AI Interactive Datasheet ATmega16A
AVR · megaAVR

ATmega16A registers

All 70 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.

TWI Two Wire Serial Interface

TWBRTWI Bit Rate register

Address
0x20 I/O 0x00
Reset
0x00
Access
read/write
  1. 7TWBR7
  2. 6TWBR6
  3. 5TWBR5
  4. 4TWBR4
  5. 3TWBR3
  6. 2TWBR2
  7. 1TWBR1
  8. 0TWBR0
1 field
FieldBitsWhat it does
TWBR7:0TWI Bit Rate bits

TWSRTWI Status Register

Address
0x21 I/O 0x01
Reset
0x00
Access
read/write
  1. 7TWS4
  2. 6TWS3
  3. 5TWS2
  4. 4TWS1
  5. 3TWS0
  6. 2–
  7. 1TWPS1
  8. 0TWPS0
2 fields
FieldBitsWhat it does
TWS7:3TWI Status
TWPS1:0TWI Prescaler
  • 0 1
  • 1 4
  • 2 16
  • 3 64

TWARTWI (Slave) Address register

Address
0x22 I/O 0x02
Reset
0x00
Access
read/write
  1. 7TWA6
  2. 6TWA5
  3. 5TWA4
  4. 4TWA3
  5. 3TWA2
  6. 2TWA1
  7. 1TWA0
  8. 0TWGCE
2 fields
FieldBitsWhat it does
TWA7:1TWI (Slave) Address register Bits
TWGCE0TWI General Call Recognition Enable Bit

TWDRTWI Data register

Address
0x23 I/O 0x03
Reset
0x00
Access
read/write
  1. 7TWD7
  2. 6TWD6
  3. 5TWD5
  4. 4TWD4
  5. 3TWD3
  6. 2TWD2
  7. 1TWD1
  8. 0TWD0
1 field
FieldBitsWhat it does
TWD7:0TWI Data bits

TWCRTWI Control Register

Address
0x56 I/O 0x36
Reset
0x00
Access
read/write
  1. 7TWINT
  2. 6TWEA
  3. 5TWSTA
  4. 4TWSTO
  5. 3TWWC
  6. 2TWEN
  7. 1–
  8. 0TWIE
7 fields
FieldBitsWhat it does
TWINT7TWI Interrupt Flag
TWEA6TWI Enable Acknowledge Bit
TWSTA5TWI Start Condition Bit
TWSTO4TWI Stop Condition Bit
TWWC3TWI Write Collision Flag
TWEN2TWI Enable Bit
TWIE0TWI Interrupt Enable

ADC Analog-to-Digital Converter

ADCADC Data Register Bytes

Address
0x24 I/O 0x04
Reset
0x0000
Access
read/write
Size
16-bit
1 field
FieldBitsWhat it does
ADC9:0ADC Data Bits
  • 0 2
  • 1 2
  • 2 4
  • 3 8
  • 4 16
  • 5 32
  • 6 64
  • 7 128

ADCSRAThe ADC Control and Status register

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
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

ADMUXThe ADC multiplexer Selection Register

Address
0x27 I/O 0x07
Reset
0x00
Access
read/write
  1. 7REFS1
  2. 6REFS0
  3. 5ADLAR
  4. 4MUX4
  5. 3MUX3
  6. 2MUX2
  7. 1MUX1
  8. 0MUX0
3 fields
FieldBitsWhat it does
REFS7:6Reference Selection Bits
  • 0 AREF, Internal Vref turned off
  • 1 AVCC with external capacitor at AREF pin
  • 2 Reserved
  • 3 Internal 2.56V Voltage Reference with external capacitor at AREF pin
ADLAR5Left Adjust Result
MUX4:0Analog Channel and Gain Selection Bits

SFIORSpecial Function IO Register

Address
0x50 I/O 0x30
Reset
0x00
Access
read/write
  1. 7ADTS2
  2. 6ADTS1
  3. 5ADTS0
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
1 field
FieldBitsWhat it does
ADTS7:5ADC Auto Trigger Sources

