AI Interactive Datasheet ATtiny828
AVR · tinyAVR

ATtiny828 registers

All 94 registers by peripheral, at their data-space address (the I/O address IN and OUT use is shown beside it), with their reset value and every bit.

PORTA I/O Port

PINAPort A Input Pins

Address
0x20 I/O 0x00
Reset
0x00
Access
read/write
  1. 7PINA7
  2. 6PINA6
  3. 5PINA5
  4. 4PINA4
  5. 3PINA3
  6. 2PINA2
  7. 1PINA1
  8. 0PINA0

DDRAData Direction Register, Port A

Address
0x21 I/O 0x01
Reset
0x00
Access
read/write
  1. 7DDA7
  2. 6DDA6
  3. 5DDA5
  4. 4DDA4
  5. 3DDA3
  6. 2DDA2
  7. 1DDA1
  8. 0DDA0

PORTAPort A Data Register

Address
0x22 I/O 0x02
Reset
0x00
Access
read/write
  1. 7PORTA7
  2. 6PORTA6
  3. 5PORTA5
  4. 4PORTA4
  5. 3PORTA3
  6. 2PORTA2
  7. 1PORTA1
  8. 0PORTA0

PUEAPull-up Enable Control Register

Address
0x23 I/O 0x03
Reset
0x00
Access
read/write
  1. 7PUEA7
  2. 6PUEA6
  3. 5PUEA5
  4. 4PUEA4
  5. 3PUEA3
  6. 2PUEA2
  7. 1PUEA1
  8. 0PUEA0

PORTB I/O Port

PINBPort B Input Pins

Address
0x24 I/O 0x04
Reset
0x00
Access
read/write
  1. 7PINB7
  2. 6PINB6
  3. 5PINB5
  4. 4PINB4
  5. 3PINB3
  6. 2PINB2
  7. 1PINB1
  8. 0PINB0

DDRBData Direction Register, Port B

Address
0x25 I/O 0x05
Reset
0x00
Access
read/write
  1. 7DDB7
  2. 6DDB6
  3. 5DDB5
  4. 4DDB4
  5. 3DDB3
  6. 2DDB2
  7. 1DDB1
  8. 0DDB0

PORTBPort B Data Register

Address
0x26 I/O 0x06
Reset
0x00
Access
read/write
  1. 7PORTB7
  2. 6PORTB6
  3. 5PORTB5
  4. 4PORTB4
  5. 3PORTB3
  6. 2PORTB2
  7. 1PORTB1
  8. 0PORTB0

PUEBPull-up Enable Control Register

Address
0x27 I/O 0x07
Reset
0x00
Access
read/write
  1. 7PUEB7
  2. 6PUEB6
  3. 5PUEB5
  4. 4PUEB4
  5. 3PUEB3
  6. 2PUEB2
  7. 1PUEB1
  8. 0PUEB0

PORTC I/O Port

PINCPort C Input Pins

Address
0x28 I/O 0x08
Reset
0x00
Access
read/write
  1. 7PINC7
  2. 6PINC6
  3. 5PINC5
  4. 4PINC4
  5. 3PINC3
  6. 2PINC2
  7. 1PINC1
  8. 0PINC0

DDRCData Direction Register, Port C

Address
0x29 I/O 0x09
Reset
0x00
Access
read/write
  1. 7DDC7
  2. 6DDC6
  3. 5DDC5
  4. 4DDC4
  5. 3DDC3
  6. 2DDC2
  7. 1DDC1
  8. 0DDC0

PORTCPort C Data Register

Address
0x2A I/O 0x0A
Reset
0x00
Access
read/write
  1. 7PORTC7
  2. 6PORTC6
  3. 5PORTC5
  4. 4PORTC4
  5. 3PORTC3
  6. 2PORTC2
  7. 1PORTC1
  8. 0PORTC0

PUECPull-up Enable Control Register

Address
0x2B I/O 0x0B
Reset
0x00
Access
read/write
  1. 7PUEC7
  2. 6PUEC6
  3. 5PUEC5
  4. 4PUEC4
  5. 3PUEC3
  6. 2PUEC2
  7. 1PUEC1
  8. 0PUEC0

PHDEPort High Drive Enable Register

Address
0x34 I/O 0x14
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2PHDEC
  7. 1–
  8. 0–
1 field
FieldBitsWhat it does
PHDEC2Port C High Drive Enable

PORTD I/O Port

PINDPort D Input Pins

Address
0x2C I/O 0x0C
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PIND3
  6. 2PIND2
  7. 1PIND1
  8. 0PIND0

