soon as an UPDATE condition has occurred.
No update of the buffered registers is performed, even though an UPDATE condition has
occurred.
Bit 0 – DIR Counter Direction
Normally this bit is controlled in hardware by the Waveform Generation mode or by event actions, but this
bit can also be changed from software.
Value
0
1
Description
The counter is counting up (incrementing)
The counter is counting down (decrementing)
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 207
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.6
Control Register E Set - Normal Mode
Name:
Offset:
Reset:
Property:
CTRLESET
0x05
0x00
-
The individual Status bit can be set by writing a '1' to its bit location. This allows each bit to be set without
the use of a read-modify-write operation on a single register.
Each Status bit can be read out either by reading TCAn.CTRLESET or TCAn.CTRLECLR.
Bit
7
6
5
4
3
2
CMD[1:0]
Access
Reset
1
0
LUPD
DIR
R/W
R/W
R/W
R/W
0
0
0
0
Bits 3:2 – CMD[1:0] Command
These bits are used for software control of update, restart, and reset the timer/counter. The command bits
are always read as zero.
Value
0x0
0x1
0x2
0x3
Name
NONE
UPDATE
RESTART
RESET
Description
No command
Force update
Force restart
Force hard Reset (ignored if TC is enabled)
Bit 1 – LUPD Lock Update
Locking the update ensures that all buffers are valid before an update is performed.
Value
0
1
Description
The buffered registers are updated as soon as an UPDATE condition has occurred.
No update of the buffered registers is performed, even though an UPDATE condition has
occurred.
Bit 0 – DIR Counter Direction
Normally this bit is controlled in hardware by the Waveform Generation mode or by event actions, but this
bit can also be changed from software.
Value
0
1
Description
The counter is counting up (incrementing)
The counter is counting down (decrementing)
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 208
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.7
Control Register F Clear
Name:
Offset:
Reset:
Property:
CTRLFCLR
0x06
0x00
-
The individual Status bit can be cleared by writing a '1' to its bit location. This allows each bit to be
cleared without the use of a read-modify-write operation on a single register.
Bit
7
6
5
Access
Reset
4
3
2
1
0
CMP2BV
CMP1BV
CMP0BV
PERBV
R/W
R/W
R/W
R/W
0
0
0
0
Bit 3 – CMP2BV Compare 2 Buffer Valid
See CMP0BV.
Bit 2 – CMP1BV Compare 1 Buffer Valid
See CMP0BV.
Bit 1 – CMP0BV Compare 0 Buffer Valid
The CMPnBV bits are set when a new value is written to the corresponding 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 209
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.8
Control Register F Set
Name:
Offset:
Reset:
Property:
CTRLFSET
0x07
0x00
-
The individual status bit can be set by writing a one to its bit location. This allows each bit to be set
without the use of a read-modify-write operation on a single register.
Bit
7
6
5
Access
Reset
4
3
2
1
0
CMP2BV
CMP1BV
CMP0BV
PERBV
R/W
R/W
R/W
R/W
0
0
0
0
Bit 3 – CMP2BV Compare 2 Buffer Valid
See CMP0BV.
Bit 2 – CMP1BV Compare 1 Buffer Valid
See CMP0BV.
Bit 1 – CMP0BV Compare 0 Buffer Valid
The CMPnBV bits are set when a new value is written to the corresponding 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 210
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.9
Event Control
Name:
Offset:
Reset:
Property:
Bit
7
EVCTRL
0x09
0x00
-
6
5
4
3
2
1
EVACT[1:0]
Access
Reset
0
CNTEI
R/W
R/W
R/W
0
0
0
Bits 2:1 – EVACT[1:0] Event Action
These bits define what type of event action the counter will increment or decrement.
Value
0x0
0x1
0x2
0x3
Name
EVACT_POSEDGE
EVACT_ANYEDGE
EVACT_HIGHLVL
EVACT_UPDOWN
Description
Count on positive edge event
Count on any edge event
Count on prescaled clock while event line is 1.
Count on prescaled clock. The Event controls the count direction. Upcounting when the event line is 0, down-counting when the event line is
1.
Bit 0 – CNTEI Enable Count on Event Input
Value
0
1
Description
Counting on Event input is disabled
Counting on Event input is enabled according to EVACT bit field
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 211
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.10 Interrupt Control Register - Normal Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
INTCTRL
0x0A
0x00
-
6
5
4
CMP2
CMP1
CMP0
3
2
1
OVF
0
R/W
R/W
R/W
R/W
0
0
0
0
Bit 6 – CMP2 Compare Channel 2 Interrupt Enable
See CMP0.
Bit 5 – CMP1 Compare Channel 1 Interrupt Enable
See CMP0.
Bit 4 – CMP0 Compare Channel 0 Interrupt Enable
Writing CMPn bit to '1' enables compare interrupt from channel n.
Bit 0 – OVF Timer Overflow/Underflow Interrupt Enable
Writing OVF bit to '1' enables overflow interrupt.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 212
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.11 Interrupt Flag Register - Normal Mode
Name:
Offset:
Reset:
Property:
INTFLAGS
0x0B
0x00
-
The individual Status bit can be cleared by writing a '1' to its bit location. This allows each bit to be set
without the use of a read-modify-write operation on a single register.
Bit
Access
Reset
7
6
5
4
3
2
1
0
CMP2
CMP1
CMP0
OVF
R/W
R/W
R/W
R/W
0
0
0
0
Bit 6 – CMP2 Compare Channel 2 Interrupt Flag
See CMP0 flag description.
Bit 5 – CMP1 Compare Channel 1 Interrupt Flag
See 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 (TCAn.CNT) and the corresponding Compare register (TCAn.CMPn). The CMPn flag will not be
cleared automatically and has to be cleared by software. This is done by writing a one to its bit location.
Bit 0 – OVF Overflow/Underflow Interrupt Flag
This flag is set either on a TOP (overflow) or BOTTOM (underflow) condition, depending on the
WGMODE setting. OVF is not automatically cleared and needs to be cleared by software. This is done by
writing a one to its bit location.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 213
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.12 Debug Control Register
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x0E
0x00
-
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN Run in Debug
Value
0
1
Description
The peripheral is halted in Break Debug mode and ignores events
The peripheral will continue to run in Break Debug mode when the CPU is halted
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 214
ATtiny406
16-bit Timer/Counter Type A (TCA)
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. See Accessing 16-Bit Registers. There is one common
Temporary register for all the 16-bit registers of this peripheral.
Bit
7
6
5
4
3
2
1
0
TEMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – TEMP[7:0] Temporary Bits for 16-bit Access
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 215
ATtiny406
16-bit Timer/Counter Type A (TCA)
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. For more details on reading and writing 16-bit registers, refer to Accessing 16-Bit Registers.
CPU and UPDI write access has priority over internal updates of the register.
Bit
15
14
13
12
11
10
9
8
R/W
R/W
R/W
R/W
Reset
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
CNT[15:8]
Access
CNT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:8 – 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 216
ATtiny406
16-bit Timer/Counter Type A (TCA)
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.
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. For more details on reading and writing 16-bit registers, refer to Accessing 16-Bit Registers.
Bit
15
14
13
12
11
10
9
8
R/W
R/W
R/W
R/W
Reset
1
1
R/W
R/W
R/W
R/W
1
1
1
1
1
1
Bit
7
6
5
4
3
2
1
0
PER[15:8]
Access
PER[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
1
1
1
1
1
1
1
Bits 15:8 – PER[15:8] Periodic High Byte
These bits hold the MSB of the 16-bit period register.
Bits 7:0 – PER[7:0] Periodic Low Byte
These bits hold the LSB of the 16-bit period register.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 217
ATtiny406
16-bit Timer/Counter Type A (TCA)
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 then used for generating 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. For more details on reading and writing 16-bit registers, refer to Accessing 16-Bit
Registers.
Bit
15
14
13
12
11
10
9
8
CMP[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
CMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 218
ATtiny406
16-bit Timer/Counter Type A (TCA)
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). Accessing this register using the
CPU or UPDI will affect the PERBV flag.
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. For more details on reading and writing 16-bit registers, refer to Accessing 16-Bit
Registers.
Bit
15
14
13
12
11
10
9
8
PERBUF[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
1
1
1
1
1
1
1
1
Bit
7
6
5
4
3
2
1
0
PERBUF[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
1
1
1
1
1
1
1
Bits 15:8 – PERBUF[15:8] Period Buffer High Byte
These bits hold the MSB of the 16-bit period buffer register.
Bits 7:0 – PERBUF[7:0] Period Buffer Low Byte
These bits hold the LSB of the 16-bit period buffer register.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 219
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.5.18 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 registers (TCAn.CMPn). Accessing any of
these registers using the CPU or UPDI will affect the corresponding CMPnBV status bit.
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. For more details on reading and writing 16-bit registers, refer to Accessing 16Bit Registers.
Bit
15
14
13
12
11
10
9
8
CMPBUF[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
CMPBUF[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:8 – CMPBUF[15:8] Compare High Byte
These bits hold the MSB of the 16-bit compare buffer register.
Bits 7:0 – CMPBUF[7:0] Compare Low Byte
These bits hold the LSB of the 16-bit compare buffer register.
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
20.6
Register Summary - TCA in Split Mode (CTRLD.SPLITM=1)
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
HCMP2EN
HCMP1EN
HCMP0EN
LCMP2EN
LCMP1EN
LCMP0EN
0x02
CTRLC
7:0
HCMP2OV
HCMP1OV
HCMP0OV
LCMP2OV
LCMP1OV
LCMP0OV
0x03
CTRLD
7:0
0x04
CTRLECLR
7:0
CMD[1:0]
CMDEN[1:0]
0x05
CTRLESET
7:0
CMD[1:0]
CMDEN[1:0]
CLKSEL[2:0]
ENABLE
SPLITM
0x06
...
Reserved
0x09
0x0A
INTCTRL
7:0
LCMP2
LCMP1
LCMP0
HUNF
LUNF
0x0B
INTFLAGS
7:0
LCMP2
LCMP1
LCMP0
HUNF
LUNF
0x0C
...
Reserved
0x0D
0x0E
DBGCTRL
7:0
DBGRUN
0x0F
...
Reserved
0x1F
0x20
LCNT
7:0
LCNT[7:0]
0x21
HCNT
7:0
HCNT[7:0]
0x22
...
Reserved
0x25
0x26
LPER
7:0
LPER[7:0]
0x27
HPER
7:0
HPER[7:0]
0x28
LCMP0
7:0
LCMP[7:0]
0x29
HCMP0
7:0
HCMP[7:0]
0x2A
LCMP1
7:0
LCMP[7:0]
0x2B
HCMP1
7:0
HCMP[7:0]
0x2C
LCMP2
7:0
LCMP[7:0]
0x2D
HCMP2
7:0
HCMP[7:0]
20.7
Register Description - Split Mode
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Datasheet Preliminary
40001976A-page 221
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
-
6
5
4
3
2
1
CLKSEL[2:0]
Access
0
ENABLE
R/W
R/W
R/W
R/W
0
0
0
0
Reset
Bits 3:1 – CLKSEL[2:0] Clock Select
These bits select the clock frequency for the timer/counter.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
DIV1
DIV2
DIV4
DIV8
DIV16
DIV64
DIV256
DIV1024
Description
fTCA = fCLK_PER/1
fTCA = fCLK_PER/2
fTCA = fCLK_PER/4
fTCA = fCLK_PER/8
fTCA = fCLK_PER/16
fTCA = fCLK_PER/64
fTCA = fCLK_PER/256
fTCA = fCLK_PER/1024
Bit 0 – ENABLE Enable
Value
0
1
Description
The peripheral is disabled
The peripheral is enabled
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.2
Control B - Split Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CTRLB
0x01
0x00
-
6
5
4
2
1
0
HCMP2EN
HCMP1EN
HCMP0EN
3
LCMP2EN
LCMP1EN
LCMP0EN
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit 6 – HCMP2EN High byte Compare 2 Enable
See LCMP0EN.
Bit 5 – HCMP1EN High byte Compare 1 Enable
See LCMP0EN.
Bit 4 – HCMP0EN High byte Compare 0 Enable
See LCMP0EN.
Bit 2 – LCMP2EN Low byte Compare 2 Enable
See LCMP0EN.
Bit 1 – LCMP1EN Low byte Compare 1 Enable
See LCMP0EN.
Bit 0 – LCMP0EN Low byte Compare 0 Enable
Setting the LCMPnEN/HCMPnEN bits in the FRQ or PWM Waveform Generation mode of operation will
override the port output register for the corresponding WOn pin.
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.3
Control C - Split Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CTRLC
0x02
0x00
-
6
5
4
2
1
0
HCMP2OV
HCMP1OV
HCMP0OV
3
LCMP2OV
LCMP1OV
LCMP0OV
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit 6 – HCMP2OV High byte Compare 2 Output Value
See LCMP0OV.
Bit 5 – HCMP1OV High byte Compare 1 Output Value
See LCMP0OV.
Bit 4 – HCMP0OV High byte Compare 0 Output Value
See LCMP0OV.
Bit 2 – LCMP2OV Low byte Compare 2 Output Value
See LCMP0OV.
Bit 1 – LCMP1OV Low byte Compare 1 Output Value
See LCMP0OV.
Bit 0 – LCMP0OV Low byte Compare 0 Output Value
The LCMPnOV/HCMPn bits allow direct access to the waveform generator's output compare value when
the timer/counter is not enabled. This is used to set or clear the WOn output value when the timer/counter
is not running.
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.4
Control D
Name:
Offset:
Reset:
Property:
Bit
7
CTRLD
0x03
0x00
-
6
5
4
3
2
1
0
SPLITM
Access
R/W
Reset
0
Bit 0 – SPLITM Enable Split Mode
This bit sets the timer/counter in Split mode operation. It will then work as two 8-bit timer/counters. The
register map will change compared to normal 16-bit mode.
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ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.5
Control Register E Clear - Split Mode
Name:
Offset:
Reset:
Property:
CTRLECLR
0x04
0x00
-
The individual Status bit can be cleared by writing a '1' to its bit location. This allows each bit to be
cleared without the use of a read-modify-write operation on a single register.
Bit
7
6
5
4
3
2
1
R/W
R/W
R/W
R/W
0
0
0
0
CMD[1:0]
Access
Reset
0
CMDEN[1:0]
Bits 3:2 – CMD[1:0] Command
These bits are used for software control of update, restart, and reset of the timer/counter. The command
bits are always read as zero.
Value
0x0
0x1
0x2
0x3
Name
NONE
RESTART
RESET
Description
No command
Reserved
Force restart
Force hard Reset (ignored if TC is enabled)
Bits 1:0 – CMDEN[1:0] Command enable
These bits are used to indicate for which timer/counter the command (CMD) is valid.
Value
0x0
0x1
0x2
0x3
Name
NONE
LOW
HIGH
BOTH
Description
None
Command valid for low-byte T/C
Command valid for high-byte T/C
Command valid for both low-byte and high-byte T/C
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.6
Control Register E Set - Split Mode
Name:
Offset:
Reset:
Property:
CTRLESET
0x05
0x00
-
The individual Status bit can be set by writing a '1' to its bit location. This allows each bit to be set without
the use of a read-modify-write operation on a single register.
Bit
7
6
5
4
3
2
1
R/W
R/W
R/W
R/W
0
0
0
0
CMD[1:0]
Access
Reset
0
CMDEN[1:0]
Bits 3:2 – CMD[1:0] Command
These bits are used for software control of update, restart, and reset of the timer/counter. The command
bits are always read as zero. The CMD bits must be used together with CMDEN. Using the reset
command requires that both low-byte and high-byte timer/counter is selected.
Value
0x0
0x1
0x2
0x3
Name
NONE
RESTART
RESET
Description
No command
Reserved
Force restart
Force hard Reset (ignored if TC is enabled)
Bits 1:0 – CMDEN[1:0] Command enable
These bits are used to indicate for which timer/counter the command (CMD) is valid.
Value
0x0
0x1
0x2
0x3
Name
NONE
LOW
HIGH
BOTH
Description
None
Command valid for low-byte T/C
Command valid for high-byte T/C
Command valid for both low-byte and high-byte T/C
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.7
Interrupt Control Register - Split Mode
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
INTCTRL
0x0A
0x00
-
6
5
4
1
0
LCMP2
LCMP1
LCMP0
3
2
HUNF
LUNF
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 6 – LCMP2 Low byte Compare Channel 0 Interrupt Enable
See LCMP0.
Bit 5 – LCMP1 Low byte Compare Channel 1 Interrupt Enable
See LCMP0.
Bit 4 – LCMP0 Low byte Compare Channel 0 Interrupt Enable
Writing LCMPn bit to '1' enables low byte compare interrupt from channel n.
Bit 1 – HUNF High byte Underflow Interrupt Enable
Writing HUNF bit to '1' enables high byte underflow interrupt.
Bit 0 – LUNF Low byte Underflow Interrupt Enable
Writing HUNF bit to '1' enables low byte underflow interrupt.
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Datasheet Preliminary
40001976A-page 228
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.8
Interrupt Flag Register - Split Mode
Name:
Offset:
Reset:
Property:
INTFLAGS
0x0B
0x00
-
The individual Status bit can be cleared by writing a ‘1’ to its bit location. This allows each bit to be set
without the use of a read-modify-write operation on a single register.
Bit
Access
Reset
7
6
5
4
LCMP2
LCMP1
R/W
R/W
0
0
3
2
1
0
LCMP0
HUNF
LUNF
R/W
R/W
R/W
0
0
0
Bit 6 – LCMP2 Low byte Compare Channel 0 Interrupt Flag
See LCMP0 flag description.
Bit 5 – LCMP1 Low byte Compare Channel 0 Interrupt Flag
See LCMP0 flag description.
Bit 4 – LCMP0 Low byte Compare Channel 0 Interrupt Flag
The Compare Interrupt flag (LCMPn) is set on a compare match on the corresponding compare channel.
For all modes of operation, the LCMPn flag will be set when a compare match occurs between the Low
Byte Count 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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Datasheet Preliminary
40001976A-page 229
ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.9
Debug Control Register
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x0E
0x00
-
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN Run in Debug
Value
0
1
Description
The peripheral is halted in Break Debug mode and ignores events
The peripheral will continue to run in Break Debug mode when the CPU is halted
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.10 Low Byte Timer Counter Register - Split Mode
Name:
Offset:
Reset:
Property:
LCNT
0x20
0x00
-
TCAn.LCNT contains the counter value in 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
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
LCNT[7:0]
Access
Reset
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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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.11 High Byte Timer Counter Register - Split Mode
Name:
Offset:
Reset:
Property:
HCNT
0x21
0x00
-
TCAn.HCNT contains the counter value in 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
R/W
R/W
R/W
0
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
HCNT[7:0]
Access
Reset
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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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
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 of low byte timer.
Bit
7
6
5
4
3
2
1
0
LPER[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
1
1
1
1
1
1
1
Bits 7:0 – LPER[7:0] Period Value Low Byte Timer
These bits hold the TOP value of low byte timer.
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
20.7.13 High Byte Period Register - Split Mode
Name:
Offset:
Reset:
Property:
HPER
0x27
0x00
-
The TCAn.HPER register contains the TOP value of high byte timer.
Bit
7
6
5
4
3
2
1
0
HPER[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
1
1
1
1
1
1
1
Bits 7:0 – HPER[7:0] Period Value High Byte Timer
These bits hold the TOP value of high byte timer.
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type A (TCA)
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 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 for generating waveforms.
Bit
7
6
5
4
3
2
1
0
LCMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – LCMP[7:0] Compare Value of Channel n
These bits hold the compare value of channel n that is compared to TCAn.LCNT.
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Datasheet Preliminary
40001976A-page 235
ATtiny406
16-bit Timer/Counter Type A (TCA)
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 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 for generating waveforms.
Bit
7
6
5
4
3
2
1
0
HCMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – HCMP[7:0] Compare Value of Channel n
These bits hold the compare value of channel n that is compared to TCAn.HCNT.
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type B (TCB)
21.
16-bit Timer/Counter Type B (TCB)
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
Optional: Operation Synchronous with TCA0
Overview
The capabilities of the 16-bit Timer/Counter type B (TCB) include frequency and waveform generation,
and input capture on event with time and frequency measurement of digital signals. The TCB consists of
a base counter and control logic which can be set in one of eight different modes, each mode providing
unique functionality. The base counter is clocked by the peripheral clock with optional prescaling.
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type B (TCB)
21.2.1
Block Diagram
Figure 21-1. Timer/Counter Type B Block Diagram
TCB
ClockSelect
CTRLA
Mode
CTRLB
EVCTRL
Edge Select
CCMP
DIV2
Counter
"count"
"clear"
CNT
CLK_PER
Control
Logic
CLK_TCA
Event System
IF
(INT Req.)
=
=0
Mode, Output enable, initial value
TOP
BOTTOM
Synchronous
output
Output control
and
Asynchronous logic
Asynchronous
output
21.2.1.1 Noise Canceler
The noise canceler improves noise immunity by using a simple digital filter scheme. When the noise filter
is enabled, the peripheral monitors the event channel and keeps a record of the last four observed
samples. If four consecutive samples are equal, the input is considered to be stable and the signal is fed
to the edge detector.
When enabled, the noise canceler introduces an additional delay of four system clock cycles between a
change applied to the input and the update of the input compare register.
The noise canceler uses the system clock and is, therefore, not affected by the prescaler.
21.2.2
Signal Description
Signal
Description
Type
WO
Digital Asynchronous Output
Waveform Output
Related Links
I/O Multiplexing and Considerations
21.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type B (TCB)
Table 21-1. TCB System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
WO
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
Interrupts
Events
21.2.3.1 Clocks
This peripheral uses the system's peripheral clock CLK_PER. The peripheral has its own local prescaler,
or can be configured to run off the prescaled clock signal of the Timer Counter type A (TCA).
Related Links
Clock Controller (CLKCTRL)
21.2.3.2 I/O Lines and Connections
Using the I/O lines of the peripheral requires configuration of the I/O pins.
Related Links
I/O Multiplexing and Considerations
I/O Pin Configuration (PORT)
21.2.3.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
Related Links
CPU Interrupt Controller (CPUINT)
SREG
Interrupts
21.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
Event System (EVSYS)
21.2.3.5 Debug Operation
When the CPU is halted in Debug mode, this peripheral will halt normal operation. This peripheral can be
forced to continue operation during debugging.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
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ATtiny406
16-bit Timer/Counter Type B (TCB)
Related Links
Unified Program and Debug Interface (UPDI)
21.3
Functional Description
21.3.1
Definitions
The following definitions are used throughout the documentation:
Table 21-2. Timer/Counter Definitions
Name
Description
BOTTOM The counter reaches BOTTOM when it becomes zero.
MAX
The counter reaches MAXimum when it becomes all ones.
TOP
The counter reaches TOP when it becomes equal to the highest value in the count
sequence.
UPDATE The update condition is met when the timer/counter reaches BOTTOM or TOP, depending on
the Waveform Generator mode.
CNT
Counter register value.
CCMP
Capture/Compare register value.
In general, the term timer is used when the timer/counter is counting periodic clock ticks. The term
counter is used when the input signal has sporadic or irregular ticks.
21.3.2
Initialization
By default, the TCB is in Periodic Interrupt mode. Follow these steps to start using it:
•
Write a TOP value to the Compare/Capture register (TCBn.CCMP).
•
Enable the counter by writing a '1' to the ENABLE bit in the Control A register (TCBn.CTRLA).
The counter will start counting clock ticks according to the prescaler setting in the Clock Select bit
field (CLKSEL in TCBn.CTRLA).
•
The counter value can be read from the Count register (TCBn.CNT). The peripheral will generate
an interrupt when the CNT value reaches TOP.
21.3.3
Operation
21.3.3.1 Modes
The timer can be configured to run in one of the eight different modes listed below. The event pulse
needs to be longer than one system clock cycle in order to ensure edge detection.
Periodic Interrupt Mode
In the Periodic Interrupt mode, the counter counts to the capture value and restarts from zero. An
interrupt is generated when the counter is equal to TOP. If TOP is updated to a value lower than count,
the counter will continue until MAX and wrap-around without generating an interrupt.
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type B (TCB)
Figure 21-2. Periodic Interrupt Mode
TOP changed to a value
lower than CNT
Counter wraps around
MAX
"Interrupt"
TOP
CNT
BOTTOM
Time-out Check Mode
In this mode, the counter counts to MAX and wraps-around. On the first edge the counter is restarted and
on the second edge, the counter is stopped. If the count register (TCBn.CNT) reaches TOP before the
second edge, an interrupt will be generated. In Freeze state, the counter will restart on a new edge.
Reading count (TCBn.CNT) or compare/capture (TCBn.CCMP) register, or writing run bit (RUN in
TCBn.STATUS) in Freeze state will have no effect.
Figure 21-3. Time-out Check Mode
Event Input
TOP changed to a value
lower than CNT
Edge detector
Counter wraps
around
MAX
“ Inter rupt”
CNT
TOP
BOTTOM
Input Capture on Event Mode
The counter will count from BOTTOM to MAX continuously. When an event is detected the counter value
will be transferred to the Compare/Capture register (TCBn.CCMP) and interrupt is generated. The module
has an edge detector that can be configured to trigger count capture on either rising or falling edges.
The figure below shows the input capture unit configured to capture on falling edge on the event input
signal. The interrupt flag is automatically cleared after the high byte of the Capture register has been
read.
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Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type B (TCB)
Figure 21-4. Input Capture on Event
" Interrupt"
Event Input
Edge detector
MAX
CNT
BOTTOM
Co py CN T to CCMP
an d in ter rup t
W rap aro un d
Co py CN T to CCMP
an d in ter rup t
It is recommended to write zero to the TCBn.CNT register when entering this mode from any other mode.
Input Capture Frequency Measurement Mode
In this mode, the TCB captures the counter value and restarts on either a positive or negative edge of the
event input signal.
The interrupt flag is automatically cleared after the high byte of the Compare/Capture register
(TCBn.CCMP) has been read, and an interrupt request is generated.
The figure below illustrates this mode when configured to act on rising edge.
Figure 21-5. Input Capture Frequency Measurement
" Interrupt "
Event Input
Edge detector
MAX
CNT
BOTTOM
Copy CNT to CCMP,
interrupt and restart
© 2018 Microchip Technology Inc.
Copy CNT to CCMP,
interrupt and restart
Datasheet Preliminary
Copy CNT to CCMP,
interrupt and restart
40001976A-page 242
ATtiny406
16-bit Timer/Counter Type B (TCB)
Input Capture Pulse-Width Measurement Mode
The input capture pulse-width measurement will restart the counter on a positive edge and capture on the
next falling edge before an interrupt request is generated. The interrupt flag is automatically cleared when
the high byte of the capture register is read. The timer will automatically switch between rising and falling
edge detection, but a minimum edge separation of two clock cycles is required for correct behavior.
Figure 21-6. Input Capture Pulse-Width Measurement
" Interrupt "
Event Input
Edge detector
MAX
CNT
BOTTOM
Re sta rt
co unter
Co py CN T to CCMP
an d in ter rup t
Re sta rt
co unter
Co py CN T to CCMP
an d g ive inte rru pt
Re sta rt
co unter
Input Capture Frequency and Pulse-Width Measurement Mode
In this mode the timer will start counting when a positive edge is detected on the even input signal. On
the following falling edge, the count value is captured. The counter stops when the second rising edge of
the event input signal is detected and this will set the interrupt flag.
Reading the capture will clear the interrupt flag. When the capture register is read or the interrupt flag is
cleared the TC is ready for a new capture sequence. The counter register should, therefore, be read
before the capture register as this is reset to zero at the next positive edge.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 243
ATtiny406
16-bit Timer/Counter Type B (TCB)
Figure 21-7. Input Capture Frequency and Pulse-Width Measurement
Ignore till
Capture is read
Trigger next
capture sequence
Event Input
Edge detector
MAX
" Interrupt"
CNT
BOTTOM
Start
counter
Copy CNT to
CCMP
Stop counter and
interrupt
CPU reads the
CCMP register
Single-Shot Mode
This mode can be used to generate a pulse with a duration that is defined by the Compare register
(TCBn.CCMP), every time a rising or falling edge is observed on a connected event channel.
When the counter is stopped, the output pin is driven to low. If an event is detected on the connected
event channel, the timer will reset and start counting from zero to TOP while driving its output high. The
RUN bit in the STATUS register can be read to see if the counter is counting or not. When the counter
register reaches the CCMP register value, the counter will stop and the output pin will go low for at least
one prescaler cycle. If a new event arrives during this time, that event will be ignored. The following figure
shows an example waveform. There is a two clock cycle delay from when the event is received until the
output is set high. If the ASYNC bit in TCBn.CTRLB is written to '1', an asynchronous edge detector is
used for input events to give immediate action. When the EDGE bit of the TCBn.EVCTRL register is
written to '1', any edge can trigger the start of the counter. If the EDGE bit is '0', only positive edges will
trigger the start.
The counter will start as soon as the module is enabled, even without triggering event. This is prevented
by writing TOP to the counter register.
Similar behavior is seen if the EDGE bit in the TCBn.EVCTRL register is '1' while the module is enabled.
Writing TOP to the Counter register prevents this as well.
It is not recommended to change configuration while the module is enabled.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 244
ATtiny406
16-bit Timer/Counter Type B (TCB)
Figure 21-8. Single-Shot Mode
Ignored
Ignored
Edge detector
TOP
CNT
" Interrupt"
BOTTOM
Output
Counter reaches
TOP value
Event starts
counter
Event starts
counter
Counter reaches
TOP value
If the ASYNC bit in TCBn.CTRLB is '0', the event pulse needs to be longer than one system clock cycle in
order to ensure edge detection.
8-Bit PWM Mode
This timer can be configured to run in 8-bit PWM mode where each of the register pairs in the 16-bit
Compare/Capture register (TCBn.CCMPH and TCBn.CCMPL) are used as individual compare registers.
The counter will continuously count from zero to CCMPL and the output will be set at BOTTOM and
cleared when the counter reaches CCMPH.
When this peripheral is enabled and in PWM mode, changing the value of the Compare/Capture register
will change the output, but the transition may output invalid values. It is hence recommended to:
1. Disable the peripheral.
2. Write Compare/Capture register to {CCMPH, CCMPL}.
3. Write 0x0000 to count register.
4. Re-enable the module.
CCMPH is the number of cycles for which the output will be driven high, CCMPL+1 is the period of the
output pulse.
Output of the module for different capture register values are explained below.
•
CCMPL = 0
•
CCMPL = 0xFF
•
CCMPH = 0
•
•
Output = 0
Output = 0
0 < CCMPH ≤ 0xFF
Output = 1 for CCMPH cycles, low for the rest of the period
For 0 < CCMPL < 0xFF
•
CCMPH = 0
Output = 0
•
If 0 < CCMPH ≤ CCMPL
•
CCMPH = CCMPL + 1
© 2018 Microchip Technology Inc.