AC Analog Comparator

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

SFIORSpecial Function IO Register

Address
0x50 I/O 0x30
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3ACME
  6. 2–
  7. 1–
  8. 0–
1 field
FieldBitsWhat it does
ACME3Analog Comparator Multiplexer Enable

USART USART

UBRRLUSART Baud Rate Register

Address
0x29 I/O 0x09
Reset
0x00
Access
read/write
  1. 7UBRR7
  2. 6UBRR6
  3. 5UBRR5
  4. 4UBRR4
  5. 3UBRR3
  6. 2UBRR2
  7. 1UBRR1
  8. 0UBRR0
1 field
FieldBitsWhat it does
UBRR7:0USART Baud Rate bits

UCSRBUSART Control and Status Register B

Address
0x2A I/O 0x0A
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

UCSRAUSART Control and Status Register A

Address
0x2B I/O 0x0B
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

UDRUSART I/O Data Register

Address
0x2C I/O 0x0C
Reset
0x00
Access
read/write
  1. 7UDR7
  2. 6UDR6
  3. 5UDR5
  4. 4UDR4
  5. 3UDR3
  6. 2UDR2
  7. 1UDR1
  8. 0UDR0
1 field
FieldBitsWhat it does
UDR7:0USART I/O Data bits

UBRRHUSART Baud Rate Register

Address
0x40 I/O 0x20
Reset
0x00
Access
read/write
  1. 7URSEL
  2. 6–
  3. 5–
  4. 4–
  5. 3UBRR3
  6. 2UBRR2
  7. 1UBRR1
  8. 0UBRR0
2 fields
FieldBitsWhat it does
URSEL7Register Select
UBRR3:0USART Baud Rate bits

UCSRCUSART Control and Status Register C

Address
0x40 I/O 0x20
Reset
0x00
Access
read/write
  1. 7URSEL
  2. 6UMSEL
  3. 5UPM1
  4. 4UPM0
  5. 3USBS
  6. 2UCSZ1
  7. 1UCSZ0
  8. 0UCPOL
6 fields
FieldBitsWhat it does
URSEL7Register Select
UMSEL6USART 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

SPI Serial Peripheral Interface

SPCRSPI Control Register

Address
0x2D I/O 0x0D
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
0x2E I/O 0x0E
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
0x2F I/O 0x0F
Reset
0x00
Access
read/write
  1. 7SPDR7
  2. 6SPDR6
  3. 5SPDR5
  4. 4SPDR4
  5. 3SPDR3
  6. 2SPDR2
  7. 1SPDR1
  8. 0SPDR0
1 field
FieldBitsWhat it does
SPDR7:0SPI Data bits

PORTD I/O Port

PINDPort D Input Pins

Address
0x30 I/O 0x10
Reset
0x00
Access
read/write
  1. 7PIND7
  2. 6PIND6
  3. 5PIND5
  4. 4PIND4
  5. 3PIND3
  6. 2PIND2
  7. 1PIND1
  8. 0PIND0

DDRDPort D Data Direction Register

Address
0x31 I/O 0x11
Reset
0x00
Access
read/write
  1. 7DDD7
  2. 6DDD6
  3. 5DDD5
  4. 4DDD4
  5. 3DDD3
  6. 2DDD2
  7. 1DDD1
  8. 0DDD0

PORTDPort D Data Register

Address
0x32 I/O 0x12
Reset
0x00
Access
read/write
  1. 7PORTD7
  2. 6PORTD6
  3. 5PORTD5
  4. 4PORTD4
  5. 3PORTD3
  6. 2PORTD2
  7. 1PORTD1
  8. 0PORTD0

PORTC I/O Port

PINCPort C Input Pins

Address
0x33 I/O 0x13
Reset
0x00
Access
read/write
  1. 7PINC7
  2. 6PINC6
  3. 5PINC5
  4. 4PINC4
  5. 3PINC3
  6. 2PINC2
  7. 1PINC1
  8. 0PINC0