DDRDData Direction Register, Port D

Address
0x2D I/O 0x0D
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3DDD3
  6. 2DDD2
  7. 1DDD1
  8. 0DDD0

PORTDPort D Data Register

Address
0x2E I/O 0x0E
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PORTD3
  6. 2PORTD2
  7. 1PORTD1
  8. 0PORTD0

PUEDPull-up Enable Control Register

Address
0x2F I/O 0x0F
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PUED3
  6. 2PUED2
  7. 1PUED1
  8. 0PUED0

TC0 Timer/Counter, 8-bit

TIFR0Timer/Counter0 Interrupt Flag register

Address
0x35 I/O 0x15
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2OCF0B
  7. 1OCF0A
  8. 0TOV0
3 fields
FieldBitsWhat it does
OCF0B2Timer/Counter0 Output Compare Flag 0B
OCF0A1Timer/Counter0 Output Compare Flag 0A
TOV00Timer/Counter0 Overflow Flag

GTCCRGeneral Timer/Counter Control Register

Address
0x43 I/O 0x23
Reset
0x00
Access
read/write
  1. 7TSM
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0PSRSYNC
2 fields
FieldBitsWhat it does
TSM7Timer/Counter Synchronization Mode
PSRSYNC0Prescaler Reset Timer/Counter1 and Timer/Counter0

TCCR0ATimer/Counter Control Register A

Address
0x44 I/O 0x24
Reset
0x00
Access
read/write
  1. 7COM0A1
  2. 6COM0A0
  3. 5COM0B1
  4. 4COM0B0
  5. 3–
  6. 2–
  7. 1WGM01
  8. 0WGM00
3 fields
FieldBitsWhat it does
COM0A7:6Compare Output Mode, Phase Correct PWM Mode
COM0B5:4Compare Output Mode, Fast PWm
WGM01:0Waveform Generation Mode

TCCR0BTimer/Counter Control Register B

Address
0x45 I/O 0x25
Reset
0x00
Access
read/write
  1. 7FOC0A
  2. 6FOC0B
  3. 5–
  4. 4–
  5. 3WGM02
  6. 2CS02
  7. 1CS01
  8. 0CS00
4 fields
FieldBitsWhat it does
FOC0A7Force Output Compare A
FOC0B6Force Output Compare B
WGM023
CS02:0Clock Select
  • 0 No Clock Source (Stopped)
  • 1 Running, No Prescaling
  • 2 Running, CLK/8
  • 3 Running, CLK/64
  • 4 Running, CLK/256
  • 5 Running, CLK/1024
  • 6 Running, ExtClk Tn Falling Edge
  • 7 Running, ExtClk Tn Rising Edge

TCNT0Timer/Counter0

Address
0x46 I/O 0x26
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

OCR0ATimer/Counter0 Output Compare Register

Address
0x47 I/O 0x27
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

OCR0BTimer/Counter0 Output Compare Register

Address
0x48 I/O 0x28
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

TIMSK0Timer/Counter0 Interrupt Mask Register

Address
0x6E
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2OCIE0B
  7. 1OCIE0A
  8. 0TOIE0
3 fields
FieldBitsWhat it does
OCIE0B2Timer/Counter0 Output Compare Match B Interrupt Enable
OCIE0A1Timer/Counter0 Output Compare Match A Interrupt Enable
TOIE00Timer/Counter0 Overflow Interrupt Enable

TC1 Timer/Counter, 16-bit

TIFR1Timer/Counter Interrupt Flag register

Address
0x36 I/O 0x16
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5ICF1
  4. 4–
  5. 3–
  6. 2OCF1B
  7. 1OCF1A
  8. 0TOV1
4 fields
FieldBitsWhat it does
ICF15Input Capture Flag 1
OCF1B2Output Compare Flag 1B
OCF1A1Output Compare Flag 1A
TOV10Timer/Counter1 Overflow Flag

GTCCRGeneral Timer/Counter Control Register

Address
0x43 I/O 0x23
Reset
0x00
Access
read/write
  1. 7TSM
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0PSRSYNC
2 fields
FieldBitsWhat it does
TSM7Timer/Counter Synchronization Mode
PSRSYNC0Prescaler Reset Timer/Counter1 and Timer/Counter0