Output = 1 for CCMPH cycles, low for the rest of the period
Output = 1
Datasheet Preliminary
40001976A-page 245
ATtiny406
16-bit Timer/Counter Type B (TCB)
Figure 21-9. 8-Bit PWM Mode
" Interrupt "
CCMPL
CNT
CCMPH
BOTTOM
Output
(CNT == CCMPL) and
output goes high
(CNT == CCMPH) and
output goes low
21.3.3.2 Output
If ASYNC in TCBn.CTRLB is written to '0' ('1'), the output pin is driven synchronously (asynchronously) to
the TCB clock. The bits CCMPINIT, CCMPEN, and CNTMODE in TCBn.CTRLB control how the
synchronous output is driven. The different configurations and their impact on the output are listed in the
table below.
Table 21-3. Synchronous Output
CNTMODE
Output, CTRLB=’0’,
CCMPEN=1
Output, CTRLB=’1’,
CCMPEN=1
Single-Shot mode
Output high when the counter
starts and output low when
counter stops
Output high when event arrives
and output low when the counter
stops
8-bit PWM mode
PWM mode output
PWM mode output
Modes except single shot and
PWM
Bit CCMPINIT in TCBn.CTRLB
Bit CCMPINIT in TCBn.CTRLB
21.3.3.3 Noise Canceler
The noise canceler improves noise immunity by using a simple digital filter scheme. When the noise filter
is enabled, the peripheral monitors the event channel and keeps a record of the last four observed
samples. If four consecutive samples are equal, the input is considered to be stable and the signal is fed
to the edge detector.
When enabled, the noise canceler introduces an additional delay of four system clock cycles between a
change applied to the input and the update of the input compare register.
The noise canceler uses the system clock and is, therefore, not affected by the prescaler.
21.3.3.4 Synchronized with TCAn
TCB can be configured to use the clock (CLK_TCA) of the 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 exect same clocks sources as selected in TCA.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 246
ATtiny406
16-bit Timer/Counter Type B (TCB)
When the Synchronize Update bit (SYNCUPD) in the Control A register (TCBn.CTRLA) is written to '1',
the TCB counter will restart when the TCA counter restarts.
Related Links
Block Diagram
21.3.4
Events
The TCB is an event generator. Any condition that causes the CAPT flag in TCBn.INTFLAGS to be set,
will also generate a one-cycle strobe on the event channel output.
The peripheral accepts one event input. If the Capture Event Input Enable bit (CAPTEI) in the Event
Control register (TCBn.EVCTRL) is written to '1', incoming events will result in an event action as defined
by the Event Edge bit (EDGE) in TCBn.EVCTRL. The Single-Shot mode event is edge triggered and will
capture changes on the event input shorter than one system clock cycle. In all other modes, the event
line must be held for at least one system clock cycle to ensure detection of an incoming event.
Related Links
EVCTRL
Event System (EVSYS)
21.3.5
Interrupts
Table 21-4. Available Interrupt Vectors and Sources
Offset Name Vector Description Conditions
0x00
CAPT TCB interrupt
Depending on operating mode. See description of CAPT in
TCB.INTFLAG.
When an interrupt condition occurs, the corresponding interrupt flag is set in the Interrupt Flags register of
the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the interrupt
flag is set. The interrupt request remains active until the interrupt flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear interrupt flags.
Related Links
CPU Interrupt Controller (CPUINT)
INTFLAGS
21.3.6
Sleep Mode Operation
TCB will halt operation in the Power-Down Sleep mode. Standby sleep operation is dependent on the
Run in Standby bit (RUNSTDBY) in the Control A register (TCB.CTRLA).
21.3.7
Synchronization
Not applicable.
21.3.8
Configuration Change Protection
Not applicable.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 247
ATtiny406
16-bit Timer/Counter Type B (TCB)
21.4
Register Summary - TCB
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
RUNSTDBY
0x01
CTRLB
7:0
ASYNC
FILTER
SYNCUPD
CCMPINIT
CCMPEN
CLKSEL[1:0]
ENABLE
CNTMODE[2:0]
0x02
...
Reserved
0x03
0x04
EVCTRL
7:0
0x05
INTCTRL
7:0
CAPT
0x06
INTFLAGS
7:0
CAPT
0x07
STATUS
7:0
RUN
0x08
DBGCTRL
7:0
0x09
TEMP
7:0
TEMP[7:0]
0x0A
CNT
7:0
CNT[7:0]
0x0C
21.5
CCMP
EDGE
CAPTEI
DBGRUN
15:8
CNT[15:8]
7:0
CCMP[7:0]
15:8
CCMP[15:8]
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 248
ATtiny406
16-bit Timer/Counter Type B (TCB)
21.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
Access
Reset
CTRLA
0x00
0x00
-
6
5
4
3
2
1
0
RUNSTDBY
SYNCUPD
CLKSEL[1:0]
ENABLE
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 6 – RUNSTDBY Run Standby
Writing a '1' to this bit will enable the peripheral to run in Standby Sleep mode. Not applicable when
CLKSEL is set to 0x2 (CLK_TCA).
Bit 4 – SYNCUPD Synchronize Update
When this bit is written to '1', the TCB will restart whenever the TCA0 counter is restarted.
Bits 2:1 – CLKSEL[1:0] Clock Select
Writing these bits selects the clock source for this peripheral.
Value
0x0
0x1
0x2
0x3
Description
CLK_PER
CLK_PER / 2
Use CLK_TCA from TCA0
Reserved
Bit 0 – ENABLE Enable
Writing this bit to '1' enables the Timer/Counter type B peripheral.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type B (TCB)
21.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
7
Access
Reset
CTRLB
0x01
0x00
-
6
5
4
ASYNC
CCMPINIT
CCMPEN
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
CNTMODE[2:0]
Bit 6 – ASYNC Asynchronous Enable
Writing this bit to '1' will allow asynchronous updates of the TCB output signal in Single-Shot mode.
Value
0
1
Description
The output will go HIGH when the counter actually starts
The output will go HIGH when an event arrives
Bit 5 – CCMPINIT Compare/Capture Pin Initial Value
This bit is used to set the initial output value of the pin when a pin output is used.
Value
0
1
Description
Initial pin state is LOW
Initial pin state is HIGH
Bit 4 – CCMPEN Compare/Capture Output Enable
This bit is used to set the output value of the Compare/Capture Output.
Value
0
1
Description
Compare/Capture Output is zero
Compare/Capture Output has a valid value
Bits 2:0 – CNTMODE[2:0] Timer Mode
Writing these bits selects the Timer mode.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Description
Periodic Interrupt mode
Time-out Check mode
Input Capture on Event mode
Input Capture Frequency Measurement mode
Input Capture Pulse-Width Measurement mode
Input Capture Frequency and Pulse-Width Measurement mode
Single-Shot mode
8-Bit PWM mode
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 250
ATtiny406
16-bit Timer/Counter Type B (TCB)
21.5.3
Event Control
Name:
Offset:
Reset:
Property:
Bit
EVCTRL
0x04
0x00
-
7
Access
6
5
4
3
2
1
0
FILTER
EDGE
CAPTEI
R/W
R/W
R/W
0
0
0
Reset
Bit 6 – FILTER Input Capture Noise Cancellation Filter
Writing this bit to '1' enables the input capture noise cancellation unit.
Bit 4 – EDGE Event Edge
This bit is used to select the event edge. The effect of this bit is dependent on the selected Count Mode
(CNTMODE) in TCBn.CTRLB. "-" means that an event or edge has no effect in this mode.
Count Mode
EDGE Positive Edge
Negative Edge
Periodic Interrupt mode
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
Input Capture Pulse-Width
Measurement mode
0
Clear and restart counter
Input Capture, interrupt
1
Input Capture, interrupt
Clear and restart counter
Input Capture Frequency and
Pulse Width Measurement mode
0
On 1st Positive: Clear and restart counter
Timeout Check mode
Input Capture on Event mode
Input Capture Frequency
Measurement mode
On following Negative: Input Capture
2nd Positive: Stop counter, interrupt
1
On 1st Negative: Clear and restart counter
On following Positive: Input Capture
2nd Negative: Stop counter, interrupt
Single-Shot mode
© 2018 Microchip Technology Inc.
0
Start counter
Datasheet Preliminary
-
40001976A-page 251
ATtiny406
16-bit Timer/Counter Type B (TCB)
Count Mode
8-Bit PWM mode
EDGE Positive Edge
Negative Edge
1
-
Start counter
0
-
-
1
-
-
Bit 0 – CAPTEI Capture Event Input Enable
Writing this bit to '1' enables the input capture event.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 252
ATtiny406
16-bit Timer/Counter Type B (TCB)
21.5.4
Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x05
0x00
-
6
5
4
3
2
1
0
CAPT
Access
R/W
Reset
0
Bit 0 – CAPT Capture Interrupt Enable
Writing this bit to '1' enables the Capture interrupt.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type B (TCB)
21.5.5
Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
INTFLAGS
0x06
0x00
-
7
6
5
4
3
2
1
0
CAPT
Access
R/W
Reset
0
Bit 0 – CAPT Interrupt Flag
This bit is set when an interrupt occurs. The interrupt conditions are dependent on the Counter Mode
(CNTMODE) in TCBn.CTRLB.
This bit is cleared by writing a '1' to it or when the Capture register is read in Capture mode.
Counter Mode
Interrupt Set Condition
Periodic Interrupt mode
Set when the counter reaches TOP
Timeout Check mode
Set when the counter reaches TOP
Input Capture on Event mode
Set when an event occurs and the Capture register is loaded, flag
clears when capture is read
Input Capture Frequency
Measurement mode
Set on edge when the Capture register is loaded and count
initialized, flag clears when capture is read
Input Capture Pulse-Width
Measurement mode
Set on a edge when the Capture register is loaded, previous edge
initialized the count, flag clears when capture is read
Input Capture Frequency and Pulse- Set on second (positive or negative) edge when the counter is
Width Measurement mode
stopped, flag clears when capture is read
Single-Shot mode
Set when counter reaches TOP
8-Bit PWM mode
Set when the counter reaches CCH
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 254
ATtiny406
16-bit Timer/Counter Type B (TCB)
21.5.6
Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x07
0x00
-
6
5
4
3
2
1
0
RUN
Access
R
Reset
0
Bit 0 – RUN Run
When the counter is running, this bit is set to '1'. When the counter is stopped, this bit is cleared to '0'.
The bit is read-only and cannot be set by UPDI.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type B (TCB)
21.5.7
Debug Control
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x08
0x00
-
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN Debug Run
Value
0
1
Description
The peripheral is halted in Break Debug mode and ignores events.
The peripheral will continue to run in Break Debug mode when the CPU is halted.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type B (TCB)
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. See Accessing 16-Bit Registers. There is one common
Temporary register for all the 16-bit registers of this peripheral.
Bit
7
6
5
4
3
2
1
0
TEMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – TEMP[7:0] Temporary Value
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 257
ATtiny406
16-bit Timer/Counter Type B (TCB)
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. For more details on reading and writing 16-bit registers, refer to Accessing 16-Bit Registers.
CPU and UPDI write access has priority over internal updates of the register.
Bit
15
14
13
12
11
10
9
8
R/W
R/W
R/W
R/W
Reset
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
CNT[15:8]
Access
CNT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:8 – 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
16-bit Timer/Counter Type B (TCB)
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. For more details on reading and writing 16-bit registers, refer to Accessing 16-Bit
Registers.
This register has different functions depending on the mode of operation:
•
For capture operation, these registers contain the captured value of the counter at the time the
capture occurs
•
In periodic interrupt/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
15
14
13
12
11
10
9
8
CCMP[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
CCMP[7:0]
Access
Reset
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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.
Real-Time Counter (RTC)
22.1
Features
•
•
•
•
•
•
•
•
22.2
16-Bit Resolution
Selectable Clock Source:
– External clock
– 32 kHz internal ULP oscillator (OSCULP32K)
– OSCULP32K divided by 32
Programmable 15-Bit Clock Prescaling
One Compare Register
One Period Register
Clear Timer On Period Overflow
Optional Interrupt/Event on Overflow and Compare Match
Periodic Interrupt and Event
Overview
The RTC peripheral offers two timing functions: the Real-Time Counter (RTC) and a Periodic Interrupt
Timer (PIT).
The PIT functionality can be enabled 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 RTC can 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 can give a compare interrupt and/or event when the counter equals the compare
register value, and an overflow interrupt and/or event when it equals the period register value.
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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
The PIT uses the same clock source (CLK_RTC) as the RTC function.
Related Links
RTC Functional Description
PIT Functional Description
22.2.1
Block Diagram
Figure 22-1. Block Diagram
Pxn
32KHz ULP int. Osc.
DIV32
RTC
CLK_RTC
22.2.2
Signal Description
Not applicable.
22.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 22-1. RTC System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Clocks
I/O Lines and Connections
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
Debug Operation
Interrupts
Events
22.2.3.1 Clocks
System clock (CLK_PER) is required to be at least four times faster than RTC clock (CLK_RTC) for
reading counter value, and this is regardless of the RTC_PRESC setting.
Related Links
Clock Controller (CLKCTRL)
22.2.3.2 I/O Lines and Connections
An external clock can be used.
Related Links
Clock Controller (CLKCTRL)
Electrical Characteristics
22.2.3.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
Related Links
CPU Interrupt Controller (CPUINT)
SREG
Interrupts
22.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
Event System (EVSYS)
22.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in Debugging
mode will halt normal operation of the peripheral.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
Related Links
Unified Program and Debug Interface (UPDI)
22.3
RTC Functional Description
The RTC peripheral offers two timing functions: the Real-Time Counter (RTC) and a Periodic Interrupt
Timer (PIT). This subsection describes the RTC.
Related Links
PIT Functional Description
22.3.1
Initialization
To operate the RTC, the source clock for the RTC counter must be configured before enabling the RTC
peripheral, and the desired actions (interrupt requests, output Events).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
Related Links
Clock Controller (CLKCTRL)
PIT Functional Description
22.3.1.1 Configure the Clock CLK_RTC
To configure CLK_RTC, follow these steps:
1.
2.
Configure the desired oscillator to operate as required, in the Clock Controller peripheral
(CLKCTRL).
Write the Clock Select bits (CLKSEL) in the Clock Selection register (RTC.CLKSEL) accordingly.
The CLK_RTC clock configuration is used by both RTC and PIT functionality.
22.3.1.2 Configure RTC
To operate the RTC, follow these steps:
1.
2.
3.
4.
Configure the RTC-internal prescaler by writing the PRESCALER bit field in the Control A register
(RTC.CTRLA).
Set the Compare value in the Compare register (RTC.CMP), and/or the Overflow value in the Top
register (RTC.PER).
Enable the desired Interrupts by writing to the respective Interrupt Enable bits (CMP, OVF) in the
Interrupt Control register (RTC.INTCTRL).
Enable the RTC by writing a '1' to the RTC Enable bit (RTCEN) in the Control A register
(RTC.CTRLA).
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.
22.3.2
Operation - RTC
22.3.2.1 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.
22.4
PIT Functional Description
The RTC peripheral offers two timing functions: the Real-Time Counter (RTC) and a Periodic Interrupt
Timer (PIT). This subsection describes the PIT.
Related Links
RTC Functional Description
22.4.1
Initialization
To operate the PIT, follow these steps:
1. Configure the RTC clock CLK_RTC as described in Configure the Clock CLK_RTC.
2. Select the period for the interrupt by writing the PERIOD bit field in the PIT Control A register
(RTC.PITCTRLA).
3. Enable the interrupt by writing a '1' to the Periodic Interrupt bit (PI) in the PIT Interrupt Control
register (RTC.PITINTCTRL).
4. Enable the PIT by writing a '1' to the PIT Enable bit (PITEN) in the PIT Control A register
(RTC.PITCTRLA).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 263
ATtiny406
Real-Time Counter (RTC)
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 - PIT
22.4.2.1 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.
22.4.2.2 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 output is depending on whether the RTC function is
already enabled or not:
•
When RTCEN in RTC.CTRLA is zero and PITEN in RTC.PITCTRLA is written to ‘1’, the prescaler
will start operating at the next edge of CLK_RTC, counting from zero. The PIT interrupt output will
then toggle from ‘0’ to ‘1’ after ½ period.
•
When the RTC function is already enabled (RTCEN is ‘1’), the prescaler is already running, too.
The timing of the first interrupt output from the PIT is depending at which exact counter value the
prescaler is enabled. Since the application can’t access that value, the first interrupt output may
occur any time between writing PITEN to ‘1’ and after a full PIT period.
Continuous Operation
After the first interrupt output, the PIT will continue toggling every ½ PIT period, resulting in a full PIT
period signal.
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.
When both RTC and PIT functions are disabled, the prescaler is off. The delay between
writing PITEN to ‘1’ and the first interrupt output is always ½ PIT period, with an
uncertainty of one leading CLK_RTC cycle.
When the RTC and hence the prescaler are already enabled with any
PRESCALER=DIVn, 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 264
ATtiny406
Real-Time Counter (RTC)
Figure 22-2. Timing Between PIT Enable and First Interrupt
Enabling PIT with RTC/Prescaler Disabled
CLK_RTC
..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
prescaler
counter
value (LSb)
prescaler bit 3
(CYC16)
Continuous Operation
PITENABLE=0
1/2 PIT period
(8 CLK_RTC)
PIT output
write PITENABLE=1
first PIT output
Enabling PIT with RTC/Prescaler Enabled
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
22.5
Events
The RTC, when enabled, will generate the following output events:
•
•
Overflow (OVF): Generated when the counter has reached its top value and wrapped to zero. 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
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 265
ATtiny406
Real-Time Counter (RTC)
•
•
•
•
•
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).
Related Links
Event System (EVSYS)
22.6
Interrupts
Table 22-2. Available Interrupt Vectors and Sources
Offset Name Vector Description
0x00
0x02
RTC
PIT
Real-time counter
overflow and compare
match interrupt
Periodic Interrupt Timer
interrupt
Conditions
•
•
Overflow (OVF): The counter has reached its top
value and wrapped to zero.
Compare (CMP): Match between the counter value
and the compare register.
A time period has passed, as configured in
RTC_PITCTRLA.PERIOD.
When an interrupt condition occurs, the corresponding interrupt flag is set in the Interrupt Flags register of
the peripheral (peripheral.INTFLAGS).
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the interrupt
flag is set. The interrupt request remains active until the interrupt flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear interrupt flags.
Related Links
CPU Interrupt Controller (CPUINT)
INTCTRL
PITINTCTRL
22.7
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.
Related Links
CTRLA
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.8
Synchronization
Both the RTC and the PIT are asynchronous, operating from a different clock source (CLK_RTC)
independently of the main clock (CLK_PER). For Control and Count register updates, it will take a
number of RTC clock and/or peripheral clock cycles before an updated register value is available in a
register or until a configuration change has an effect on the RTC or PIT, respectively. This synchronization
time is described for each register in the Register Description.
For some RTC registers, a Synchronization Busy flag is available (CMPBUSY, PERBUSY, CNTBUSY,
CTRLABUSY) in the STATUS register (RTC.STATUS).
For the RTC.PITCTRLA register, a Synchronization Busy flag (SYNCBUSY) is available in the PIT
STATUS register (RTC.PITSTATUS).
Check for busy should be performed before writing to the mentioned registers.
Related Links
Clock Controller (CLKCTRL)
22.9
Configuration Change Protection
Not applicable.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 267
ATtiny406
Real-Time Counter (RTC)
22.10
Register Summary - RTC
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
STATUS
7:0
0x02
INTCTRL
7:0
0x03
INTFLAGS
7:0
0x04
TEMP
7:0
0x05
DBGCTRL
7:0
0x06
Reserved
0x07
CLKSEL
0x08
0x0A
0x0C
CNT
PER
CMP
RUNSTDBY
PRESCALER[3:0]
RTCEN
CMPBUSY
PERBUSY
CNTBUSY
CTRLABUSY
CMP
OVF
CMP
OVF
TEMP[7:0]
DBGRUN
7:0
CLKSEL[1:0]
7:0
CNT[7:0]
15:8
CNT[15:8]
7:0
PER[7:0]
15:8
PER[15:8]
7:0
CMP[7:0]
15:8
CMP[15:8]
0x0E
...
Reserved
0x0F
0x10
PITCTRLA
7:0
0x11
PITSTATUS
7:0
CTRLBUSY
0x12
PITINTCTRL
7:0
PI
0x13
PITINTFLAGS
7:0
PI
0x14
Reserved
0x15
PITDBGCTRL
7:0
DBGRUN
22.11
PERIOD[3:0]
PITEN
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 268
ATtiny406
Real-Time Counter (RTC)
22.11.1 Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
-
6
RUNSTDBY
Access
Reset
5
4
3
PRESCALER[3:0]
2
1
0
RTCEN
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit 7 – RUNSTDBY Run in Standby
Value
0
1
Description
RTC disabled in Standby Sleep mode
RTC enabled in Standby Sleep mode
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
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC
0xD
0xE
0xF
Name
DIV1
DIV2
DIV4
DIV8
DIV16
DIV32
DIV64
DIV128
DIV256
DIV512
DIV1024
DIV2048
DIV4096
DIV8192
DIV16384
DIV32768
Description
RTC clock/1 (no prescaling)
RTC clock/2
RTC clock/4
RTC clock/8
RTC clock/16
RTC clock/32
RTC clock/64
RTC clock/128
RTC clock/256
RTC clock/512
RTC clock/1024
RTC clock/2048
RTC clock/4096
RTC clock/8192
RTC clock/16384
RTC clock/32768
Bit 0 – RTCEN RTC Enable
Value
0
1
Description
RTC disabled
RTC enabled
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 269
ATtiny406
Real-Time Counter (RTC)
22.11.2 Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x01
0x00
-
6
5
4
3
2
1
0
CMPBUSY
PERBUSY
CNTBUSY
CTRLABUSY
Access
R
R
R
R
Reset
0
0
0
0
Bit 3 – CMPBUSY Compare Synchronization Busy
This bit is indicating whether the RTC is busy synchronizing the Compare register (RTC.CMP) in RTC
clock domain.
Bit 2 – PERBUSY Period Synchronization Busy
This bit is indicating whether the RTC is busy synchronizing the Period register (RTC.PER) in RTC clock
domain.
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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.11.3 Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x02
0x00
-
6
5
4
3
Access
Reset
2
1
0
CMP
OVF
R/W
R/W
0
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).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.11.4 Interrupt Flag
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x03
0x00
-
6
5
4
3
2
1
0
CMP
OVF
Access
R
R
Reset
0
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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.11.5 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. See Accessing 16-Bit Registers. There is one common
Temporary register for all the 16-bit registers of this peripheral.
Bit
7
6
5
4
3
2
1
0
TEMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – TEMP[7:0] Temporary
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.11.6 Debug Control
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x05
0x00
-
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN Debug Run
Value
0
1
Description
The peripheral is halted in Break Debug mode and ignores events.
The peripheral will continue to run in Break Debug mode when the CPU is halted.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.11.7 Clock Selection
Name:
Offset:
Reset:
Property:
Bit
7
CLKSEL
0x07
0x00
-
6
5
4
3
2
1
0
CLKSEL[1:0]
Access
Reset
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).
Value
0x0
0x1
0x2
0x3
Name
INT32K
INT1K
EXTCLK
© 2018 Microchip Technology Inc.
Description
32.768 kHz from OSCULP32K
1.024 kHz from OSCULP32K
Reserved
External clock from EXTCLK pin
Datasheet Preliminary
40001976A-page 275
ATtiny406
Real-Time Counter (RTC)
22.11.8 Count
Name:
Offset:
Reset:
Property:
CNT
0x08
0x00
-
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.
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
CNT[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
CNT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:8 – 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.11.9 Period
Name:
Offset:
Reset:
Property:
PER
0x0A
0xFF
-
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.
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
PER[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
1
1
1
1
1
1
1
1
Bit
7
6
5
4
3
2
1
0
PER[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
1
1
1
1
1
1
1
Bits 15:8 – PER[15:8] Period High Byte
These bits hold the MSB of the 16-bit Period register.
Bits 7:0 – PER[7:0] Period Low Byte
These bits hold the LSB of the 16-bit Period register.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.11.10 Compare
Name:
Offset:
Reset:
Property:
CMP
0x0C
0x00
-
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.
Bit
15
14
13
12
11
10
9
8
CMP[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
CMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.11.11 Periodic Interrupt Timer Control A
Name:
Offset:
Reset:
Property:
Bit
7
PITCTRLA
0x10
0x00
-
6
5
4
3
2
PERIOD[3:0]
Access
Reset
1
0
PITEN
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bits 6:3 – PERIOD[3:0] Period
Writing this bit field selects the number of RTC clock cycles between each interrupt.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC
0xD
0xE
0xF
Name
OFF
CYC4
CYC8
CYC16
CYC32
CYC64
CYC128
CYC256
CYC512
CYC1024
CYC2048
CYC4096
CYC8192
CYC16384
CYC32768
-
Description
No interrupt
4 cycles
8 cycles
16 cycles
32 cycles
64 cycles
128 cycles
256 cycles
512 cycles
1024 cycles
2048 cycles
4096 cycles
8192 cycles
16384 cycles
32768 cycles
Reserved
Bit 0 – PITEN Periodic Interrupt Timer Enable
Writing a '1' to this bit enables the Periodic Interrupt Timer.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Real-Time Counter (RTC)
22.11.12 Periodic Interrupt Timer Status
Name:
Offset:
Reset:
Property:
Bit
7
PITSTATUS
0x11
0x00
-
6
5
4
3
2
1
0
CTRLBUSY
Access
R
Reset
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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ATtiny406
Real-Time Counter (RTC)
22.11.13 PIT Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
PITINTCTRL
0x12
0x00
-
6
5
4
3
2
1
0
PI
Access
R/W
Reset
0
Bit 0 – PI Periodic interrupt
Value
0
1
Description
The periodic interrupt is disabled
The periodic interrupt is enabled
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Real-Time Counter (RTC)
22.11.14 PIT Interrupt Flag
Name:
Offset:
Reset:
Property:
Bit
7
PITINTFLAGS
0x13
0x00
-
6
5
4
3
2
1
0
PI
Access
R
Reset
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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ATtiny406
Real-Time Counter (RTC)
22.11.15 Periodic Interrupt Timer Debug Control
Name:
Offset:
Reset:
Property:
Bit
7
PITDBGCTRL
0x15
0x00
-
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
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
0
1
Description
The peripheral is halted in Break Debug mode and ignores events.
The peripheral will continue to run in Break Debug mode when the CPU is halted.
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Universal Synchronous and Asynchronous Recei...
23.
Universal Synchronous and Asynchronous Receiver and Transmitter
(USART)
23.1
Features
•
•
•
•
•
•
•
•
•
•
•
•
23.2
Full-Duplex or One-Wire Half-Duplex Operation
Asynchronous or Synchronous Operation:
– Synchronous clock rates up to 1/2 of the device clock frequency
– Asynchronous clock rates up to 1/8 of the device clock frequency
Supports Serial Frames with:
– 5, 6, 7, 8, or 9 data bits
– Optionally even and odd parity bits
– 1 or 2 Stop bits
Fractional Baud Rate Generator:
– Can generate desired baud rate from any system clock frequency
– No need for external oscillator with certain frequencies
Built-In Error Detection and Correction Schemes:
– Odd or even parity generation and parity check
– Data overrun and framing error detection
– Noise filtering includes false Start bit detection and digital low-pass filter
Separate Interrupts for:
– Transmit complete
– Transmit Data register empty
– Receive complete
Multiprocessor Communication mode:
– Addressing scheme to address specific devices on a multi-device bus
– Enable unaddressed devices to automatically ignore all frames
Start Frame Detection in UART mode
Master SPI mode:
– Double buffered operation
– Configurable data order
– Operation up to 1/2 of the peripheral clock frequency
IRCOM Module for IrDA Compliant Pulse Modulation/Demodulation
LIN Slave Support:
– Auto-baud and Break character detection
RS-485 Support
Overview
The Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) peripheral is a
fast and flexible serial communication module. The USART supports full duplex communication,
asynchronous and synchronous operation and one-wire configurations. The USART can be set in SPI
Master mode and used for SPI communication.
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The USART uses three communication lines for data transfer:
•
•
•
RxD for receiving
TxD for transmitting
XCK for the transmission clock in synchronous operation
Communication is frame based, and the frame format can be customized to support a wide range of
standards. One frame can be directly followed by a new frame, or the communication line can return to
the idle (high) state. A serial frame consists of:
•
1 Start bit
•
5, 6, 7, 8, or 9 data bits (MSB or LSB first)
•
Parity bit: Even, odd, or none
•
1 or 2 Stop bits
The USART is buffered in both directions, enabling continued data transmission without any delay
between frames. Separate interrupts for receive and transmit completion allow fully interrupt driven
communication. Frame error and buffer overflow are detected in hardware and indicated with separate
status flags. Even or odd parity generation and parity check can also be enabled.
The main functional blocks are the clock generator, the transmitter, and the receiver:
•
•
•
The clock generator includes a fractional Baud Rate Generator that is able to generate a wide
range of USART baud rates from any system clock frequencies. This removes the need to use an
oscillator with a specific frequency to achieve a required baud rate. It also supports external clock
input in synchronous slave operation.
The transmitter consists of a single write buffer (DATA), a shift register and a parity generator. The
write buffer allows continuous data transmission without any delay between frames.
The receiver consists of a two-level receive buffer (DATA) and a Shift register. Data and clock
recovery units ensure robust synchronization and noise filtering during asynchronous data
reception. It includes frame error, buffer overflow, and parity error detection.
When the USART is set in one-wire mode, the transmitter and the receiver share the same RxD I/O pin.
When the USART is set in master SPI mode, all USART-specific logic is disabled, leaving the transmit
and receive buffers, Shift registers, and Baud Rate Generator enabled. Pin control and interrupt
generation are identical in both modes. The registers are used in both modes, but their functionality
differs for some control settings.
An IRCOM module can be enabled for one USART to support IrDA 1.4 physical compliant pulse
modulation and demodulation for baud rates up to 115.2 kbps.
The USART can be linked to the Configurable Custom Logic unit (CCL). When used with the CCL, the
TxD/RxD data can be encoded/decoded before the signal is fed into the USART receiver or after the
signal is output from the transmitter when the USART is connected to CCL LUT outputs.
This device provides one instance of the USART peripheral, USART0.
23.2.1
Signal Description
Signal
Type
Description
RxD
Input/output
Receiving line
TxD
Output
Transmitting line
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Universal Synchronous and Asynchronous Recei...
Signal
Type
Description
XCK
Input/output
Clock for synchronous operation
XDIR
Output
Transmit Enable for RS485
Related Links
I/O Multiplexing and Considerations
23.2.2
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 23-1. USART System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
Debug Operation
Clocks
I/O Lines and Connections
Interrupts
Events
23.2.2.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
Clock Controller (CLKCTRL)
23.2.2.2 I/O Lines and Connections
Using the I/O lines of the peripheral requires configuration of the I/O pins.
Related Links
I/O Pin Configuration (PORT)
I/O Multiplexing and Considerations
23.2.2.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
Related Links
CPU Interrupt Controller (CPUINT)
SREG
Interrupts
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23.2.2.4 Events
The events of this peripheral are connected to the Event System.
Related Links
Event System (EVSYS)
23.2.2.5 Debug Operation
When the CPU is halted in Debug mode, this peripheral will continue normal operation. If the peripheral is
configured to require periodical service by the CPU through interrupts or similar, improper operation or
data loss may result during debugging. This peripheral can be forced to halt operation during debugging.
