AI Interactive Datasheet ATtiny261A
AVR · tinyAVR

ATtiny261A registers

All 63 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.

TC1 Timer/Counter, 8-bit

TCCR1ETimer/Counter1 Control Register E

Address
0x20 I/O 0x00
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5OC1OE5
  4. 4OC1OE4
  5. 3OC1OE3
  6. 2OC1OE2
  7. 1OC1OE1
  8. 0OC1OE0
1 field
FieldBitsWhat it does
OC1OE5:0Output Compare Override Enable Bits

DT1Timer/Counter 1 Dead Time Value

Address
0x44 I/O 0x24
Reset
0x00
Access
read/write
  1. 7DT1H3
  2. 6DT1H2
  3. 5DT1H1
  4. 4DT1H0
  5. 3DT1L3
  6. 2DT1L2
  7. 1DT1L1
  8. 0DT1L0
2 fields
FieldBitsWhat it does
DT1H7:4
DT1L3:0

TC1HTimer/Counter 1 Register High

Address
0x45 I/O 0x25
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

TCCR1DTimer/Counter Control Register D

Address
0x46 I/O 0x26
Reset
0x00
Access
read/write
  1. 7FPIE1
  2. 6FPEN1
  3. 5FPNC1
  4. 4FPES1
  5. 3FPAC1
  6. 2FPF1
  7. 1WGM11
  8. 0WGM10
7 fields
FieldBitsWhat it does
FPIE17Fault Protection Interrupt Enable
FPEN16Fault Protection Mode Enable
FPNC15Fault Protection Noise Canceler
FPES14Fault Protection Edge Select
FPAC13Fault Protection Analog Comparator Enable
FPF12Fault Protection Interrupt Flag
WGM11:0Waveform Generation Mode Bit
  • 0 Fast PWM (NB! PWMx must be set!)
  • 1 Phase and Frequency Correct PWM
  • 2 PWM6/Single-slope
  • 3 PWM6/Dual-slope

TCCR1CTimer/Counter Control Register C

Address
0x47 I/O 0x27
Reset
0x00
Access
read/write
  1. 7COM1A1S
  2. 6COM1A0S
  3. 5COM1B1S
  4. 4COM1B0S
  5. 3COM1D1
  6. 2COM1D0
  7. 1FOC1D
  8. 0PWM1D
7 fields
FieldBitsWhat it does
COM1A1S7COM1A1 Shadow Bit
COM1A0S6COM1A0 Shadow Bit
COM1B1S5COM1B1 Shadow Bit
COM1B0S4COM1B0 Shadow Bit
COM1D3:2Comparator D output mode
FOC1D1Force Output Compare Match 1D
PWM1D0Pulse Width Modulator D Enable

OCR1DOutput compare register

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–

OCR1COutput compare register

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–

OCR1BOutput Compare Register

Address
0x4C I/O 0x2C
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

OCR1AOutput Compare Register

Address
0x4D I/O 0x2D
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

TCNT1Timer/Counter 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–

TCCR1BTimer/Counter Control Register B

Address
0x4F I/O 0x2F
Reset
0x00
Access
read/write
  1. 7PWM1X
  2. 6PSR1
  3. 5DTPS11
  4. 4DTPS10
  5. 3CS13
  6. 2CS12
  7. 1CS11
  8. 0CS10
4 fields
FieldBitsWhat it does
PWM1X7PWM Inversion Mode
PSR16Timer/Counter 1 Prescaler reset
DTPS15:4Dead Time Prescaler
  • 0 1x
  • 1 2x
  • 2 4x
  • 3 8x
CS13:0Clock Select Bits
  • 0 No Clock Source (Stopped)
  • 1 Running, No Prescaling
  • 2 Running, CLK/2
  • 3 Running, CLK/4
  • 4 Running, CLK/8
  • 5 Running, CLK/16
  • 6 Running, CLK/32
  • 7 Running, CLK/64
  • 8 Running, CLK/128
  • 9 Running, CLK/256
  • 10 Running, CLK/512
  • 11 Running, CLK/1024
  • 12 Running, CLK/2048
  • 13 Running, CLK/4096
  • 14 Running, CLK/8192
  • 15 Running, CLK/16384

TCCR1ATimer/Counter Control Register A

Address
0x50 I/O 0x30
Reset
0x00
Access
read/write
  1. 7COM1A1
  2. 6COM1A0
  3. 5COM1B1
  4. 4COM1B0
  5. 3FOC1A
  6. 2FOC1B
  7. 1PWM1A
  8. 0PWM1B
6 fields
FieldBitsWhat it does
COM1A7:6Compare Output Mode, Bits
COM1B5:4Compare Output Mode, Bits
FOC1A3Force Output Compare Match 1A
FOC1B2Force Output Compare Match 1B
PWM1A1Pulse Width Modulator Enable
PWM1B0Pulse Width Modulator Enable

