AI Interactive Datasheet ATtiny44A
AVR · tinyAVR

ATtiny44A registers

All 55 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.

CPU CPU Registers

PRRPower Reduction Register

Address
0x20 I/O 0x00
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PRTIM1
  6. 2PRTIM0
  7. 1PRUSI
  8. 0PRADC
4 fields
FieldBitsWhat it does
PRTIM13Power Reduction Timer/Counter1
PRTIM02Power Reduction Timer/Counter0
PRUSI1Power Reduction USI
PRADC0Power Reduction ADC

GPIOR0General Purpose I/O Register 0

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–

GPIOR1General Purpose I/O Register 1

Address
0x34 I/O 0x14
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
0x35 I/O 0x15
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

CLKPRClock Prescale Register

Address
0x46 I/O 0x26
Reset
0x00
Access
read/write
  1. 7CLKPCE
  2. 6–
  3. 5–
  4. 4–
  5. 3CLKPS3
  6. 2CLKPS2
  7. 1CLKPS1
  8. 0CLKPS0
2 fields
FieldBitsWhat it does
CLKPCE7Clock Prescaler Change Enable
CLKPS3:0Clock Prescaler Select Bits
  • 0 1
  • 1 2
  • 2 4
  • 3 8
  • 4 16
  • 5 32
  • 6 64
  • 7 128
  • 8 256

OSCCALOscillator Calibration Value

Address
0x51 I/O 0x31
Reset
0x00
Access
read/write
  1. 7OSCCAL7
  2. 6OSCCAL6
  3. 5OSCCAL5
  4. 4OSCCAL4
  5. 3OSCCAL3
  6. 2OSCCAL2
  7. 1OSCCAL1
  8. 0OSCCAL0
1 field
FieldBitsWhat it does
OSCCAL7:0Oscillator Calibration

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. 6PUD
  3. 5SE
  4. 4SM1
  5. 3SM0
  6. 2–
  7. 1–
  8. 0–
3 fields
FieldBitsWhat it does
PUD6Pull-up Disable
SE5Sleep Enable
SM4:3Sleep Mode Select Bits
  • 0 Idle
  • 1 ADC Noise Reduction (If Available)
  • 2 Power Down
  • 3 Standby

SPStack Pointer

Address
0x5D I/O 0x3D
Reset
0x015F
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

AC Analog Comparator

DIDR0

Address
0x21 I/O 0x01
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1ADC1D
  8. 0ADC0D
2 fields
FieldBitsWhat it does
ADC1D1ADC 1 Digital input buffer disable
ADC0D0ADC 0 Digital input buffer disable

ADCSRBADC Control and Status Register B

Address
0x23 I/O 0x03
Reset
0x00
Access
read/write
  1. 7–
  2. 6ACME
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
1 field
FieldBitsWhat it does
ACME6Analog Comparator Multiplexer Enable

ACSRAnalog Comparator Control And Status Register

Address
0x28 I/O 0x08
Reset
0x00
Access
read/write
  1. 7ACD
  2. 6ACBG
  3. 5ACO
  4. 4ACI
  5. 3ACIE
  6. 2ACIC
  7. 1ACIS1
  8. 0ACIS0
7 fields
FieldBitsWhat it does
ACD7Analog Comparator Disable
ACBG6Analog Comparator Bandgap Select
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

ADC Analog-to-Digital Converter

DIDR0Digital Input Disable Register 0

Address
0x21 I/O 0x01
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

ADCSRBADC Control and Status Register B

Address
0x23 I/O 0x03
Reset
0x00
Access
read/write
  1. 7BIN
  2. 6–
  3. 5–
  4. 4ADLAR
  5. 3–
  6. 2ADTS2
  7. 1ADTS1
  8. 0ADTS0
3 fields
FieldBitsWhat it does
BIN7Bipolar Input Mode
ADLAR4ADC Left Adjust Result
ADTS2:0ADC Auto Trigger Source bits
  • 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

ADCADC Data Register Bytes

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

ADCSRAADC Control and Status Register A

Address
0x26 I/O 0x06
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

ADMUXADC Multiplexer Selection Register

Address
0x27 I/O 0x07
Reset
0x00
Access
read/write
  1. 7REFS1
  2. 6REFS0
  3. 5MUX5
  4. 4MUX4
  5. 3MUX3
  6. 2MUX2
  7. 1MUX1
  8. 0MUX0
2 fields
FieldBitsWhat it does
REFS7:6Reference Selection Bits
  • 0 VCC used as analog reference, disconnected from PA0 (AREF)
  • 1 External voltage reference at PA0 (AREF) pin, internal reference turned off
  • 2 Internal 1.1V voltage reference
  • 3 Reserved
MUX5:0Analog Channel and Gain Selection Bits