Related Links
Unified Program and Debug Interface (UPDI)
23.2.2.6 Block Diagram
Figure 23-1. USART Block Diagram
Clock Generator
BAUD
OSC
Fractional Baud Rate
Generator
Sync Logic
Pin
Control
XCK
Transmitter
TXDATA
Parity
Generator
Transmit Shift Register
TX
Control
XDIR
Pin
Control
TxD
Receiver
Clock
Recovery
RX
Control
Receive Shift Register
Data
Recovery
Pin
Control
RXDATA Buffer
Parity
Checker
RxD
RXDATA
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ATtiny406
Universal Synchronous and Asynchronous Recei...
23.3
Functional Description
23.3.1
Initialization
For setting the USART in Full-Duplex mode, the following initialization sequence is recommended:
1.
2.
3.
4.
5.
Set the TxD pin value high, and optionally set the XCK pin low (OUT[n] in PORTx.OUT).
Set the TxD and optionally the XCK pin as an output (DIR[n] in PORTx.DIR).
Set the baud rate (in the USARTn.BAUD register) and frame format.
Set the mode of operation (enables XCK pin output in Synchronous mode).
Enable the transmitter or the receiver, depending on the usage.
For interrupt-driven USART operation, global interrupts should be disabled during the initialization.
Before doing a re-initialization with a changed baud rate or frame format, be sure that there are no
ongoing transmissions while the registers are changed.
For setting the USART in One-Wire mode, the following initialization sequence is recommended:
1.
2.
3.
4.
5.
6.
Set the TxD/RxD pin value high, and optionally set the XCK pin low.
Optionally, write the ODME bit in the USARTn.CTRLB register to '1' for Wired-AND functionality.
Set the TxD/RxD and optionally the XCK pin as an output.
Select the baud rate and frame format.
Select the mode of operation (enables XCK pin output in Synchronous mode).
Enable the transmitter or the receiver, depending on the usage.
For interrupt-driven USART operation, global interrupts should be disabled during the initialization.
Before doing a re-initialization with a changed baud rate or frame format, be sure that there are no
ongoing transmissions while the registers are changed.
23.3.2
Operation
23.3.2.1 Clock Generation
The clock used for baud rate generation and for shifting and sampling data bits is generated internally by
the fractional Baud Rate Generator or externally from the transfer clock (XCK) pin. Five modes of clock
generation are supported; Normal and Double-Speed Asynchronous mode, Master and Slave
Synchronous mode, and Master SPI mode.
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Figure 23-2. Clock Generation Logic Block Diagram
BAUD
RXMODE
BAUD Rate
Generator
fBAUD
/2
/4
/2
txclk
1
DDR_XCK
PORT_INV
XCK
Pin
0
1
CLK_PER
xcki
0
Sync
Register
Edge
Detector
CMODE[0]
0
1
xcko
1
0
DDR_XCK
rxclk
Internal Clock Generation - The Fractional Baud Rate Generator
The Baud Rate Generator is used for internal clock generation for Asynchronous modes, Aynchronous
Master mode, and Master SPI mode operation. The output frequency generated (fBAUD) is determined by
the baud register value (USARTn.BAUD) and the peripheral clock frequency (fCLK_PER). The following
table contains equations for calculating the baud rate (in bits per second) and for calculating the
USARTn.BAUD value for each mode of operation. It also shows the maximum baud rate versus
peripheral clock frequency. For asynchronous operation, the USARTn.BAUD register value is 16 bits. The
10 MSBs (BAUD[15:6]) hold the integer part, while the 6 LSBs (BAUD[5:0]) hold the fractional part. In
Synchronous mode, only the integer part of the BAUD register determine the baud rate.
Table 23-2. Equations for Calculating Baud Rate Register Setting
Operating Mode Conditions
Asynchronous
Synchronous
����� ≤
����� ≤
Baud Rate (Bits Per Seconds) USART.BAUD Register Value
Calculation
����_���
64 × ����_���
����� =
�
� × ����
����_���
����_���
����� =
2
2 × ���� 15: 6
���� =
64 × ����_���
� × �����
���� 15: 6 =
����_���
2 × �����
S is the number of samples per bit. In Asynchronous operating mode (CMODE[0]=0), it could be set as
16 (NORMAL mode) or 8 (CLK2X mode) by RXMODE in USARTn.CTRLB. For Synchronous operating
mode (CMODE[0]=1), S equals 2.
External Clock
External clock (XCK) is used in Synchronous Slave mode operation. The XCK clock input is sampled on
the peripheral clock frequency and the maximum XCK clock frequency (fXCK) is limited by the following:
����<
����_���
4
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For each high and low period, the XCK clock cycles must be sampled twice by the peripheral clock. If the
XCK clock has jitter, or if the high/low period duty cycle is not 50/50, the maximum XCK clock speed must
be reduced accordingly.
Double Speed Operation
Double speed operation allows for higher baud rates under asynchronous operation with lower peripheral
clock frequencies. This operation mode is enabled by writing the RXMODE bit in the Control B register
(USARTn.CTRLB) to CLK2X.
When enabled, the baud rate for a given asynchronous baud rate setting shown in Table 23-2 will be
doubled. In this mode, the receiver will use half the number of samples (reduced from 16 to 8) for data
sampling and clock recovery. This requires a more accurate baud rate setting and peripheral clock. See
Asynchronous Data Reception for more details.
Synchronous Clock Operation
When Synchronous mode is used, the XCK pin controls whether the transmission clock is input (Slave
mode) or output (Saster mode). The corresponding port pin must be set to output for Master mode or to
input for Slave mode (PORTx.DIR[n]). The normal port operation of the XCK pin will be overridden. The
dependency between the clock edges and data sampling or data change is the same. Data input (on
RxD) is sampled at the XCK clock edge which is opposite the edge where data output (TxD) is changed.
Figure 23-3. Synchronous Mode XCK Timing
INVEN = 1
XCK
RxD / TxD
Sample
INVEN = 0
XCK
RxD / TxD
Sample
The I/O pin can be inverted by writing a '1' to the Inverted I/O Enable bit (INVEN) in the Pin n Control
register of the port peripheral (PORTx.PINnCTRL). Using the inverted I/O setting for the corresponding
XCK port pin, the XCK clock edges used for data sampling and data change can be selected. If inverted
I/O is disabled (INVEN=0), data will be changed at the rising XCK clock edge and sampled at the falling
XCK clock edge. If inverted I/O is enabled (INVEN=1), data will be changed at the falling XCK clock edge
and sampled at the rising XCK clock edge.
Master SPI Mode Clock Generation
For Master SPI mode operation, only internal clock generation is supported. This is identical to the
USART Synchronous Master mode, and the baud rate or BAUD setting is calculated using the same
equations (see Table 23-2).
There are four combinations of the SPI clock (SCK) phase and polarity with respect to the serial data, and
these are determined by the Clock Phase bit (UCPHA) in the Control C register (USARTn.CTRLC) and
the Inverted I/O Enable bit (INVEN) in the Pin n Control register of the port peripheral
(PORTx.PINnCTRL). The data transfer timing diagrams are shown in Figure 23-4.
Data bits are shifted out and latched in on opposite edges of the XCK signal, ensuring sufficient time for
data signals to stabilize. The settings are summarized in the table below. Changing the setting of any of
these bits during transmission will corrupt both the receiver and transmitter.
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Table 23-3. Functionality of INVEN in PORTx.PINnCTRL and UCPHA in USARTn.CTRLC
SPI Mode
INVEN
UCPHA
Leading Edge
Trailing Edge
0
0
0
Rising, sample
Falling, setup
1
0
1
Rising, setup
Falling, sample
2
1
0
Falling, sample
Rising, setup
3
1
1
Falling, setup
Rising, sample
The leading edge is the first clock edge of a clock cycle. The trailing edge is the last clock edge of a clock
cycle.
Figure 23-4. UCPHA and INVEN Data Transfer Timing Diagrams
UCPHA=0
UCPHA=1
INVEN=0
INVEN=1
SPI Mode 1
SPI Mode 3
XCK
Data setup (TXD)
Data sample (RXD)
XCK
Data setup (TXD)
Data sample (RXD)
SPI Mode 0
SPI Mode 2
XCK
Data setup (TXD)
Data sample (RXD)
XCK
Data setup (TXD)
Data sample (RXD)
Related Links
CTRLC
23.3.2.2 Frame Formats
Data transfer is frame based, where a serial frame consists of one character of data bits with
synchronization bits (Start and Stop bits) and an optional parity bit for error checking. This does not apply
to master SPI operation (see SPI Frame Formats.) The USART accepts all combinations of the following
as valid frame formats:
•
•
•
•
1 Start bit
5, 6, 7, 8, or 9 Data bits
No, even, or odd Parity bit
1 or 2 Stop bits
Figure 23-5 illustrates the possible combinations of frame formats. Bits inside brackets are optional.
Figure 23-5. Frame Formats
St Start bit, always low.
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Universal Synchronous and Asynchronous Recei...
(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.
Parity
Even or odd parity can be selected for error checking by writing the Parity Mode bits (PMODE) in the
Control C register (USARTn.CTRLC). If even parity is selected, the parity bit is set to '1' if the number of
logical one data bits is odd (making the total number of logical ones even). If odd parity is selected, the
parity bit is set to '1' if the number of logical one data bits is even (making the total number of ones odd).
When enabled, the parity checker calculates the parity of the data bits in incoming frames and compares
the result with the parity bit of the corresponding frame. If a parity error is detected, the parity error flag is
set.
SPI Frame Formats
The serial frame in SPI mode is defined to be one character of eight data bits. The USART in master SPI
mode has two valid frame formats:
•
•
8-bit data, MSb first
8-bit data, LSb first
The data order is selected by writing to the Data Order bit (UDORD) in the Control C register
(USARTn.CTRLC).
After a complete frame is transmitted, a new frame can directly follow it, or the communication line can
return to the idle (high) state.
23.3.2.3 Data Transmission - USART Transmitter
When the transmitter has been enabled, the normal port operation of the TxD pin is overridden by the
USART and given the function as the transmitter's serial output. The direction of the pin n must be
configured as output by writing the Direction register for the corresponding port (PORTx.DIR[n]). If the
USART is configured for one-wire operation, the USART will automatically override the RxD/TxD pin to
output, when the transmitter is enabled.
Related Links
Port Multiplexer (PORTMUX)
I/O Pin Configuration (PORT)
Sending Frames
A data transmission is initiated by loading the Transmit buffer (DATA in USARTn.TXDATA) with the data
to be sent. The data in the transmit buffer is moved to the Shift register when the Shift register is empty
and ready to send a new frame. The Shift register is loaded if it is in Idle state (no ongoing transmission)
or immediately after the last Stop bit of the previous frame is transmitted. When the Shift register is
loaded with data, it will transfer one complete frame.
When the entire frame in the Shift register has been shifted out and there is no new data present in the
transmit buffer, the Transmit Complete Interrupt Flag (TXCIF in USARTn.STATUS) is set and the optional
interrupt is generated.
TXDATA can only be written when the Data Register Empty Flag (DREIF in USARTn.STATUS) is set,
indicating that the register is empty and ready for new data.
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When using frames with fewer than eight bits, the Most Significant bits written to TXDATA are ignored. If
9-bit characters are used, DATA[8] in USARTn.TXDATAH has to be written before DATA[7:0] in
USARTn.TXDATAL.
Disabling the Transmitter
A disabling of the transmitter will not become effective until ongoing and pending transmissions are
completed; i.e., when the Transmit Shift register and Transmit Buffer register do not contain data to be
transmitted. When the transmitter is disabled, it will no longer override the TxDn pin, and the pin direction
is set as input automatically by hardware, even if it was configured as output by the user.
23.3.2.4 Data Reception - USART Receiver
When the receiver is enabled, the RxD pin functions as the receiver's serial input. The direction of the pin
n must be set as an input in the Direction register of the Port (PORTx.DIR[n]=0), which is the default pin
setting.
Receiving Frames
The receiver starts data reception when it detects a valid Start bit. Each bit that follows the Start bit will be
sampled at the baud rate or XCK clock, and shifted into the Receive Shift register until the first Stop bit of
a frame is received. A second Stop bit will be ignored by the receiver. When the first Stop bit is received
and a complete serial frame is present in the Receive Shift register, the contents of the Shift register will
be moved into the receive buffer. The receive complete interrupt flag (RXCIF in USARTn.STATUS) is set,
and the optional interrupt is generated.
The receiver buffer can be read by reading RXDATA, comprising of DATA[7:0] in USARTn.RXDATAL, and
DATA[8] in USARTn.RXDATAH. RXDATA should not be read unless the Receive Complete Interrupt Flag
(RXCIF in USARTn.STATUS) is set. When using frames with fewer than eight bits, the unused Most
Significant bits are read as zero. If 9-bit characters are used, the ninth bit (DATA[8] in
USARTn.RXDATAH) must be read before the low byte (DATA[7.0] in USARTn.RXDATAL).
Receiver Error Flags
The USART receiver has three error flags in the Receiver Data Register High Byte register
(USARTn.RXDATAH):
•
Frame Error (FERR)
•
Buffer Overflow (BUFOVF)
•
Parity Error (PERR)
The error flags are located in the receive FIFO buffer together with their corresponding frame. Due to the
buffering of the error flags, the USARTn.RXDATAH must be read before the USARTn.RXDATAL, since
reading the USARTn.RXDATAL changes the FIFO buffer.
Parity Checker
When enabled, the parity checker calculates the parity of the data bits in incoming frames and compares
the result with the parity bit of the corresponding frame. If a parity error is detected, the Parity Error flag
(PERR in USARTn.RXDATAH) is set.
If USART LIN mode is enabled (by writing RXMODE to '1' in USARTn.CTRLB), 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 PERR in USARTn.RXDATAH.
�0 = ��0 ⊕ ��1 ⊕ ��2 ⊕ ��4
�1 = ¬ ��1 ⊕ ��3 ⊕ ��4 ⊕ ��5
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Figure 23-6. Protected Identifier Field and Mapping of Identifier and Parity Bits
Protected identifier field
St
ID0 ID1 ID2 ID3 ID4 ID5 P0
P1
Sp
Disabling the Receiver
A disabling of the receiver will be immediate. The receiver buffer will be flushed, and data from ongoing
receptions will be lost.
Flushing the Receive Buffer
If the receive buffer has to be flushed during normal operation, read the DATA location
(USARTn.RXDATAH and USARTn.RXDATAL registers) until the Receive Complete Interrupt Flag (RXCIF
in USARTn.RXDATAH) is cleared.
Asynchronous Data Reception
The USART includes a clock recovery and a data recovery unit for handling asynchronous data reception.
The clock recovery unit is used for synchronizing the incoming asynchronous serial frames at the RxD pin
to the internally generated baud rate clock. It samples and low-pass filters each incoming bit, thereby
improving the noise immunity of the receiver. The asynchronous reception operational range depends on
the accuracy of the internal baud rate clock, the rate of the incoming frames, and the frame size in a
number of bits.
Asynchronous Clock Recovery
The clock recovery unit synchronizes the internal clock to the incoming serial frames. Figure 23-7
illustrates the sampling process for the Start bit of an incoming frame:
•
In Normal mode, the sample rate is 16 times the baud rate.
•
In Double-Speed mode, the sample rate is eight times the baud rate.
•
The horizontal arrows illustrate the synchronization variation due to the sampling process. Note that
in Double-Speed mode, the variation is larger.
•
Samples denoted as zero are sampled with the RxD line idle (i.e., when there is no communication
activity).
Figure 23-7. Start Bit Sampling
RxD
IDLE
START
BIT 0
Sample
(RXMODE = 0x0)
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
2
3
Sample
(RXMODE = 0x1)
0
1
2
3
4
5
6
7
8
1
2
When the clock recovery logic detects a high-to-low (i.e., idle-to-start) transition on the RxD line, the Start
bit detection sequence is initiated. Sample 1 denotes the first zero-sample, as shown in the figure. The
clock recovery logic then uses three subsequent samples (samples 8, 9, and 10 in Normal mode,
samples 4, 5, and 6 in Double-Speed mode) to decide if a valid Start bit is received:
•
If two or three samples have a low level, the Start bit is accepted. The clock recovery unit is
synchronized, and the data recovery can begin.
•
If two or three samples have a high level, the Start bit is rejected as a noise spike, and the receiver
looks for the next high-to-low transition.
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The process is repeated for each Start bit.
Asynchronous Data Recovery
The data recovery unit uses sixteen samples in Normal mode and eight samples in Double-Speed mode
for each bit. The following figure shows the sampling process of data and parity bits.
Figure 23-8. Sampling of Data and Parity Bits
RxD
BIT n
Sample
(CLK2X = 0)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
Sample
(CLK2X = 1)
1
2
3
4
5
6
7
8
1
As for Start bit detection, an identical majority voting technique is used on the three center samples for
deciding of the logic level of the received bit. The process is repeated for each bit until a complete frame
is received. It includes the first Stop bit but excludes additional ones. If the sampled Stop bit is a '0' value,
the Frame Error (FERR in USARTn.RXDATAH) flag will be set. The next figure shows the sampling of the
Stop bit in relation to the earliest possible beginning of the next frame's Start bit.
Figure 23-9. Stop Bit and Next Start Bit Sampling
RxD
STOP 1
(A)
(B)
(C)
Sample
(CLK2X = 0)
1
2
3
4
5
6
7
8
9
10
0/1
0/1
0/1
Sample
(CLK2X = 1)
1
2
3
4
5
6
0/1
A new high-to-low transition indicating the Start bit of a new frame can come right after the last of the bits
used for majority voting. For Normal-Speed mode, the first low-level sample can be at the point marked
(A) in Stop Bit Sampling and Next Start Bit Sampling. For Double-Speed mode, the first low level must be
delayed to point (B). Point (C) marks a Stop bit of full length at the nominal baud rate. The early Start bit
detection influences the operational range of the receiver.
Asynchronous Operational Range
The operational range of the receiver is dependent on the mismatch between the received bit rate and
the internally generated baud rate. If an external transmitter is sending using bit rates that are too fast or
too slow, or if the internally generated baud rate of the receiver does not match the external source’s base
frequency, the receiver will not be able to synchronize the frames to the Start bit.
The following equations can be used to calculate the ratio of the incoming data rate and internal receiver
baud rate.
����� =
16 � + 1
16 � + 1 + 6
����� =
D Sum of character size and parity size (D = 5 to 10 bit).
16 � + 2
16 � + 1 + 8
Rslow Is the ratio of the slowest incoming data rate that can be accepted in relation to the receiver baud
rate.
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Rfast Is the ratio of the fastest incoming data rate that can be accepted in relation to the receiver baud
rate.
The following tables list the maximum receiver baud rate error that can be tolerated. Normal Speed mode
has higher toleration of baud rate variations.
Table 23-4. Recommended Maximum Receiver Baud Rate Error for Normal Speed Mode (CLK2X =
0)
D #(Data + Parity Bit) Rslow [%] Rfast [%] Maximum Total Error [%] Receiver Max. Receiver
Error [%]
5
93.20
106.67
+6.67/-6.80
±3.0
6
94.12
105.79
+5.79/-5.88
±2.5
7
94.81
105.11
+5.11/-5.19
±2.0
8
95.36
104.58
+4.58/-4.54
±2.0
9
95.81
104.14
+4.14/-4.19
±1.5
10
96.17
103.78
+3.78/-3.83
±1.5
Table 23-5. Recommended Maximum Receiver Baud Rate Error for Double Speed Mode (CLK2X =
1)
D #(Data + Parity Bit) Rslow [%] Rfast [%] Maximum Total Error [%] Receiver Max. Receiver
Error [%]
5
94.12
105.66
+5.66/-5.88
±2.5
6
94.92
104.92
+4.92/-5.08
±2.0
7
95.52
104.35
+4.35/-4.48
±1.5
8
96.00
103.90
+3.90/-4.00
±1.5
9
96.39
103.53
+3.53/-3.61
±1.5
10
96.70
103.23
+3.23/-3.30
±1.0
The recommendations of the maximum receiver baud rate error were made under the assumption that
the receiver and transmitter equally divide the maximum total error.
23.3.2.5 USART in Master SPI mode
Using the USART in Master SPI mode requires the transmitter to be enabled. The receiver can optionally
be enabled to serve as the serial input. The XCK pin will be used as the transfer clock.
As for the USART, a data transfer is initiated by writing to the USARTn.DATA register. This is the case for
both sending and receiving data since the transmitter controls the transfer clock. The data written to
USARTn.DATA are moved from the transmit buffer to the Shift register when the Shift register is ready to
send a new frame.
The transmitter and receiver interrupt flags and corresponding USART interrupts used in Master SPI
mode are identical in function to their use in normal USART operation. The receiver error status flags are
not in use and are always read as zero.
Disabling of the USART transmitter or receiver in Master SPI mode is identical to their disabling in normal
USART operation.
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CTRLC
USART SPI vs. SPI
The USART in Master SPI mode is fully compatible with the stand-alone SPI module in that:
•
•
•
Timing diagrams are the same
UCPHA bit functionality is identical to that of the SPI CPHA bit
UDORD bit functionality is identical to that of the SPI DORD bit
When the USART is set in Master SPI mode, configuration and use are in some cases different from
those of the stand-alone SPI module. In addition, the following difference exists:
•
The USART in Master SPI mode does not include the SPI (Write Collision) feature
The USART in Master SPI mode does not include the SPI Double-Speed mode feature, but this can be
achieved by configuring the Baud Rate Generator accordingly:
•
•
Interrupt timing is not compatible
Pin control differs due to the master-only operation of the USART in SPI Master mode
A comparison of the USART in Master SPI mode and the SPI pins is shown in Table 23-6.
Table 23-6. Comparison of USART in Master SPI Mode and SPI Pins
USART
SPI
Comment
TxD
MOSI
Master out only
RxD
MISO
Master in only
XCK
SCK
Functionally identical
-
SS
Not supported by USART in Master SPI mode
Related Links
CTRLC
23.3.2.6 RS-485 Mode of Operation
The RS-485 feature enables the support of external components to comply with the RS-485 standard.
Either an external line driver is supported as shown in the figure below (RS-485=0x1 in USARTn.CTRLA),
or control of the transmitter driving the TxD pin is provided (RS-485=0x2).
While operating in RS-485 mode, the Transmit Direction pin (XDIR) is driven high when the transmitter is
active.
Figure 23-10. RS-485 Bus Connection
VDD
USART
RxD
XDIR
TxD
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bus
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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
Related Links
Signal Description
23.3.2.7 Start Frame Detection
The start frame detection is supported in UART mode only. The UART start frame detector is limited to
Standby Sleep mode only and can wake-up the system when a Start bit is detected.
When a high-to-low transition is detected on RxDn, the oscillator is powered up and the UART clock is
enabled. After start-up, the rest of the data frame can be received, provided that the baud rate is slow
enough in relation to the oscillator start-up time. Start-up time of the oscillators varies with supply voltage
and temperature. For details on oscillator start-up time characteristics, refer to the Electrical
Characteristics.
If a false Start bit is detected and if the system has not been woken-up by another source, the clock will
automatically be turned off and the UART waits for the next transition.
The UART start frame detection works in Asynchronous mode only. It is enabled by writing the Start
Frame Detection bit (SFDEN) in USARTn.CTLB. If the Start bit is detected while the device is in Standby
Sleep mode, the UART Start Interrupt Flag (RXSIF) bit is set.
In Active, Idle, and Power-Down Sleep modes, the asynchronous detection is automatically disabled.
The UART receive complete flag and UART start interrupt flag share the same interrupt line, but each has
its dedicated interrupt settings. Table 21-5 shows the USART start frame detection modes, depending on
interrupt setting.
Table 23-7. USART Start Frame Detection Modes
SFDEN RXSIF Interrupt RXCIF Interrupt Comment
0
x
x
Standard mode.
1
Disabled
Disabled
Only the oscillator is powered during the frame reception.
If the interrupts are disabled and buffer overflow is
ignored, all incoming frames will be lost.
1 (1)
Disabled
Enabled
System/all clocks are awakened on Receive Complete
interrupt.
1 (1)
Enabled
x
System/all clocks are awakened on UART Start Detection.
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Note:
1. The SLEEP instruction will not shut down the oscillator if there is ongoing communication.
Related Links
Electrical Characteristics
23.3.2.8 Break Character Detection and Auto-Baud
When USART receive mode is set to LINAUTO mode (RXMODE in USARTn.CTRLB), it follows the LIN
format. All LIN frames start with a break field followed by a sync field. The USART uses a break detection
threshold of greater than 11 nominal bit times at the configured baud rate. At any time, if more than 11
consecutive dominant bits are detected on the bus, the USART detects a break field. When a break field
has been detected, the USART expects the sync field character to be 0x55. This field is used to update
the actual baud rate in order to stay synchronized. If the received sync character is not 0x55, then the
Inconsistent Sync Field Error flag (ISFIF in USARTn.STATUS) is set and the baud rate is unchanged.
Figure 23-12. LIN Break and Sync Fields
Break Field
Sync Field
Tbit
8 Tbit
After a break field is detected and the Start bit of the sync field is detected, a counter is started. The
counter is then incremented for the next eight Tbit of the sync field. At the end of these 8-bit times, the
counter is stopped. At this moment, the ten Most Significant bits of the counter (value divided by 64) gives
the new clock divider and the six Least Significant bits of this value (the remainder) gives the new
fractional part. When the sync field has been received and all bits are found valid, the clock divider and
the fractional part are updated in the Baud Rate Generator register (USARTn.BAUD). After the break and
sync fields, n characters of data can be received.
When the USART receive mode is set to GENAUTO mode, a generic Auto-baud mode is enabled. In this
mode there are no checks of the sync character to equal 0x55. After detection of a break field, the
USART expects the next character to be a sync field, counting eight low and high bit times. If the
measured sync field results in a valid BAUD value (0x0064-0xffff), the BAUD register is updated. Setting
the Wait for Break bit (WFB in USARTn.STATUS) before receiving the next break character, the next
negative plus positive edge of RxD line is detected as a break. This makes it possible to set an arbitrary
new baud rate without knowing the current baud rate.
23.3.2.9 One-Wire Mode
In this mode, the TxD pin is connected to the RxD pin internally. If the receiver is enabled when
transmitting it will receive what the transmitter is sending. This can be used to check that no one else is
trying to transmit since received data will not be the same as the transmitted data.
23.3.2.10 Multiprocessor Communication Mode
The Multiprocessor Communication mode (MCPM) effectively reduces the number of incoming frames
that have to be handled by the receiver in a system with multiple microcontrollers communicating via the
same serial bus. This mode is enabled by writing a '1' to the MCPM bit in the Control B register
(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 one, the frame contains an address. When the frame type
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bit is zero, the frame is a data frame. If 5- to 8-bit character frames are used, the transmitter must be set
to use two Stop bits, since the first Stop bit is used for indicating the frame type.
If a particular slave MCU has been addressed, it will receive the following data frames as usual, while the
other slave MCUs will ignore the frames until another address frame is received.
Using Multiprocessor Communication Mode
The following procedure should be used to exchange data in Multiprocessor Communication mode
(MPCM):
1.
2.
3.
4.
5.
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.
The process then repeats from step 2.
Using any of the 5- to 8-bit character frame formats is impractical, as the receiver must change between
using n and n+1 character frame formats. This makes full-duplex operation difficult since the transmitter
and receiver must use the same character size setting.
23.3.2.11 IRCOM Mode of Operation
®
The IRCOM mode enables IrDA 1.4 compliant modulation and demodulation for baud rates up to 115.2
kbps. When IRCOM mode is enabled, Double-Speed mode cannot be used for the USART.
Overview
A USART can be configured in infrared communication mode (IRCOM) that is IrDA compatible for baud
rates up to 115.2 kbps. When enabled, the IRCOM mode enables infrared pulse encoding/decoding for
the USART.
A USART is set in IRCOM mode by writing 0x2 to the CMODE bits in USARTn.CTRLC.. The data on the
TX/RX pins are the inverted value of the transmitted/received infrared pulse. It is also possible to select
an event channel from the Event System as an input for the IRCOM receiver. This will disable the RX
input from the USART pin.
For transmission, three pulse modulation schemes are available:
•
•
•
3/16 of the baud rate period
Fixed programmable pulse time based on the peripheral clock frequency
Pulse modulation disabled
For 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.
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Block Diagram
Figure 23-13. Block Diagram
IRCOM
Event System
Events
Encoded RXD
Pulse
Decoding
Decoded RXD
USART
Pulse
Encoding
RXD
TXD
Decoded RXD
Encoded RXD
IRCOM and Event System
The Event System can be used as the receiver input. This enables the IRCOM or USART input from the
I/O pins or sources other than the corresponding RX pin. If the Event System input is enabled, input from
the USART's RX pin is automatically disabled.
Related Links
Event System (EVSYS)
23.3.3
Events
The USART can accept the following input events:
•
IREI - IrDA Event Input
The event is enabled by writing a '1' to the IrDA Event Input bit (IREI) in the Event Control register
(USART.EVCTRL).
Related Links
Event System (EVSYS)
EVCTRL
23.3.4
Interrupts
Table 23-8. Available Interrupt Vectors and Sources
Offset Name Vector Description
Conditions
0x00
RXC
Receive Complete
Interrupt
0x02
DRE
Data Register Empty
Interrupt
The transmit buffer is empty/ready to receive new data
(DREIE).
0x04
TXC
Transmit Complete
Interrupt
The entire frame in the Transmit Shift register has been shifted
out and there are no new data in the transmit buffer (TXCIE).
© 2018 Microchip Technology Inc.
•
•
•
There are 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
(USART.STATUS).
An interrupt source is enabled or disabled by writing to the corresponding bit in the Control A register
(USART.CTRLA).
An interrupt request is generated when the corresponding interrupt source is enabled and the interrupt
flag is set. The interrupt request remains active until the interrupt flag is cleared. See the USART.STATUS
register for details on how to clear interrupt flags.
Related Links
CPU Interrupt Controller (CPUINT)
STATUS
CTRLA
23.3.5
Configuration Change Protection
Not applicable.
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23.4
Register Summary - USART
Offset
Name
Bit Pos.
0x00
RXDATAL
7:0
0x01
RXDATAH
7:0
0x02
TXDATAL
7:0
0x03
TXDATAH
7:0
0x04
STATUS
7:0
RXCIF
TXCIF
DREIF
RXSIF
ISFIF
0x05
CTRLA
7:0
RXCIE
TXCIE
DREIE
RXSIE
LBME
0x06
CTRLB
7:0
RXEN
TXEN
0x07
CTRLC
7:0
CMODE[1:0]
0x07
CTRLC
7:0
CMODE[1:0]
0x08
BAUD
DATA[7:0]
RXCIF
BUFOVF
FERR
PERR
DATA[8]
DATA[7:0]
DATA[8]
SFDEN
PMODE[1:0]
ODME
BDF
ABEIE
RXMODE[1:0]
SBMODE
7:0
BAUD[7:0]
BAUD[15:8]
MPCM
CHSIZE[2:0]
UDORD
15:8
WFB
RS-485[1:0]
UCPHA
0x0A
Reserved
0x0B
DBGCTRL
7:0
DBGRUN
0x0C
EVCTRL
7:0
IREI
0x0D
TXPLCTRL
7:0
0x0E
RXPLCTRL
7:0
23.5
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
R
Reading the USARTn.RXDATAL Register will return the contents of the Receive Data Buffer register
(RXB).