DDRCPort C Data Direction Register

Address
0x34 I/O 0x14
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
0x35 I/O 0x15
Reset
0x00
Access
read/write
  1. 7PORTC7
  2. 6PORTC6
  3. 5PORTC5
  4. 4PORTC4
  5. 3PORTC3
  6. 2PORTC2
  7. 1PORTC1
  8. 0PORTC0

PORTB I/O Port

PINBPort B Input Pins

Address
0x36 I/O 0x16
Reset
0x00
Access
read/write
  1. 7PINB7
  2. 6PINB6
  3. 5PINB5
  4. 4PINB4
  5. 3PINB3
  6. 2PINB2
  7. 1PINB1
  8. 0PINB0

DDRBPort B Data Direction Register

Address
0x37 I/O 0x17
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
0x38 I/O 0x18
Reset
0x00
Access
read/write
  1. 7PORTB7
  2. 6PORTB6
  3. 5PORTB5
  4. 4PORTB4
  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. 5–
  4. 4–
  5. 3EERIE
  6. 2EEMWE
  7. 1EEWE
  8. 0EERE
4 fields
FieldBitsWhat it does
EERIE3EEPROM Ready Interrupt Enable
EEMWE2EEPROM Master Write Enable
EEWE1EEPROM Write Enable
EERE0EEPROM Read Enable

EEDREEPROM Data Register

Address
0x3D I/O 0x1D
Reset
0x00
Access
read/write
  1. 7EEDR7
  2. 6EEDR6
  3. 5EEDR5
  4. 4EEDR4
  5. 3EEDR3
  6. 2EEDR2
  7. 1EEDR1
  8. 0EEDR0
1 field
FieldBitsWhat it does
EEDR7:0EEPROM Data bits

EEAREEPROM Address Register Bytes

Address
0x3E I/O 0x1E
Reset
0x0000
Access
read/write
Size
16-bit
1 field
FieldBitsWhat it does
EEAR8:0EEPROM Address bits

WDT Watchdog Timer

WDTCRWatchdog Timer Control Register

Address
0x41 I/O 0x21
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4WDTOE
  5. 3WDE
  6. 2WDP2
  7. 1WDP1
  8. 0WDP0
3 fields
FieldBitsWhat it does
WDTOE4RW
WDE3Watch Dog Enable
WDP2:0Watch Dog Timer Prescaler bits
  • 0 Oscillator Cycles 16K
  • 1 Oscillator Cycles 32K
  • 2 Oscillator Cycles 64K
  • 3 Oscillator Cycles 128K
  • 4 Oscillator Cycles 256K
  • 5 Oscillator Cycles 512K
  • 6 Oscillator Cycles 1024K
  • 7 Oscillator Cycles 2048K

TC2 Timer/Counter, 8-bit Async

ASSRAsynchronous Status Register

Address
0x42 I/O 0x22
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3AS2
  6. 2TCN2UB
  7. 1OCR2UB
  8. 0TCR2UB
4 fields
FieldBitsWhat it does
AS23Asynchronous Timer/counter2
TCN2UB2Timer/Counter2 Update Busy
OCR2UB1Output Compare Register2 Update Busy
TCR2UB0Timer/counter Control Register2 Update Busy

OCR2Timer/Counter2 Output Compare Register

Address
0x43 I/O 0x23
Reset
0x00
Access
read/write
  1. 7OCR27
  2. 6OCR26
  3. 5OCR25
  4. 4OCR24
  5. 3OCR23
  6. 2OCR22
  7. 1OCR21
  8. 0OCR20
1 field
FieldBitsWhat it does
OCR27:0Timer/Counter2 Output Compare bits