TC1 Timer/Counter, 16-bit

TIFR1Timer/Counter Interrupt Flag register

Address
0x2B I/O 0x0B
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
ICF15Timer/Counter1 Input Capture Flag
OCF1B2Timer/Counter1 Output Compare B Match Flag
OCF1A1Timer/Counter1 Output Compare A Match Flag
TOV10Timer/Counter1 Overflow Flag

TIMSK1Timer/Counter1 Interrupt Mask Register

Address
0x2C I/O 0x0C
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 Compare B Match Interrupt Enable
OCIE1A1Timer/Counter1 Output Compare A Match Interrupt Enable
TOIE10Timer/Counter1 Overflow Interrupt Enable

TCCR1CTimer/Counter1 Control Register C

Address
0x42 I/O 0x22
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
FOC1A7Force Output Compare for Channel A
FOC1B6Force Output Compare for Channel B

ICR1Timer/Counter1 Input Capture Register Bytes

Address
0x44 I/O 0x24
Reset
0x0000
Access
read/write
Size
16-bit

OCR1BTimer/Counter1 Output Compare Register B Bytes

Address
0x48 I/O 0x28
Reset
0x0000
Access
read/write
Size
16-bit

OCR1ATimer/Counter1 Output Compare Register A Bytes

Address
0x4A I/O 0x2A
Reset
0x0000
Access
read/write
Size
16-bit

TCNT1Timer/Counter1 Bytes

Address
0x4C I/O 0x2C
Reset
0x0000
Access
read/write
Size
16-bit

TCCR1BTimer/Counter1 Control Register B

Address
0x4E I/O 0x2E
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 Bits
CS12:0Clock Select1 bits
  • 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

TCCR1ATimer/Counter1 Control Register A

Address
0x4F I/O 0x2F
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
WGM11:0Pulse Width Modulator Select Bits

USI Universal Serial Interface

USICRUSI Control Register

Address
0x2D I/O 0x0D
Reset
0x00
Access
read/write
  1. 7USISIE
  2. 6USIOIE
  3. 5USIWM1
  4. 4USIWM0
  5. 3USICS1
  6. 2USICS0
  7. 1USICLK
  8. 0USITC
6 fields
FieldBitsWhat it does
USISIE7Start Condition Interrupt Enable
USIOIE6Counter Overflow Interrupt Enable
USIWM5:4USI Wire Mode Bits
  • 0 Normal Operation
  • 1 Three-Wire Mode
  • 2 Two-Wire Mode
  • 3 Two-Wire Mode Held Low
USICS3:2USI Clock Source Select Bits
USICLK1Clock Strobe
USITC0Toggle Clock Port Pin

USISRUSI Status Register

Address
0x2E I/O 0x0E
Reset
0x00
Access
read/write
  1. 7USISIF
  2. 6USIOIF
  3. 5USIPF
  4. 4USIDC
  5. 3USICNT3
  6. 2USICNT2
  7. 1USICNT1
  8. 0USICNT0
5 fields
FieldBitsWhat it does
USISIF7Start Condition Interrupt Flag
USIOIF6Counter Overflow Interrupt Flag
USIPF5Stop Condition Flag
USIDC4Data Output Collision
USICNT3:0USI Counter Value Bits

USIDRUSI Data Register

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

USIBRUSI Buffer Register

Address
0x30 I/O 0x10
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

EXINT External Interrupts

PCMSK0Pin Change Enable Mask 0

Address
0x32 I/O 0x12
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

PCMSK1Pin Change Enable Mask 1

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–

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. 1ISC01
  8. 0ISC00
1 field
FieldBitsWhat it does
ISC01:0Interrupt Sense Control 0
  • 0 Low Level of INTX
  • 1 Any Logical Change of INTX
  • 2 Falling Edge of INTX
  • 3 Rising Edge of INTX