The receive buffer consists of a two-level FIFO. The FIFO and the corresponding flags in the high byte of
RXDATA will change state whenever the receive buffer is accessed (read). If CHSIZE in USARTn.CTRLC
is set to 9BIT Low byte first, read USARTn.RXDATAL before USARTn.RXDATAH. Otherwise, always read
USARTn.RXDATAH before USARTn.RXDATAL in order to get the correct flags.
Bit
7
6
5
4
3
2
1
0
Access
R
R
R
R
Reset
0
0
0
R
R
R
R
0
0
0
0
0
DATA[7:0]
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 DATA bit plus Status
bits.
The receive buffer consists of a two-level FIFO. The FIFO and the corresponding flags in the high byte of
USARTn.RXDATAH will change state whenever the receive buffer is accessed (read). If CHSIZE in
USARTn.CTRLC is set to 9BIT Low byte first, read USARTn.RXDATAL before USARTn.RXDATAH.
Otherwise, always read USARTn.RXDATAH before USARTn.RXDATAL in order to get the correct flags.
Bit
7
6
2
1
0
RXCIF
BUFOVF
5
4
3
FERR
PERR
DATA[8]
Access
R
R
R
R
R
Reset
0
0
0
0
0
Bit 7 – RXCIF USART Receive Complete Interrupt Flag
This flag is set when there is unread data in the receive buffer and cleared when the receive buffer is
empty (i.e., does not contain any unread data). When the receiver is disabled, the receive buffer will be
flushed and consequently, the RXCIF will become zero.
Bit 6 – BUFOVF Buffer Overflow
The BUFOVF flag indicates data loss due to a receiver buffer full condition. This flag is set if a Buffer
Overflow condition is detected. A Buffer Overflow occurs when the receive buffer is full (two characters), it
is a new character waiting in the Receive Shift register, and a new Start bit is detected. This flag is valid
until the receive buffer (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. The bit is set if the received character had a Frame Error (i.e., when the first Stop bit was zero and
cleared when the Stop bit of the received data is '1'. This bit is valid until the receive buffer
(USARTn.RXDATAL) is read. The FERR is not affected by the SBMODE bit in USARTn.CTRLC since the
receiver ignores all, except for the first Stop bit.
This flag is not used in Master SPI mode of operation.
Bit 1 – PERR Parity Error
If parity checking is enabled and the next character in the receive buffer has a Parity Error this flag is set.
If Parity Check is not enabled the PERR will always be read as zero. This bit is valid until the receive
buffer (USARTn.RXDATAL) is read. For details on parity calculation refer to Parity . If USART is set to
LINAUTO mode, this bit will be a Parity Check of the protected identifier field and will be valid when
DATA[8] in USARTn.RXDATAH reads low.
This flag is not used in Master SPI mode of operation.
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Bit 0 – DATA[8] Receiver Data Register
When USART receiver is set to LINAUTO mode, this bit indicates if the received data is within the
response space of a LIN frame. If the received data is the protected identifier field, this bit will be read as
zero. Otherwise, the bit will be read as one. For Receiver mode other than LINAUTO mode, DATA[8]
holds the ninth data bit in the received character when operating with serial frames with nine data bits.
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23.5.3
Transmit Data Register Low Byte
Name:
Offset:
Reset:
Property:
TXDATAL
0x02
0x00
R/W
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 DATA when the DREIF flag is not set will be ignored by the USART transmitter. When data is
written to the transmit buffer, and the transmitter is enabled, the transmitter will load the data into the
Transmit Shift register when the Shift register is empty. The data is then transmitted on the TxD pin.
Bit
7
6
5
4
3
2
1
0
DATA[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DATA[7:0] Transmit Data Register
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23.5.4
Transmit Data Register High Byte
Name:
Offset:
Reset:
Property:
TXDATAH
0x03
0x00
-
USARTn.TXDATAH holds the ninth data bit in the character to be transmitted when operating with serial
frames with nine data bits. When used this bit must be written before writing to USARTn.TXDATAL except
if CHSIZE in USARTn.CTRLC is set to 9BIT Low byte first where USARTn.TXDATAL should be written
first.
This bit is unused in Master SPI mode of operation.
Bit
7
6
5
4
3
2
1
0
DATA[8]
Access
W
Reset
0
Bit 0 – DATA[8] Transmit Data Register
This bit is used when CHSIZE=9BIT in USARTn.CTRLC.
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23.5.5
USART Status Register
Name:
Offset:
Reset:
Property:
Bit
STATUS
0x04
0x00
-
7
6
5
4
3
1
0
RXCIF
TXCIF
DREIF
RXSIF
ISFIF
2
BDF
WFB
Access
R
R/W
R
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
Bit 7 – RXCIF USART Receive Complete Interrupt Flag
This flag is set to '1' when there is unread data in the receive buffer and cleared when the receive buffer
is empty (i.e., does not contain any unread data). When the receiver is disabled, the receive buffer will be
flushed and consequently, the RXCIF will become zero.
When interrupt-driven data reception is used, the receive complete interrupt routine must read the
received data from RXDATA in order to clear the RXCIF. If not, a new interrupt will occur directly after the
return from the current interrupt.
Bit 6 – TXCIF USART Transmit Complete Interrupt Flag
This flag is set when the entire frame in the Transmit Shift register has been shifted out and there are no
new data in the transmit buffer (TXDATA).
This flag is automatically cleared when the transmit complete interrupt vector is executed. The flag can
also be cleared by writing a '1' to its bit location.
Bit 5 – DREIF USART Data Register Empty Flag
The DREIF indicates if the transmit buffer (TXDATA) is ready to receive new data. The flag is set to '1'
when the transmit buffer is empty and is '0' when the transmit buffer contains data to be transmitted that
has not yet been moved into the Shift register. DREIF is set after a Reset to indicate that the transmitter is
ready. Always write this bit to '0' when writing the STATUS register.
DREIF is cleared to '0' by writing TXDATAL. When interrupt-driven data transmission is used, the Data
Register Empty interrupt routine must either write new data to TXDATA in order to clear DREIF or disable
the Data Register Empty interrupt. If not, a new interrupt will occur directly after the return from the
current interrupt.
Bit 4 – RXSIF USART Receive Start Interrupt Flag
The RXSIF flag indicates a valid Start condition on RxD line. The flag is set when the system is in
standby modes and a high (IDLE) to low (START) valid transition is detected on the RxD line. If the start
detection is not enabled, the RXSIF will always be read as zero. This flag can only be cleared by writing a
'1' to its bit location. This flag is not used in the Master SPI mode operation.
Bit 3 – ISFIF Inconsistent Sync Field Interrupt Flag
This bit is set when the auto-baud is enabled and the sync field bit time are too fast or too slow to give a
valid baud setting. It will also be set when USART is set to LINAUTO mode and the SYNC character differ
from data value 0x55.
Writing a '1' to this bit will clear the flag and bring the USART back to Idle state.
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Bit 1 – BDF Break Detected Flag
This bit 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 next data is received. The bit will behave
identically when USART is set to GENAUTO mode. In NORMAL or CLK2X receive mode, the BDF bit is
unused.
This bit is cleared by writing a '1' to it.
Bit 0 – WFB Wait For Break
Writing this bit to '1' will register the next low and high transition on RxD line as a Break character. This
can be used to wait for a Break character of arbitrary width. Combined with USART set to GENAUTO
mode, this 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
CTRLA
0x05
0x00
-
7
6
5
4
3
2
RXCIE
TXCIE
DREIE
RXSIE
LBME
ABEIE
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Access
Reset
1
0
RS-485[1:0]
Bit 7 – RXCIE Receive Complete Interrupt Enable
The bit enables the Receive Complete Interrupt (interrupt vector RXC). The enabled interrupt will be
triggered when RXCIF in the 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 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 in the USART.STATUS register is set.
Bit 4 – RXSIE Receiver Start Frame Interrupt Enable
Writing a '1' to this bit enables the Start Frame Detector to generate an interrupt on interrupt vector RXC
when a start-of-frame condition is detected.
Bit 3 – LBME Loop-back Mode Enable
Writing this bit to '1' enables an internal connection between the TxD and RxD pin.
Bit 2 – ABEIE Auto-baud Error Interrupt Enable
Writing this bit to '1' enables the auto-baud error interrupt on interrupt vector RXC. The enabled interrupt
will trigger for conditions where the ISFIF flag is set.
Bits 1:0 – RS-485[1:0] RS-485 Mode
These bits enable the RS-485 and select the operation mode.
Value
0x0
0x1
0x2
0x3
Name Description
OFF Disabled.
EXT Enables RS-485 mode with control of an external line driver through a dedicated
Transmit Enable (TE) pin.
INT
Enables RS-485 mode with control of the internal USART transmitter.
Reserved.
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23.5.7
Control B
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
CTRLB
0x06
0x00
-
7
6
4
3
RXEN
TXEN
5
SFDEN
ODME
2
1
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
RXMODE[1:0]
0
MPCM
Bit 7 – RXEN Receiver Enable
Writing this bit to '1' enables the USART receiver. The receiver will override normal port operation for the
RxD pin when enabled. Disabling the receiver will flush the receive buffer invalidating the FERR,
BUFOVF, and PERR flags. In GENAUTO and LINAUTO mode, disabling the receiver will reset the autobaud detection logic.
Bit 6 – TXEN Transmitter Enable
Writing this bit to '1' enables the USART transmitter. The transmitter will override normal port operation for
the TxD pin when enabled. Disabling the transmitter (writing TXEN to zero) will not become effective until
ongoing and pending transmissions are completed (i.e., when the Transmit Shift register and Transmit
Buffer register does not contain data to be transmitted). When the transmitter is disabled, it will no longer
override the TxDn pin, and the pin direction is set as input automatically by hardware, even if it was
configured as output by the user.
Bit 4 – SFDEN Start Frame Detection Enable
Writing this bit to '1' enables the USART Start Frame Detection mode. The Start Frame detector is able to
wake-up the system from Idle or Standby Sleep modes when a high (IDLE) to low (START) transition is
detected on the RxD line.
Bit 3 – ODME Open Drain Mode Enable
Writing this bit to '1' makes the TxD pin to have open-drain functionality. A pull-up resistor is needed to
prevent the line from floating when a logic one is output to the TxD pin.
Bits 2:1 – RXMODE[1:0] Receiver Mode
In CLK2X mode, the divisor of the baud rate divider will be reduced from 16 to 8 effectively doubling the
transfer rate for asynchronous communication modes. For synchronous operation, the CLK2X mode has
no effect and RXMODE should always be written to zero. RXMODE must be zero when the USART
Communication mode is configured to IRCOM. Setting RXMODE to GENAUTO enables generic autobaud where the SYNC character is valid when eight low and high bits 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 each two bits falls within 32 ±6 baud samples of the internal
baud rate and match data value 0x55. The GENAUTO and LINAUTO mode is only supported for USART
operated in Asynchronous Slave mode.
Value
0x0
0x1
Name
NORMAL
CLK2X
© 2018 Microchip Technology Inc.
Description
Normal USART mode, Standard Transmission Speed
Normal USART mode, Double Transmission Speed
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Value
0x2
0x3
Name
GENAUTO
LINAUTO
Description
Generic Auto-baud mode
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
the incoming frames that do not contain address information. The transmitter is unaffected by the MPCM
setting. For more detailed information see Multiprocessor Communication Mode.
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23.5.8
Control C - Async Mode
Name:
Offset:
Reset:
Property:
CTRLC
0x07
0x03
-
This register description is valid for all modes except Master SPI mode. When the USART
Communication mode bits (CMODE) in this register are written to 'MSPI', see Control C - Master SPI
Mode for the correct description.
Bit
7
6
5
CMODE[1:0]
Access
Reset
4
PMODE[1:0]
3
2
SBMODE
1
0
CHSIZE[2:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
1
1
Bits 7:6 – CMODE[1:0] USART Communication Mode
Writing these bits select the Communication mode of the USART.
Writing a 0x3 to these bits alters the available bit fields in this register, see Control C - Master SPI Mode.
Value
0x0
0x1
0x2
0x3
Name
ASYNCHRONOUS
SYNCHRONOUS
IRCOM
MSPI
Description
Asynchronous USART
Synchronous USART
Infrared Communication
Master SPI
Bits 5:4 – PMODE[1:0] Parity Mode
Writing these bits 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 flag (PERR) in the STATUS register (USARTn.STATUS) if a
mismatch is detected.
Value
0x0
0x1
0x2
0x3
Name
DISABLED
EVEN
ODD
Description
Disabled
Reserved
Enabled, Even Parity
Enabled, Odd Parity
Bit 3 – SBMODE Stop Bit Mode
Writing this bit selects the number of Stop bits to be inserted by the transmitter.
The receiver ignores this setting.
Value
0
1
Description
1 Stop bit
2 Stop bits
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Bits 2:0 – CHSIZE[2:0] Character Size
Writing these bits select the number of data bits in a frame. The receiver and transmitter use the same
setting. For 9BIT character size, the order of which byte to read or write first, low or high byte of RXDATA
or TXDATA is selectable.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
5BIT
6BIT
7BIT
8BIT
9BITL
9BITH
© 2018 Microchip Technology Inc.
Description
5-bit
6-bit
7-bit
8-bit
Reserved
Reserved
9-bit (Low byte first)
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 Control C - Async Mode.
See USART in Master SPI mode for a full description of the Master SPI mode operation.
Bit
7
6
5
4
3
CMODE[1:0]
Access
Reset
2
1
UDORD
UCPHA
R/W
R/W
R/W
R/W
0
0
0
0
0
Bits 7:6 – CMODE[1:0] USART Communication Mode
Writing these bits select the communication mode of the USART.
Writing a value different than 0x3 to these bits alters the available bit fields in this register, see Control C Async Mode.
Value
0x0
0x1
0x2
0x3
Name
ASYNCHRONOUS
SYNCHRONOUS
IRCOM
MSPI
Description
Asynchronous USART
Synchronous USART
Infrared Communication
Master SPI
Bit 2 – UDORD Data Order
Writing this bit selects the frame format.
The receiver and transmitter use the same setting. Changing the setting of UDORD will corrupt all
ongoing communication for both the receiver and the transmitter.
Value
0
1
Description
MSB of the data word is transmitted first
LSB of the data word is transmitted first
Bit 1 – UCPHA Clock Phase
The UCPHA bit setting determines if data is sampled on the leading (first) edge or tailing (last) edge of
XCKn. Refer to the Master SPI Mode Clock Generation for details.
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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. For more details on reading and writing 16-bit registers, refer to Accessing 16Bit Registers.
Ongoing transmissions of the transmitter and receiver will be corrupted if the baud rate is changed.
Writing this register will trigger an immediate update of the baud rate prescaler. For more information on
how to set the baud rate, see Table 23-2.
Bit
15
14
13
12
11
10
9
8
BAUD[15:8]
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
BAUD[7:0]
Access
Reset
Bits 15:8 – BAUD[15:8] USART Baud Rate High Byte
These bits hold the MSB of the 16-bit Baud register.
Bits 7:0 – BAUD[7:0] USART Baud Rate Low Byte
These bits hold the LSB of the 16-bit Baud register.
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23.5.11 Debug Control Register
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x0B
0x00
-
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN Debug Run
Value
0
1
Description
The peripheral is halted in Break Debug mode and ignores events.
The peripheral will continue to run in Break Debug mode when the CPU is halted.
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23.5.12 IrDA Control Register
Name:
Offset:
Reset:
Property:
Bit
7
EVCTRL
0x0C
0x00
-
6
5
4
3
2
1
0
IREI
Access
R/W
Reset
0
Bit 0 – IREI IrDA Event Input Enable
This bit enables the event source for the IRCOM Receiver. If event input is selected for the IRCOM
Receiver, the input from the USART’s RX pin is automatically disabled.
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23.5.13 IRCOM Transmitter Pulse Length Control Register
Name:
Offset:
Reset:
Property:
Bit
7
TXPLCTRL
0x0D
0x00
-
6
5
4
3
2
1
0
TXPL[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – TXPL[7:0] Transmitter Pulse Length
The 8-bit value sets the pulse modulation scheme for the transmitter. Setting this register will have effect
only if IRCOM mode is selected by a USART. By leaving this register value to zero, 3/16 of the baud rate
period pulse modulation is used. Setting this value from 1 to 254 will give a fixed pulse length coding. The
8-bit value sets the number of system clock periods for the pulse. The start of the pulse will be
synchronized with the rising edge of the baud rate clock. Setting the value to 255 (0xFF) will disable pulse
coding, letting the RX and TX signals pass through the IRCOM module unaltered. This enables other
features through the IRCOM module, such as half duplex USART, Loop-back testing, and USART RX
input from an event channel.
TXPL must be configured before the USART transmitter is enabled (TXEN).
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23.5.14 IRCOM Receiver Pulse Length Control Register
Name:
Offset:
Reset:
Property:
Bit
7
RXPLCTRL
0x0E
0x00
-
6
5
4
3
2
1
0
RXPL[6:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
Bits 6:0 – RXPL[6:0] Receiver Pulse Length
The 8-bit value sets the filter coefficient for the IRCOM transceiver. Setting this register will only have
effect if IRCOM mode is selected by a USART.
By leaving this register value to zero, filtering is disabled. Setting this value between 0x01 and 0xFF will
enable filtering, where x+1 equal samples are required for the pulse to be accepted.
RXPL must be configured before USART receiver is enabled (RXEN).
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Serial Peripheral Interface (SPI)
24.
Serial Peripheral Interface (SPI)
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.
This device provides one instance of the SPI peripheral, SPI0.
Related Links
Block Diagram
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Serial Peripheral Interface (SPI)
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
8-bit Shift Register
MSb
LSb
8-bit Shift Register
SPI CLOCK
GENERATOR
SCK
SCK
SS
SS
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.
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Serial Peripheral Interface (SPI)
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
SS
Slave select
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.
Related Links
I/O Multiplexing and Considerations
24.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 24-2. SPI System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
I/O Lines and Connections
Debug Operation
Interrupts
Clocks
24.2.3.1 Clocks
This peripheral depends on the peripheral clock.
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Serial Peripheral Interface (SPI)
Related Links
Clock Controller (CLKCTRL)
24.2.3.2 I/O Lines and Connections
The SPI signals (MOSI, MISO, SCK, SS) are either inputs or outputs, depending on whether the SPI is in
Master or Slave mode, as described in the Signal Description.
Using the I/O lines requires configuration of the I/O pins as described in the Signal Description.
Related Links
I/O Multiplexing and Considerations
I/O Pin Configuration (PORT)
Signal Description
24.2.3.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
Related Links
CPU Interrupt Controller (CPUINT)
SREG
Interrupts
24.2.3.4 Events
Not applicable.
24.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in Debugging
mode will halt normal operation of the peripheral.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
Unified Program and Debug Interface (UPDI)
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).
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Serial Peripheral Interface (SPI)
7.
8.
Optional: To disable the multimaster support in Master mode, write '1' to the Slave Select Disable
bit (SSD) in SPIn.CTRLB.
Enable the SPI by writing a '1' to the ENABLE bit in SPIn.CTRLA.
Related Links
I/O Multiplexing and Considerations
I/O Pin Configuration (PORT)
Signal Description
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.
SS Pin Functionality in Master Mode - Multimaster 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 zero, 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 one, 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 zero 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 zero 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:
1. The master bit in the SPI Control A Register (MASTER bit in SPIn.CTRLA) is cleared and the SPI
system becomes a slave. The direction of the pins will be switched according to Table 24-3.
2. The interrupt flag in the Interrupt Flags register (IF flag in SPIn.INTFLAGS) will be set. If the
interrupt is enabled and the global interrupts are enabled the interrupt routine will be executed.
Table 24-3. 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
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Serial Peripheral Interface (SPI)
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 re-enable the SPI Master mode.
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 flag in SPIn.INTFLAGS).
2. Received bytes are written to 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 flag 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.
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 a 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.
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
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Serial Peripheral Interface (SPI)
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 24-4. Overview of the SS Pin Functionality
SS Configuration
Always Input
SS Pin-Level
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.
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.
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Serial Peripheral Interface (SPI)
Figure 24-2. SPI Timing Diagram in Normal Mode (Buffer Mode Not Enabled)
SS
SCK
Write DATA
Write value
0x43
0x46
0x45
0x44
WRCOL
IF
Shift Register
0x43
Data sent
0x46
0x44
0x43
0x44
0x46
The figure 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.
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 Set to Zero
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
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Serial Peripheral Interface (SPI)
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.
Figure 24-4. SPI Timing Diagram in Buffer Mode with CTRLB.BUFWR Set to One
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, 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 over 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 zero.
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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Serial Peripheral Interface (SPI)
Figure 24-5. SPI Data Transfer Modes
SPI Mode 0
Cycle #
4
3
SS
SCK
sampling
MISO
4
MOSI
4
SPI Mode 1
Cycle #
4
SS
SCK
sampling
MISO
4
MOSI
4
SPI Mode 2
Cycle #
4
SS
SCK
sampling
MISO
4
MOSI
4
SPI Mode 3
Cycle #
4
SS
SCK
sampling
MISO
MOSI
24.3.3
Interrupts
Table 24-5. Available Interrupt Vectors and Sources
Offset
Name
Vector Description
0x00
SPI
SPI interrupt
© 2018 Microchip Technology Inc.
Conditions
•
•
•
SSI: Slave Select Trigger Interrupt
DRE: Data Register Empty Interrupt
TXC: Transfer Complete Interrupt
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ATtiny406
Serial Peripheral Interface (SPI)
Offset
Name
Vector Description
Conditions
•
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 register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the interrupt
flag is set. The interrupt request remains active until the interrupt flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear interrupt flags.
Related Links
SREG
CPU Interrupt Controller (CPUINT)
24.3.4
Sleep Mode Operation
The SPI will continue working in Idle Sleep mode. When entering any deeper sleep mode, an active
transaction will be stopped.
Related Links
Sleep Controller (SLPCTRL)
24.3.5
Configuration Change Protection
Not applicable.
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Serial Peripheral Interface (SPI)
24.4
Register Summary - SPI
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
BUFEN
BUFWR
0x02
INTCTRL
7:0
RXCIE
TXCIE
0x03
INTFLAGS
7:0
RXCIF/IF
0x04
DATA
7:0
24.5
DORD
TXCIF/
WRCOL
MASTER
CLK2X
PRESC[1:0]
DREIE
SSIE
IE
DREIF
SSIF
BUFOVF
SSD
ENABLE
MODE[1:0]
DATA[7:0]
Register Description
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Serial Peripheral Interface (SPI)
24.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
Access
Reset
CTRLA
0x00
0x00
-
6
5
4
DORD
MASTER
CLK2X
3
2
1
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
PRESC[1:0]
0
ENABLE
Bit 6 – DORD Data Order
Value
0
1
Description
The MSB of the data word is transmitted first
The LSB of the data word is transmitted first
Bit 5 – MASTER Master/Slave Select
Write this bit to configure SPI in desired 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
0
1
Description
SPI Slave mode selected
SPI Master mode selected
Bit 4 – CLK2X Clock Double
When this bit is written to '1' the SPI speed (SCK frequency, after internal prescaler) is doubled in Master
mode.
Value
0
1
Description
SPI speed (SCK frequency) is not doubled
SPI speed (SCK frequency) is doubled in Master mode
Bits 2:1 – PRESC[1:0] Prescaler
This bit field controls the SPI clock rate configured in Master mode. These bits have no effect in Slave
mode. The relationship between SCK and the peripheral clock frequency (fCLK_PER) is shown below.
The output of the SPI prescaler can be doubled by writing the CLK2X bit to '1'.
Value
0x0
0x1
0x2
0x3
Name
DIV4
DIV16
DIV64
DIV128
Description
CLK_PER/4
CLK_PER/16
CLK_PER/64
CLK_PER/128
Bit 0 – ENABLE SPI Enable
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Serial Peripheral Interface (SPI)
Value
0
1
Description
SPI is disabled
SPI is enabled
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Serial Peripheral Interface (SPI)
24.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
CTRLB
0x01
0x00
-
7
6
BUFEN
BUFWR
SSD
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Access
Reset
5
4
3
2
1
0
MODE[1:0]
Bit 7 – BUFEN Buffer Mode Enable
Writing this bit to '1' enables Buffer mode, meaning two buffers in receive direction, one buffer in transmit
direction, and separate interrupt flags for both transmit complete and receive complete.
Bit 6 – BUFWR Buffer Mode Wait for Receive
When writing this bit to '0' the first data transferred will be a dummy sample.
Value
0
1
Description
One SPI transfer must be completed before the data is copied into the Shift register.
When writing to the data register when the SPI is enabled and SS is high, the first write will
go directly to the Shift register.
Bit 2 – SSD Slave Select Disable
When this bit is set and when operating as SPI Master (MASTER=1 in SPIn.CTRLA), SS does not
disable Master mode.
Value
0
1
Description
Enable the Slave Select line when operating as SPI Master
Disable the Slave Select line when operating as SPI Master
Bits 1:0 – MODE[1:0] Mode
These bits select the Transfer mode. The four combinations of SCK phase and polarity with respect to the
serial data are shown in the table below. These bits decide whether the first edge of a clock cycle (leading
edge) is rising or falling and whether data setup and sample occur on the leading or trailing edge. When
the leading edge is rising, the SCK signal is low when idle, and when the leading edge is falling, the SCK
signal is high when idle.
Value
0x0
Name
0
0x1
1
0x2
2
0x3
3
© 2018 Microchip Technology Inc.
Description
Leading edge: Rising, sample
Trailing edge: Falling, setup
Leading edge: Rising, setup
Trailing edge: Falling, sample
Leading edge: Falling, sample
Trailing edge: Rising, setup
Leading edge: Falling, setup
Trailing edge: Rising, sample
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Serial Peripheral Interface (SPI)
Related Links
Data Modes
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Serial Peripheral Interface (SPI)
24.5.3
Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
INTCTRL
0x02
0x00
-
7
6
5
4
RXCIE
TXCIE
DREIE
SSIE
3
2
1
IE
0
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 7 – RXCIE Receive Complete Interrupt Enable
In Buffer mode, this bit enables the receive complete interrupt. The enabled interrupt will be triggered
when the RXCIF flag in the SPIn.INTFLAGS register is set. In Non-Buffer mode this bit is zero.
Bit 6 – TXCIE Transfer Complete Interrupt Enable
In Buffer mode, this bit enables the transfer complete interrupt. The enabled interrupt will be triggered
when the TXCIF flag in the SPIn.INTFLAGS register is set. In Non-Buffer mode, this bit is zero.
Bit 5 – DREIE Data Register Empty Interrupt Enable
In Buffer mode this bit enables the data register empty interrupt. The enabled interrupt will be triggered
when the DREIF flag in the SPIn.INTFLAGS register is set. In Non-Buffer mode, this bit is zero.
Bit 4 – SSIE Slave Select Trigger Interrupt Enable
In Buffer mode, this bit enables the Slave Select interrupt. The enabled interrupt will be triggered when
the SSIF flag in the SPIn.INTFLAGS register is set. In Non-Buffer mode, this bit is zero.
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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Serial Peripheral Interface (SPI)
24.5.4
Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
INTFLAGS
0x03
0x00
-
7
6
5
4
RXCIF/IF
TXCIF/WRCOL
DREIF
SSIF
3
2
1
BUFOVF
0
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
Bit 7 – RXCIF/IF Receive Complete Interrupt Flag/Interrupt Flag
RXCIF: In Buffer mode, this flag is set when there is unread data in the receive buffer and cleared when
the receive buffer is empty (i.e., does not contain any unread data). In Non-Buffer mode, this bit does not
have any effect.
When interrupt-driven data reception is used, the receive complete interrupt routine must read the
received data from 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.
IF: 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 – TXCIF/WRCOL Transfer Complete Interrupt Flag/Write Collision Flag
TXCIF: In Buffer mode, this flag is set when all the data in the transmit shift register has been shifted out
and there is no new data in the transmit buffer (SPIn.DATA). The flag is cleared by writing a 1 to its bit
location. In Non-Buffer mode, this bit does not have any effect.
WRCOL: 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.
Bit 5 – DREIF Data Register Empty Interrupt Flag
In Buffer mode, 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 set to '0' after a reset to indicate
that the transmitter is ready. In Non-Buffer mode, this bit is always 0.
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
In Buffer mode, this flag indicates that the SPI has been in Master mode and the SS line has been pulled
low externally so the SPI is now working in Slave mode. The flag will only be set if the Slave Select
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Serial Peripheral Interface (SPI)
Disable bit (SSD) is not '1'. The flag is cleared by writing a 1 to its bit location. In Non-Buffer mode, this bit
is always 0.
Bit 0 – BUFOVF Buffer Overflow
This flag is only used in Buffer mode. This flag indicates data loss due to a receiver buffer full condition.
This flag is set if a buffer overflow condition is detected. A buffer overflow occurs when the receive buffer
is full (two characters) and a third byte has been received in the Shift register. If there is no transmit data
the buffer overflow will not be set before the start of a new serial transfer. This flag is valid until the
receive buffer (SPIn.DATA) is read. Always write this bit location to 0 when writing the SPIn.INTFLAGS
register. In Non-Buffer mode, this bit is always 0.
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Serial Peripheral Interface (SPI)
24.5.5
Data
Name:
Offset:
Reset:
Property:
Bit
7
DATA
0x04
0x00
-
6
5
4
3
2
1
0
DATA[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DATA[7:0] 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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ATtiny406
Two-Wire Interface (TWI)
25.
Two-Wire Interface (TWI)
25.1
Features
•
•
•
•
•
•
•
•
•
•
•
25.2
Bidirectional, Two-wire Communication Interface
– Philips I2C compatible
– System Management Bus (SMBus) compatible
Bus Master and Slave Operation Supported
– Slave operation
– Single bus master operation
– Bus master in multi-master bus environment
– Multi-master arbitration
Flexible Slave Address Match Functions
– 7-bit and general call address recognition in hardware
– 10-bit addressing supported
– Address mask register for dual address match or address range masking
– Optional software address recognition for unlimited number of addresses
Slave Can Operate In All Sleep modes, Including Power-Down
Slave Address Match Can Wake Device From All Sleep modes
Up to 1 MHz Bus Frequency Support
Input Filter For Bus Noise and Spike Suppression
Support Arbitration Between Start/Repeated Start and Data Bit (SMBus)
Slave Arbitration Allows Support For Address Resolution Protocol (ARP) (SMBus)
Supports SMBus Layer 1 Timeouts
Configurable Timeout Values
Overview
The Two-Wire Interface (TWI) peripheral is a bidirectional, two-wire communication interface. It is I2C and
System Management Bus (SMBus) compatible. The only external hardware needed to implement the bus
is one pull-up resistor on each bus line.
Any device connected to the bus must act as a master or a slave. The master initiates a data transaction
by addressing a slave on the bus and telling whether it wants to transmit or receive data. One bus can
have many slaves and one or several masters that can take control of the bus. An arbitration process
handles priority if more than one master tries to transmit data at the same time. Mechanisms for resolving
bus contention are inherent in the protocol.
