AI Interactive Datasheet ATtiny4
AVR · tinyAVR

ATtiny4 registers

All 36 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.

PORTB I/O Port

PINBPort B Data register

Address
0x00
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PINB3
  6. 2PINB2
  7. 1PINB1
  8. 0PINB0

DDRBData Direction Register, Port B

Address
0x01
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3DDB3
  6. 2DDB2
  7. 1DDB1
  8. 0DDB0

PORTBInput Pins, Port B

Address
0x02
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PORTB3
  6. 2PORTB2
  7. 1PORTB1
  8. 0PORTB0

PUEBPull-up Enable Control Register

Address
0x03
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PUEB3
  6. 2PUEB2
  7. 1PUEB1
  8. 0PUEB0

PORTCRPort Control Register

Address
0x0C
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1BBMB
  8. 0–
1 field
FieldBitsWhat it does
BBMB1Break-Before-Make Mode Enable

EXINT External Interrupts

PCMSKPin Change Mask Register

Address
0x10
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

PCIFRPin Change Interrupt Flag Register

Address
0x11
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0PCIF0
1 field
FieldBitsWhat it does
PCIF00Pin Change Interrupt Flag 0

PCICRPin Change Interrupt Control Register

Address
0x12
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0PCIE0
1 field
FieldBitsWhat it does
PCIE00Pin Change Interrupt Enable 0

EIMSKExternal Interrupt Mask register

Address
0x13
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0INT0
1 field
FieldBitsWhat it does
INT00External Interrupt Request 0 Enable

EIFRExternal Interrupt Flag register

Address
0x14
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0INTF0
1 field
FieldBitsWhat it does
INTF00External Interrupt Flag 0

EICRAExternal Interrupt Control Register A

Address
0x15
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1ISC01
  8. 0ISC00
2 fields
FieldBitsWhat it does
ISC011Interrupt Sense Control 0 Bit 1
ISC000Interrupt Sense Control 0 Bit 0

AC Analog Comparator

DIDR0

Address
0x17
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1AIN1D
  8. 0AIN0D
2 fields
FieldBitsWhat it does
AIN1D1AIN1 Digital Input Disable
AIN0D0AIN0 Digital Input Disable

ACSRAnalog Comparator Control And Status Register

Address
0x1F
Reset
0x00
Access
read/write
  1. 7ACD
  2. 6–
  3. 5ACO
  4. 4ACI
  5. 3ACIE
  6. 2ACIC
  7. 1ACIS1
  8. 0ACIS0
6 fields
FieldBitsWhat it does
ACD7Analog Comparator Disable
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

TC0 Timer/Counter, 16-bit

ICR0Input Capture Register Bytes

Address
0x22 I/O 0x02
Reset
0x0000
Access
read/write
Size
16-bit

OCR0BTimer/Counter0 Output Compare Register B

Address
0x24 I/O 0x04
Reset
0x0000
Access
read/write
Size
16-bit

OCR0ATimer/Counter 0 Output Compare Register A

Address
0x26 I/O 0x06
Reset
0x0000
Access
read/write
Size
16-bit

TCNT0Timer/Counter0

Address
0x28 I/O 0x08
Reset
0x0000
Access
read/write
Size
16-bit

TIFR0Overflow Interrupt Enable

Address
0x2A I/O 0x0A
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5ICF0
  4. 4–
  5. 3–
  6. 2OCF0B
  7. 1OCF0A
  8. 0TOV0
4 fields
FieldBitsWhat it does
ICF05Input Capture Flag
OCF0B2Timer Output Compare Flag 0B
OCF0A1Timer Output Compare Flag 0A
TOV00Timer Overflow Flag

TIMSK0Timer Interrupt Mask Register 0

Address
0x2B I/O 0x0B
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5ICIE0
  4. 4–
  5. 3–
  6. 2OCIE0B
  7. 1OCIE0A
  8. 0TOIE0
4 fields
FieldBitsWhat it does
ICIE05Input Capture Interrupt Enable
OCIE0B2Output Compare B Match Interrupt Enable
OCIE0A1Output Compare A Match Interrupt Enable
TOIE00Overflow Interrupt Enable