TIFRTimer/Counter Interrupt Flag Register

Address
0x58 I/O 0x38
Reset
0x00
Access
read/write
  1. 7OCF1D
  2. 6OCF1A
  3. 5OCF1B
  4. 4–
  5. 3–
  6. 2TOV1
  7. 1–
  8. 0–
4 fields
FieldBitsWhat it does
OCF1D7Timer/Counter1 Output Compare Flag 1D
OCF1A6Timer/Counter1 Output Compare Flag 1A
OCF1B5Timer/Counter1 Output Compare Flag 1B
TOV12Timer/Counter1 Overflow Flag

TIMSKTimer/Counter Interrupt Mask Register

Address
0x59 I/O 0x39
Reset
0x00
Access
read/write
  1. 7OCIE1D
  2. 6OCIE1A
  3. 5OCIE1B
  4. 4–
  5. 3–
  6. 2TOIE1
  7. 1–
  8. 0–
4 fields
FieldBitsWhat it does
OCIE1D7OCIE1D: Timer/Counter1 Output Compare Interrupt Enable
OCIE1A6OCIE1A: Timer/Counter1 Output Compare Interrupt Enable
OCIE1B5OCIE1A: Timer/Counter1 Output Compare B Interrupt Enable
TOIE12Timer/Counter1 Overflow Interrupt Enable

ADC Analog-to-Digital Converter

DIDR0Digital Input Disable Register 0

Address
0x21 I/O 0x01
Reset
0x00
Access
read/write
  1. 7ADC6D
  2. 6ADC5D
  3. 5ADC4D
  4. 4ADC3D
  5. 3AREFD
  6. 2ADC2D
  7. 1ADC1D
  8. 0ADC0D
8 fields
FieldBitsWhat it does
ADC6D7ADC6 Digital input Disable
ADC5D6ADC5 Digital input Disable
ADC4D5ADC4 Digital input Disable
ADC3D4ADC3 Digital input Disable
AREFD3AREF Digital Input Disable
ADC2D2ADC2 Digital input Disable
ADC1D1ADC1 Digital input Disable
ADC0D0ADC0 Digital input Disable

DIDR1Digital Input Disable Register 1

Address
0x22 I/O 0x02
Reset
0x00
Access
read/write
  1. 7ADC10D
  2. 6ADC9D
  3. 5ADC8D
  4. 4ADC7D
  5. 3–
  6. 2–
  7. 1–
  8. 0–
4 fields
FieldBitsWhat it does
ADC10D7ADC10 Digital input Disable
ADC9D6ADC9 Digital input Disable
ADC8D5ADC8 Digital input Disable
ADC7D4ADC7 Digital input Disable

ADCSRBADC Control and Status Register B

Address
0x23 I/O 0x03
Reset
0x00
Access
read/write
  1. 7BIN
  2. 6GSEL
  3. 5IPR
  4. 4REFS2
  5. 3MUX5
  6. 2ADTS2
  7. 1ADTS1
  8. 0ADTS0
6 fields
FieldBitsWhat it does
BIN7Bipolar Input Mode
GSEL6Gain Select
IPR5Input Polarity Mode
REFS24
MUX53
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 Watchdog Interrupt Request

ADCADC Data Register Bytes

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

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 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

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
ADLAR5Left Adjust Result
MUX4:0Analog Channel and Gain Selection Bits

AC Analog Comparator

ACSRAAnalog Comparator Control And Status Register A

Address
0x28 I/O 0x08
Reset
0x00
Access
read/write
  1. 7ACD
  2. 6ACBG
  3. 5ACO
  4. 4ACI
  5. 3ACIE
  6. 2ACME
  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
ACME2Analog Comparator Multiplexer Enable
ACIS1:0Analog Comparator Interrupt Mode Select bits
  • 0 Interrupt on Toggle
  • 1 Reserved
  • 2 Interrupt on Falling Edge
  • 3 Interrupt on Rising Edge

ACSRBAnalog Comparator Control And Status Register B

Address
0x29 I/O 0x09
Reset
0x00
Access
read/write
  1. 7HSEL
  2. 6HLEV
  3. 5–
  4. 4–
  5. 3–
  6. 2ACM2
  7. 1ACM1
  8. 0ACM0
3 fields
FieldBitsWhat it does
HSEL7Hysteresis Select
HLEV6Hysteresis Level
ACM2:0Analog Comparator Multiplexer

CPU CPU Registers

GPIOR0General purpose register 0

Address
0x2A I/O 0x0A
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

GPIOR1General Purpose register 1

Address
0x2B I/O 0x0B
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
0x2C I/O 0x0C
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