The TWI peripheral supports master and slave functionality. The master and slave functionality are
separated from each other and can be enabled and configured separately. The master module supports
multi-master bus operation and arbitration. It contains the Baud Rate Generator. All 100 kHz, 400 kHz,
and 1 MHz bus frequencies are supported. Quick command and Smart mode can be enabled to autotrigger operations and reduce software complexity.
The slave module implements 7-bit address match and general address call recognition in hardware. 10bit addressing is supported. A dedicated Address Mask register can act as a Second Address match
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ATtiny406
Two-Wire Interface (TWI)
register or as a register for address range masking. The slave continues to operate in all Sleep modes,
including Power-Down mode. This enables the slave to wake-up the device from all Sleep modes on TWI
address match. It is possible to disable the address matching to let this be handled in software instead.
The TWI peripheral will detect Start and Stop conditions, bus collisions, and bus errors. Arbitration lost,
errors, collision, and clock hold on the bus are also detected and indicated in separate status flags
available in both Master and Slave modes.
This device provides one instance of the TWI peripheral; TWI0.
25.2.1
Block Diagram
Figure 25-1. TWI Block Diagram
Master
BAUD
TxDATA
SCL
0
baud rate generator
Slave
TxDATA
SCL hold low
0
SCL hold low
shift register
shift register
SDA
0
0
RxDATA
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
Related Links
I/O Multiplexing and Considerations
25.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 25-1. TWI System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
No
-
Debug
Yes
UPDI
Related Links
Clocks
Debug Operation
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ATtiny406
Two-Wire Interface (TWI)
I/O Lines and Connections
Interrupts
25.2.3.1 Clocks
This peripheral requires the system clock (CLK_PER). The relationship between CLK_PER and the TWI
bus clock (SCL) is explained in the TWI.MBAUD register.
Related Links
Clock Controller (CLKCTRL)
MBAUD
25.2.3.2 I/O Lines and Connections
Using the I/O lines of the peripheral requires configuration of the I/O pins.
25.2.3.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
25.2.3.4 Events
Not applicable.
25.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in Debugging
mode will halt normal operation of the peripheral.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
When the CPU is halted in Debug mode and DBGRUN=1, reading/writing the DATA register will neither
trigger a bus operation nor cause transmit and clear flags.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
Related Links
Unified Program and Debug Interface (UPDI)
25.3
Functional Description
25.3.1
Initialization
To start the TWI as master, write a '1' to the ENABLE bit in the Master Control A register
(TWIn.MCTRLA), followed by writing the slave address to the Master Address (TWIn.MADDR) register.
The TWIn.MADDR register has an R/W bit, which indicates whether the master is transmitting or
receiving. The Master DATA register (TWIn.MDATA) is written in case the master is transmitting data.
To enable the TWI as slave, write the Slave Address (ADDR) in 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.
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The TWI bus is a simple and efficient method of interconnecting multiple devices on a serial bus. A device
connected to the bus can be a master or slave, where the master controls the bus and all communication.
Figure 25-2 illustrates the TWI bus topology.
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
DATA
A/A
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
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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.
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.
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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 zero (ADDRESS+W).
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 one (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
ADDRESS
R
A
DATA
A
DATA
A
P
N data packets
Assuming the slave acknowledges the address, the master can start receiving data from the slave. There
are no limitations to the number of data packets that can be transferred. The slave transmits the data
while the master signals ACK or NACK after each data byte. The master terminates the transfer with a
NACK before issuing a Stop condition.
Figure 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
A
DATA
A/A
P
Direction
Direction
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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.
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 multimaster bus, it is possible that two devices may initiate a transaction at the same time. This results in
multiple masters owning the bus simultaneously. This is solved using an arbitration scheme where the
master loses control of the bus if it is not able to transmit a high level on the SDA line. The masters who
lose arbitration must then wait until the bus becomes idle (i.e., wait for a Stop condition) before attempting
to reacquire bus ownership. Slave devices are not involved in the arbitration procedure.
Figure 25-10. TWI Arbitration
DEVICE1 Loses arbitration
DEVICE1_SDA
DEVICE2_SDA
SDA
(wired-AND)
bit 7
bit 6
bit 5
bit 4
SCL
S
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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.
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 idle by writing to the Bus State bits accordingly. If no state is set by the application
software, the bus state will become idle when the first Stop condition is detected. If the master inactive
bus timeout is enabled, the bus state will change to idle on the occurrence of a timeout. After a known
bus state is established, only a system Reset or disabling of the TWI master will set the state to unknown.
When the bus is idle, it is ready for a new transaction. If a Start condition generated externally is
detected, the bus becomes busy until a Stop condition is detected. The Stop condition will change the
bus state to idle. If the master inactive bus timeout is enabled, the bus state will change from busy to idle
on the occurrence of a timeout.
If a Start condition is generated internally while in 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 the issuing of the repeated Start.
Arbitration during repeated Start can be lost only if the arbitration has been ongoing since the first Start
condition. This happens if two masters send the exact same ADDRESS+DATA before one of the masters'
issues a repeated Start (Sr).
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 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
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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 diamond-shaped symbols (SW) indicate where software interaction is required. Clearing
the interrupt flags releases the SCL line.
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
A/A
BUSY
P
Bus state
Mn
A/A Sr
Diagram connections
IDLE
M4
M2
M3
A/A
R
A
DATA
The number of interrupts generated is kept to a minimum by an automatic handling of most conditions.
Clock Generation
The BAUD must be set to a value that results in a TWI bus clock frequency (fSCL) equal or less than 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 (BAUD), while the rise
(TRISE) and fall (TFALL) times are determined by the bus topology. Because of the wired-AND logic of the
bus, TFALL will be considered as part of TLOW. Likewise, TRISE will be in a state between TLOW and THIGH
until a high state has been detected.
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Figure 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
TSU;STA – Set-up time for repeated Start condition
THIGH is timed using the SCL high time count from TWI.MBAUD
TRISE is determined by the bus impedance; for internal pull-ups. Refer to Electrical Characteristics.
TFALL is determined by the open-drain current limit and bus impedance; can typically be regarded
as zero. Refer to Electrical Characteristics for details.
The SCL frequency is given by:
�SCL =
1
�LOW + �HIGH + �RISE
�SCL =
�CLK_PER
10 + 2���� + �CLK_PER ⋅ �RISE
The TWI.MBAUD value is used to time both SCL high and SCL low which gives the following formula of
SCL frequency:
If the TWI is in Fm+ mode, only TWI.MBAUD value of three or higher is supported. This means that for
Fm+ mode to achieve baud rate of 1 MHz, the peripheral clock (CLK_PER) has to run at 16 MHz or
faster.
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.
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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.
Transmitting Data Packets
The slave will know when an address packet with R/W direction bit set has been successfully received. It
can then start sending data by writing to the slave data register. When a data packet transmission is
completed, the data interrupt flag is set. If the master indicates NACK, the slave must stop transmitting
data and expect a Stop or repeated Start condition.
Receiving Data Packets
The slave will know when an address packet with R/W direction bit cleared has been successfully
received. After acknowledging this, the slave must be ready to receive data. When a data packet is
received, the data interrupt flag is set and the slave must indicate ACK or NACK. After indicating a NACK,
the slave must expect a Stop or repeated Start condition.
Quick Command Mode
With Quick Command enabled (QCEN in TWIn.MCTRLA), the R/W# bit of the slave address denotes the
command. This is a SMBus specific command where the R/W bit may be used to simply turn a device
function ON or OFF, or enable/disable a low-power Standby mode. There is no data sent or received.
After the master receives an acknowledge from the slave, either RIF or WIF flag in 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.
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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
Driversoftware
The master provides data
on the bus
Slave provides data on
the bus
Sn
S1
A
A
SW
SLAVE DATA INTERRUPT
W
SW
Interrupton STOP
ConditionEnabled
SW
A/A
DATA
SW
A/A
Diagramconnections
The number of interrupts generated is kept to a minimum by automatic handling of most conditions. Quick
command can be enabled to auto-trigger operations and reduce software complexity.
Address Recognition mode can be enabled to allow the slave to respond to all received addresses.
Receiving Address Packets
When the TWI slave is properly configured, it will wait for a Start condition to be detected. When this
happens, the successive address byte will be received and checked by the address match logic, and the
slave will ACK a correct address and store the address in the 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.
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Case S3: Collision
If the slave is not able to send a high level or NACK, the collision flag is set, and it will disable the data
and acknowledge output from the slave logic. The clock hold is released. A Start or repeated Start
condition will be accepted.
Case S4: STOP Condition Received
When the Stop condition is received, the slave address/stop flag will be set, indicating that a Stop
condition, and not an address match, occurred.
Receiving Data Packets
The slave will know when an address packet with R/W direction bit cleared has been successfully
received. After acknowledging this, the slave must be ready to receive data. When a data packet is
received, the data interrupt flag is set and the slave must indicate ACK or NACK. After indicating a NACK,
the slave must expect a Stop or repeated Start condition.
Transmitting Data Packets
The slave will know when an address packet with R/W direction bit set has been successfully received. It
can then start sending data by writing to the slave data register. When a data packet transmission is
completed, the data interrupt flag is set. If the master indicates NACK, the slave must stop transmitting
data and expect a Stop or repeated Start condition.
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.
25.3.5
Events
Not applicable.
25.3.6
Interrupts
Table 25-2. Available Interrupt Vectors and Sources
Offset Name
Vector Description
0x00
Slave
TWI Slave interrupt
0x02
Master TWI Master interrupt
Conditions
•
•
DIF: Data Interrupt Flag in SSTATUS set
APIF: Address or Stop Interrupt Flag in SSTATUS set
•
•
RIF: Read Interrupt Flag in MSTATUS set
WIF: Write Interrupt Flag in MSTATUS set
When an interrupt condition occurs, the corresponding interrupt flag is set in the Master register
(TWI.MSTATUS) or Slave Status register (TWI.SSTATUS).
When several interrupt request conditions are supported by an interrupt vector, the interrupt requests are
ORed together into one combined interrupt request to the interrupt controller. The user must read the
peripheral's INTFLAGS register to determine which of the interrupt conditions are present.
Related Links
CPU Interrupt Controller (CPUINT)
SREG
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25.3.7
Sleep Mode Operation
The bus state logic and slave continue to operate in all Sleep modes, including Power-Down Sleep mode.
If a slave device is in Sleep mode and a Start condition is detected, clock stretching is active during the
wake-up period until the system clock is available. The master will stop operation in all Sleep modes.
25.3.8
Synchronization
Not applicable.
25.3.9
Configuration Change Protection
Not applicable.
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25.4
Register Summary - TWI
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
SDASETUP
SDAHOLD[1:0]
0x01
Reserved
0x02
DBGCTRL
7:0
0x03
MCTRLA
7:0
0x04
MCTRLB
7:0
0x05
MSTATUS
7:0
0x06
MBAUD
7:0
BAUD[7:0]
0x07
MADDR
7:0
ADDR[7:0]
0x08
MDATA
7:0
DATA[7:0]
0x09
SCTRLA
7:0
0x0A
SCTRLB
7:0
DBGRUN
RIEN
RIF
DIEN
WIEN
WIF
APIEN
QCEN
CLKHOLD
RXACK
TIMEOUT[1:0]
SMEN
ACKACT
MCMD[1:0]
ARBLOST
BUSERR
BUSSTATE[1:0]
PIEN
PMEN
SMEN
ACKACT
DIF
APIF
CLKHOLD
RXACK
ENABLE
FLUSH
0x0B
SSTATUS
7:0
0x0C
SADDR
7:0
ADDR[7:0]
0x0D
SDATA
7:0
DATA[7:0]
0x0E
SADDRMASK
7:0
25.5
FMPEN
COLL
ADDRMASK[6:0]
BUSERR
ENABLE
SCMD[1:0]
DIR
AP
ADDREN
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Two-Wire Interface (TWI)
25.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
CTRLA
0x00
0x00
-
7
6
5
4
SDASETUP
Access
Reset
3
2
SDAHOLD[1:0]
1
0
FMPEN
R/W
R/W
R/W
R/W
0
0
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
0
1
Name
4CYC
8CYC
Description
SDA setup time is four clock cycles
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 25-3. SDA Hold Time
SDAHOLD[1:0] Nominal Hold Time Hold Time Range Across
All Corners (ns)
Description
0x0
OFF
0
Hold time off.
0x1
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.
Value
0
1
Description
Fm+ disabled
Fm+ enabled
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 358
ATtiny406
Two-Wire Interface (TWI)
25.5.2
Debug Control
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x02
0x00
-
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN Debug Run
Value
0
1
Description
The peripheral is halted in Break Debug mode and ignores events.
The peripheral will continue to run in Break Debug mode when the CPU is halted.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Two-Wire Interface (TWI)
25.5.3
Master Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
MCTRLA
0x03
0x00
-
7
6
RIEN
WIEN
5
QCEN
4
3
2
R/W
R/W
R/W
R/W
0
0
0
0
1
0
SMEN
ENABLE
R/W
R/W
R/W
0
0
0
TIMEOUT[1:0]
Bit 7 – RIEN Read Interrupt Enable
Writing this bit to '1' enables interrupt on the Master Read Interrupt Flag (RIF) in the Master Status
register (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 Timeout
Setting the inactive bus timeout (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
0x0
0x1
0x2
0x3
Name
DISABLED
50US
100US
200US
Description
Bus timeout disabled. I2C.
50 µs - SMBus (assume baud is set to 100 kHz)
100 µs (assume baud is set to 100 kHz)
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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Datasheet Preliminary
40001976A-page 360
ATtiny406
Two-Wire Interface (TWI)
25.5.4
Master Control B
Name:
Offset:
Reset:
Property:
Bit
MCTRLB
0x04
0x00
-
7
6
5
Access
Reset
4
3
2
FLUSH
ACKACT
1
0
R/W
R/W
R/W
R/W
0
0
0
0
MCMD[1:0]
Bit 3 – FLUSH Flush
Writing a '1' to this bit generates a strobe for one clock cycle disabling and then enabling the master.
Writing '0' has no effect.
The purpose is to clear the internal state of master: For TWI master to transmit successfully, it is
recommended to write the Master Address register (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
0
1
Description
Send ACK
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.
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ATtiny406
Two-Wire Interface (TWI)
MCMD[1:0] DIR Description
0x3
1
Execute Acknowledge Action (no action) succeeded by a byte send operation.(1)
X
STOP - Execute Acknowledge Action succeeded by issuing a Stop condition.
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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ATtiny406
Two-Wire Interface (TWI)
25.5.5
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
6
5
4
3
2
RIF
WIF
CLKHOLD
RXACK
ARBLOST
BUSERR
1
0
R/W
R/W
R/W
R
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
BUSSTATE[1:0]
Bit 7 – RIF Read Interrupt Flag
This bit is set to '1' when the master byte read operation is successfully completed (i.e., no arbitration lost
or bus error occurred during the operation). The read operation is triggered by software reading DATA or
writing to ADDR registers with bit ADDR[0] written to '1'. A slave device must have responded with an
ACK to the address and direction byte transmitted by the master for this flag to be set.
Writing a '1' to this bit will clear the RIF. However, normal use of the TWI does not require the flag to be
cleared by this method.
Clearing the RIF bit will follow the same software interaction as the CLKHOLD flag.
The RIF flag can generate a master read interrupt (see description of the RIEN control bit in the
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.
2.
Writing a '1' to it.
Writing to the TWIn.MADDR register.
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ATtiny406
Two-Wire Interface (TWI)
3.
4.
5.
Writing to the TWIn.MDATA register.
Reading the TWIn.DATA register while the ACKACT control bits in TWIn.MCTRLB are set to either
send ACK or NACK.
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.
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.
Writing a '1' to it will clear the ARBLOST flag. However, normal use of the TWI does not require the flag to
be cleared by this method. However, as for the CLKHOLD flag, clearing the ARBLOST flag is not required
during normal use of the TWI.
Clearing the ARBLOST bit will follow the same software interaction as the CLKHOLD flag.
Given the condition where the bus ownership is lost to another master, the software must either abort
operation or resend the data packet. Either way, the next required software interaction is in both cases to
write to the 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 reenabling, the TWI master bus state will be unknown. The change of bus state is dependent on bus
activity.
Writing 0x1 to the BUSSTATE bits forces the bus state logic into its Idle state. However, the bus state
logic cannot be forced into any other state. When the master is disabled, the bus state is 'unknown'.
Value
0x0
0x1
0x2
0x3
Name
UNKNOWN
IDLE
OWNER
BUSY
© 2018 Microchip Technology Inc.
Description
Unknown bus state
Bus is idle
This TWI controls the bus
The bus is busy
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ATtiny406
Two-Wire Interface (TWI)
25.5.6
Master Baud Rate
Name:
Offset:
Reset:
Property:
Bit
7
MBAUD
0x06
0x00
-
6
5
4
3
2
1
0
BAUD[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – BAUD[7:0] Baud Rate
This bit field is used to derive the SCL high and low time and should be written while the master is
disabled (ENABLE bit in TWIn.MCTRLA is '0').
For more information on how to calculate the frequency, see Clock Generation.
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ATtiny406
Two-Wire Interface (TWI)
25.5.7
Master Address
Name:
Offset:
Reset:
Property:
Bit
7
MADDR
0x07
0x00
-
6
5
4
3
2
1
0
ADDR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – ADDR[7:0] Address
When this bit field is written, a Start condition and slave address protocol sequence is initiated dependent
on the bus state.
If the bus state is unknown the Master Write Interrupt Flag (WIF) and Bus Error flag (BUSERR) in the
Master Status register (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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Datasheet Preliminary
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ATtiny406
Two-Wire Interface (TWI)
25.5.8
Master DATA
Name:
Offset:
Reset:
Property:
Bit
7
MDATA
0x08
0x00
-
6
5
4
3
2
1
0
DATA[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DATA[7:0] Data
The bit field gives direct access to the 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).
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Datasheet Preliminary
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ATtiny406
Two-Wire Interface (TWI)
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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ATtiny406
Two-Wire Interface (TWI)
25.5.9
Slave Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
SCTRLA
0x09
0x00
-
7
6
5
2
1
0
DIEN
APIEN
PIEN
4
3
PMEN
SMEN
ENABLE
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit 7 – DIEN Data Interrupt Enable
Writing this bit to '1' enables interrupt on the Slave Data Interrupt Flag (DIF) in the Slave Status register
(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 the this
bit, APIF, PIEN in this register, and the Global Interrupt Flag (I) in CPU.SREG are all '1'.
The slave stop interrupt shares the interrupt vector with the slave address interrupt. The AP bit
determines what 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 slaves 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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ATtiny406
Two-Wire Interface (TWI)
25.5.10 Slave Control B
Name:
Offset:
Reset:
Property:
Bit
SCTRLB
0x0A
0x00
-
7
6
5
4
3
2
1
ACKACT
Access
0
SCMD[1:0]
R/W
R/W
R/W
0
0
0
Reset
Bit 2 – ACKACT Acknowledge Action
This bit defines the slave’s behavior under certain conditions defined by the bus protocol state and
software interaction. The table below lists the acknowledge procedure performed by the slave if action is
initiated by software. The acknowledge action is performed when 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
0
1
Name
ACK
NACK
Description
Send ACK
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.
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ATtiny406
Two-Wire Interface (TWI)
The acknowledge action bits and command bits can be written at the same time.
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ATtiny406
Two-Wire Interface (TWI)
25.5.11 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
6
5
4
3
2
1
0
DIF
APIF
CLKHOLD
RXACK
COLL
BUSERR
DIR
AP
R/W
R/W
R
R
R/W
R/W
R
R
0
0
0
0
0
0
0
0
Bit 7 – DIF Data Interrupt Flag
This flag is set when a slave byte transmit or byte receive operation is successfully completed without any
bus error. The flag can be set with an unsuccessful transaction in case of collision detection (see 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.
2.
3.
Writing to the Slave DATA register.
Reading the Slave DATA register.
Writing a valid command to the CTRLB register.
The DIF flag can be used to generate a slave data interrupt (see 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 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.
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,
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ATtiny406
Two-Wire Interface (TWI)
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 NACK bit, it means the address match already happened and APIF
flag is set as a result. APIF/DIF flags can only generate interrupt whose handlers can be used to check
for the collision. Writing a '1' to its bit location will clear the COLL flag. However, the flag is automatically
cleared if any Start condition (S/Sr) is detected.
This flag is intended for systems where address resolution protocol (ARP) is employed. However, a
detected collision in non-ARP situations indicates that there has been a protocol violation and should be
treated as a bus error.
Bit 2 – BUSERR Bus Error
The BUSERR flag indicates that an illegal bus condition has occurred. An illegal bus condition is detected
if a protocol violating Start (S), Repeated Start (Sr), or Stop (P) is detected on the TWI bus lines. A Start
condition directly followed by a Stop condition is one example of protocol violation. Writing a '1' to its bit
location will clear the BUSERR flag. However, normal use of the TWI does not require the BUSERR to be
cleared by this method. A robust TWI driver software design will assume that the entire packet of data
has been corrupted and restart by waiting for a new Start condition (S). 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
0
1
Name
STOP
ADR
Description
A Stop condition generated the interrupt on APIF
Address detection generated the interrupt on APIF
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 373
ATtiny406
Two-Wire Interface (TWI)
25.5.12 Slave Address
Name:
Offset:
Reset:
Property:
Bit
7
SADDR
0x0C
0x00
-
6
5
4
3
2
1
0
ADDR[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – ADDR[7:0] Address
The Slave Address register in combination with the Slave Address Mask register (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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 374
ATtiny406
Two-Wire Interface (TWI)
25.5.13 Slave Data
Name:
Offset:
Reset:
Property:
Bit
7
SDATA
0x0D
0x00
-
6
5
4
3
2
1
0
DATA[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – DATA[7:0] Data
The Slave Data register I/O location (DATA) provides direct access to the slave's physical Shift register,
which is used both to shift data out onto the bus (transmit) and to shift in data received from the bus
(receive). The direct access implies that the Data register cannot be accessed during byte transmissions.
Built-in logic prevents any write accesses to the Data register during the shift operations. Reading valid
data or writing data to be transmitted can only be successfully done when the bus clock (SCL) is held low
by the slave (i.e., when the slave CLKHOLD bit is set). However, it is not necessary to check the
CLKHOLD bit in software before accessing the slave DATA register if the software keeps track of the
present protocol state by using interrupts or observing the interrupt flags. Accessing the slave DATA
register, assumed that clock hold is active, auto-trigger bus operations dependent of the state of the
Slave Acknowledge Action Command bits (ACKACT) and type of register access (read or write).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 375
ATtiny406
Two-Wire Interface (TWI)
25.5.14 Slave Address Mask
Name:
Offset:
Reset:
Property:
Bit
7
SADDRMASK
0x0E
0x00
-
6
5
4
3
2
1
0
ADDRMASK[6:0]
Access
Reset
ADDREN
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:1 – 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 376
ATtiny406
Cyclic Redundancy Check Memory Scan (CRCSCAN...
26.
Cyclic Redundancy Check Memory Scan (CRCSCAN)
26.1
Features
•
•
•
•
•
•
26.2
CRC-16-CCITT
Can Check Full Flash, Application Code and/or Boot Section
Priority Check Mode
Selectable NMI Trigger on Failure
User Configurable Check During Internal Reset Initialization
Paused in all CPU Sleep Modes
Overview
A Cyclic Redundancy Check (CRC) takes a data stream of bytes from the NVM (either entire Flash, only
Boot section, or both application code and Boot section) and generates a checksum. The CRC peripheral
(CRCSCAN) can be used to detect errors in program memory.
The last location in the section to check has to contain the correct pre-calculated checksum for
comparison. If the checksum calculated by the CRCSCAN and the pre-calculated checksums match, a
Status bit in the CRCSCAN is set. If they do not match, the Status register will indicate that it failed. The
user can choose to let the CRCSCAN generate a Non-Maskable Interrupt (NMI) if the checksums do not
match.
An n-bit CRC, applied to a data block of arbitrary length, will detect any single alteration (error burst) up to
n bits in length. For longer error bursts, a fraction 1-2-n will be detected.
The CRC-generator supports CRC-16-CCITT.
Polynomial:
•
CRC-16-CCITT: x16 + x12 + x5 + 1
The CRC reads in byte-by-byte of the content of the section(s) it is set up to check, starting with byte 0,
and generates a new checksum per byte. The byte is sent through an implementation corresponding to
Figure 26-1, starting with the Most Significant bit. If the last two bytes in the section contain the correct
checksum, the CRC will pass. See 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
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 377
ATtiny406
Cyclic Redundancy Check Memory Scan (CRCSCAN...
26.2.1
Block Diagram
Figure 26-2. Cyclic Redundancy Check Block Diagram
CTRLA
Enable, Reset
CTRLB
Mode, Source
BUSY
Memory
(Boot, App., Flash)
CRC-16-CCIT
CHECKSUM
STATUS
CRC OK
Non-Maskable
Interrupt
26.2.2
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 26-1. System Product Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
No
-
Interrupts
Yes
CPUINT
Events
No
-
Debug
Yes
UPDI
Related Links
Clocks
Interrupts
26.2.2.1 Clocks
This peripheral depends on the peripheral clock.
Related Links
Clock Controller (CLKCTRL)
26.2.2.2 I/O Lines and Connections
Not applicable.
26.2.2.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
Related Links
CPU Interrupt Controller (CPUINT)
SREG
Interrupts
26.2.2.4 Events
Not applicable.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 378
ATtiny406
Cyclic Redundancy Check Memory Scan (CRCSCAN...
26.2.2.5 Debug Operation
Whenever the debugger accesses the device, for instance, reading or writing a peripheral or memory
location, the CRCSCAN peripheral will be disabled.
If the CRCSCAN is busy when the debugger accesses the device, the CRCSCAN will restart the ongoing
operation when the debugger accesses an internal register or when the debugger disconnects.
The BUSY bit in the Status register (CRCSCAN.STATUS) will read '1' if the CRCSCAN was busy when
the debugger caused it to disable, but it will not actively check any section as long as the debugger keeps
it disabled. There are synchronized CRC Status bits in the debugger's internal register space, which can
be read by the debugger without disabling the CRCSCAN. Reading the debugger's internal CRC status
bits will make sure that the CRCSCAN is enabled.
It is possible to write the CRCSCAN.STATUS register directly from the debugger:
•
BUSY bit in CRCSCAN.STATUS:
– Writing the BUSY bit to '0' will stop the ongoing CRC operation (so that the CRCSCAN does
not restart its operation when the debugger allows it).
– Writing the BUSY bit to '1' will make the CRC start a single check with the settings in the
Control B register (CRCSCAN.CTRLB), but not until the debugger allows it.
•
As long as the BUSY bit in CRCSCAN.STATUS is '1', CRCSCAN.CRCTRLB and the NonMaskable Interrupt Enable bit (NMIEN) in the Control A register (CRCSCAN.CTRLA) cannot be
altered.
OK bit in CRCSCAN.STATUS:
– Writing the OK bit to '0' can trigger a Non-Maskable Interrupt (NMI) if the NMIEN bit in
CRCSCAN.CTRLA is '1'. If an NMI has been triggered, no writes to the CRCSCAN are
allowed.
– Writing the OK bit to '1' will make the OK bit read as '1' when the BUSY bit in
CRCSCAN.STATUS is '0'.
Writes to CRCSCAN.CTRLA and CRCSCAN.CTRLB from the debugger are treated in the same way as
writes from the CPU.
Related Links
Unified Program and Debug Interface (UPDI)
CTRLA
CTRLB
26.3
Functional Description
26.3.1
Initialization
To enable a CRC in software (or via the debugger):
1. Enable the CRCSCAN by writing a '1' to the ENABLE bit in the Control A register
(CRCSCAN.CTRLA).
2. The CRC will start after three cycles, and the CPU will continue executing during these three
cycles.
The CRCSCAN can be enabled during the internal Reset initialization to ensure the Flash is OK before
letting the CPU execute code. If the CRCSCAN fails during the internal Reset initialization, the CPU is not
allowed to start normal code execution - the device remains in Reset state instead of executing code with
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 379
ATtiny406
Cyclic Redundancy Check Memory Scan (CRCSCAN...
unexpected behavior. The full source settings are available during the internal Reset initialization. See the
Fuse description for more information.
If the CRCSCAN was enabled during the internal Reset initialization, the CRC Control A and B registers
will reflect this when normal code execution is started:
•
The ENABLE bit in CRCSCAN.CTRLA will be '1'
•
The MODE bit field in CRCSCAN.CTRLB will be
•
The SRC bit field in CRCSCAN.CTRLB will reflect the checked section(s).
The CRCSCAN can be enabled during Reset by configuring the CRCSRC fuse in FUSE.SYSCFG0.
Related Links
CTRLA
CTRLB
Configuration and User Fuses (FUSE)
Reset Time
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 start-up.
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 16-bit checksum must be saved in the last two bytes of the BOOT
section, and similarly for APPLICATION and entire Flash. Table 26-2 shows explicitly how the checksum
should be stored for the different 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 26-2. How to Place the Pre-Calculated 16-Bit 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 26-3. Available Interrupt Vectors and Sources
Offset
Name
Vector Description
Conditions
0x00
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
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 380
ATtiny406
Cyclic Redundancy Check Memory Scan (CRCSCAN...
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.
Related Links
CTRLA
STATUS
CPU Interrupt Controller (CPUINT)
26.3.4
Sleep Mode Operation
In all CPU Sleep modes, the CRCSCAN peripheral is halted and will resume operation when the CPU
wakes up.
It is possible to enter Sleep mode after setting up the CRCSCAN to start a PRIORITY check (see
CRCSCAN.CTRLB for more information), but before the actual check is started. If the CPU is able to
enter Sleep mode before the check starts and a Priority check was configured, the check will start and
complete (halting the CPU) immediately after waking up and before entering any interrupt handler.
26.3.5
Configuration Change Protection
Not applicable.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 381
ATtiny406
Cyclic Redundancy Check Memory Scan (CRCSCAN...
26.4
Register Summary - CRCSCAN
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
STATUS
7:0
26.5
RESET
NMIEN
ENABLE
SRC[1:0]
OK
BUSY
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 382
ATtiny406
Cyclic Redundancy Check Memory Scan (CRCSCAN...
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
1
0
RESET
7
6
5
4
3
2
NMIEN
ENABLE
R/W
R/W
R/W
0
0
0
Bit 7 – RESET Reset CRCSCAN
Writing this bit to '1' resets the CRCSCAN peripheral: The CRCSCAN Control registers and STATUS
register (CTRLA, CTRLB, STATUS) will be cleared one clock cycle after the RESET bit was written to '1'.
If NMIEN is '0', this bit is writable both when the CRCSCAN is busy (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). A failure in the ongoing check will still be detected and can cause
an NMI if the NMIEN bit is '1'.
The CRCSCAN can be enabled during the internal Reset initialization to verify Flash sections before
letting the CPU start normal code execution (see device data sheet fuse description). If the CRCSCAN is
enabled during the internal Reset initialization, the ENABLE bit will read as '1' when normal code
execution starts.
To see whether the CRCSCAN peripheral is busy with an ongoing check, poll the Busy bit (BUSY) in the
STATUS register (CRCSCAN.STATUS).