TIMSK1Timer/Counter Interrupt Mask Register

Address
0x6F
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5ICIE1
  4. 4–
  5. 3–
  6. 2OCIE1B
  7. 1OCIE1A
  8. 0TOIE1
4 fields
FieldBitsWhat it does
ICIE15Timer/Counter1 Input Capture Interrupt Enable
OCIE1B2Timer/Counter1 Output CompareB Match Interrupt Enable
OCIE1A1Timer/Counter1 Output CompareA Match Interrupt Enable
TOIE10Timer/Counter1 Overflow Interrupt Enable

TCCR1ATimer/Counter1 Control Register A

Address
0x80
Reset
0x00
Access
read/write
  1. 7COM1A1
  2. 6COM1A0
  3. 5COM1B1
  4. 4COM1B0
  5. 3–
  6. 2–
  7. 1WGM11
  8. 0WGM10
3 fields
FieldBitsWhat it does
COM1A7:6Compare Output Mode 1A, bits
COM1B5:4Compare Output Mode 1B, bits
WGM11:0Waveform Generation Mode

TCCR1BTimer/Counter1 Control Register B

Address
0x81
Reset
0x00
Access
read/write
  1. 7ICNC1
  2. 6ICES1
  3. 5–
  4. 4WGM11
  5. 3WGM10
  6. 2CS12
  7. 1CS11
  8. 0CS10
4 fields
FieldBitsWhat it does
ICNC17Input Capture 1 Noise Canceler
ICES16Input Capture 1 Edge Select
WGM14:3Waveform Generation Mode
CS12:0Prescaler source of Timer/Counter 1
  • 0 No Clock Source (Stopped)
  • 1 Running, No Prescaling
  • 2 Running, CLK/8
  • 3 Running, CLK/64
  • 4 Running, CLK/256
  • 5 Running, CLK/1024
  • 6 Running, ExtClk Tn Falling Edge
  • 7 Running, ExtClk Tn Rising Edge

TCCR1CTimer/Counter1 Control Register C

Address
0x82
Reset
0x00
Access
read/write
  1. 7FOC1A
  2. 6FOC1B
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
2 fields
FieldBitsWhat it does
FOC1A7
FOC1B6

TCNT1Timer/Counter1 Bytes

Address
0x84
Reset
0x0000
Access
read/write
Size
16-bit

ICR1Timer/Counter1 Input Capture Register Bytes

Address
0x86
Reset
0x0000
Access
read/write
Size
16-bit

OCR1ATimer/Counter1 Output Compare Register Bytes

Address
0x88
Reset
0x0000
Access
read/write
Size
16-bit

OCR1BTimer/Counter1 Output Compare Register Bytes

Address
0x8A
Reset
0x0000
Access
read/write
Size
16-bit

EXINT External Interrupts

PCIFRPin Change Interrupt Flag Register

Address
0x3B I/O 0x1B
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PCIF3
  6. 2PCIF2
  7. 1PCIF1
  8. 0PCIF0
1 field
FieldBitsWhat it does
PCIF3:0Pin Change Interrupt Flags

EIFRExternal Interrupt Flag Register

Address
0x3C I/O 0x1C
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1INTF1
  8. 0INTF0
1 field
FieldBitsWhat it does
INTF1:0External Interrupt Flags

EIMSKExternal Interrupt Mask Register

Address
0x3D I/O 0x1D
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1INT1
  8. 0INT0
1 field
FieldBitsWhat it does
INT1:0External Interrupt Request Enables

PCICRPin Change Interrupt Control Register

Address
0x68
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PCIE3
  6. 2PCIE2
  7. 1PCIE1
  8. 0PCIE0
1 field
FieldBitsWhat it does
PCIE3:0Pin Change Interrupt Enables

EICRAExternal Interrupt Control Register

Address
0x69
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3ISC11
  6. 2ISC10
  7. 1ISC01
  8. 0ISC00
2 fields
FieldBitsWhat it does
ISC13:2External Interrupt Sense Control 1 Bits
  • 0 Low Level of INTX
  • 1 Any Logical Change of INTX
  • 2 Falling Edge of INTX
  • 3 Rising Edge of INTX
ISC01:0External Interrupt Sense Control 0 Bits
  • 0 Low Level of INTX
  • 1 Any Logical Change of INTX
  • 2 Falling Edge of INTX
  • 3 Rising Edge of INTX

PCMSK0Pin Change Mask Register 0

Address
0x6B
Reset
0x00
Access
read/write
  1. 7PCINT7
  2. 6PCINT6
  3. 5PCINT5
  4. 4PCINT4
  5. 3PCINT3
  6. 2PCINT2
  7. 1PCINT1
  8. 0PCINT0
1 field
FieldBitsWhat it does
PCINT7:0Pin Change Enable Masks