DWDRdebugWire 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–

CLKPRClock Prescale Register

Address
0x48 I/O 0x28
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

PLLCSRPLL Control and status register

Address
0x49 I/O 0x29
Reset
0x00
Access
read/write
  1. 7LSM
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2PCKE
  7. 1PLLE
  8. 0PLOCK
4 fields
FieldBitsWhat it does
LSM7Low speed mode
PCKE2PCK Enable
PLLE1PLL Enable
PLOCK0PLL Lock detector

OSCCALOscillator Calibration Register

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. 7BODS
  2. 6PUD
  3. 5SE
  4. 4SM1
  5. 3SM0
  6. 2BODSE
  7. 1ISC01
  8. 0ISC00
6 fields
FieldBitsWhat it does
BODS7BOD Sleep
PUD6Pull-up Disable
SE5Sleep Enable
SM4:3Sleep Mode Select Bits
  • 0 Idle
  • 1 ADC Noise Reduction (If Available)
  • 2 Power Down
  • 3 Standby
BODSE2BOD Sleep Enable
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

PRRPower Reduction Register

Address
0x56 I/O 0x36
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

SPLStack Pointer Low Byte

Address
0x5D I/O 0x3D
Reset
0xDF
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

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

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–

USIPPUSI Pin Position

Address
0x31 I/O 0x11
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

TC0 Timer/Counter, 8-bit

OCR0BTimer/Counter0 Output Compare Register

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–

OCR0ATimer/Counter0 Output Compare Register

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–

TCNT0HTimer/Counter0 High

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–

TCCR0ATimer/Counter Control Register A

Address
0x35 I/O 0x15
Reset
0x00
Access
read/write
  1. 7TCW0
  2. 6ICEN0
  3. 5ICNC0
  4. 4ICES0
  5. 3ACIC0
  6. 2–
  7. 1–
  8. 0WGM00
6 fields
FieldBitsWhat it does
TCW07Timer/Counter 0 Width
ICEN06Input Capture Mode Enable
ICNC05Input Capture Noise Canceler
ICES04Input Capture Edge Select
ACIC03Analog Comparator Input Capture Enable
WGM000Waveform Generation Mode

TCNT0LTimer/Counter0 Low

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. 7–
  2. 6–
  3. 5–
  4. 4TSM
  5. 3PSR0
  6. 2CS02
  7. 1CS01
  8. 0CS00
3 fields
FieldBitsWhat it does
TSM4Timer/Counter Synchronization Mode
PSR03Timer/Counter 0 Prescaler Reset
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

TIFRTimer/Counter0 Interrupt Flag register

Address
0x58 I/O 0x38
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4OCF0A
  5. 3OCF0B
  6. 2–
  7. 1TOV0
  8. 0ICF0
4 fields
FieldBitsWhat it does
OCF0A4Timer/Counter0 Output Compare Flag 0A
OCF0B3Timer/Counter0 Output Compare Flag 0B
TOV01Timer/Counter0 Overflow Flag
ICF00Timer/Counter0 Input Capture Flag

TIMSKTimer/Counter Interrupt Mask Register

Address
0x59 I/O 0x39
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4OCIE0A
  5. 3OCIE0B
  6. 2–
  7. 1TOIE0
  8. 0TICIE0
4 fields
FieldBitsWhat it does
OCIE0A4Timer/Counter0 Output Compare Match A Interrupt Enable
OCIE0B3Timer/Counter0 Output Compare Match B Interrupt Enable
TOIE01Timer/Counter0 Overflow Interrupt Enable
TICIE00Timer/Counter0 Input Capture Interrupt Enable

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. 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

WDTCRWatchdog 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

EXINT External Interrupts

PCMSK1Pin Change Enable Mask 1

Address
0x42 I/O 0x22
Reset
0x00
Access
read/write
  1. 7–
  2. 6–
  3. 5–
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–

PCMSK0Pin Change Enable Mask 0

Address
0x43 I/O 0x23
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
2 fields
FieldBitsWhat it does
ISC011Interrupt Sense Control 0 Bit 1
ISC000Interrupt 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

GIFRGeneral Interrupt Flag register

Address
0x5A I/O 0x3A
Reset
0x00
Access
read/write
  1. 7INTF1
  2. 6INTF0
  3. 5PCIF
  4. 4–
  5. 3–
  6. 2–
  7. 1–
  8. 0–
2 fields
FieldBitsWhat it does
INTF7:6External Interrupt Flags
PCIF5Pin Change Interrupt Flag

GIMSKGeneral Interrupt Mask Register

Address
0x5B I/O 0x3B
Reset
0x00
Access
read/write
  1. 7INT1
  2. 6INT0
  3. 5PCIE1
  4. 4PCIE0
  5. 3–
  6. 2–
  7. 1–
  8. 0–
2 fields
FieldBitsWhat it does
INT7:6External Interrupt Request 1 Enable
PCIE5:4Pin Change Interrupt Enables

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