ATmega164A/PA/324A/PA/644A/PA/1284/P
¤ 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 636
32. Register summary
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Page
(0xFF) Reserved - - - - - - -
(0xFE) Reserved - - - - - - - -
(0xFD) Reserved - - - - - - - -
(0xFC) Reserved - - - - - - - -
(0xFB) Reserved - - - - - - -
(0xFA) Reserved - - - - - - - -
(0xF9) Reserved - - - - - - -
(0xF8) Reserved - - - - - - - -
(0xF7) Reserved - - - - - - - -
(0xF6) Reserved - - - - - - - -
(0xF5) Reserved - - - - - - -
(0xF4) Reserved - - - - - - - -
(0xF3) Reserved - - - - - - - -
(0xF2) Reserved - - - - - - - -
(0xF1) Reserved - - - - - - -
(0xF0) Reserved - - - - - - - -
(0xEF) Reserved - - - - - - -
(0xEE) Reserved - - - - - - - -
(0xED) Reserved - - - - - - - -
(0xEC) Reserved - - - - - - - -
(0xEB) Reserved - - - - - - -
(0xEA) Reserved - - - - - - - -
(0xE9) Reserved - - - - - - - -
(0xE8) Reserved - - - - - - - -
(0xE7) Reserved - - - - - - -
(0xE6) Reserved - - - - - - - -
(0xE5) Reserved - - - - - - - -
(0xE4) Reserved - - - - - - - -
(0xE3) Reserved - - - - - - -
(0xE2) Reserved - - - - - - - -
(0xE1) Reserved - - - - - - -
(0xE0) Reserved - - - - - - -
(0xDF) Reserved - - - - - - - -
(0xDE) Reserved - - - - - - - -
(0xDD) Reserved - - - - - - - -
(0xDC) Reserved - - - - - - -
(0xDB) Reserved - - - - - - - -
(0xDA) Reserved - - - - - - - -
(0xD9) Reserved - - - - - - - -
(0xD8) Reserved - - - - - - - -
(0xD7) Reserved - - - - - - - -
(0xD6) Reserved - - - - - - - -
(0xD5) Reserved - - - - - - - -
(0xD4) Reserved - - - - - - - -
(0xD3) Reserved - - - - - - - -
(0xD2) Reserved - - - - - - - -
(0xD1) Reserved - - - - - - - -
(0xD0) Reserved - - - - - - - -
(0xCF) Reserved - - - - - - - -
(0xCE) UDR1 USART1 I/O Data Register 193
(0xCD) UBRR1H - - - - USART1 Baud Rate Register High Byte 197/210
(0xCC) UBRR1L USART1 Baud Rate Register Low Byte 197/210
(0xCB) Reserved - - - - - - - -
(0xCA) UCSR1C UMSEL11 UMSEL10 UPM11 UPM10 USBS1 UCSZ11/UDORD0(5) UCSZ10/UCPHA0(5) UCPOL1 195/209
(0xC9) UCSR1B RXCIE1 TXCIE1 UDRIE1 RXEN1 TXEN1 UCSZ12 RXB81 TXB81 194/208
(0xC8) UCSR1A RXC1 TXC1 UDRE1 FE1 DOR1 UPE1 U2X1 MPCM1 193/208
(0xC7) Reserved - - - - - - - -
(0xC6) UDR0 USART0 I/O Data Register 193
(0xC5) UBRR0H - - - - USART0 Baud Rate Register High Byte 197/210
(0xC4) UBRR0L USART0 Baud Rate Register Low Byte 197/210
(0xC3) Reserved - - - - - - - -
(0xC2) UCSR0C UMSEL01 UMSEL00 UPM01 UPM00 USBS0 UCSZ01/UDORD0(5) UCSZ00/UCPHA0(5) UCPOL0 195/209
