AI Interactive Datasheet ATmega169A
AVR · megaAVR

ATmega169A registers

All 106 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

DDRAPort A Data Direction Register

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

PORTB I/O Port

PINBPort B Input Pins

Address
0x23 I/O 0x03
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
0x24 I/O 0x04
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
0x25 I/O 0x05
Reset
0x00
Access
read/write
  1. 7PORTB7
  2. 6PORTB6
  3. 5PORTB5
  4. 4PORTB4
  5. 3PORTB3
  6. 2PORTB2
  7. 1PORTB1
  8. 0PORTB0

PORTC I/O Port

PINCPort C Input Pins

Address
0x26 I/O 0x06
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
0x27 I/O 0x07
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
0x28 I/O 0x08
Reset
0x00
Access
read/write
  1. 7PORTC7
  2. 6PORTC6
  3. 5PORTC5
  4. 4PORTC4
  5. 3PORTC3
  6. 2PORTC2
  7. 1PORTC1
  8. 0PORTC0

PORTD I/O Port

PINDPort D Input Pins

Address
0x29 I/O 0x09
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
0x2A I/O 0x0A
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
0x2B I/O 0x0B
Reset
0x00
Access
read/write
  1. 7PORTD7
  2. 6PORTD6
  3. 5PORTD5
  4. 4PORTD4
  5. 3PORTD3
  6. 2PORTD2
  7. 1PORTD1
  8. 0PORTD0

PORTE I/O Port

PINEInput Pins, Port E

Address
0x2C I/O 0x0C
Reset
0x00
Access
read/write
  1. 7PINE7
  2. 6PINE6
  3. 5PINE5
  4. 4PINE4
  5. 3PINE3
  6. 2PINE2
  7. 1PINE1
  8. 0PINE0

DDREData Direction Register, Port E

Address
0x2D I/O 0x0D
Reset
0x00
Access
read/write
  1. 7DDE7
  2. 6DDE6
  3. 5DDE5
  4. 4DDE4
  5. 3DDE3
  6. 2DDE2
  7. 1DDE1
  8. 0DDE0

PORTEData Register, Port E

Address
0x2E I/O 0x0E
Reset
0x00
Access
read/write
  1. 7PORTE7
  2. 6PORTE6
  3. 5PORTE5
  4. 4PORTE4
  5. 3PORTE3
  6. 2PORTE2
  7. 1PORTE1
  8. 0PORTE0

PORTF I/O Port

PINFInput Pins, Port F

Address
0x2F I/O 0x0F
Reset
0x00
Access
read/write
  1. 7PINF7
  2. 6PINF6
  3. 5PINF5
  4. 4PINF4
  5. 3PINF3
  6. 2PINF2
  7. 1PINF1
  8. 0PINF0

DDRFData Direction Register, Port F

Address
0x30 I/O 0x10
Reset
0x00
Access
read/write
  1. 7DDF7
  2. 6DDF6
  3. 5DDF5
  4. 4DDF4
  5. 3DDF3
  6. 2DDF2
  7. 1DDF1
  8. 0DDF0

PORTFData Register, Port F

Address
0x31 I/O 0x11
Reset
0x00
Access
read/write
  1. 7PORTF7
  2. 6PORTF6
  3. 5PORTF5
  4. 4PORTF4
  5. 3PORTF3
  6. 2PORTF2
  7. 1PORTF1
  8. 0PORTF0

PORTG I/O Port

PINGPort G Input Pins

Address
0x32 I/O 0x12
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5PING5
  4. 4PING4
  5. 3PING3
  6. 2PING2
  7. 1PING1
  8. 0PING0

DDRGPort G Data Direction Register

Address
0x33 I/O 0x13
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5DDG5
  4. 4DDG4
  5. 3DDG3
  6. 2DDG2
  7. 1DDG1
  8. 0DDG0

PORTGPort G Data Register

Address
0x34 I/O 0x14
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5PORTG5
  4. 4PORTG4
  5. 3PORTG3
  6. 2PORTG2
  7. 1PORTG1
  8. 0PORTG0

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. 2–
  7. 1OCF0A
  8. 0TOV0
2 fields
FieldBitsWhat it does
OCF0A1Timer/Counter0 Output Compare Flag 0
TOV00Timer/Counter0 Overflow Flag

GTCCRGeneral Timer/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/Counter1 and Timer/Counter0