PCMSK1Pin Change Mask Register 1

Address
0x6C
Reset
0x00
Access
read/write
  1. 7PCINT7
  2. 6PCINT6
  3. 5PCINT5
  4. 4PCINT4
  5. 3PCINT3
  6. 2PCINT2
  7. 1PCINT1
  8. 0PCINT0
1 field
FieldBitsWhat it does
PCINT7:0Pin Change Enable Masks

PCMSK2Pin Change Mask Register 2

Address
0x6D
Reset
0x00
Access
read/write
  1. 7PCINT7
  2. 6PCINT6
  3. 5PCINT5
  4. 4PCINT4
  5. 3PCINT3
  6. 2PCINT2
  7. 1PCINT1
  8. 0PCINT0
1 field
FieldBitsWhat it does
PCINT7:0Pin Change Enable Masks

PCMSK3Pin Change Mask Register 3

Address
0x73
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PCINT3
  6. 2PCINT2
  7. 1PCINT1
  8. 0PCINT0
1 field
FieldBitsWhat it does
PCINT3:0Pin Change Enable Masks

CPU CPU Registers

GPIOR0General Purpose I/O Register 0

Address
0x3E I/O 0x1E
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

GPIOR1General Purpose I/O Register 1

Address
0x4A I/O 0x2A
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

GPIOR2General Purpose I/O Register 2

Address
0x4B I/O 0x2B
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

SMCRSleep Mode Control Register

Address
0x53 I/O 0x33
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2SM1
  7. 1SM0
  8. 0SE
2 fields
FieldBitsWhat it does
SM2:1Sleep Mode Select Bits
  • 0 Idle
  • 1 ADC Noise Reduction (If Available)
  • 2 Power Down
  • 3 Reserved
SE0Sleep Enable

MCUSRMCU Status Register

Address
0x54 I/O 0x34
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3WDRF
  6. 2BORF
  7. 1EXTRF
  8. 0PORF
4 fields
FieldBitsWhat it does
WDRF3Watchdog Reset Flag
BORF2Brown-out Reset Flag
EXTRF1External Reset Flag
PORF0Power-on reset flag

MCUCRMCU Control Register

Address
0x55 I/O 0x35
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1IVSEL
  8. 0–
1 field
FieldBitsWhat it does
IVSEL1Interrupt Vector Select

CCPConfiguration Change Protection

Address
0x56 I/O 0x36
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

SPMCSRStore Program Memory Control and Status Register

Address
0x57 I/O 0x37
Reset
0x00
Access
read/write
  1. 7SPMIE
  2. 6RWWSB
  3. 5RSIG
  4. 4RWWSRE
  5. 3RWFLB
  6. 2PGWRT
  7. 1PGERS
  8. 0SPMEN
8 fields
FieldBitsWhat it does
SPMIE7SPM Interrupt Enable
RWWSB6Read-While-Write Section Busy
RSIG5Read Device Signature Imprint Table
RWWSRE4Read-While-Write section read enable
RWFLB3Read/Write Fuse and Lock Bits
PGWRT2Page Write
PGERS1Page Erase
SPMEN0Store Program Memory Enable

SPStack Pointer

Address
0x5D I/O 0x3D
Reset
0x02FF
Access
read/write
Size
16-bit

SREGStatus Register

Address
0x5F I/O 0x3F
Reset
0x00
Access
read/write
  1. 7I
  2. 6T
  3. 5H
  4. 4S
  5. 3V
  6. 2N
  7. 1Z
  8. 0C
8 fields
FieldBitsWhat it does
I7Global Interrupt Enable
T6Bit Copy Storage
H5Half Carry Flag
S4Sign Bit
V3Two's Complement Overflow Flag
N2Negative Flag
Z1Zero Flag
C0Carry Flag

CLKPRClock Prescale Register

Address
0x61
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3CLKPS3
  6. 2CLKPS2
  7. 1CLKPS1
  8. 0CLKPS0
1 field
FieldBitsWhat it does
CLKPS3:0Clock Prescaler Select Bits
  • 0 1
  • 1 2
  • 2 4
  • 3 8
  • 4 16
  • 5 32
  • 6 64
  • 7 128
  • 8 256

PRRPower Reduction Register

Address
0x64
Reset
0x00
Access
read/write
  1. 7PRTWI
  2. 6–
  3. 5PRTIM0
  4. 4–
  5. 3PRTIM1
  6. 2PRSPI
  7. 1PRUSART0
  8. 0PRADC
6 fields
FieldBitsWhat it does
PRTWI7Power Reduction TWI
PRTIM05Power Reduction Timer/Counter0
PRTIM13Power Reduction Timer/Counter1
PRSPI2Power Reduction SPI
PRUSART01Power Reduction USART 0
PRADC0Power Reduction ADC