Related Links
Configuration and User Fuses (FUSE)
Reset Time
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 383
ATtiny406
Cyclic Redundancy Check Memory Scan (CRCSCAN...
26.5.2
Control B
Name:
Offset:
Reset:
Property:
CTRLB
0x01
0x00
-
The CTRLB register contains the mode and source settings for the CRC. It is not writable when the CRC
is busy or when an NMI has been triggered.
Bit
7
6
5
4
3
2
1
0
SRC[1:0]
Access
Reset
R/W
R/W
0
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 fuse description). If the CRC is enabled during internal Reset initialization, the SRC bit
field will read out as FLASH, BOOTAPP, or BOOT when normal code execution starts (depending on the
configuration).
Value
0x0
0x1
0x2
0x3
Name
FLASH
Description
The CRC is performed on the entire Flash (boot, application code, and
application data sections).
BOOTAPP The CRC is performed on the boot and application code sections of Flash.
BOOT
The CRC is performed on the boot section of Flash.
Reserved.
Related Links
Configuration and User Fuses (FUSE)
Reset Time
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 384
ATtiny406
Cyclic Redundancy Check Memory Scan (CRCSCAN...
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
2
1
0
OK
BUSY
Access
R
R
Reset
1
0
Bit 1 – OK CRC OK
When this bit is read as 1, the previous CRC completed successfully. The bit is set to '1' from Reset but is
cleared to '0' when enabling. As long as the CRC module is busy, it will be read '0'. When running
continuously, the CRC status must be assumed OK until it fails or is stopped by the user.
Bit 0 – BUSY CRC Busy
When this bit is read as 1, the CRC module is busy. As long as the module is busy, the access to the
control registers is limited.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 385
ATtiny406
Configurable Custom Logic (CCL)
27.
Configurable Custom Logic (CCL)
27.1
Features
•
•
•
•
•
•
•
•
27.2
Glue Logic for General Purpose PCB Design
Up to two Programmable Look-Up Tables LUT[1:0]
Combinatorial Logic Functions: Any Logic Expression That is a Function of up to Three Inputs.
Sequential Logic Functions:
Gated D Flip-Flop, JK Flip-Flop, gated D Latch, RS Latch
Flexible Look-Up Table Inputs Selection:
– I/Os
– Events
– Subsequent LUT output
– Internal peripherals
• Analog comparator
• Timer/counters
• USART
• SPI
Clocked by System Clock or Other Peripherals
Output Can be Connected to I/O pins or Event System
Optional Synchronizer, Filter, or Edge Detector Available on Each LUT Output
Overview
The Configurable Custom Logic (CCL) is a programmable logic peripheral which can be connected to the
device pins, to events, or to other internal peripherals. The CCL can serve as "glue logic" between the
device peripherals and external devices. The CCL can eliminate the need for external logic components,
and can also help the designer to overcome real-time constraints by combining core independent
peripherals to handle the most time-critical parts of the application independent of the CPU.
The CCL peripheral has one pair of Look-Up Tables (LUT). Each LUT consists of three inputs, a truth
table, and a filter/edge detector. Each LUT can generate an output as a user programmable logic
expression with three inputs. Inputs can be individually masked.
The output can be generated from the inputs combinatorially and can be filtered to remove spikes. An
optional sequential module can be enabled. The inputs to the sequential module are individually
controlled by two independent, adjacent LUT (LUT0/LUT1) outputs, enabling complex waveform
generation.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 386
ATtiny406
Configurable Custom Logic (CCL)
27.2.1
Block Diagram
Figure 27-1. Configurable Custom Logic
LUT0
INSEL
Internal
Events
I/O
Peripherals
FILTSEL
TRUTH
Filter/
Synch
CLKSRC
EDGEDET
Edge
Detector
LUT0-OUT
CLK_MUX_OUT
LUT0-IN[2]
clkCCL
SEQSEL
Sequential
ENABLE
LUT1
INSEL
Internal
Events
I/O
Peripherals
FILTSEL
TRUTH
Filter/
Synch
CLKSRC
LUT1-IN[2]
clkCCL
EDGEDET
Edge
Detector
LUT1-OUT
CLK_MUX_OUT
ENABLE
27.2.2
Signal Description
Pin Name
Type
Description
LUTn-OUT
Digital output
Output from look-up table
LUTn-IN[2:0]
Digital input
Input to look-up table
Refer to I/O Multiplexing and Considerations for details on the pin mapping for this peripheral. One signal
can be mapped to several pins.
Related Links
I/O Multiplexing and Considerations
27.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 27-1. CCL System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 387
ATtiny406
Configurable Custom Logic (CCL)
27.2.3.1 Clocks
By default, the CCL is using the peripheral clock of the device (CLK_PER).
Alternatively, the CCL can be clocked by a peripheral input that is available on LUT n input line 2
(LUTn_IN[2]). This is configured by writing a '1' to the Clock Source Selection bit (CLKSRC) in the LUTn
Control A register (CCL.LUTnCTRLA). The sequential block is clocked by the same clock as that of the
even LUT in the LUT pair (SEQn.clk = LUT2n.clk). It is advised to disable the peripheral by writing a '0' to
the Enable bit (ENABLE) in the Control A register (CCL.CTRLA) before configuring the CLKSRC bit in
CCL.LUTnCTRLA.
Alternatively, the input line 2 (IN[2]) of an LUT can be used to clock the LUT and the corresponding
Sequential block. This is enabled by writing a '1' to the Clock Source Selection bit (CLKSRC) in the LUTn
Control A register (CCL.LUTnCTRLA).
The CCL must be disabled before changing the LUT clock source: write a '0' to the Enable bit (ENABLE)
in Control A register (CCL.CTRLA).
Related Links
Clock Controller (CLKCTRL)
27.2.3.2 I/O Lines
The CCL can take inputs and generate output through I/O pins. For this to function properly, the I/O pins
must be configured to be used by a Look Up Table (LUT).
Related Links
I/O Pin Configuration (PORT)
27.2.3.3 Interrupts
Not applicable.
27.2.3.4 Events
The CCL can use events from other peripherals and generate events that can be used by other
peripherals. For this feature to function, the events have to be configured properly. Refer to the Related
Links below for more information about the event users and event generators.
27.2.3.5 Debug Operation
When the CPU is halted in Debug mode the CCL continues normal operation. However, the CCL cannot
be halted when the CPU is halted in Debug mode. If the CCL is configured in a way that requires it to be
periodically serviced by the CPU, improper operation or data loss may result during debugging.
27.3
Functional Description
27.3.1
Initialization
The following bits are enable-protected, meaning that they can only be written when the corresponding
even LUT is disabled (ENABLE=0 in CCL.LUT0CTRLA):
•
Sequential Selection (SEQSEL) in Sequential Control 0 register (CCL.SEQCTRL0)
The following registers are enable-protected, meaning that they can only be written when the
corresponding LUT is disabled (ENABLE=0 in CCL.LUT0CTRLA):
•
LUT n Control x register, except ENABLE bit (CCL.LUTnCTRLx)
Enable-protected bits in the CCL.LUTnCTRLx registers can be written at the same time as ENABLE in
CCL.LUTnCTRLx is written to '1', but not at the same time as ENABLE is written to '0'.
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Datasheet Preliminary
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ATtiny406
Configurable Custom Logic (CCL)
Enable-protection is denoted by the Enable-Protected property in the register description.
27.3.2
Operation
27.3.2.1 Enabling, Disabling, and Resetting
The CCL is enabled by writing a '1' to the ENABLE bit in the Control register (CCL.CTRLA). The CCL is
disabled by writing a '0' to that ENABLE bit.
Each LUT is enabled by writing a '1' to the LUT Enable bit (ENABLE) in the LUT n Control A register
(CCL.LUTnCTRLA). Each LUT is disabled by writing a '0' to the ENABLE bit in CCL.LUTnCTRLA.
27.3.2.2 Look-Up Table Logic
The look-up table in each LUT unit can generate a combinational logic output as a function of up to three
inputs IN[2:0]. Unused inputs can be masked (tied low). The truth table for the combinational logic
expression is defined by the bits in the CCL.TRUTHn registers. Each combination of the input bits
(IN[2:0]) corresponds to one bit in the TRUTHn register, as shown in the table below.
Table 27-2. Truth Table of LUT
IN[2]
IN[1]
IN[0]
OUT
0
0
0
TRUTH[0]
0
0
1
TRUTH[1]
0
1
0
TRUTH[2]
0
1
1
TRUTH[3]
1
0
0
TRUTH[4]
1
0
1
TRUTH[5]
1
1
0
TRUTH[6]
1
1
1
TRUTH[7]
27.3.2.3 Truth Table Inputs Selection
Input Overview
The inputs can be individually:
•
•
•
•
Masked
Driven by peripherals:
– Analog comparator output (AC)
– Timer/Counters waveform outputs (TC)
Driven by internal events from Event System
Driven by other CCL sub-modules
The Input Selection for each input y of LUT n is configured by writing the Input y Source Selection bit in
the LUT n Control x=[B,C] registers:
•
INSEL0 in CCL.LUTnCTRLB
•
INSEL1 in CCL.LUTnCTRLB
•
INSEL2 in CCL.LUTnCTRLC
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Datasheet Preliminary
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ATtiny406
Configurable Custom Logic (CCL)
Internal Feedback Inputs (FEEDBACK)
When selected (INSELy=FEEDBACK in CCL.LUTnCTRLx), the Sequential (SEQ) output is used as input
for the corresponding LUT.
The output from an internal sequential module can be used as input source for the LUT, see the figure
below for an example for LUT0 and LUT1. The sequential selection for each LUT follows the formula:
IN 2N � = SEQ �
IN 2N+1 � = SEQ �
With N representing the sequencer number and i=0,1 representing the LUT input index.
For details, refer to Sequential Logic.
Figure 27-2. Feedback Input Selection
Linked LUT (LINK)
When selecting the LINK input option, the next LUT's direct output is used as the LUT input. In general,
LUT[n+1] is linked to the input of LUT[n]. As example, LUT1 is the input for LUT0.
Figure 27-3. Linked LUT Input Selection
LUT0
SEQ 0
CTRL
(ENABLE)
LUT1
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ATtiny406
Configurable Custom Logic (CCL)
Internal Events Inputs Selection (EVENT)
Asynchronous events from the Event System can be used as input to the LUT. Two event input lines
(EVENT0 and EVENT1) are available, and can be selected as LUT input. Before selecting the EVENT
input option by writing to the LUT CONTROL A or B register (CCL.LUTnCTRLB or LUTnCTRLC), the
Event System must be configured.
I/O Pin Inputs (I/O)
When selecting the I/O option, the LUT input will be connected to its corresponding I/O pin. Refer to the
I/O Multiplexing section for more details about where the LUTnINy is located.
Figure 27-4. I/O Pin Input Selection
Peripherals
The different peripherals on the three input lines of each LUT are selected by writing to the respective
LUT n Input y bit fields in the LUT n Control B and C registers:
•
INSEL0 in CCL.LUTnCTRLB
•
INSEL1 in CCL.LUTnCTRLB
•
INSEL2 in CCL.LUTnCTRLC
Related Links
I/O Multiplexing and Considerations
I/O Pin Configuration (PORT)
Clock Controller (CLKCTRL)
Analog Comparator (AC)
16-bit Timer/Counter Type A (TCA)
Universal Synchronous and Asynchronous Receiver and Transmitter (USART)
Serial Peripheral Interface (SPI)
Two-Wire Interface (TWI)
I/O Multiplexing and Considerations
27.3.2.4 Filter
By default, the LUT output is a combinational function of the LUT inputs. This may cause some short
glitches when the inputs change the value. These glitches can be removed by clocking through filters if
demanded by application needs.
The Filter Selection bits (FILTSEL) in the LUT Control registers (CCL.LUTnCTRLA) define the digital filter
options. When a filter is enabled, the output will be delayed by two to five CLK cycles (peripheral clock or
alternative clock). One clock cycle after the corresponding LUT is disabled, all internal filter logic is
cleared.
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Datasheet Preliminary
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ATtiny406
Configurable Custom Logic (CCL)
Figure 27-5. Filter
FILTSEL
Input
OUT
Q
D
R
Q
D
R
Q
D
R
D
G
Q
R
CLK_MUX_OUT
CLR
27.3.2.5 Edge Detector
The edge detector can be used to generate a pulse when detecting a rising edge on its input. To detect a
falling edge, the TRUTH table should be programmed to provide inverted output.
The edge detector is enabled by writing '1' to the Edge Selection bit (EDGEDET) in the LUT n Control A
register (CCL.LUTnCTRLA). In order to avoid unpredictable behavior, a valid filter option must be enabled
as well.
Edge detection is disabled by writing a '0' to EDGEDET in CCL.LUTnCTRLA. After disabling an LUT, the
corresponding internal Edge Detector logic is cleared one clock cycle later.
Figure 27-6. Edge Detector
CLK_MUX_OUT
27.3.2.6 Sequential Logic
Each LUT pair can be connected to an internal Sequential block. A Sequential block can function as
either D flip-flop, JK flip-flop, gated D-latch, or RS-latch. The function is selected by writing the Sequential
Selection bits (SEQSEL) in the Sequential Control register (CCL.SEQCTRLn).
The Sequential block receives its input from either LUT, filter, or edge detector, depending on the
configuration.
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ATtiny406
Configurable Custom Logic (CCL)
The Sequential block is clocked by the same clock as the corresponding LUT, which is either the
peripheral clock or input line 2 (IN[2]). This is configured by the Clock Source bit (CLKSRC) in the LUT n
Control A register (CCL.LUTnCTRLA).
When the even LUT (LUT0) is disabled, the latch is asynchronously cleared, during which the flip-flop
Reset signal (R) is kept enabled for one clock cycle. In all other cases, the flip-flop output (OUT) is
refreshed on the rising edge of the clock, as shown in the respective Characteristics tables.
Gated D Flip-Flop (DFF)
The D-input is driven by the even LUT output (LUT0), and the G-input is driven by the odd LUT output
(LUT1).
Figure 27-7. D Flip-Flop
even LUT
CLK_MUX_OUT
odd LUT
Table 27-3. DFF Characteristics
R
G
D
OUT
1
X
X
Clear
0
1
1
Set
0
Clear
X
Hold state (no change)
0
JK Flip-Flop (JK)
The J-input is driven by the even LUT output (LUT0), and the K-input is driven by the odd LUT output
(LUT1).
Figure 27-8. JK Flip-Flop
even LUT
CLK_MUX_OUT
odd LUT
Table 27-4. JK Characteristics
R
J
K
OUT
1
X
X
Clear
0
0
0
Hold state (no change)
0
0
1
Clear
0
1
0
Set
0
1
1
Toggle
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ATtiny406
Configurable Custom Logic (CCL)
Gated D-Latch (DLATCH)
The D-input is driven by the even LUT output (LUT0), and the G-input is driven by the odd LUT output
(LUT1).
Figure 27-9. D-Latch
even LUT
D
odd LUT
G
Q
OUT
Table 27-5. D-Latch Characteristics
G
D
OUT
0
X
Hold state (no change)
1
0
Clear
1
1
Set
RS-Latch (RS)
The S-input is driven by the even LUT output (LUT0), and the R-input is driven by the odd LUT output
(LUT1).
Figure 27-10. RS-Latch
even LUT
S
odd LUT
R
Q
OUT
Table 27-6. RS-Latch Characteristics
S
R
OUT
0
0
Hold state (no change)
0
1
Clear
1
0
Set
1
1
Forbidden state
27.3.2.7 Clock Source Settings
The Filter, Edge Detector, and Sequential logic are by default clocked by the system clock (CLK_PER). It
is also possible to use the LUT input 2 (IN[2]) to clock these blocks (CLK_MUX_OUT in Figure 27-11).
This is configured by writing the Clock Source bit (CLKSRC) in the LUT Control A register
(CCL.LUTnCTRLA) to '1'.
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ATtiny406
Configurable Custom Logic (CCL)
Figure 27-11. Clock Source Settings
Edge
Detector
IN[2]
Filter
CLK_MUX_OUT
CLK_CCL
CLKSRC
LUT0
Edge
Detector
IN[2]
Sequential
logic
Filter
CLK_MUX_OUT
CLK_CCL
CLKSRC
LUT1
When the Clock Source bit (CLKSRC) is '1', IN[2] is used to clock the corresponding Filter and Edge
Detector (CLK_MUX_OUT). The Sequential logic is clocked by CLK_MUX_OUT of the even LUT in the
pair. When CLKSRC bit is '1', IN[2] is treated as MASKed (low) in the TRUTH table.
The CCL peripheral must be disabled while changing the clock source to avoid undetermined outputs
from the peripheral.
27.3.3
Events
The CCL can generate the following output events:
•
LUTnOUT: Look-Up Table Output Value
The CCL can take the following actions on an input event:
•
INx: The event is used as input for the TRUTH table
Related Links
Event System (EVSYS)
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,
or Sequential logic is enabled, the LUT output will be forced to zero in Standby Sleep mode. In Idle sleep
mode, the TRUTH table decoder will continue operation and the LUT output will be refreshed accordingly,
regardless of the RUNSTDBY bit.
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Datasheet Preliminary
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ATtiny406
Configurable Custom Logic (CCL)
If the Clock Source bit (CLKSRC) in the LUT n Control A register (CCL.LUTnCTRLA) is written to '1', the
LUT input 2 (IN[2]) will always clock the Filter, Edge Detector, and Sequential block. The availability of the
IN[2] clock in sleep modes will depend on the sleep settings of the peripheral employed.
27.3.5
Configuration Change Protection
Not applicable.
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ATtiny406
Configurable Custom Logic (CCL)
27.4
Register Summary - CCL
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
SEQCTRL0
7:0
RUNSTDBY
ENABLE
SEQSEL[3:0]
0x02
...
Reserved
0x04
0x05
LUT0CTRLA
7:0
0x06
LUT0CTRLB
7:0
0x07
LUT0CTRLC
7:0
0x08
TRUTH0
7:0
0x09
LUT1CTRLA
7:0
0x0A
LUT1CTRLB
7:0
0x0B
LUT1CTRLC
7:0
0x0C
TRUTH1
7:0
27.5
EDGEDET
CLKSRC
FILTSEL[1:0]
OUTEN
INSEL1[3:0]
ENABLE
INSEL0[3:0]
INSEL2[3:0]
TRUTH[7:0]
EDGEDET
CLKSRC
FILTSEL[1:0]
OUTEN
INSEL1[3:0]
ENABLE
INSEL0[3:0]
INSEL2[3:0]
TRUTH[7:0]
Register Description
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ATtiny406
Configurable Custom Logic (CCL)
27.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
Access
Reset
CTRLA
0x00
0x00
-
6
5
4
3
2
1
0
RUNSTDBY
ENABLE
R/W
R/W
0
0
Bit 6 – RUNSTDBY Run in Standby
This bit indicates if the peripheral clock (CLK_PER) is kept running in Standby Sleep mode. The setting is
ignored for configurations where the CLK_PER is not required.
Value
0
1
Description
System clock is not required in Standby Sleep mode
System clock is required in Standby Sleep mode
Bit 0 – ENABLE Enable
Value
0
1
Description
The peripheral is disabled
The peripheral is enabled
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Datasheet Preliminary
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ATtiny406
Configurable Custom Logic (CCL)
27.5.2
Sequential Control 0
Name:
Offset:
Reset:
Property:
Bit
7
SEQCTRL0
0x01 [ID-00000485]
0x00
Enable-Protected
6
5
4
3
2
1
0
SEQSEL[3:0]
Access
Reset
R/W
R/W
R/W
R/W
0
0
0
0
Bits 3:0 – SEQSEL[3:0] Sequential Selection
These bits select the sequential configuration.
Value
0x0
0x1
0x2
0x3
0x4
Other
Name
DISABLE
DFF
JK
LATCH
RS
-
© 2018 Microchip Technology Inc.
Description
Sequential logic is disabled
D flip-flop
JK flip-flop
D latch
RS latch
Reserved
Datasheet Preliminary
40001976A-page 399
ATtiny406
Configurable Custom Logic (CCL)
27.5.3
LUT n Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
LUTCTRLA
0x05 + n*0x04 [n=0..1]
0x00
Enable-Protected
7
6
EDGEDET
CLKSRC
5
4
R/W
R/W
R/W
0
0
0
FILTSEL[1:0]
3
2
1
0
OUTEN
ENABLE
R/W
R/W
R/W
0
0
0
Bit 7 – EDGEDET Edge Detection
Value
0
1
Description
Edge detector is disabled
Edge detector is enabled
Bit 6 – CLKSRC Clock Source Selection
This bit selects whether the peripheral clock (CLK_PER) or any input present on input line 2 (IN[2]) is
used as clock (CLK_MUX_OUT) for an LUT.
The CLK_MUX_OUT of the even LUT is used for clocking the Sequential block of an LUT pair.
Value
0
1
Description
CLK_PER is clocking the LUT
IN[2] is clocking the LUT
Bits 5:4 – FILTSEL[1:0] Filter Selection
These bits select the LUT output filter options:
Filter Selection
Value
0x0
0x1
0x2
0x3
Name
DISABLE
SYNCH
FILTER
-
Description
Filter disabled
Synchronizer enabled
Filter enabled
Reserved
Bit 3 – OUTEN Output Enable
This bit enables the LUT output to the LUTnOUT pin. When written to '1', the pin configuration of the
PORT I/O Controller is overridden.
Value
0
1
Description
Output to pin disabled
Output to pin enabled
Bit 0 – ENABLE LUT Enable
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ATtiny406
Configurable Custom Logic (CCL)
Value
0
1
Description
The LUT is disabled
The LUT is enabled
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ATtiny406
Configurable Custom Logic (CCL)
27.5.4
LUT n Control B
Name:
Offset:
Reset:
Property:
LUTCTRLB
0x06 + n*0x04 [n=0..1]
0x00
Enable-Protected
SPI connections to the CCL work only in master SPI mode.
USART connections to the CCL work only in asynchronous/synchronous USART Master mode.
Bit
7
6
5
4
3
2
INSEL1[3:0]
Access
Reset
1
0
INSEL0[3:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:4 – INSEL1[3:0] LUT n Input 1 Source Selection
These bits select the source for input 1 of LUT n:
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
Name
MASK
FEEDBACK
LINK
EVENT0/EVENT1
EVENT2/EVENT3
IO
AC0
TCB0
TCA0
USART0
SPI0
Description
Masked input
Feedback input
Linked other LUT as input source
Event 0 as input source for LUT0/Event 1 as input source for LUT1
Event 2 as input source for LUT0/Event 3 as input source for LUT1
I/O pin LUTn-IN1 input source
AC0 OUT input source
TCB WO input source
TCA WO1 input source
Reserved
USART TXD input source
SPI MOSI input source
Bits 3:0 – INSEL0[3:0] LUT n Input 0 Source Selection
These bits select the source for input 0 of LUT n:
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
Other
Name
MASK
FEEDBACK
LINK
EVENT0/EVENT1
EVENT2/EVENT3
IO
AC0
TCB0
TCA0
USART0
SPI0
-
© 2018 Microchip Technology Inc.
Description
Masked input
Feedback input
Linked other LUT as input source
Event 0 as input source for LUT0/Event 1 as input source for LUT1
Event 2 as input source for LUT0/Event 3 as input source for LUT1
I/O pin LUTn-IN0 input source
AC0 OUT input source
TCB WO input source
TCA WO0 input source
Reserved
USART XCK input source
SPI SCK input source
Reserved
Datasheet Preliminary
40001976A-page 402
ATtiny406
Configurable Custom Logic (CCL)
27.5.5
LUT n Control C
Name:
Offset:
Reset:
Property:
Bit
7
LUTCTRLC
0x07 + n*0x04 [n=0..1]
0x00
Enable-Protected
6
5
4
3
2
1
0
INSEL2[3:0]
Access
Reset
R/W
R/W
R/W
R/W
0
0
0
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
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
other
Name
MASK
FEEDBACK
LINK
EVENT0
EVENT1
IO
AC0
TCB0
TCA0
SPI0
-
© 2018 Microchip Technology Inc.
Description
Masked input
Feedback input
Linked other LUT as input source
Event input source 0
Event input source 1
I/O pin LUTn-IN2 input source
AC0 OUT input source
TCB WO input source
TCA WO2 input source
Reserved
Reserved
SPI MISO input source
Reserved
Datasheet Preliminary
40001976A-page 403
ATtiny406
Configurable Custom Logic (CCL)
27.5.6
TRUTHn
Name:
Offset:
Reset:
Property:
Bit
7
TRUTH
0x08 + n*0x04 [n=0..1]
0x00
Enable-Protected
6
5
4
3
2
1
0
TRUTH[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – TRUTH[7:0] Truth Table
These bits define the value of truth logic as a function of inputs IN[2:0].
© 2018 Microchip Technology Inc.
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ATtiny406
Analog Comparator (AC)
28.
Analog Comparator (AC)
28.1
Features
•
•
•
•
•
•
•
•
28.2
One Instance of the AC Controller, AC0
Zero-Cross Detection
Selectable Hysteresis:
– None
– 10 mV
– 25 mV
– 50 mV
Analog Comparator Output Available on Pin
Comparator Output Inversion Available
Flexible Input Selection:
– Two Positive pins
– Two Negative pins
– Internal reference voltage
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 internal references. The analog comparator output state
can also be output on a pin for use by external devices.
The AC has one positive input and one negative input. The positive input source is one of a selection of
two analog input pins. The negative inputs are chosen either from analog input pins or from internal
inputs, such as an internal voltage reference.
The digital output from the comparator is '1' when the difference between the positive and the negative
input voltage is positive and '0' otherwise.
This device provides one instance of the AC controller, AC0.
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ATtiny406
Analog Comparator (AC)
28.2.1
Block Diagram
Figure 28-1. Analog Comparator
AC Controller
AINP0
MUXCTRLA
:
Invert
+
AINPn
Controller
Logic
AC
AINN0
OUT
-
:
AINNn
Hysteresis
Enable
VREF
Event
System
CTRLA
Note: Refer to Signal Description for the number of AINN and AINP.
28.2.2
28.2.3
Signal Description
Signal
Description
Type
AINN0
Negative Input 0
Analog
AINN1
Negative Input 1
Analog
AINP0
Positive Input 0
Analog
AINP1
Positive Input 1
Analog
OUT
Comparator Output for AC
Digital
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 28-1. AC System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
28.2.3.1 Clocks
This peripheral depends on the peripheral clock.
28.2.3.2 I/O Lines and Connections
I/O pins AINN0-AINN1 and AINP0- AINP1 are all analog inputs to the AC.
For correct operation, the pins must be configured in the port and port multiplexing peripherals.
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ATtiny406
Analog Comparator (AC)
It is recommended to disable the GPIO input when using the AC.
28.2.3.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
28.2.3.4 Events
The events of this peripheral are connected to the Event System.
28.2.3.5 Debug Operation
This peripheral is unaffected by entering Debug mode.
If the peripheral is configured to require periodical service by the CPU through interrupts or similar,
improper operation or data loss may result during halted debugging.
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 startup time is normally longer than the AC start-up time. The VREF start-up time is 60 µs at most.
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
The AC has one positive and one negative input. The inputs can be pins and internal sources, such as a
voltage reference.
Each input is selected by writing to the Positive and Negative Input MUX Selection bit field (MUXPOS and
MUXNEG) in the MUX Control A register (AC.MUXTRLA).
Pin Inputs
The following Analog input pins on the port can be selected as input to the analog comparator
•
•
•
•
AINN0
AINN1
AINP0
AINP1
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ATtiny406
Analog Comparator (AC)
Internal Inputs
One internal input is available for the analog comparator:
•
AC voltage reference
28.3.2.3 Low-Power Mode
For power sensitive applications, the AC provides a Low-Power mode with reduced power consumption
and increased propagation delay.
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 28-2. Available Interrupt Vectors and Sources
Offset Name
0x00
Vector Description
Conditions
COMP0 Analog comparator interrupt AC output is toggling as configured by INTMODE in
AC.CTRLA
When an interrupt condition occurs, the corresponding interrupt flag is set in the STATUS register
(AC.STATUS).
An interrupt source is enabled or disabled by writing to the corresponding bit in the peripheral's Interrupt
Control register (AC.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the interrupt
flag is set. The interrupt request remains active until the interrupt flag is cleared. See the AC.STATUS
register description for details on how to clear interrupt flags.
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 (AC.CTRLA) is written to '1', the AC will continue to operate, but
the Status register will not be updated, and no Interrupts are generated if no other modules request the
CLK_PER, but events and the pad output will be updated.
In Power-Down Sleep mode, the AC and the output to the pad are disabled.
28.3.6
Configuration Change Protection
Not applicable.
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ATtiny406
Analog Comparator (AC)
28.4
Register Summary - AC
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
RUNSTDBY
7:0
INVERT
0x01
Reserved
0x02
MUXCTRLA
OUTEN
INTMODE[1:0]
HYSMODE[1:0]
MUXPOS
ENABLE
MUXNEG[1:0]
0x03
...
Reserved
0x05
0x06
INTCTRL
7:0
0x07
STATUS
7:0
28.5
CMP
STATE
CMP
Register Description
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ATtiny406
Analog Comparator (AC)
28.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
CTRLA
0x00
0x00
-
7
6
RUNSTDBY
OUTEN
5
4
3
2
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
INTMODE[1:0]
1
HYSMODE[1:0]
0
ENABLE
Bit 7 – RUNSTDBY Run in Standby Mode
Writing a '1' to this bit allows the AC to continue operation in Standby Sleep mode. Since the clock is
stopped, interrupts and status flags are not updated.
Value
0
1
Description
In Standby Sleep mode, the peripheral is halted
In Standby Sleep mode, the peripheral continues operation
Bit 6 – OUTEN Analog Comparator Output Pad Enable
Writing this bit to '1' makes the OUT signal available on the pin.
Bits 5:4 – INTMODE[1:0] Interrupt Modes
Writing to these bits selects what edges of the AC output triggers an interrupt request.
Value
0x0
0x1
0x2
0x3
Name
BOTHEDGE
NEGEDGE
POSEDGE
Description
Both negative and positive edge
Reserved
Negative edge
Positive edge
Bits 2:1 – HYSMODE[1:0] Hysteresis Mode Select
Writing these bits selects the Hysteresis mode for the AC input.
Value
0x0
0x1
0x2
0x3
Name
OFF
10
25
50
Description
OFF
±10 mV
±25 mV
±50 mV
Bit 0 – ENABLE Enable AC
Writing this bit to '1' enables the AC.
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ATtiny406
Analog Comparator (AC)
28.5.2
Mux Control A
Name:
Offset:
Reset:
Property:
MUXCTRLA
0x02
0x00
-
AC.MUXCTRLA controls analog comparator muxes
Bit
Access
Reset
7
6
5
4
3
2
1
0
INVERT
MUXPOS
MUXNEG[1:0]
R/W
R/W
R/W
R/W
0
0
0
0
Bit 7 – INVERT Invert AC Output
Writing a '1' to this bit enables inversion of the output of the AC. This effectively inverts the input to all the
peripherals connected to the signal, and affects the internal status signals.
Bit 3 – MUXPOS Positive Input MUX Selection
Writing to this bit field selects the input signal to the positive input of the AC.