TCCR0ATimer/Counter0 Control Register

Address
0x44 I/O 0x24
Reset
0x00
Access
read/write
  1. 7FOC0A
  2. 6WGM00
  3. 5COM0A1
  4. 4COM0A0
  5. 3WGM01
  6. 2CS02
  7. 1CS01
  8. 0CS00
5 fields
FieldBitsWhat it does
FOC0A7Force Output Compare
WGM006Waveform Generation Mode 0
  • 0 Normal
  • 1 CTC
  • 2 PWM, Phase Correct
  • 3 Fast PWM
COM0A5:4Compare 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

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–

TIMSK0Timer/Counter0 Interrupt Mask Register

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

TC1 Timer/Counter, 16-bit

TIFR1Timer/Counter1 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

TIMSK1Timer/Counter1 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 Compare B Match Interrupt Enable
OCIE1A1Timer/Counter1 Output Compare A 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/Counter 1 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
FOC1A7Force Output Compare 1A
FOC1B6Force Output Compare 1B

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 A Bytes

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

OCR1BTimer/Counter1 Output Compare Register B Bytes

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

TC2 Timer/Counter, 8-bit Async

TIFR2Timer/Counter2 Interrupt Flag Register

Address
0x37 I/O 0x17
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1OCF2A
  8. 0TOV2
2 fields
FieldBitsWhat it does
OCF2A1Timer/Counter2 Output Compare Flag 2
TOV20Timer/Counter2 Overflow Flag

GTCCRGeneral Timer/Counter Control Register

Address
0x43 I/O 0x23
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

TIMSK2Timer/Counter2 Interrupt Mask register

Address
0x70
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1OCIE2A
  8. 0TOIE2
2 fields
FieldBitsWhat it does
OCIE2A1Timer/Counter2 Output Compare Match Interrupt Enable
TOIE20Timer/Counter2 Overflow Interrupt Enable

TCCR2ATimer/Counter2 Control Register

Address
0xB0
Reset
0x00
Access
read/write
  1. 7FOC2A
  2. 6WGM20
  3. 5COM2A1
  4. 4COM2A0
  5. 3WGM21
  6. 2CS22
  7. 1CS21
  8. 0CS20
5 fields
FieldBitsWhat it does
FOC2A7Force Output Compare A
WGM206Waveform Generation Mode
  • 0 Normal
  • 1 CTC
  • 2 PWM, Phase Correct
  • 3 Fast PWM
COM2A5:4Compare 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

TCNT2Timer/Counter2

Address
0xB2
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

OCR2ATimer/Counter2 Output Compare Register

Address
0xB3
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

ASSRAsynchronous Status Register

Address
0xB6
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4EXCLK
  5. 3AS2
  6. 2TCN2UB
  7. 1OCR2UB
  8. 0TCR2UB
5 fields
FieldBitsWhat it does
EXCLK4Enable External Clock Interrupt
AS23AS2: Asynchronous Timer/Counter2
TCN2UB2TCN2UB: Timer/Counter2 Update Busy
OCR2UB1Output Compare Register2 Update Busy
TCR2UB0TCR2UB: Timer/Counter Control Register2 Update Busy

EXINT External Interrupts

EIFRExternal Interrupt Flag Register

Address
0x3C I/O 0x1C
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5PCIF1
  4. 4PCIF0
  5. 3–
  6. 2–
  7. 1–
  8. 0INTF0
2 fields
FieldBitsWhat it does
PCIF5:4Pin Change Interrupt Flags
INTF00External Interrupt Flag 0

EIMSKExternal Interrupt Mask Register

Address
0x3D I/O 0x1D
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5PCIE1
  4. 4PCIE0
  5. 3–
  6. 2–
  7. 1–
  8. 0INT0
2 fields
FieldBitsWhat it does
PCIE5:4Pin Change Interrupt Enables
INT00External Interrupt Request 0 Enable

EICRAExternal Interrupt Control Register

Address
0x69
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
ISC011External Interrupt Sense Control 0 Bit 1
ISC000External Interrupt Sense Control 0 Bit 0
  • 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

CPU CPU Registers

GPIOR0General Purpose IO 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 IO 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 IO 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. 3SM2
  6. 2SM1
  7. 1SM0
  8. 0SE
2 fields
FieldBitsWhat it does
SM3:1Sleep Mode Select bits
  • 0 Idle
  • 1 ADC Noise Reduction (If Available)
  • 2 Power Down
  • 3 Power Save
  • 4 Reserved
  • 5 Reserved
  • 6 Standby
  • 7 Reserved
SE0Sleep Enable