OSCCAL0Oscillator Calibration Register 8MHz

Address
0x66
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

OSCCAL1Oscillator Calibration Register 32kHz

Address
0x67
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

OSCTCAL0AOscillator Temperature Calibration Register A

Address
0xF0
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

OSCTCAL0BOscillator Temperature Calibration Register B

Address
0xF1
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

EEPROM EEPROM

EECREEPROM Control Register

Address
0x3F I/O 0x1F
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5EEPM1
  4. 4EEPM0
  5. 3EERIE
  6. 2EEMPE
  7. 1EEPE
  8. 0EERE
5 fields
FieldBitsWhat it does
EEPM5:4EEPROM Programming Mode Bits
  • 0 Erase and Write in one operation
  • 1 Erase Only
  • 2 Write Only
EERIE3EEProm Ready Interrupt Enable
EEMPE2EEPROM Master Write Enable
EEPE1EEPROM Write Enable
EERE0EEPROM Read Enable

EEDREEPROM Data Register

Address
0x40 I/O 0x20
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

EEAREEPROM Read/Write Access

Address
0x41 I/O 0x21
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

EEARLEEPROM Read/Write Access

Address
0x41 I/O 0x21
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

SPI Serial Peripheral Interface

SPCRSPI Control Register

Address
0x4C I/O 0x2C
Reset
0x00
Access
read/write
  1. 7SPIE
  2. 6SPE
  3. 5DORD
  4. 4MSTR
  5. 3CPOL
  6. 2CPHA
  7. 1SPR1
  8. 0SPR0
7 fields
FieldBitsWhat it does
SPIE7SPI Interrupt Enable
SPE6SPI Enable
DORD5Data Order
MSTR4Master/Slave Select
CPOL3Clock polarity
CPHA2Clock Phase
SPR1:0SPI Clock Rate Selects
  • 0 fosc/4
  • 1 fosc/16
  • 2 fosc/64
  • 3 fosc/128
  • 4 fosc/2
  • 5 fosc/8
  • 6 fosc/32
  • 7 fosc/64

SPSRSPI Status Register

Address
0x4D I/O 0x2D
Reset
0x00
Access
read/write
  1. 7SPIF
  2. 6WCOL
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0SPI2X
3 fields
FieldBitsWhat it does
SPIF7SPI Interrupt Flag
WCOL6Write Collision Flag
SPI2X0Double SPI Speed Bit

SPDRSPI Data Register

Address
0x4E I/O 0x2E
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

AC Analog Comparator

ACSRBAnalog Comparator Control And Status Register B

Address
0x4F I/O 0x2F
Reset
0x00
Access
read/write
  1. 7HSEL
  2. 6HLEV
  3. 5–
  4. 4–
  5. 3ACNMUX1
  6. 2ACNMUX0
  7. 1ACPMUX1
  8. 0ACPMUX0
4 fields
FieldBitsWhat it does
HSEL7Hysteresis Select
HLEV6Hysteresis Level
ACNMUX3:2Analog Comparator Negative Input Multiplexer
ACPMUX1:0Analog Comparator Positive Input Multiplexer Bits 1:0

ACSRAAnalog Comparator Control And Status Register A

Address
0x50 I/O 0x30
Reset
0x00
Access
read/write
  1. 7ACD
  2. 6ACPMUX2
  3. 5ACO
  4. 4ACI
  5. 3ACIE
  6. 2ACIC
  7. 1ACIS1
  8. 0ACIS0
7 fields
FieldBitsWhat it does
ACD7Analog Comparator Disable
ACPMUX26Analog Comparator Positive Input Multiplexer Bit 2
ACO5Analog Compare Output
ACI4Analog Comparator Interrupt Flag
ACIE3Analog Comparator Interrupt Enable
ACIC2Analog Comparator Input Capture Enable
ACIS1:0Analog Comparator Interrupt Mode Select bits
  • 0 Interrupt on Toggle
  • 1 Reserved
  • 2 Interrupt on Falling Edge
  • 3 Interrupt on Rising Edge