GIFRGeneral Interrupt Flag register

Address
0x5A I/O 0x3A
Reset
0x00
Access
read/write
  1. 7–
  2. 6INTF0
  3. 5PCIF1
  4. 4PCIF0
  5. 3–
  6. 2–
  7. 1–
  8. 0–
2 fields
FieldBitsWhat it does
INTF06External Interrupt Flag 0
PCIF5:4Pin Change Interrupt Flags

GIMSKGeneral Interrupt Mask Register

Address
0x5B I/O 0x3B
Reset
0x00
Access
read/write
  1. 7–
  2. 6INT0
  3. 5PCIE1
  4. 4PCIE0
  5. 3–
  6. 2–
  7. 1–
  8. 0–
2 fields
FieldBitsWhat it does
INT06External Interrupt Request 0 Enable
PCIE5:4Pin Change Interrupt Enables

PORTB I/O Port

PINBInput Pins, Port B

Address
0x36 I/O 0x16
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
0x37 I/O 0x17
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3DDB3
  6. 2DDB2
  7. 1DDB1
  8. 0DDB0

PORTBData Register, Port B

Address
0x38 I/O 0x18
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3PORTB3
  6. 2PORTB2
  7. 1PORTB1
  8. 0PORTB0

PORTA I/O Port

PINAPort A Input Pins

Address
0x39 I/O 0x19
Reset
0x00
Access
read/write
  1. 7PINA7
  2. 6PINA6
  3. 5PINA5
  4. 4PINA4
  5. 3PINA3
  6. 2PINA2
  7. 1PINA1
  8. 0PINA0

DDRAPort A Data Direction Register

Address
0x3A I/O 0x1A
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
0x3B I/O 0x1B
Reset
0x00
Access
read/write
  1. 7PORTA7
  2. 6PORTA6
  3. 5PORTA5
  4. 4PORTA4
  5. 3PORTA3
  6. 2PORTA2
  7. 1PORTA1
  8. 0PORTA0

EEPROM EEPROM

EECREEPROM Control Register

Address
0x3C I/O 0x1C
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
0x3D I/O 0x1D
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

EEAREEPROM Address Register Bytes

Address
0x3E I/O 0x1E
Reset
0x0000
Access
read/write
Size
16-bit

WDT Watchdog Timer

WDTCSRWatchdog Timer Control Register

Address
0x41 I/O 0x21
Reset
0x00
Access
read/write
  1. 7WDIF
  2. 6WDIE
  3. 5WDP5
  4. 4WDCE
  5. 3WDE
  6. 2WDP2
  7. 1WDP1
  8. 0WDP0
5 fields
FieldBitsWhat it does
WDIF7Watchdog Timeout Interrupt Flag
WDIE6Watchdog Timeout 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
WDCE4Watchdog Change Enable
WDE3Watch Dog Enable

TC0 Timer/Counter, 8-bit

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. 0PSR10
2 fields
FieldBitsWhat it does
TSM7Timer/Counter Synchronization Mode
PSR100Prescaler Reset Timer/CounterN

TCCR0ATimer/Counter Control Register A

Address
0x50 I/O 0x30
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 Match Output A Mode bits
COM0B5:4Compare Match Output B Mode bits
WGM01:0Waveform Generation Mode bits

TCNT0Timer/Counter0

Address
0x52 I/O 0x32
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

TCCR0BTimer/Counter Control Register B

Address
0x53 I/O 0x33
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
WGM023Waveform Generation Mode bit 2
CS02:0Clock Select bits
  • 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

OCR0ATimer/Counter0 Output Compare Register A

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–

TIFR0Timer/Counter0 Interrupt Flag Register

Address
0x58 I/O 0x38
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 B
OCF0A1Timer/Counter0 Output Compare Flag A
TOV00Timer/Counter0 Overflow Flag

TIMSK0Timer/Counter Interrupt Mask Register

Address
0x59 I/O 0x39
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

OCR0BTimer/Counter0 Output Compare Register B

Address
0x5C I/O 0x3C
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

BOOT_LOAD Bootloader

SPMCSRStore Program Memory Control Register

Address
0x57 I/O 0x37
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4CTPB
  5. 3RFLB
  6. 2PGWRT
  7. 1PGERS
  8. 0SPMEN
5 fields
FieldBitsWhat it does
CTPB4Clear temporary page buffer
RFLB3Read fuse and lock bits
PGWRT2Page Write
PGERS1Page Erase
SPMEN0Store Program Memory Enable