TCCR0CTimer/Counter 0 Control Register C

Address
0x2C I/O 0x0C
Reset
0x00
Access
read/write
  1. 7FOC0A
  2. 6FOC0B
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
2 fields
FieldBitsWhat it does
FOC0A7Force Output Compare for Channel A
FOC0B6Force Output Compare for Channel B

TCCR0BTimer/Counter 0 Control Register B

Address
0x2D I/O 0x0D
Reset
0x00
Access
read/write
  1. 7ICNC0
  2. 6ICES0
  3. 5–
  4. 4WGM01
  5. 3WGM00
  6. 2CS02
  7. 1CS01
  8. 0CS00
4 fields
FieldBitsWhat it does
ICNC07Input Capture Noise Canceler
ICES06Input Capture Edge Select
WGM04:3Waveform Generation Mode
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

TCCR0ATimer/Counter 0 Control Register A

Address
0x2E I/O 0x0E
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 for Channel A bits
COM0B5:4Compare Output Mode for Channel B bits
WGM01:0Waveform Generation Mode

GTCCRGeneral Timer/Counter Control Register

Address
0x2F I/O 0x0F
Reset
0x00
Access
read/write
  1. 7TSM
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0PSR
2 fields
FieldBitsWhat it does
TSM7Timer Synchronization Mode
PSR0Prescaler Reset

WDT Watchdog Timer

WDTCSRWatchdog Timer Control and Status Register

Address
0x31 I/O 0x11
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 2K
  • 1 Oscillator Cycles 4K
  • 2 Oscillator Cycles 8K
  • 3 Oscillator Cycles 16K
  • 4 Oscillator Cycles 32K
  • 5 Oscillator Cycles 64K
  • 6 Oscillator Cycles 128K
  • 7 Oscillator Cycles 256K
  • 8 Oscillator Cycles 512K
  • 9 Oscillator Cycles 1024K
WDE3Watch Dog Enable

CPU CPU Registers

NVMCSRNon-Volatile Memory Control and Status Register

Address
0x32 I/O 0x12
Reset
0x00
Access
read/write
  1. 7NVMBSY
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
1 field
FieldBitsWhat it does
NVMBSY7Non-Volatile Memory Busy

NVMCMDNon-Volatile Memory Command

Address
0x33 I/O 0x13
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

VLMCSRVcc Level Monitoring Control and Status Register

Address
0x34 I/O 0x14
Reset
0x00
Access
read/write
  1. 7VLMF
  2. 6VLMIE
  3. 5–
  4. 4–
  5. 3–
  6. 2VLM2
  7. 1VLM1
  8. 0VLM0
3 fields
FieldBitsWhat it does
VLMF7VLM Flag
VLMIE6VLM Interrupt Enable
VLM2:0Trigger Level of Voltage Level Monitor bits

PRRPower Reduction Register

Address
0x35 I/O 0x15
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1PRADC
  8. 0PRTIM0
2 fields
FieldBitsWhat it does
PRADC1Power Reduction ADC
PRTIM00Power Reduction Timer/Counter0

CLKPSRClock Prescale Register

Address
0x36 I/O 0x16
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

CLKMSRClock Main Settings Register

Address
0x37 I/O 0x17
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1CLKMS1
  8. 0CLKMS0
1 field
FieldBitsWhat it does
CLKMS1:0Clock Main Select Bits

OSCCALOscillator Calibration Value

Address
0x39 I/O 0x19
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
0x3A I/O 0x1A
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3SM2
  6. 2SM1
  7. 1SM0
  8. 0SE
2 fields
FieldBitsWhat it does
SM3:1Sleep Mode Select Bits
  • 0 Idle
  • 1 ADC Noise Reduction
  • 2 Power Down
  • 3 Reserved
  • 4 Standby
  • 5 Reserved
  • 6 Reserved
  • 7 Reserved
SE0Sleep Enable

RSTFLRReset Flag Register

Address
0x3B I/O 0x1B
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3WDRF
  6. 2–
  7. 1EXTRF
  8. 0PORF
3 fields
FieldBitsWhat it does
WDRF3Watchdog Reset Flag
EXTRF1External Reset Flag
PORF0Power-on Reset Flag

CCPConfiguration Change Protection

Address
0x3C I/O 0x1C
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

SPStack Pointer

Address
0x3D I/O 0x1D
Reset
0x005F
Access
read/write
Size
16-bit

SREGStatus Register

Address
0x3F I/O 0x1F
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