WDT Watchdog Timer

WDTCSRWatchdog Timer Control and Status Register

Address
0x60
Reset
0x00
Access
read/write
  1. 7WDIF
  2. 6WDIE
  3. 5WDP5
  4. 4–
  5. 3WDE
  6. 2WDP2
  7. 1WDP1
  8. 0WDP0
4 fields
FieldBitsWhat it does
WDIF7Watchdog Timer Interrupt Flag
WDIE6Watchdog Timer Interrupt Enable
WDP5,2,1,0Watchdog Timer Prescaler Bits
  • 0 Oscillator Cycles 512 (16 ms)
  • 1 Oscillator Cycles 1K (32 ms)
  • 2 Oscillator Cycles 2K (64 ms)
  • 3 Oscillator Cycles 4K (0.125 s)
  • 4 Oscillator Cycles 8K (0.25 s)
  • 5 Oscillator Cycles 16K (0.5 s)
  • 6 Oscillator Cycles 32K (1.0 s)
  • 7 Oscillator Cycles 64K (2.0 s)
  • 8 Oscillator Cycles 128K (4.0 s)
  • 9 Oscillator Cycles 256K (8.0 s)
WDE3Watch Dog Enable

ADC Analog-to-Digital Converter

ADCADC Data Register Bytes

Address
0x78
Reset
0x0000
Access
read/write
Size
16-bit

ADCSRAThe ADC Control and Status register

Address
0x7A
Reset
0x00
Access
read/write
  1. 7ADEN
  2. 6ADSC
  3. 5ADATE
  4. 4ADIF
  5. 3ADIE
  6. 2ADPS2
  7. 1ADPS1
  8. 0ADPS0
6 fields
FieldBitsWhat it does
ADEN7ADC Enable
ADSC6ADC Start Conversion
ADATE5ADC Auto Trigger Enable
ADIF4ADC Interrupt Flag
ADIE3ADC Interrupt Enable
ADPS2:0ADC Prescaler Select Bits
  • 0 2
  • 1 2
  • 2 4
  • 3 8
  • 4 16
  • 5 32
  • 6 64
  • 7 128

ADCSRBADC Control and Status Register B

Address
0x7B
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3ADLAR
  6. 2ADTS2
  7. 1ADTS1
  8. 0ADTS0
2 fields
FieldBitsWhat it does
ADLAR3
ADTS2:0ADC Auto Trigger Sources
  • 0 Free Running mode
  • 1 Analog Comparator
  • 2 External Interrupt Request 0
  • 3 Timer/Counter0 Compare Match A
  • 4 Timer/Counter0 Overflow
  • 5 Timer/Counter1 Compare Match B
  • 6 Timer/Counter1 Overflow
  • 7 Timer/Counter1 Capture Event

ADMUXAThe ADC multiplexer Selection Register A

Address
0x7C
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4MUX4
  5. 3MUX3
  6. 2MUX2
  7. 1MUX1
  8. 0MUX0
1 field
FieldBitsWhat it does
MUX4:0Analog Channel Selection Bits 4:0

ADMUXBThe ADC multiplexer Selection Register B

Address
0x7D
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5REFS
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0MUX5
2 fields
FieldBitsWhat it does
REFS5Reference Selection Bit
MUX50Analog Channel Selection Bit 5

DIDR0Digital Input Disable Register 0

Address
0x7E
Reset
0x00
Access
read/write
  1. 7ADC7D
  2. 6ADC6D
  3. 5ADC5D
  4. 4ADC4D
  5. 3ADC3D
  6. 2ADC2D
  7. 1ADC1D
  8. 0ADC0D
8 fields
FieldBitsWhat it does
ADC7D7ADC7 Digital input Disable
ADC6D6ADC6 Digital input Disable
ADC5D5ADC5 Digital input Disable
ADC4D4ADC4 Digital input Disable
ADC3D3ADC3 Digital input Disable
ADC2D2ADC2 Digital input Disable
ADC1D1ADC1 Digital input Disable
ADC0D0ADC0 Digital input Disable

DIDR1Digital Input Disable Register 1

Address
0x7F
Reset
0x00
Access
read/write
  1. 7ADC15D
  2. 6ADC14D
  3. 5ADC13D
  4. 4ADC12D
  5. 3ADC11D
  6. 2ADC10D
  7. 1ADC9D
  8. 0ADC8D
8 fields
FieldBitsWhat it does
ADC15D7ADC15 Digital input Disable
ADC14D6ADC14 Digital input Disable
ADC13D5ADC13 Digital input Disable
ADC12D4ADC12 Digital input Disable
ADC11D3ADC11 Digital input Disable
ADC10D2ADC10 Digital input Disable
ADC9D1ADC9 Digital input Disable
ADC8D0ADC8 Digital input Disable