Value
0x0
0x1
Name
AINP0
AINP1
Description
Positive Pin 0
Positive Pin 1
Bits 1:0 – MUXNEG[1:0] Negative Input MUX Selection
Writing to this bit field selects the input signal to the negative input of the AC.
Value
0x0
0x1
0x2
0x3
Name
AINN0
AINN1
VREF
Reserved
© 2018 Microchip Technology Inc.
Description
Negative Pin 0
Negative Pin 1
Voltage Reference
Reserved
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ATtiny406
Analog Comparator (AC)
28.5.3
Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x06
0x00
-
6
5
4
3
2
1
0
CMP
Access
R/W
Reset
0
Bit 0 – CMP Analog Comparator Interrupt Enable
Writing this bit to '1' enables analog comparator interrupt.
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ATtiny406
Analog Comparator (AC)
28.5.4
Status
Name:
Offset:
Reset:
Property:
Bit
7
STATUS
0x07
0x00
-
6
5
4
3
2
1
0
STATE
CMP
Access
R
R/W
Reset
0
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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ATtiny406
Analog-to-Digital Converter (ADC)
29.
Analog-to-Digital Converter (ADC)
29.1
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
29.2
10-Bit Resolution
±2 LSB Absolute Accuracy
6.5 - 260 μs Conversion Time
Up to 115 ksps at 10-Bit Resolution (150 ksps at 8-bit)
Up to Twelve Multiplexed Single-ended Input Channels
Temperature Sensor Input Channel
0V to VDD ADC Input Voltage Range
Multiple Internal ADC Reference Voltages Between 0.55V and VDD
Free-running or Single Conversion mode
Interrupt Available on ADC Conversion Complete
Optional Event Triggered Conversion
Optional Interrupt on Conversion Results
Compare Function for Accurate Monitoring or User-Defined Thresholds (Window Comparator
mode)
Accumulation up to 64 Samples per Conversion
Overview
The Analog-to-Digital Converter (ADC) peripheral features a 10-bit Successive Approximation ADC
(SAR), with a sampling rate up to 115 ksps at 10-bit resolution (150 ksps at 8-bit). The ADC is connected
to a 12-channel analog multiplexer, which allows twelve single-ended voltage inputs. The single-ended
voltage inputs refer to 0V (GND). The ADC input channel can either be internal (e.g. a voltage reference)
or external through the analog input pins.
An ADC conversion can be started by software or by using the Event System (EVSYS) to route an event
from other peripherals, making it possible to do a periodic sampling of input signals, trigger an ADC
conversion on a special condition, or trigger an ADC conversion in Standby Sleep mode. A window
compare feature is available for monitoring the input signal and can be configured to only trigger an
interrupt on user-defined thresholds for under, over, inside, or outside a window, with minimum software
intervention required.
The ADC input signal is fed through a sample-and-hold circuit that ensures that the input voltage to the
ADC is held at a constant level during sampling.
The ADC supports sampling in bursts where a configurable number of conversion results are
accumulated into a single ADC result (Sample Accumulation). Further, a sample delay can be configured
to tune the ADC sampling frequency associated with a single burst. This is to tune the sampling
frequency away from any harmonic noise aliased with the ADC sampling frequency (within the burst) from
the sampled signal. An automatic sampling delay variation feature can be used to randomize this delay to
slightly change the time between samples.
Internal reference voltages from Voltage Reference (VREF) or VDD are provided on-chip.
This device has one instance of the ADC peripheral; ADC0.
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ATtiny406
Analog-to-Digital Converter (ADC)
29.2.1
Block Diagram
Figure 29-1. Block Diagram
The analog input channel is selected by writing to the MUXPOS bits in the MUXPOS register
(ADC.MUXPOS). Any of the ADC input pins, GND, 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 (ADC.CTRLA). Voltage reference and input channel selections will not go into effect before the
ADC is enabled. The ADC does not consume power when the ENABLE bit in ADC.CTRLA is zero.
The ADC generates a 10-bit result that can be read from the Result Register (ADC.RES). The result is
presented right adjusted.
29.2.2
Signal Description
Pin Name
Type
Description
AIN[11:0]
Analog input
Analog input to be converted
Related Links
Configuration Summary
I/O Multiplexing and Considerations
29.2.3
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 29-1. ADC System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
Yes
CPUINT
Events
Yes
EVSYS
Debug
Yes
UPDI
29.2.3.1 Clocks
The ADC uses the peripheral clock CLK_PER and has an internal prescaler to generate the ADC clock
source CLK_ADC.
Related Links
Clock Controller (CLKCTRL)
Clock Generation
29.2.3.2 I/O Lines and Connections
The I/O pins (AINx) are configured by the port - I/O Pin Controller.
The digital input buffer should be disabled on the pin used as input for the ADC to disconnect the digital
domain from the analog domain to obtain the best possible ADC results. This is configured by the port I/O Pin Controller.
Related Links
I/O Pin Configuration (PORT)
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ATtiny406
Analog-to-Digital Converter (ADC)
29.2.3.3 Interrupts
Using the interrupts of this peripheral requires the interrupt controller to be configured first.
Related Links
CPU Interrupt Controller (CPUINT)
SREG
Interrupts
29.2.3.4 Events
The events of this peripheral are connected to the Event System.
Related Links
Event System (EVSYS)
29.2.3.5 Debug Operation
When run-time debugging, this peripheral will continue normal operation. Halting the CPU in Debugging
mode will halt normal operation of the peripheral.
This peripheral can be forced to operate with halted CPU by writing a '1' to the Debug Run bit (DBGRUN)
in the Debug Control register of the peripheral (peripheral.DBGCTRL).
29.2.4
Definitions
An ideal n-bit single-ended ADC converts a voltage linearly between GND and VREF in 2n steps (LSBs).
The lowest code is read as 0, and the highest code is read as 2n-1. Several parameters describe the
deviation from the ideal behavior:
Offset Error
The deviation of the first transition (0x000 to 0x001) compared to the ideal
transition (at 0.5 LSB). Ideal value: 0 LSB.
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.
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ATtiny406
Analog-to-Digital Converter (ADC)
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
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.
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ATtiny406
Analog-to-Digital Converter (ADC)
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.
Related Links
ADC Characteristics
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 (ADC.CTRLA).
2. Optional: Enable the Free-Running mode by writing a '1' to the Free-Running bit (FREERUN) in
ADC.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 (ADC.CTRLB).
4. Configure a voltage reference by writing to the Reference Selection bit (REFSEL) in the Control C
register (ADC.CTRLC). Default is the internal voltage reference of the device (VREF, as configured
there).
5. Configure the CLK_ADC by writing to the Prescaler bit field (PRESC) in the Control C register
(ADC.CTRLC).
6. Configure an input by writing to the MUXPOS bit field in the MUXPOS register (ADC.MUXPOS).
7. Optional: Enable Start Event input by writing a '1' to the Start Event Input bit (STARTEI) in the
Event Control register (ADC.EVCTRL). Configure the Event System accordingly.
8. Enable the ADC by writing a '1' to the ENABLE bit in ADC.CTRLA.
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ATtiny406
Analog-to-Digital Converter (ADC)
Following these steps will initialize the ADC for basic measurements, which can be triggered by an event
(if configured) or by writing a '1' to the Start Conversion bit (STCONV) in the Command register
(ADC.COMMAND).
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 one as long as the conversion is in progress. In Single Conversion mode,
STCONV is cleared by hardware when the conversion is completed.
If a different input channel is selected while a conversion is in progress, the ADC will finish the current
conversion before changing the channel.
Depending on the accumulator setting, the conversion result is from a single sensing operation, or from a
sequence of accumulated samples. Once the triggered operation is finished, the Result Ready flag
(RESRDY) in the Interrupt Flag register (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 one and the Global Interrupt Enable bit is one.
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.
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ATtiny406
Analog-to-Digital Converter (ADC)
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 (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 one. The prescaler counter is reset to zero when the ENABLE bit is zero.
When initiating a conversion by writing a '1' to the Start Conversion bit (STCONV) in the Command
register (ADCn.COMMAND) or from event, the conversion starts at the following rising edge of the
CLK_ADC clock cycle. The prescaler is kept reset as long as there is no ongoing conversion. This
assures a fixed delay from the trigger to the actual start of a conversion in CLK_PER cycles as:
PRESCfactor
+2
2
Figure 29-7. Start Conversion and Clock Generation
StartDelay =
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
ADC.COMMAND. When a conversion is complete, the result is available in the Result register
(ADC.RES), and the Result Ready interrupt flag is set (RESRDY in ADC.INTFLAG). The interrupt flag will
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ATtiny406
Analog-to-Digital Converter (ADC)
be cleared when the result is read from the Result registers, or by writing a '1' to the RESRDY bit in
ADC.INTFLAG.
Figure 29-8. ADC Timing Diagram - Single Conversion
2
3
4
6
8
5
7
1
Cycle Number
9
10
11
13
12
ADC clock
ADC enable
STCONV
RESRDY IF
RESH
RESL
Result MSB
Result LSB
conversion
complete
sample
Both sampling time and sampling length can be adjusted using Sample Delay bit field in Control D
(ADC.CTRLD) and sampling Sample Length bit field in the Sample Control register (ADC.SAMPCTRL).
Both of these control the ADC sampling time in a number of CLK_ADC cycles. This allows sampling highimpedance sources without relaxing conversion speed. See register description for further information.
Total sampling time is given by:
SampleTime =
2 + SAMPDLY + SAMPLEN
�CLK_ADC
Figure 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 one. 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
Cycle Number
1
2
3
4
5
6
7
8
9
10
11
12
13
1
2
ADC clock
ADC enable
Input event
STCONV
RESRDY IF
RESH
RESL
Result MSB
Result LSB
sample
© 2018 Microchip Technology Inc.
conversion
complete
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ATtiny406
Analog-to-Digital Converter (ADC)
29.3.2.4 Changing Channel or Reference Selection
The MUXPOS bits 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'.
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.
Related Links
Electrical Characteristics
ADC Voltage Reference
The reference voltage for the ADC (VREF) controls the conversion range of the ADC. Input voltages that
exceed the selected VREF will be converted to the maximum result value of the ADC, for an ideal 10-bit
ADC this is 0x3FF. VREF can be selected by writing the Reference Selection bits (REFSEL) in the Control
C register (ADC.CTRLC) as either VDD or an internal reference from the VREF peripheral. VDD is
connected to the ADC through a passive switch.
The internal reference is generated from an internal bandgap reference through an internal amplifier, and
is controlled by the Voltage Reference (VREF) peripheral.
Related Links
Voltage Reference (VREF)
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
source is used, the sampling time will be negligible. If a source with higher impedance is used, the
sampling time will depend on how long the source needs to charge the S/H capacitor, which can vary
substantially.
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ATtiny406
Analog-to-Digital Converter (ADC)
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 in 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 = 5 pF
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
In order to achieve accurate results, the result of the temperature sensor measurement must be
processed in the application software using factory calibration values. The temperature (in Kelvin) is
calculated by this rule:
Temp = (((RESH > 8
RESH and RESL are the high and low byte of the Result register (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;
uint8_t sigrow_gain = SIGROW.TEMPSENSE0;
© 2018 Microchip Technology Inc.
// Read signed value from signature row
// Read unsigned value from signature row
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ATtiny406
Analog-to-Digital Converter (ADC)
uint16_t adc_reading = 0;
// ADC conversion result with 1.1 V internal reference
uint32_t temp = adc_reading - sigrow_offset;
temp *= sigrow_gain; // Result might overflow 16 bit variable (10bit+8bit)
temp += 0x80;
// Add 1/2 to get correct rounding on division below
temp >>= 8;
// Divide result to get Kelvin
uint16_t temperature_in_K = temp;
Related Links
TEMPSENSEn
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 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 only raised 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'.
See also the description of the Asynchronous User Channel n Input Selection in the Event System
(EVSYS.ASYNCUSERn).
29.3.4
Interrupts
Table 29-2. Available Interrupt Vectors and Sources
Offset Name
Vector Description
Conditions
0x00
RESRDY Result Ready interrupt
The conversion result is available in the Result
register (ADC.RES).
0x02
WCOMP Window Comparator interrupt As defined by WINCM in ADC.CTRLE.
When an interrupt condition occurs, the corresponding interrupt flag is set in the Interrupt Flags register of
the peripheral (peripheral.INTFLAGS).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Analog-to-Digital Converter (ADC)
An interrupt source is enabled or disabled by writing to the corresponding enable bit in the peripheral's
Interrupt Control register (peripheral.INTCTRL).
An interrupt request is generated when the corresponding interrupt source is enabled and the interrupt
flag is set. The interrupt request remains active until the interrupt flag is cleared. See the peripheral's
INTFLAGS register for details on how to clear interrupt flags.
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 (ADC.CTRLA) is written to '1'.
When the device is entering Standby Sleep mode when RUNSTDBY is one, the ADC will stay active,
hence any ongoing conversions will be completed and interrupts will be executed as configured.
In Standby Sleep mode an ADC conversion must be triggered via the Event System (EVSYS), 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 (ADC.COMMAND) set, and the conversion will start. When the
conversion is completed, the Result Ready Flag (RESRDY) in the Interrupt Flags register
(ADC.INTFLAGS) is set and the STCONV bit in ADC.COMMAND is cleared.
The reference source and supply infrastructure need time to stabilize when activated in Standby Sleep
mode. Configure a delay for the start of the first conversion by writing a non-zero value to the Initial Delay
bits (INITDLY) in the Control D register (ADC.CTRLD).
In Power-Down Sleep mode, no conversions are possible. Any ongoing conversions are halted and will
be resumed when going out of sleep. At end of conversion, the Result Ready Flag (RESRDY) will be set,
but the content of the result registers (ADC.RES) is invalid since the ADC was halted in the middle of a
conversion.
Related Links
Sleep Controller (SLPCTRL)
29.3.6
Synchronization
Not applicable.
29.3.7
Configuration Change Protection
Not applicable.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Analog-to-Digital Converter (ADC)
29.4
Register Summary - ADCn
Offset
Name
Bit Pos.
0x00
CTRLA
7:0
0x01
CTRLB
7:0
0x02
CTRLC
7:0
SAMPCAP
0x03
CTRLD
7:0
INITDLY[2:0]
0x04
CTRLE
7:0
0x05
SAMPCTRL
7:0
SAMPLEN[4:0]
0x06
MUXPOS
7:0
MUXPOS[4:0]
RUNSTBY
RESSEL
FREERUN
ENABLE
SAMPNUM[2:0]
REFSEL[1:0]
PRESC[2:0]
ASDV
SAMPDLY[3:0]
WINCM[2:0]
0x07
Reserved
0x08
COMMAND
7:0
STCONV
0x09
EVCTRL
7:0
STARTEI
0x0A
INTCTRL
7:0
WCOMP
0x0B
INTFLAGS
7:0
WCOMP
0x0C
DBGCTRL
7:0
0x0D
TEMP
7:0
RESRDY
RESRDY
DBGRUN
TEMP[7:0]
0x0E
...
Reserved
0x0F
0x10
RES
0x12
WINLT
0x14
WINHT
0x16
CALIB
29.5
7:0
RES[7:0]
15:8
RES[15:8]
7:0
WINLT[7:0]
15:8
WINLT[15:8]
7:0
WINHT[7:0]
15:8
WINHT[15:8]
7:0
DUTYCYC
Register Description
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.1
Control A
Name:
Offset:
Reset:
Property:
Bit
7
CTRLA
0x00
0x00
-
6
5
4
3
RUNSTBY
Access
Reset
2
1
0
RESSEL
FREERUN
ENABLE
R/W
R
R
R
R
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 – RUNSTBY Run in Standby
This bit determines whether the ADC needs to run when the chip is in Standby Sleep mode.
Bit 2 – RESSEL Resolution Selection
This bit selects the ADC resolution.
Value
0
1
Description
Full 10-bit resolution. The 10-bit ADC results are accumulated or stored to the ADC Result
register (ADC.RES).
8-bit resolution. The conversion results are truncated to eight bits (MSBs) before they are
accumulated or stored to 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 COMMAND.STCONV bit 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
INTFLAGS.RESRDY.
Bit 0 – ENABLE ADC Enable
Value
0
1
Description
ADC is disabled
ADC is enabled
© 2018 Microchip Technology Inc.
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.2
Control B
Name:
Offset:
Reset:
Property:
Bit
7
CTRLB
0x01
0x00
-
6
5
4
3
2
1
0
SAMPNUM[2:0]
Access
Reset
R/W
R/W
R/W
0
0
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
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
NONE
ACC2
ACC4
ACC8
ACC16
ACC32
ACC64
-
© 2018 Microchip Technology Inc.
Description
No accumulation.
2 results accumulated.
4 results accumulated.
8 results accumulated.
16 results accumulated.
32 results accumulated.
64 results accumulated.
Reserved.
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.3
Control C
Name:
Offset:
Reset:
Property:
Bit
7
CTRLC
0x02
0x00
-
6
5
SAMPCAP
4
3
2
REFSEL[1:0]
1
0
PRESC[2:0]
Access
R
R/W
R/W
R/W
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit 6 – SAMPCAP Sample Capacitance Selection
This bit selects the sample capacitance, and hence, the input impedance. The best value is dependent on
the reference voltage and the application's electrical properties.
Value
0
1
Description
Recommended for reference voltage values below 1V.
Reduced size of sampling capacitance. Recommended for higher reference voltages.
Bits 5:4 – REFSEL[1:0] Reference Selection
These bits select the voltage reference for the ADC.
Value
0x0
0x1
Other
Name
INTERNAL
VDD
-
Description
Internal reference
VDD
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
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Name
DIV2
DIV4
DIV8
DIV16
DIV32
DIV64
DIV128
DIV256
© 2018 Microchip Technology Inc.
Description
CLK_PER divided by 2
CLK_PER divided by 4
CLK_PER divided by 8
CLK_PER divided by 16
CLK_PER divided by 32
CLK_PER divided by 64
CLK_PER divided by 128
CLK_PER divided by 256
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.4
Control D
Name:
Offset:
Reset:
Property:
Bit
7
CTRLD
0x03
0x00
-
6
5
4
INITDLY[2:0]
Access
Reset
3
2
ASDV
1
0
SAMPDLY[3:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:5 – INITDLY[2:0] Initialization Delay
These bits 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
0x0
0x1
0x2
0x3
0x4
0x5
Other
Name
DLY0
DLY16
DLY32
DLY64
DLY128
DLY256
-
Description
Delay 0 CLK_ADC cycles.
Delay 16 CLK_ADC cycles.
Delay 32 CLK_ADC cycles.
Delay 64 CLK_ADC cycles.
Delay 128 CLK_ADC cycles.
Delay 256 CLK_ADC cycles.
Reserved
Bit 4 – ASDV Automatic Sampling Delay Variation
Writing this bit to '1' enables automatic sampling delay variation between ADC conversions. The purpose
of varying sampling instant is to randomize the sampling instant and thus avoid standing frequency
components in the frequency spectrum. The value of the SAMPDLY bits are automatically incremented by
one after each sample.
When the Automatic Sampling Delay Variation is enabled and the SAMPDLY value reaches 0xF, it wraps
around to 0x0.
Value
0
1
Name
ASVOFF
ASVON
Description
The Automatic Sampling Delay Variation is disabled.
The Automatic Sampling Delay Variation is enabled.
Bits 3:0 – SAMPDLY[3:0] Sampling Delay Selection
These bits define the delay between consecutive ADC samples. The programmable Sampling Delay
allows modifying the sampling frequency during hardware accumulation, to suppress periodic noise
sources that may otherwise disturb the sampling. The SAMPDLY field can be also modified automatically
from one sampling cycle to another, by setting the ASDV bit. The delay is expressed as CLK_ADC cycles
and is given directly by the bitfield setting. The sampling cap is kept open during the delay.
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.5
Control E
Name:
Offset:
Reset:
Property:
Bit
7
CTRLE
0x4
0x00
-
6
5
4
3
2
1
0
WINCM[2:0]
Access
Reset
R/W
R/W
R/W
0
0
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
0x0
0x1
0x2
0x3
0x4
Other
Name
NONE
BELOW
ABOVE
INSIDE
OUTSIDE
-
© 2018 Microchip Technology Inc.
Description
No Window Comparison (default)
RESULT < WINLT
RESULT > WINHT
WINLT < RESULT < WINHT
RESULT < WINLT or RESULT >WINHT)
Reserved
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.6
Sample Control
Name:
Offset:
Reset:
Property:
Bit
7
SAMPCTRL
0x5
0x00
-
6
5
4
3
2
1
0
SAMPLEN[4:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
0
0
0
0
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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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.7
MUXPOS
Name:
Offset:
Reset:
Property:
Bit
7
MUXPOS
0x06
0x00
-
6
5
4
3
2
1
0
MUXPOS[4:0]
Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bits 4:0 – MUXPOS[4:0] MUXPOS
This bit field selects which single-ended analog input is connected to the ADC. If these bits are changed
during a conversion, the change will not take effect until this conversion is complete.
Value
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x1C
0x1D
0x1E
0x1F
Other
Name
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
AIN10
AIN11
Reserved
INTREF
TEMPSENSE
GND
-
© 2018 Microchip Technology Inc.
Description
ADC input pin 0
ADC input pin 1
ADC input pin 2
ADC input pin 3
ADC input pin 4
ADC input pin 5
ADC input pin 6
ADC input pin 7
ADC input pin 8
ADC input pin 9
ADC input pin 10
ADC input pin 11
Reserved
Internal reference (from VREF peripheral)
Temperature sensor
0V (GND)
Reserved
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.8
Command
Name:
Offset:
Reset:
Property:
Bit
7
COMMAND
0x08
0x00
-
6
5
4
3
2
1
0
STCONV
Access
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
Bit 0 – STCONV Start Conversion
Writing a '1' to this bit will start a single measurement. 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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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.9
Event Control
Name:
Offset:
Reset:
Property:
Bit
7
EVCTRL
0x09
0x00
-
6
5
4
3
2
1
0
STARTEI
Access
R/W
Reset
0
Bit 0 – STARTEI Start Event Input
This bit enables event input as source for conversion start.
© 2018 Microchip Technology Inc.
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.10 Interrupt Control
Name:
Offset:
Reset:
Property:
Bit
7
INTCTRL
0x0A
0x00
-
6
5
4
3
Access
Reset
2
1
0
WCOMP
RESRDY
R/W
R/W
0
0
Bit 1 – WCOMP Window Comparator Interrupt Enable
Writing a '1' to this bit enables window comparator interrupt.
Bit 0 – RESRDY Result Ready Interrupt Enable
Writing a '1' to this bit enables result ready interrupt.
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.11 Interrupt Flags
Name:
Offset:
Reset:
Property:
Bit
7
INTFLAGS
0x0B
0x00
-
6
5
4
3
Access
Reset
2
1
0
WCOMP
RESRDY
R/W
R/W
0
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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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.12 Debug Run
Name:
Offset:
Reset:
Property:
Bit
7
DBGCTRL
0x0C
0x00
-
6
5
4
3
2
1
0
DBGRUN
Access
R/W
Reset
0
Bit 0 – DBGRUN Debug Run
Value
0
1
Description
The peripheral is halted in Break Debug mode and ignores events.
The peripheral will continue to run in Break Debug mode when the CPU is halted.
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ATtiny406
Analog-to-Digital Converter (ADC)
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. See Accessing 16-Bit Registers. There is one common
Temporary register for all the 16-bit registers of this peripheral.
Bit
7
6
5
4
3
2
1
0
TEMP[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – TEMP[7:0] Temporary
Temporary register for read/write operations in 16-bit registers.
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.14 Result
Name:
Offset:
Reset:
Property:
RES
0x10
0x00
-
The ADCn.RESL and ADCn.RESH register pair represent 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. For more details on reading and writing 16-bit registers, refer to Accessing 16-Bit Registers.
If the analog input is higher than the reference level of the ADC, the 10-bit ADC result will be equal the
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
RES[15:8]
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
Access
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
RES[7:0]
Bits 15:8 – RES[15:8] Result high byte
These bits constitute the MSB of ADCn.RES register, where the MSb is RES[15]. The ADC itself has 10bit 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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ATtiny406
Analog-to-Digital Converter (ADC)
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 10-bit output, RES[9:0], where the MSb is RES[9]. The data format in ADC and Digital
Accumulation is one’s complement, where 0x0000 represents the zero and 0xFFFF represents the
largest number (full scale).
The ADCn.WINLTH and ADCn.WINLTL register pair represent 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. For more details on reading and writing 16-bit registers, refer to Accessing 16-Bit
Registers.
When accumulating samples, the window comparator thresholds are applied on the accumulated value
and not on each sample.
Bit
15
14
13
12
11
10
9
8
R/W
R/W
R/W
R/W
Reset
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
WINLT[15:8]
Access
WINLT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:8 – 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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ATtiny406
Analog-to-Digital Converter (ADC)
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 10-bit output, RES[9:0], where the MSb is RES[9]. The data format in ADC and Digital
Accumulation is one’s complement, where 0x0000 represents the zero and 0xFFFF 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. For more details on reading and writing 16-bit registers, refer to Accessing 16-Bit
Registers.
Bit
15
14
13
12
11
10
9
8
R/W
R/W
R/W
R/W
Reset
0
0
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
WINHT[15:8]
Access
WINHT[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 15:8 – 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Analog-to-Digital Converter (ADC)
29.5.17 Calibration
Name:
Offset:
Reset:
Property:
Bit
7
CALIB
0x16
0x01
-
6
5
4
3
2
1
0
DUTYCYC
Access
R/W
Reset
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
0
1
Description
50% Duty Cycle must be used if ADCclk > 1.5 MHz
25% Duty Cycle (high 25% and low 75%) must be used for ADCclk ≤ 1.5 MHz
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Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
30.
Unified Program and Debug Interface (UPDI)
30.1
Features
•
•
•
30.2
Programming:
– External programming through UPDI 1-wire (1W) interface
• Enable programming by 12V or fuse
• Uses the RESET pin of the device for programming
• No GPIO pins occupied during operation
• Asynchronous Half-Duplex UART protocol towards the programmer
Debugging:
– Memory mapped access to device address space (NVM, RAM, I/O)
– No limitation on device clock frequency
– Unlimited number of user program breakpoints
– 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 1wire UART-based half duplex interface using the RESET pin for data reception and transmission.
Clocking of UPDI PHY is done by an internal oscillator. Enabling of the 1-wire interface, by disabling the
Reset functionality, is either done by 12V programming or by fusing the RESET pin to UPDI by setting the
RESET Pin Configuration (RSTPINCFG) bits in FUSE.SYSCFG0. The UPDI access layer grants access
to the bus matrix, with memory mapped access to system blocks such as memories, NVM, and
peripherals.
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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Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
Related Links
Nonvolatile Memory Controller (NVMCTRL)
Enabling of KEY Protected Interfaces
30.2.1
Block Diagram
Figure 30-1. UPDI Block Diagram
ASI
Memories
UPDI PAD
(RX/TX Data)
UPDI
Physical
layer
Bus Matrix
UPDI Controller
UPDI
Access
layer
NVM
Peripherals
ASI Access
ASI Internal Interfaces
OCD
NVM
Controller
System
Management
30.2.2
System Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
Table 30-1. UPDI System Dependencies
Dependency
Applicable
Peripheral
Clocks
Yes
CLKCTRL
I/O Lines and Connections
Yes
PORT
Interrupts
No
-
Events
Yes
EVSYS
Debug
Yes
UPDI
Related Links
I/O Lines and Connections
Power Management
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
30.2.2.1 Clocks
The UPDI Physical (UPDI PHY) layer and UPDI Access (UPDI ACC) layer can operate on different clock
domains. The UPDI PHY layer clock is derived from an internal oscillator, and the UPDI ACC layer clock
is the same as the system clock. There is a synchronization boundary between the UPDI PHY layer and
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 UPDICLKSEL bits in the
ASI_CTRLA register.
Figure 30-2. UPDI Clock Domains
ASI
SYNCH
UPDI Controller
UPDI
Physical
layer
Clock
Controller
UPDI clk
source
~
UPDI
Access
layer
Clock
Controller
Clk_UPDI
Clk_sys
Clk_sys
UPDI
CLKSEL
~
Related Links
Clock Controller (CLKCTRL)
30.2.2.2 I/O Lines and Connections
To operate the UPDI, the RESET pin must be set to UPDI mode. This is not done through the port I/O pin
configuration as regular I/O pins, but through setting the RESET Pin Configuration (RSTPINCFG) bits in
FUSE.SYSCFG0 as described in UPDI Enable with Fuse Override of RESET Pin, or by following the
UPDI 12V enable sequence from UPDI Enable with 12V Override of RESET Pin. Pull enable, input
enable and output enable settings are automatically controlled by the UPDI when active.
30.2.2.3 Events
The events of this peripheral are connected to the Event System.
Related Links
Event System (EVSYS)
30.2.2.4 Power Management
The UPDI physical layer continues to operate in any Sleep mode and is always accessible for a
connected debugger, but read/write access to the system bus is restricted in Sleep modes where the
CPU clock is switched off. The UPDI can be enabled at any time, independent of the system Sleep state.
See Sleep Mode Operation for details on UPDI operation during Sleep modes.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
30.3
Functional Description
30.3.1
Principle of Operation
Communication through the UPDI is based on standard UART communication, using a fixed frame
format, and automatic baud rate detection for clock and data recovery. In addition to the data frame, there
are several control frames which are important to the communication. The supported frame formats are
presented in Figure 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
Data
Frame
IDLE
Frame
BREAK
SYNCH
ACK
Data frame consist of one Start bit (always low), eight data bits, one parity bit (even parity),
and two Stop bits (always high). If the Start bit, parity bit, or Stop bits have an incorrect value,
an error will be detected and signalized by the UPDI. The parity bit-check in the UPDI can be
disabled by writing the PARD bit in UPDI.CTRLA, in which case the parity generation from the
debugger can be ignored.
Special frame 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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
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) side, and every transmission must
start with a SYNCH character upon which the UPDI can recover the transmission baud rate, and store
this setting for the coming data. The baud rate set by the SYNCH character will be used for both
reception and transmission for the instruction byte received after the SYNCH. See UPDI Instruction Set
for details on when the next SYNCH character is expected in the instruction stream.
There is no writable baud rate register in the UPDI, so the baud rate sampled from the SYNCH character
is used for data recovery by sampling the Start bit, and performing a majority vote on the middle samples.
This process is repeated for all bits in the frame, including the parity bit and two Stop bits. The baud
generator uses 16 samples, and the majority voting is done on sample 7, 8, and 9.
Figure 30-4. UPDI UART Start Bit and Data/Parity/Stop Bit Sampling
RxD
IDLE
Sample
0 0
START
1
2
3
4
5
6
7
RxD
BIT 0
8 9 10 11 12 13 14 15 16 1
2
3
BIT n
Sample
1
2
3
4
5
6
7
8 9 10 11 12 13 14 15 16 1
The transmission baud rate must be set up in relation to the selected UPDI clock, which can be adjusted
by UPDICLKSEL in UPDI.ASI_CTRLA. See Table 30-2 for recommended maximum and minimum baud
rate settings.
Table 30-2. 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 30-3. Receiver Baud Rate Error
Data + Parity Bits
Rslow
Rfast
Max. Total Error
[%]
Recommended
Max. RX Error [%]
9
96.39
104.76
+4.76/-3.61
+1.5/-1.5
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 synchronization between the
debugger and the UPDI is lost.