TCNT2Timer/Counter2

Address
0x44 I/O 0x24
Reset
0x00
Access
read/write
  1. 7TCNT27
  2. 6TCNT26
  3. 5TCNT25
  4. 4TCNT24
  5. 3TCNT23
  6. 2TCNT22
  7. 1TCNT21
  8. 0TCNT20
1 field
FieldBitsWhat it does
TCNT27:0Timer/Counter2

TCCR2Timer/Counter2 Control Register

Address
0x45 I/O 0x25
Reset
0x00
Access
read/write
  1. 7FOC2
  2. 6WGM20
  3. 5COM21
  4. 4COM20
  5. 3WGM21
  6. 2CS22
  7. 1CS21
  8. 0CS20
5 fields
FieldBitsWhat it does
FOC27Force Output Compare
WGM206Waveform Generation Mode
  • 0 Normal
  • 1 CTC
  • 2 PWM, Phase Correct
  • 3 Fast PWM
COM25:4Compare Output Mode bits
WGM213Waveform Generation Mode
CS22:0Clock Select bits
  • 0 No Clock Source (Stopped)
  • 1 Running, No Prescaling
  • 2 Running, CLK/8
  • 3 Running, CLK/32
  • 4 Running, CLK/64
  • 5 Running, CLK/128
  • 6 Running, CLK/256
  • 7 Running, CLK/1024

SFIORSpecial Function IO Register

Address
0x50 I/O 0x30
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1PSR2
  8. 0–
1 field
FieldBitsWhat it does
PSR21Prescaler Reset Timer/Counter2

TIFRTimer/Counter Interrupt Flag Register

Address
0x58 I/O 0x38
Reset
0x00
Access
read/write
  1. 7OCF2
  2. 6TOV2
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
2 fields
FieldBitsWhat it does
OCF27Output Compare Flag 2
TOV26Timer/Counter2 Overflow Flag

TIMSKTimer/Counter Interrupt Mask register

Address
0x59 I/O 0x39
Reset
0x00
Access
read/write
  1. 7OCIE2
  2. 6TOIE2
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
2 fields
FieldBitsWhat it does
OCIE27Timer/Counter2 Output Compare Match Interrupt Enable
TOIE26Timer/Counter2 Overflow Interrupt Enable

TC1 Timer/Counter, 16-bit

ICR1Timer/Counter1 Input Capture Register Bytes

Address
0x46 I/O 0x26
Reset
0x0000
Access
read/write
Size
16-bit
1 field
FieldBitsWhat it does
ICR115:0Timer/Counter1 Input Capture bits

OCR1BTimer/Counter1 Output Compare Register Bytes

Address
0x48 I/O 0x28
Reset
0x0000
Access
read/write
Size
16-bit
1 field
FieldBitsWhat it does
OCR1B15:0Timer/Counter1 Output Compare B bits

OCR1ATimer/Counter1 Output Compare Register Bytes

Address
0x4A I/O 0x2A
Reset
0x0000
Access
read/write
Size
16-bit
1 field
FieldBitsWhat it does
OCR1A15:0Timer/Counter1 Output Compare A bits

TCNT1Timer/Counter1 Bytes

Address
0x4C I/O 0x2C
Reset
0x0000
Access
read/write
Size
16-bit
1 field
FieldBitsWhat it does
TCNT115:0Timer/Counter1 bits

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
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

TCCR1ATimer/Counter1 Control Register A

Address
0x4F I/O 0x2F
Reset
0x00
Access
read/write
  1. 7COM1A1
  2. 6COM1A0
  3. 5COM1B1
  4. 4COM1B0
  5. 3FOC1A
  6. 2FOC1B
  7. 1WGM11
  8. 0WGM10
5 fields
FieldBitsWhat it does
COM1A7:6Compare Output Mode 1A, bits
COM1B5:4Compare Output Mode 1B, bits
FOC1A3Force Output Compare 1A
FOC1B2Force Output Compare 1B
WGM11:0Waveform Generation Mode