DIDR2Digital Input Disable Register 2

Address
0xDE
Reset
0x00
Access
read/write
  1. 7ADC23D
  2. 6ADC22D
  3. 5ADC21D
  4. 4ADC20D
  5. 3ADC19D
  6. 2ADC18D
  7. 1ADC17D
  8. 0ADC16D
8 fields
FieldBitsWhat it does
ADC23D7ADC23 Digital input Disable
ADC22D6ADC22 Digital input Disable
ADC21D5ADC21 Digital input Disable
ADC20D4ADC20 Digital input Disable
ADC19D3ADC19 Digital input Disable
ADC18D2ADC18 Digital input Disable
ADC17D1ADC17 Digital input Disable
ADC16D0ADC16 Digital input Disable

DIDR3Digital Input Disable Register 2

Address
0xDF
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3ADC27D
  6. 2ADC26D
  7. 1ADC25D
  8. 0ADC24D
4 fields
FieldBitsWhat it does
ADC27D3ADC27 Digital input Disable
ADC26D2ADC26 Digital input Disable
ADC25D1ADC25 Digital input Disable
ADC24D0ADC24 Digital input Disable

TWI Two Wire Serial Interface

TWSCRATWI Slave Control Register A

Address
0xB8
Reset
0x00
Access
read/write
  1. 7TWSHE
  2. 6–
  3. 5TWDIE
  4. 4TWASIE
  5. 3TWEN
  6. 2TWSIE
  7. 1TWPME
  8. 0TWSME
7 fields
FieldBitsWhat it does
TWSHE7TWI SDA Hold Time Enable
TWDIE5TWI Data Interrupt Enable
TWASIE4TWI Address/Stop Interrupt Enable
TWEN3Two-Wire Interface Enable
TWSIE2TWI Stop Interrupt Enable
TWPME1TWI Promiscuous Mode Enable
TWSME0TWI Smart Mode Enable

TWSCRBTWI Slave Control Register B

Address
0xB9
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3TWHNM
  6. 2TWAA
  7. 1TWCMD1
  8. 0TWCMD0
3 fields
FieldBitsWhat it does
TWHNM3TWI High Noise Mode
TWAA2TWI Acknowledge Action
TWCMD1:0

TWSSRATWI Slave Status Register A

Address
0xBA
Reset
0x00
Access
read/write
  1. 7TWDIF
  2. 6TWASIF
  3. 5TWCH
  4. 4TWRA
  5. 3TWC
  6. 2TWBE
  7. 1TWDIR
  8. 0TWAS
8 fields
FieldBitsWhat it does
TWDIF7TWI Data Interrupt Flag.
TWASIF6TWI Address/Stop Interrupt Flag
TWCH5TWI Clock Hold
TWRA4TWI Receive Acknowledge
TWC3TWI Collision
TWBE2TWI Bus Error
TWDIR1TWI Read/Write Direction
TWAS0TWI Address or Stop

TWSAMTWI Slave Address Mask Register

Address
0xBB
Reset
0x00
Access
read/write
  1. 7TWSAM6
  2. 6TWSAM5
  3. 5TWSAM4
  4. 4TWSAM3
  5. 3TWSAM2
  6. 2TWSAM1
  7. 1TWSAM0
  8. 0TWAE
2 fields
FieldBitsWhat it does
TWSAM7:1TWI Address Mask Bits
TWAE0TWI Address Enable

TWSATWI Slave Address Register

Address
0xBC
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

TWSDTWI Slave Data Register

Address
0xBD
Reset
0x00
Access
read/write
  1. 7TWSD7
  2. 6TWSD6
  3. 5TWSD5
  4. 4TWSD4
  5. 3TWSD3
  6. 2TWSD2
  7. 1TWSD1
  8. 0TWSD0
1 field
FieldBitsWhat it does
TWSD7:0TWI slave data bit

USART USART

UCSRAUSART Control and Status Register A

Address
0xC0
Reset
0x00
Access
read/write
  1. 7RXC
  2. 6TXC
  3. 5UDRE
  4. 4FE
  5. 3DOR
  6. 2UPE
  7. 1U2X
  8. 0MPCM
8 fields
FieldBitsWhat it does
RXC7USART Receive Complete
TXC6USART Transmit Complete
UDRE5USART Data Register Empty
FE4Framing Error
DOR3Data Overrun
UPE2Parity Error
U2X1Double the USART transmission speed
MPCM0Multi-processor Communication Mode