MCUSRMCU Status Register

Address
0x54 I/O 0x34
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4JTRF
  5. 3WDRF
  6. 2BORF
  7. 1EXTRF
  8. 0PORF
5 fields
FieldBitsWhat it does
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. 7–
  2. 6–
  3. 5–
  4. 4PUD
  5. 3–
  6. 2–
  7. 1IVSEL
  8. 0IVCE
3 fields
FieldBitsWhat it does
PUD4Pull-up disable
IVSEL1Interrupt Vector Select
IVCE0Interrupt Vector Change Enable

SPStack Pointer

Address
0x5D I/O 0x3D
Reset
0x04FF
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. 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

PRRPower Reduction Register

Address
0x64
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4PRLCD
  5. 3PRTIM1
  6. 2PRSPI
  7. 1PRUSART0
  8. 0PRADC
5 fields
FieldBitsWhat it does
PRLCD4Power Reduction LCD
PRTIM13Power Reduction Timer/Counter1
PRSPI2Power Reduction Serial Peripheral Interface
PRUSART01Power Reduction USART
PRADC0Power Reduction ADC

OSCCALOscillator Calibration Value

Address
0x66
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

EEPROM EEPROM

EECREEPROM Control Register

Address
0x3F I/O 0x1F
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
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 Address Register Bytes

Address
0x41 I/O 0x21
Reset
0x0000
Access
read/write
Size
16-bit

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

ACSRAnalog Comparator Control And Status Register

Address
0x50 I/O 0x30
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

ADCSRBADC Control and Status Register B

Address
0x7B
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

DIDR1Digital Input Disable Register 1

Address
0x7F
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

JTAG JTAG Interface

OCDROn-Chip Debug Related Register in I/O Memory

Address
0x51 I/O 0x31
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

MCUSRMCU Status Register

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

MCUCRMCU Control Register

Address
0x55 I/O 0x35
Reset
0x00
Access
read/write
  1. 7JTD
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
1 field
FieldBitsWhat it does
JTD7JTAG Interface Disable

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

WDT Watchdog Timer

WDTCRWatchdog Timer Control Register

Address
0x60
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4WDCE
  5. 3WDE
  6. 2WDP2
  7. 1WDP1
  8. 0WDP0
3 fields
FieldBitsWhat it does
WDCE4Watchdog Change Enable
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

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. 3–
  6. 2ADTS2
  7. 1ADTS1
  8. 0ADTS0
1 field
FieldBitsWhat it does
ADTS2:0ADC Auto Trigger Sources

ADMUXThe ADC multiplexer Selection Register

Address
0x7C
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 1.1V Voltage Reference with external capacitor at AREF pin
ADLAR5Left Adjust Result
MUX4:0Analog Channel and Gain Selection Bits

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

USI Universal Serial Interface

USICRUSI Control Register

Address
0xB8
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
0xB9
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
0xBA
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

USART0 USART

UCSR0AUSART Control and Status Register A

Address
0xC0
Reset
0x00
Access
read/write
  1. 7RXC0
  2. 6TXC0
  3. 5UDRE0
  4. 4FE0
  5. 3DOR0
  6. 2UPE0
  7. 1U2X0
  8. 0MPCM0
8 fields
FieldBitsWhat it does
RXC07USART Receive Complete
TXC06USART Transmit Complete
UDRE05USART Data Register Empty
FE04Framing Error
DOR03Data overRun
UPE02USART Parity Error
U2X01Double the USART Transmission Speed
MPCM00Multi-processor Communication Mode

UCSR0BUSART Control and Status Register B

Address
0xC1
Reset
0x00
Access
read/write
  1. 7RXCIE0
  2. 6TXCIE0
  3. 5UDRIE0
  4. 4RXEN0
  5. 3TXEN0
  6. 2UCSZ02
  7. 1RXB80
  8. 0TXB80
8 fields
FieldBitsWhat it does
RXCIE07RX Complete Interrupt Enable
TXCIE06TX Complete Interrupt Enable
UDRIE05USART Data Register Empty Interrupt Enable
RXEN04Receiver Enable
TXEN03Transmitter Enable
UCSZ022Character Size
RXB801Receive Data Bit 8
TXB800Transmit Data Bit 8

UCSR0CUSART Control and Status Register C

Address
0xC2
Reset
0x00
Access
read/write
  1. 7–
  2. 6UMSEL0
  3. 5UPM01
  4. 4UPM00
  5. 3USBS0
  6. 2UCSZ01
  7. 1UCSZ00
  8. 0UCPOL0
5 fields
FieldBitsWhat it does
UMSEL06USART Mode Select
  • 0 Asynchronous Operation
  • 1 Synchronous Operation
UPM05:4Parity Mode Bits
  • 0 Disabled
  • 1 Reserved
  • 2 Enabled, Even Parity
  • 3 Enabled, Odd Parity
USBS03Stop Bit Select
  • 0 1-bit
  • 1 2-bit
UCSZ02:1Character Size
UCPOL00Clock Polarity