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Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
A single BREAK character is enough to reset the UPDI, but in some special cases where the BREAK
character is sent when the UPDI has not yet entered the error state, a double BREAK character might be
needed. A double BREAK is ensured to reset the UPDI from any state. When sending a double BREAK it
is required to have at least one Stop bit between the BREAK characters.
No SYNCH character is required before the BREAK because the BREAK is used to reset the UPDI from
any state. This means that the UPDI will sample the BREAK based on the last stored baud rate setting,
derived from the last received valid SYNCH character. If the communication error was due to an incorrect
sampling of the SYNCH character, the baud rate is unknown to the connected debugger. For this reason,
the BREAK character should be transmitted at the slowest recommended baud rate setting for the
selected UPDI clock according to Table 30-4:
Table 30-4. 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:
•
UPDI Enable with 12V Override of RESET Pin
•
UPDI Enable with Fuse Override of RESET Pin
30.3.2.1 UPDI Enable with Fuse Override of RESET Pin
When the RESET Pin Configuration (RSTPINCFG) bits in FUSE.SYSCFG0 are 0x1, the RESET pin will
be overridden, and the UPDI will take control of the pin and configure it as input with pull-up. When the
pull-up is detected by a connected debugger, the UPDI enable sequence, as depicted below, is started.
Figure 30-5. UPDI Enable Sequence with UPDI PAD Enabled By Fuse
1
Fuse read in. Pull-up enabled. Ready to receive init.
2
Drive low from debugger to request UPDI clock
3
UPDI clock ready; Communication channel ready.
RESET
1
2
Hi-Z
St
D0
D1
D2
Handshake / BREAK
TRES
UPDI.rxd
UPDI.txd
D3
D4
D5
D6
D7
Sp
SYNC (0x55)
(Autobaud)
(Ignore)
3
Hi-Z
Hi-Z
UPDI.txd = 0
TUPDI
debugger.
UPDI.txd
Hi-Z
Hi-Z
Debugger.txd = 0
TDeb0
Debugger.txd = z
TDebZ
When the pull-up is detected, the debugger initiates the enable sequence by driving the line low for a
duration of TDeb0 to ensure that the line is released from the debugger before the UPDI enable sequence
is done.
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ATtiny406
Unified Program and Debug Interface (UPDI)
The negative edge is detected by the UPDI, which requests the UPDI clock. The UPDI will continue to
drive the line low until the clock is stable and ready for the UPDI to use. The duration of this 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 sent to
properly enable the UPDI for communication. If the Start bit of the SYNCH character is not sent well
within maximum TDebZ, the UPDI will disable itself, and the enable sequence must be repeated. This time
is based on counted cycles on the 4 MHz UPDI clock, which is the default when enabling the UPDI. The
disable is performed to avoid the UPDI being enabled unintentionally.
After successful SYNCH character transmission, the first instruction frame can be transmitted.
Related Links
UPDI Timing
30.3.2.2 UPDI Enable with 12V Override of RESET Pin
GPIO or Reset functionality on the RESET pin can be overridden by the UPDI by using 12V
programming. By applying a 12V pulse to the RESET pin, the pin functionality is switched to UPDI,
independent of RSTPINCFG in FUSE.SYSCFG0. It is recommended to always reset the device before
starting the 12V enable sequence.
During power-up, the Power-on Reset (POR) must be released before the 12V pulse can be applied. The
duration of the pulse is recommended in the range from 100 μs to 1 ms, before tri-stating. When applying
the rising edge of the 12V pulse, the UPDI will be reset. After tri-stating, the UPDI will remain in Reset
until the RESET pin is driven low by the debugger. This will release the UPDI Reset and initiate the same
enable sequence as explained in UPDI Enable with Fuse Override of RESET Pin.
The following figure shows the 12V enable sequence.
Figure 30-6. UPDI Enable Sequence by 12V Programming
1 Fused pin Function disabled; UPDI pin function enabled.
2
UPDI interface enabled with pull-up.
1
(Ignore)
St
Hi-Z
D0
D1
D2
D3
D4
D5
D6
D7
Sp
UPDIPAD
12V ramp
Tmin10ns
Tmax4ms
Handshake / BREAK
Debugger.txd = z
Tmin10us
Tmin1us
Tmax200us
Tmax10us
SYNC (0x55)
(Autobaud)
(Ignore)
UPDI.rxd
Hi-Z
UPDI.txd
Hi-Z
2
UPDI.txd = 0
Tmin10us,
Tmax200us
debugger.
UPDI.txd
debugger.
UPDI.o12v
Hi-Z
12V
Hi-Z
Debugger.txd = 0
Tmin200ns
Tmax1us
Debugger.txd = z.
Tmin200us,
Tmax14ms
Vdd
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Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
When enabled by 12V, only a POR will disable the UPDI configuration on the RESET pin, and restore the
default setting. If issuing a UPDI Disable command through the UPDIDIS bit in UPDI.CTRLB, the UPDI
will be reset and the clock request will be canceled, but the RESET pin will remain in UPDI configuration.
Note: If insufficient external protection is added to the UPDI Pin, an ESD pulse can be interpreted as a
12V override by the microcontroller and enables the UPDI.
30.3.2.3 UPDI Disable
Any programming or debug session should be terminated by writing the UPDIDIS bit in UPDI.CTRLB.
Writing this bit will reset the UPDI including any decoded KEYs and disable the oscillator request for the
module. If the disable operation is not performed the UPDI will stay enabled and request its oscillator,
causing increased power consumption for the application.
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 UPDI
Enable with Fuse Override of RESET Pin.
•
The first SYNCH character after an initiated enable is too short or too long to register as a valid
SYNCH character. See Table 30-2 for recommended baud rate operating ranges.
30.3.2.4 Output Enable Timer Protection for GPIO Configuration
When the RESET Pin Configuration (RSTPINCFG) bits in FUSE.SYSCFG0 are 0x0, the RESET pin
configured as GPIO. To avoid the potential conflict between the GPIO actively driving the output and a
12V UPDI enable sequence initiation, a timer protection is disabling the output enable for a minimum time
of 8.8 ms after each System Reset.
It is always recommended to issue a System Reset before entering the 12V programming sequence.
30.3.2.5 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 start bit error, parity error, contention error, and frame error, to more high-level errors like
access timeout error. See the PESIG bits in UPDI_STATUSB for an overview of the available error
signatures.
Whenever the UPDI detects an error, it will immediately transfer to an internal error state to avoid
unwanted system communication. In the error state the UPDI will ignore all incoming data requests,
except if a BREAK character is transmitted. The following procedure should always be applied when
recovering from an error condition.
•
Send a BREAK character. See BREAK Character for recommended BREAK character handling.
•
Send a SYNCH character at the desired baud rate for the next data transfer. Upon receiving a
BREAK the UPDI oscillator setting in UPDI.ASI_CTRLA is reset to the 4 MHz default UPDI clock
selection. This affects the baud rate range of the UPDI according to Table 30-2.
•
Do a Load Control Status (LDCS) to UPDI.STATUSB register to read the PESIG field. PESIG gives
information about the occurred error, and the error signature will be cleared when read.
•
The UPDI is now recovered from the error state and ready to receive the next SYNCH character
and instruction.
30.3.2.6 Direction Change
In order to ensure correct timing for half duplex UART operation, the UPDI has a built-in Guard Time
mechanism to relax the timing when changing direction from RX mode to TX mode. The Guard Time is a
number of IDLE bits inserted before the next Start bit is transmitted. The number of IDLE bits can be
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
configured through GTVAL in UPDI.CTRLA. The duration of each IDLE bit is given by the baud rate used
by the current transmission.
It is not recommended to use GTVAL setting 0x7, with no additional IDLE bits.
Figure 30-7. UPDI Direction Change by Inserting IDLE Bits
RX Data Frame
St
R X D a ta F ra m e
Dir Change
P
Data from
debugger to UPDI
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 that the connected debugger will experience when
waiting for data from the UPDI. Because of the asynchronous interface to the system, as presented in
Clocks, the ratio between the UPDI clock and the system clock will affect the synchronization time, and
how long it takes before the UPDI can transmit data. In the cases where the synchronization delay is
shorter than the current Guard Time setting, the Guard Time will be given by GTVAL directly.
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 UPDI UART for information about setting the baud rate for the
transmission. The following figure gives an overview of the UPDI instruction set.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
Figure 30-8. UPDI Instruction Set Overview
Opcode
L DS
STS
0
0
0
1
Size A
0
0
0
0
Opcode
LD
ST
0
0
0
1
Ptr
1
1
Size B
Size A/B
0
STCS
1
1
0
1
0
0
0
0
0
LD S
0
0
1
LD
0
1
0
STS
0
1
1
ST
1
0
0
L D C S ( L D S C o n t r o l/ S ta t u s )
1
0
1
REPEAT
1
1
0
S T C S ( S T S C o n tr o l/ S ta t u s )
1
1
1
KEY
S ize A - A d d re s s s ize
0
CS Address
L DCS
OPCODE
0
0
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
P tr - P o in ter a c c es s
0
0
* (p tr)
0
1
* (p tr+ + )
1
0
p tr
1
1
R e s e rv e d
S ize B - D ata s ize
Size B
REPEA T
1
0
1
0
0
0
SIB
K EY
1
1
1
0
0
Size C
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
C S A d d r e s s (C S - C o n t r o l /S t a t u s r e g .)
0
0
0
0
R eg 0
0
0
0
1
R eg 1
0
0
1
0
R eg 2
0
0
1
1
R eg 3
0
1
0
0
R e g 4 (A S I C S s p a c e )
......
1
1
1
1
R e s e rv e d
S ize C - K ey s ize
0
0
0
1
6 4 b it s ( 8 B y t e s )
1 2 8 b it s ( 1 6 B y t e s )
1
0
R e s e rv e d
1
1
R e s e rv e d
S IB – S y s t e m I n f o r m a t i o n B l o c k s e l .
© 2018 Microchip Technology Inc.
0
R e c e iv e K E Y
1
S e n d S IB
Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
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 30-9, after issuing the SYNCH character followed by the LDS instruction, the number
of desired address bytes, as indicated by the SizeA field in the instruction, must be transmitted. The
output data size is selected by the SizeB field and is issued after the specified Guard Time. When
combined with the REPEAT instruction, the address must be sent in for each iteration of the repeat,
meaning after each time the output data sampling is done. There is no automatic address increment
when using REPEAT with LDS, as it uses a direct addressing protocol.
Figure 30-9. LDS Instruction Operation
OPCODE
Size A
Size B
S ize A - A d d re s s s ize
0
L DS
0
0
0
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
S ize B - D ata s ize
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
ADR SIZE
Synch
(0x55)
LDS
A d r_ 0
Rx
A d r_ n
D a ta _ 0
D a ta _ n
Tx
ΔGT
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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
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ATtiny406
Unified Program and Debug Interface (UPDI)
Figure 30-10. STS Instruction Operation
OPCODE
Size A
Size B
S ize A - A d d re s s s ize
0
STS
1
0
0
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
S ize B - D ata s ize
0
0
B y te
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
1
R e s e rv e d
ADR SIZE
Synch
(0x55)
STS
A d r_ 0
DATA SIZE
A d r_ n
D a ta _ 0
Rx
D a ta _ n
ACK
ΔGT
ACK
Tx
ΔGT
The transfer protocol for an STS instruction is depicted in the figure as well, following this sequence:
1.
2.
3.
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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ATtiny406
Unified Program and Debug Interface (UPDI)
Figure 30-11. LD Instruction Operation
OPCODE
LD
Synch
(0x55)
0
0
Ptr
1
Size A/B
P tr - P o in ter a c c es s
0
0
0
* (p tr)
0
1
* (p tr+ + )
1
0
p tr
1
1
R e s e rv e d
S ize A - A d d re s s s ize
S ize B - D ata s ize
0
0
B y te
0
0
B y te
0
1
W o rd (2 B y te s )
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
0
R e s e rv e d
1
1
R e s e rv e d
1
1
R e s e rv e d
LD
DATA SIZE
D a ta _ 0
Rx
D a ta _ n
Tx
ΔGT
The figure above shows an example of a typical LD sequence, where data is received after the Guard
Time period. Loading data from the UPDI Pointer register follows the same transmission protocol.
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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ATtiny406
Unified Program and Debug Interface (UPDI)
Figure 30-12. ST Instruction Operation
OPCODE
ST
0
1
Ptr
1
Size A/B
P tr - P o in ter a c c es s
0
0
0
* (p tr)
0
1
* (p tr+ + )
1
0
p tr
1
1
R e s e rv e d
S ize A - A d d re s s s ize
S ize B - D ata s ize
0
0
B y te
0
0
B y te
0
1
W o rd (2 B y te s )
0
1
W o rd (2 B y te s )
1
0
R e s e rv e d
1
0
R e s e rv e d
1
1
R e s e rv e d
1
1
R e s e rv e d
ADDRESS_SIZE
Synch
(0x55)
ST
ADR _0
ADR _n
Rx
ACK
Tx
ΔGT
Block SIZE
Synch
(0x55)
ST
D a ta _ 0
Rx
D a ta _ n
ACK
Tx
ΔGT
The figure above gives an example of ST to the UPDI Pointer register and store of regular data. In both
cases an Acknowledge (ACK) is sent back by the UPDI if the store was successful and a SYNCH
character is sent before each instruction. To write the UPDI Pointer register, the following procedure
should be followed.
•
Set the PTR field in the ST instruction to the signature 0x2
•
•
Set the address size field SizeA to the desired address size
After issuing the ST instruction, send SizeA bytes of address data
•
Wait for the ACK character, which signifies a successful write to the Address register
After the Address register is written, sending data is done in a similar fashion.
•
Set the PTR field in the ST instruction to the signature 0x0 to write to the address specified by the
UPDI Pointer register. If the PTR field is set to 0x1, the UPDI pointer is automatically updated to the
next address according to the data size SizeD field of the instruction after the write is executed
•
Set the SizeD field in the instruction to the desired data size
•
After sending the ST instruction, send SizeD bytes of address data
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Unified Program and Debug Interface (UPDI)
•
Wait for the ACK character which signifies a successful write to the bus matrix
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 SizeD 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 30-13. LCDS Instruction Operation
OPCODE
L DCS
1
0
CS Address
0
CS Address (CS - Control/Status reg.)
0 0 0 0 Reg 0
0 0 0 1 Reg 1
0 0 1 0 Reg 2
0 0 1 1 Reg 3
0 1 0 0 Reg 4 (ASI CS Space)
......
1 1 1 1 Reserved
0
Synch
(0x55)
LDCS
Rx
Data
Tx
Δgt
The figure above shows a typical example of LCDS data transmission. A data byte from the LCDS space is
transmitted from the UPDI after the Guard Time is completed.
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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ATtiny406
Unified Program and Debug Interface (UPDI)
Figure 30-14. STCS Instruction Operation
OPCODE
STCS
1
1
CS Address
0
C S A d d r e s s (C S - C o n t r o l /S t a t u s r e g .)
0
Synch
(0x55)
STCS
0
0
0
0
R eg 0
0
0
0
1
R eg 1
0
0
1
0
R eg 2
0
0
1
1
R eg 3
0
1
0
0
R e g 4 (A S I C S S p a c e )
......
1
1
1
1
R e s e rv e d
D a ta
Rx
Tx
Figure 30-14 shows the data frame transmitted after the SYNCH and instruction frames. There is no
response generated from the STCS instruction, as is the case for ST and STS.
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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ATtiny406
Unified Program and Debug Interface (UPDI)
Figure 30-15. REPEAT Instruction Operation
OPCODE
REPEA T
1
0
Size B
1
0
0
0
S ize B - D ata s ize
0
0
B y te
0
1
R e s e rv e d
1
0
R e s e rv e d
1
1
R e s e rv e d
REPEAT SIZE
Synch
(0x55)
REPEA T
RPT_0
Rpt nr of Blocks of DATA_SIZE
DATA_SIZE
Synch
(0x55)
ST
(p t r + + )
D a ta _ 0
D a ta _ n
DATA_SIZE
DATA_SIZE
D a ta B _ 1
D a ta B _ n
Rx
ACK
Δd
ACK
Δd
Δd
Δd
Tx
Δd
The figure above gives an example of repeat operation with an ST instruction using pointer postincrement 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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ATtiny406
Unified Program and Debug Interface (UPDI)
Figure 30-16. KEY Instruction Operation
SIB
K EY
1
1
1
0
Size C
0
S ize C - K ey s ize
0
0
6 4 b it s ( 8 B y t e s )
0
1
1 2 8 b it s ( 1 6 B y t e s ) ( S IB o n ly )
1
0
R e s e rv e d
1
1
R e s e rv e d
S IB – S y s t e m I n f o r m a t i o n B l o c k s e l .
0
Send KEY
1
R e c e iv e S I B
KEY SIZE
Synch
(0x55)
K EY
KEY_0
KEY_n
Rx
Tx
Synch
(0x55)
Rx
K EY
S IB _ 0
Δgt
S IB _ n
Tx
SIB SIZE
The figure above shows the transmission of a KEY and the reception of a SIB. In both cases, the SIZE_C
field in the opcode determines the number of frames 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 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
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ATtiny406
Unified Program and Debug Interface (UPDI)
•
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 readout 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.
Figure 30-17. 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 30-18. Interbyte Delay Example with LD and RPT
Too fast transm ission, no interbyte delay
RX
Debugger
Data
TX
RPT
CNT
LD*(ptr)
GT
Debugger
Processing
S
D0
B
D1
S
B
D2
D1lots
D0
S
B
D3
S
B
D4
D1lost
D2
S
B
D5
S
B
D4
Data sam pling ok with interbyte delay
RX
Debugger
Data
TX
RPT
CNT
Debugger
Processing
LD*(ptr)
GT
S IB
B
D0
D0
S IB
B
D1
D1
D2
D2
S IB
B
D3
S
B
D3
In Figure 30-18, GT denotes the Guard Time insertion, SB are Stop bits and IB is the inserted interbyte
delay. The rest of the frames are data and instructions.
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ATtiny406
Unified Program and Debug Interface (UPDI)
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 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 30-19 for SIB format description, and which data is available at different readout sizes.
Figure 30-19. 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.
Programming Done/
ASI_SYS_STATUS.NVM UPDI Reset
PROG set.
USERROW-Write
Program User Row on
Locked part
Lockbits Set.
Write to KEY status bit/
ASI_SYS_STATUS.URO UPDI Reset
WPROG set.
Table 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
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ATtiny406
Unified Program and Debug Interface (UPDI)
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.
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.
Follow the Chip erase procedure as described in Chip Erase. If the part is already unlocked, this
point can be skipped.
2. Enter the NVMPROG KEY by using the KEY instruction. See Table 30-6 for the NVMPROG
signature.
3. Optional: Read the NVMPROG field in the KEY_STATUS register to see that the KEY has been
activated.
4. Write the Reset signature into the ASI_RESET_REQ register. This will issue a System Reset.
5. Write 0x00 to the Reset signature in the ASI_RESET_REQ register to clear the System Reset.
6. Read NVMPROG in ASI_SYS_STATUS.
7. NVM Programming can start when NVMPROG == 1 in the ASI_SYS_STATUS register. If
NVMPROG == 0, go to point 6 again.
8. Write data to NVM through the UPDI.
9. Write the Reset signature into the ASI_RESET_REQ register. This will issue a System Reset.
10. Write 0x00 to the Reset signature in ASI_RESET_REQ register to clear the System Reset.
11. Programming is complete.
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.
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ATtiny406
Unified Program and Debug Interface (UPDI)
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 the UPDI.ASI_RESET_REQ register to clear the System
Reset.
Read the UROWPROG bit in UPDI.ASI_SYS_STATUS.
User Row Programming can start when UROWPROG == 1. If UROWPROG == 0, go to point 5
again.
The writable area has a size of one EEPROM page, 32 bytes, and it is only possible to write User
Row data to the first 32 byte addresses of the RAM. Addressing outside this memory range will
result in a non-executed write. The data will map 1:1 with the User Row space when the data is
copied into the User Row upon completion of the Programming sequence.
When all User Row data has been written to the RAM, write the UROWWRITEFINAL bit in
UPDI.ASI_SYS_CTRLA.
Read the UROWPROG bit in UPDI.ASI_SYS_STATUS.
The User Row Programming is completed when UROWPROG == 0. If UROWPROG == 1, go to
point 9 again.
Write the UROWWRITE bit in UPDI.ASI_KEY_STATUS.
Write the Reset signature into the UPDI.ASI_RESET_REQ register. This will issue a System Reset.
Write 0x00 to the Reset signature in the 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 writing to the first 32 bytes of the
SRAM is allowed.
30.3.8
Events
The UPDI is connected to the Event System (EVSYS) as described in the register Asynchronous Channel
n Generator Selection.
The UPDI can generate the following output events:
•
SYNCH Character Positive Edge Event
This event is set on the UPDI clock for each detected positive edge in the SYNCH character, and it is not
possible to disable this event from the UPDI. The recommended application for this event is system clock
frequency measurement through the UPDI. Section System Clock Measurement with UPDI provides the
details on how to set up the system for this operation.
Related Links
Event System (EVSYS)
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
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Unified Program and Debug Interface (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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Unified Program and Debug Interface (UPDI)
30.4
Register Summary - UPDI
Offset
Name
Bit Pos.
0x00
STATUSA
7:0
0x01
STATUSB
7:0
0x02
CTRLA
7:0
0x03
CTRLB
7:0
UPDIREV[3:0]
PESIG[2:0]
IBDLY
PARD
DTD
RSD
NACKDIS
CCDETDIS
GTVAL[2:0]
UPDIDIS
0x04
...
Reserved
0x06
0x07
ASI_KEY_STATUS
7:0
0x08
ASI_RESET_REQ
7:0
0x09
ASI_CTRLA
7:0
0x0A
ASI_SYS_CTRLA
7:0
0x0B
ASI_SYS_STATUS
7:0
0x0C
ASI_CRC_STATUS
7:0
30.5
UROWWRITE NVMPROG
CHIPERASE
RSTREQ[7:0]
UPDICLKSEL[1:0]
UROWWRITE
CLKREQ
_FINAL
RSTSYS
INSLEEP
NVMPROG UROWPROG
LOCKSTATUS
CRC_STATUS[2:0]
Register Description
These registers are 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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ATtiny406
Unified Program and Debug Interface (UPDI)
30.5.1
Status A
Name:
Offset:
Reset:
Property:
Bit
7
STATUSA
0x00
0x10
-
6
5
4
3
2
1
0
UPDIREV[3:0]
Access
R
R
R
R
Reset
0
0
0
1
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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Unified Program and Debug Interface (UPDI)
30.5.2
Status B
Name:
Offset:
Reset:
Property:
Bit
STATUSB
0x01
0x00
-
7
6
5
4
3
2
1
0
PESIG[2:0]
Access
R
R
R
Reset
0
0
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
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 469
ATtiny406
Unified Program and Debug Interface (UPDI)
30.5.3
Control A
Name:
Offset:
Reset:
Property:
Bit
Access
Reset
7
CTRLA
0x02
0x00
-
5
4
3
IBDLY
6
PARD
DTD
RSD
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
GTVAL[2:0]
Bit 7 – IBDLY Inter-Byte Delay Enable
Writing a '1' to this bit enables a fixed inter-byte delay between each data byte transmitted from the UPDI
when doing multi-byte LD(S). The fixed length is two IDLE characters. Before the first transmitted byte,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. The guard time is equal to the baud rate used in 1-Wire mode.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Description
UPDI Guard Time: 128 cycles (default)
UPDI Guard Time: 64 cycles
UPDI Guard Time: 32 cycles
UPDI Guard Time: 16 cycles
UPDI Guard Time: 8 cycles
UPDI Guard Time: 4 cycles
UPDI Guard Time: 2 cycles
GT off (no extra Idle bits inserted)
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 470
ATtiny406
Unified Program and Debug Interface (UPDI)
30.5.4
Control B
Name:
Offset:
Reset:
Property:
Bit
7
CTRLB
0x03
0x00
-
6
5
4
3
2
NACKDIS
CCDETDIS
UPDIDIS
Access
R
R
R
Reset
0
0
0
1
0
Bit 4 – NACKDIS Disable NACK Response
Writing this bit to '1' disables the NACK signature sent by the UPDI if a System Reset is issued during an
ongoing LD(S) and ST(S) operation.
Bit 3 – CCDETDIS Collision and Contention Detection Disable
If this bit is written to '0', contention detection is enabled for the 1W mode. This means that the UPDI can
detect a collision in an ongoing 1-Wire transmission.
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.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 471
ATtiny406
Unified Program and Debug Interface (UPDI)
30.5.5
ASI Key Status
Name:
Offset:
Reset:
Property:
Bit
7
ASI_KEY_STATUS
0x07
0x00
-
6
5
4
3
UROWWRITE
NVMPROG
CHIPERASE
Access
R
R
R
Reset
0
0
0
2
1
0
Bit 5 – UROWWRITE User Row Write Key Status
This bit is set to '1' if the UROWWRITE KEY is active. Otherwise, this bit reads as zero.
Bit 4 – NVMPROG NVM Programming
This bit is set to '1' if the NVMPROG KEY is active. This bit is automatically reset after the programming
sequence is done. Otherwise, this bit reads as zero.
Bit 3 – CHIPERASE Chip Erase
This bit is set to '1' if the CHIPERASE KEY is active. This bit will automatically be reset when the Chip
Erase sequence is completed. Otherwise, this bit reads as zero.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 472
ATtiny406
Unified Program and Debug Interface (UPDI)
30.5.6
ASI Reset Request
Name:
Offset:
Reset:
Property:
Bit
7
ASI_RESET_REQ
0x08
0x00
-
6
5
4
3
2
1
0
RSTREQ[7:0]
Access
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7:0 – RSTREQ[7:0] Reset Request
A Reset is signalized to the System when writing the Reset signature 0x59h to this address.
Writing any other signature to this register will clear the Reset.
When reading this register, reading bit RSTREQ[0] will tell if the UPDI is holding an active Reset on the
system. If this bit is '1', the UPDI has an active Reset request to the system. All other bits will read as '0'.
The UPDI will not be reset when issuing a System Reset from this register.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 473
ATtiny406
Unified Program and Debug Interface (UPDI)
30.5.7
ASI Control A
Name:
Offset:
Reset:
Property:
Bit
7
ASI_CTRLA
0x09
0x02
-
6
5
4
3
2
1
0
UPDICLKSEL[1:0]
Access
Reset
R/W
R/W
1
1
Bits 1:0 – UPDICLKSEL[1:0] UPDI Clock Select
Writing these bits 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
0x0
0x1
0x2
0x3
Description
Reserved
16 MHz UPDI clock
8 MHz UPDI clock
4 MHz UPDI clock (Default Setting)
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 474
ATtiny406
Unified Program and Debug Interface (UPDI)
30.5.8
ASI System Control A
Name:
Offset:
Reset:
Property:
Bit
7
ASI_SYS_CTRLA
0x0A
0x00
-
6
5
4
3
2
1
0
UROWWRITE_
CLKREQ
FINAL
Access
R
R
R
R
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
Bit 1 – UROWWRITE_FINAL User Row Programming Done
This bit should be written through the UPDI when the user row data has been written to the RAM. Writing
this bit will start the process of programming the user row data to the Flash.
If this bit is written before the User Row code is written to RAM by the UPDI, the CPU will progress
without the written data.
This bit is only writable if the Userrow-write KEY is successfully decoded.
Bit 0 – CLKREQ Request System Clock
If this bit is written to '1', the ASI is requesting the system clock, independent of system Sleep modes.
This makes it possible for the UPDI to access the ACC layer, also if the system is in Sleep mode.
Writing a zero to this bit will lower the clock request.
This bit will be reset when the UPDI is disabled.
This bit is set by default when the UPDI is enabled in any mode (Fuse, 12V).
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 475
ATtiny406
Unified Program and Debug Interface (UPDI)
30.5.9
ASI System Status
Name:
Offset:
Reset:
Property:
Bit
7
ASI_SYS_STATUS
0x0B
0x01
-
6
5
4
3
2
RSTSYS
INSLEEP
NVMPROG
UROWPROG
1
LOCKSTATUS
0
Access
R
R
R
R
R
Reset
0
0
0
0
1
Bit 5 – RSTSYS System Reset Active
If this bit is set, there is an active Reset on the system domain. If this bit is cleared, the system is not in
Reset.
This bit is cleared on read.
A Reset held from the ASI_RESET_REQ register will also affect this bit.
Bit 4 – INSLEEP System Domain in Sleep
If this bit is set, the system domain is in IDLE or deeper Sleep mode. If this bit is cleared, the system is
not in Sleep.
Bit 3 – NVMPROG Start NVM Programming
If this bit is set, NVM Programming can start from the UPDI.
When the UPDI is done, it must reset the system through the UPDI Reset register.
Bit 2 – UROWPROG Start User Row Programming
If this bit is set, User Row Programming can start from the UPDI.
When the UPDI is done, it must write the UROWWRITE_FINAL bit in ASI_SYS_CTRLA.
Bit 0 – LOCKSTATUS NVM Lock Status
If this bit is set, the device is locked. If a Chip Erase is done, and the Lockbits are cleared, this bit will
read as zero.
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 476
ATtiny406
Unified Program and Debug Interface (UPDI)
30.5.10 ASI CRC Status
Name:
Offset:
Reset:
Property:
Bit
7
ASI_CRC_STATUS
0x0C
0x00
-
6
5
4
3
2
1
0
CRC_STATUS[2:0]
Access
R
R
R
Reset
0
0
0
Bits 2:0 – CRC_STATUS[2:0] CRC Execution Status
These bits signalize the status of the CRC conversion. The bits are one-hot encoded.
Value
0x0
0x1
0x2
0x4
Other
Description
Not enabled
CRC enabled, busy
CRC enabled, done with OK signature
CRC enabled, done with FAILED signature
Reserved
© 2018 Microchip Technology Inc.
Datasheet Preliminary
40001976A-page 477
ATtiny406
Electrical Characteristics
31.
Electrical Characteristics
31.1
Disclaimer
All typical values are measured at T = 25°C and VDD = 3V unless otherwise specified. All minimum and
maximum values are valid across operating temperature and voltage unless otherwise specified.
31.2
Absolute Maximum Ratings
Stresses beyond those listed in this section may cause permanent damage to the device. This is a stress
rating only and functional operation of the device at these or other conditions beyond those indicated in
the operational sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
Table 31-1. Absolute Maximum Ratings
Symbol Description
VDD
Power Supply Voltage
IVDD
Current into a VDD pin
IGND
Conditions
Current out of a GND pin
Min. Max.
Unit
-0.5 6
V
T=[-40, 85]°C
-
200
mA
T=[85, 125]°C
-
100
mA
T=[-40, 85]°C
-
200
mA
T=[85, 125]°C
-
100
mA
VRST
RESET pin voltage with respect to GND
-0.5 13
VPIN
Pin voltage with respect to GND
-0.5 VDD+0.5 V
IPIN
I/O pin sink/source current
-40
40
mA
Ic1(1)
I/O pin injection current except RESET pin
Vpin
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