UCSRBUSART Control and Status Register B

Address
0xC1
Reset
0x00
Access
read/write
  1. 7RXCIE
  2. 6TXCIE
  3. 5UDRIE
  4. 4RXEN
  5. 3TXEN
  6. 2UCSZ2
  7. 1RXB8
  8. 0TXB8
8 fields
FieldBitsWhat it does
RXCIE7RX Complete Interrupt Enable
TXCIE6TX Complete Interrupt Enable
UDRIE5USART Data register Empty Interrupt Enable
RXEN4Receiver Enable
TXEN3Transmitter Enable
UCSZ22Character Size
RXB81Receive Data Bit 8
TXB80Transmit Data Bit 8

UCSRCUSART Control and Status Register C

Address
0xC2
Reset
0x00
Access
read/write
  1. 7UMSEL1
  2. 6UMSEL0
  3. 5UPM1
  4. 4UPM0
  5. 3USBS
  6. 2UCSZ1
  7. 1UCSZ0
  8. 0UCPOL
5 fields
FieldBitsWhat it does
UMSEL7:6USART Mode Select
  • 0 Asynchronous Operation
  • 1 Synchronous Operation
UPM5:4Parity Mode Bits
  • 0 Disabled
  • 1 Reserved
  • 2 Enabled, Even Parity
  • 3 Enabled, Odd Parity
USBS3Stop Bit Select
  • 0 1-bit
  • 1 2-bit
UCSZ2:1Character Size
UCPOL0Clock Polarity

UCSRDUSART Control and Status Register D

Address
0xC3
Reset
0x00
Access
read/write
  1. 7RXSIE
  2. 6RXS
  3. 5SFDE
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
3 fields
FieldBitsWhat it does
RXSIE7USART RX Start Interrupt Enable
RXS6USART RX Start Flag
SFDE5USART RX Start Frame Detection Enable

UBRRUSART Baud Rate Register Bytes

Address
0xC4
Reset
0x0000
Access
read/write
Size
16-bit

UDRUSART I/O Data Register

Address
0xC6
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

TOCPM Timer/Counter Output Compare Pin

TOCPMCOETimer Output Compare Pin Mux Channel Output Enable

Address
0xE2
Reset
0x00
Access
read/write
  1. 7TOCC7OE
  2. 6TOCC6OE
  3. 5TOCC5OE
  4. 4TOCC4OE
  5. 3TOCC3OE
  6. 2TOCC2OE
  7. 1TOCC1OE
  8. 0TOCC0OE
8 fields
FieldBitsWhat it does
TOCC7OE7Timer Output Compare Channel 7 Output Enable
TOCC6OE6Timer Output Compare Channel 6 Output Enable
TOCC5OE5Timer Output Compare Channel 5 Output Enable
TOCC4OE4Timer Output Compare Channel 4 Output Enable
TOCC3OE3Timer Output Compare Channel 3 Output Enable
TOCC2OE2Timer Output Compare Channel 2 Output Enable
TOCC1OE1Timer Output Compare Channel 1 Output Enable
TOCC0OE0Timer Output Compare Channel 0 Output Enable

TOCPMSA0Timer Output Compare Pin Mux Selection 0

Address
0xE8
Reset
0x00
Access
read/write
  1. 7TOCC3S1
  2. 6TOCC3S0
  3. 5TOCC2S1
  4. 4TOCC2S0
  5. 3TOCC1S1
  6. 2TOCC1S0
  7. 1TOCC0S1
  8. 0TOCC0S0
4 fields
FieldBitsWhat it does
TOCC3S7:6Timer Output Compare Channel 3 Selection Bits
TOCC2S5:4Timer Output Compare Channel 2 Selection Bits
TOCC1S3:2Timer Output Compare Channel 1 Selection Bits
TOCC0S1:0Timer Output Compare Channel 0 Selection Bits

TOCPMSA1Timer Output Compare Pin Mux Selection 1

Address
0xE9
Reset
0x00
Access
read/write
  1. 7TOCC7S1
  2. 6TOCC7S0
  3. 5TOCC6S1
  4. 4TOCC6S0
  5. 3TOCC5S1
  6. 2TOCC5S0
  7. 1TOCC4S1
  8. 0TOCC4S0
4 fields
FieldBitsWhat it does
TOCC7S7:6Timer Output Compare Channel 7 Selection Bits
TOCC6S5:4Timer Output Compare Channel 6 Selection Bits
TOCC5S3:2Timer Output Compare Channel 5 Selection Bits
TOCC4S1:0Timer Output Compare Channel 4 Selection Bits