UBRR0USART Baud Rate Register Bytes

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

UDR0USART 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–

LCD Liquid Crystal Display

LCDCRALCD Control Register A

Address
0xE4
Reset
0x00
Access
read/write
  1. 7LCDEN
  2. 6LCDAB
  3. 5–
  4. 4LCDIF
  5. 3LCDIE
  6. 2LCDBD
  7. 1LCDCCD
  8. 0LCDBL
7 fields
FieldBitsWhat it does
LCDEN7LCD Enable
LCDAB6LCD A or B waveform
LCDIF4LCD Interrupt Flag
LCDIE3LCD Interrupt Enable
LCDBD2LCD Buffer Disable
LCDCCD1LCD Contrast Control Disable
LCDBL0LCD Blanking

LCDCRBLCD Control and Status Register B

Address
0xE5
Reset
0x00
Access
read/write
  1. 7LCDCS
  2. 6LCD2B
  3. 5LCDMUX1
  4. 4LCDMUX0
  5. 3–
  6. 2LCDPM2
  7. 1LCDPM1
  8. 0LCDPM0
4 fields
FieldBitsWhat it does
LCDCS7LCD CLock Select
LCD2B6LCD 1/2 Bias Select
LCDMUX5:4LCD Mux Selects
LCDPM2:0LCD Port Masks
  • 0 SEG0:12
  • 1 SEG0:14
  • 2 SEG0:15
  • 3 SEG0:18
  • 4 SEG0:20
  • 5 SEG0:22
  • 6 SEG0:23
  • 7 SEG0:24

LCDFRRLCD Frame Rate Register

Address
0xE6
Reset
0x00
Access
read/write
  1. 7–
  2. 6LCDPS2
  3. 5LCDPS1
  4. 4LCDPS0
  5. 3–
  6. 2LCDCD2
  7. 1LCDCD1
  8. 0LCDCD0
2 fields
FieldBitsWhat it does
LCDPS6:4LCD Prescaler Selects
  • 0 ClkLCD/16
  • 1 ClkLCD/64
  • 2 ClkLCD/128
  • 3 ClkLCD/256
  • 4 ClkLCD/512
  • 5 ClkLCD/1024
  • 6 ClkLCD/2048
  • 7 ClkLCD/4096
LCDCD2:0LCD Clock Dividers
  • 0 1
  • 1 2
  • 2 3
  • 3 4
  • 4 5
  • 5 6
  • 6 7
  • 7 8

LCDCCRLCD Contrast Control Register

Address
0xE7
Reset
0x00
Access
read/write
  1. 7LCDDC2
  2. 6LCDDC1
  3. 5LCDDC0
  4. 4LCDMDT
  5. 3LCDCC3
  6. 2LCDCC2
  7. 1LCDCC1
  8. 0LCDCC0
3 fields
FieldBitsWhat it does
LCDDC7:5LCD Display Configuration Bits
  • 0 300us
  • 1 70us
  • 2 150us
  • 3 450us
  • 4 575us
  • 5 850us
  • 6 1150us
  • 7 50% of LCD clock
LCDMDT4LCD Maximum Drive Time
LCDCC3:0LCD Contrast Controls
  • 0 2.60V
  • 1 2.65V
  • 2 2.70V
  • 3 2.75V
  • 4 2.80V
  • 5 2.85V
  • 6 2.90V
  • 7 2.95V
  • 8 3.00V
  • 9 3.05V
  • 10 3.10V
  • 11 3.15V
  • 12 3.20V
  • 13 3.25V
  • 14 3.30V
  • 15 3.35V

LCDDR0LCD Data Register 0

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

LCDDR1LCD Data Register 1

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

LCDDR2LCD Data Register 2

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

LCDDR3LCD Data Register 3

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

LCDDR5LCD Data Register 5

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

LCDDR6LCD Data Register 6

Address
0xF2
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

LCDDR7LCD Data Register 7

Address
0xF3
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

LCDDR8LCD Data Register 8

Address
0xF4
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

LCDDR10LCD Data Register 10

Address
0xF6
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

LCDDR11LCD Data Register 11

Address
0xF7
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

LCDDR12LCD Data Register 12

Address
0xF8
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

LCDDR13LCD Data Register 13

Address
0xF9
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

LCDDR15LCD Data Register 15

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

LCDDR16LCD Data Register 16

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

LCDDR17LCD Data Register 17

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

LCDDR18LCD Data Register 18

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