TIFRTimer/Counter Interrupt Flag register

Address
0x58 I/O 0x38
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5ICF1
  4. 4OCF1A
  5. 3OCF1B
  6. 2TOV1
  7. 1–
  8. 0–
4 fields
FieldBitsWhat it does
ICF15Input Capture Flag 1
OCF1A4Output Compare Flag 1A
OCF1B3Output Compare Flag 1B
TOV12Timer/Counter1 Overflow Flag

TIMSKTimer/Counter Interrupt Mask Register

Address
0x59 I/O 0x39
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5TICIE1
  4. 4OCIE1A
  5. 3OCIE1B
  6. 2TOIE1
  7. 1–
  8. 0–
4 fields
FieldBitsWhat it does
TICIE15Timer/Counter1 Input Capture Interrupt Enable
OCIE1A4Timer/Counter1 Output CompareA Match Interrupt Enable
OCIE1B3Timer/Counter1 Output CompareB Match Interrupt Enable
TOIE12Timer/Counter1 Overflow Interrupt Enable

CPU CPU Registers

SFIORSpecial function I/O register

Address
0x50 I/O 0x30
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2PUD
  7. 1PSR2
  8. 0PSR10
3 fields
FieldBitsWhat it does
PUD2Pull-up Disable
PSR21Prescaler reset
PSR100Prescaler reset

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

MCUCSRMCU Control And Status Register

Address
0x54 I/O 0x34
Reset
0x00
Access
read/write
  1. 7JTD
  2. 6–
  3. 5–
  4. 4JTRF
  5. 3WDRF
  6. 2BORF
  7. 1EXTRF
  8. 0PORF
6 fields
FieldBitsWhat it does
JTD7JTAG Interface Disable
JTRF4JTAG Reset Flag
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. 7SM3
  2. 6SE
  3. 5SM1
  4. 4SM0
  5. 3ISC11
  6. 2ISC10
  7. 1ISC01
  8. 0ISC00
4 fields
FieldBitsWhat it does
SM7,5,4Sleep Mode Select
  • 0 Idle
  • 1 ADC Noise Reduction (If Available)
  • 2 Power Down
  • 3 Power Save
  • 8 Reserved
  • 9 Reserved
  • 10 Standby
  • 11 Extended Standby
SE6Sleep Enable
ISC13:2Interrupt Sense Control 1 Bits
  • 0 Low Level of INTX
  • 1 Any Logical Change in INTX
  • 2 Falling Edge of INTX
  • 3 Rising Edge of INTX
ISC01:0Interrupt Sense Control 0 Bits
  • 0 Low Level of INTX
  • 1 Any Logical Change in INTX
  • 2 Falling Edge of INTX
  • 3 Rising Edge of INTX

SPStack Pointer

Address
0x5D I/O 0x3D
Reset
0x045F
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

TC0 Timer/Counter, 8-bit

SFIORSpecial Function IO Register

Address
0x50 I/O 0x30
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0PSR10
1 field
FieldBitsWhat it does
PSR100Prescaler Reset Timer/Counter1 and Timer/Counter0

TCNT0Timer/Counter 0 Register

Address
0x52 I/O 0x32
Reset
0x00
Access
read/write
  1. 7TCNT07
  2. 6TCNT06
  3. 5TCNT05
  4. 4TCNT04
  5. 3TCNT03
  6. 2TCNT02
  7. 1TCNT01
  8. 0TCNT00
1 field
FieldBitsWhat it does
TCNT07:0Timer/Counter 0 bits

TCCR0Timer/Counter Control Register

Address
0x53 I/O 0x33
Reset
0x00
Access
read/write
  1. 7FOC0
  2. 6WGM00
  3. 5COM01
  4. 4COM00
  5. 3WGM01
  6. 2CS02
  7. 1CS01
  8. 0CS00
5 fields
FieldBitsWhat it does
FOC07Force Output Compare
WGM006Waveform Generation Mode 0
  • 0 Normal
  • 1 CTC
  • 2 PWM, Phase Correct
  • 3 Fast PWM
COM05:4Compare Match Output Modes
WGM013Waveform Generation Mode 1
CS02:0Clock Selects
  • 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

TIFRTimer/Counter Interrupt Flag register

Address
0x58 I/O 0x38
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1OCF0
  8. 0TOV0
2 fields
FieldBitsWhat it does
OCF01Output Compare Flag 0
TOV00Timer/Counter0 Overflow Flag

TIMSKTimer/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. 2–
  7. 1OCIE0
  8. 0TOIE0
2 fields
FieldBitsWhat it does
OCIE01Timer/Counter0 Output Compare Match Interrupt register
TOIE00Timer/Counter0 Overflow Interrupt Enable

OCR0Output Compare 0 Register

Address
0x5C I/O 0x3C
Reset
0x00
Access
read/write
  1. 7OCR07
  2. 6OCR06
  3. 5OCR05
  4. 4OCR04
  5. 3OCR03
  6. 2OCR02
  7. 1OCR01
  8. 0OCR00
1 field
FieldBitsWhat it does
OCR07:0Output Compare bits

JTAG JTAG Interface

OCDROn-Chip Debug Related Register in I/O Memory

Address
0x51 I/O 0x31
Reset
0x00
Access
read/write
  1. 7OCDR7
  2. 6OCDR6
  3. 5OCDR5
  4. 4OCDR4
  5. 3OCDR3
  6. 2OCDR2
  7. 1OCDR1
  8. 0OCDR0
1 field
FieldBitsWhat it does
OCDR7:0On-Chip Debug Register Bits

MCUCSRMCU Control And Status Register

Address
0x54 I/O 0x34
Reset
0x00
Access
read/write
  1. 7JTD
  2. 6–
  3. 5–
  4. 4JTRF
  5. 3–
  6. 2–
  7. 1–
  8. 0–
2 fields
FieldBitsWhat it does
JTD7JTAG Interface Disable
JTRF4JTAG Reset Flag

EXINT External Interrupts

MCUCSRMCU Control And Status Register

Address
0x54 I/O 0x34
Reset
0x00
Access
read/write
  1. 7–
  2. 6ISC2
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
1 field
FieldBitsWhat it does
ISC26Interrupt Sense Control 2

MCUCRGeneral Interrupt Control Register

Address
0x55 I/O 0x35
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
ISC13:2Interrupt 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
ISC01:0Interrupt 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

GIFRGeneral Interrupt Flag Register

Address
0x5A I/O 0x3A
Reset
0x00
Access
read/write
  1. 7INTF1
  2. 6INTF0
  3. 5INTF2
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
2 fields
FieldBitsWhat it does
INTF7:6External Interrupt Flags
INTF25External Interrupt Flag 2

GICRGeneral Interrupt Control Register

Address
0x5B I/O 0x3B
Reset
0x00
Access
read/write
  1. 7INT1
  2. 6INT0
  3. 5INT2
  4. 4–
  5. 3–
  6. 2–
  7. 1IVSEL
  8. 0IVCE
5 fields
FieldBitsWhat it does
INT17External Interrupt Request 1 Enable
INT06External Interrupt Request 0 Enable
INT25External Interrupt Request 2 Enable
IVSEL1Interrupt Vector Select
IVCE0Interrupt Vector Change Enable

BOOT_LOAD Bootloader

SPMCSRStore Program Memory Control Register

Address
0x57 I/O 0x37
Reset
0x00
Access
read/write
  1. 7SPMIE
  2. 6RWWSB
  3. 5–
  4. 4RWWSRE
  5. 3BLBSET
  6. 2PGWRT
  7. 1PGERS
  8. 0SPMEN
7 fields
FieldBitsWhat it does
SPMIE7SPM Interrupt Enable
RWWSB6Read While Write Section Busy
RWWSRE4Read While Write section read enable
BLBSET3Boot Lock Bit Set
PGWRT2Page Write
PGERS1Page Erase
SPMEN0Store Program Memory Enable