(0xC1) UCSR0B RXCIE0 TXCIE0 UDRIE0 RXEN0 TXEN0 UCSZ02 RXB80 TXB80 194/208
ATmega164A/PA/324A/PA/644A/PA/1284/P
¤ 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 637
(0xC0) UCSR0A RXC0 TXC0 UDRE0 FE0 DOR0 UPE0 U2X0 MPCM0 193/208
(0xBF) Reserved - - - - - - - -
(0xBE) Reserved - - - - - - - -
(0xBD) TWAMR TWAM6 TWAM5 TWAM4 TWAM3 TWAM2 TWAM1 TWAM0 - 239
(0xBC) TWCR TWINT TWEA TWSTA TWSTO TWWC TWEN - TWIE 236
(0xBB) TWDR two-wire Serial Interface Data Register 238
(0xBA) TWAR TWA6 TWA5 TWA4 TWA3 TWA2 TWA1 TWA0 TWGCE 239
(0xB9) TWSR TWS7 TWS6 TWS5 TWS4 TWS3 - TWPS1 TWPS0 237
(0xB8) TWBR two-wire Serial Interface Bit Rate Register 236
(0xB7) Reserved - - - - - - - -
(0xB6) ASSR - EXCLK AS2 TCN2UB OCR2AUB OCR2BUB TCR2AUB TCR2BUB 163
(0xB5) Reserved - - - - - - - -
(0xB4) OCR2B Timer/Counter2 Output Compare Register B 163
(0xB3) OCR2A Timer/Counter2 Output Compare Register A 163
(0xB2) TCNT2 Timer/Counter2 (8 Bit) 162
(0xB1) TCCR2B FOC2A FOC2B - - WGM22 CS22 CS21 CS20 161
(0xB0) TCCR2A COM2A1 COM2A0 COM2B1 COM2B0 - - WGM21 WGM20 159
(0xAF) Reserved - - - - - - - -
(0xAE) Reserved - - - - - - - -
(0xAD) Reserved - - - - - - - -
(0xAC) Reserved - - - - - - - -
(0xAB) Reserved - - - - - - - -
(0xAA) Reserved - - - - - - - -
(0xA9) Reserved - - - - - - - -
(0xA8) Reserved - - - - - - - -
(0xA7) Reserved - - - - - - - -
(0xA6) Reserved - - - - - - - -
(0xA5) Reserved - - - - - - - -
(0xA4) Reserved - - - - - - - -
(0xA3) Reserved - - - - - - - -
(0xA2) Reserved - - - - - - - -
(0xA1) Reserved - - - - - - - -
(0xA0) Reserved - - - - - - - -
(0x9F) Reserved - - - - - - - -
(0x9E) Reserved - - - - - - - -
(0x9D) Reserved - - - - - - - -
(0x9C) Reserved - - - - - - - -
(0x9B) OCR3BH Timer/Counter3 - Output Compare Register B High Byte(7) 140
(0x9A) OCR3BL Timer/Counter3 - Output Compare Register B Low Byte(7) 140
(0x99) OCR3AH Timer/Counter3 - Output Compare Register A High Byte(7) 140
(0x98) OCR3AL Timer/Counter3 - Output Compare Register A Low Byte(7) 140
(0x97) ICR3H Timer/Counter3 - Input Capture Register High Byte(7) 141
(0x96) ICR3L Timer/Counter3 - Input Capture Register Low Byte(7) 141
(0x95) TCNT3H Timer/Counter3 - Counter Register High Byte(7) 140
(0x94) TCNT3L Timer/Counter3 - Counter Register Low Byte(7) 140
(0x93) Reserved - - - - - - - -
(0x92) TCCR3C FOC3A FOC3B - - - - - - 139
(0x91) TCCR3B ICNC3 ICES3 - WGM33 WGM32 CS32 CS31 CS30 138
(0x90) TCCR3A COM3A1 COM3A0 COM3B1 COM3B0 - - WGM31 WGM30 136
(0x8F) Reserved - - - - - - - -
(0x8E) Reserved - - - - - - - -
(0x8D) Reserved - - - - - - - -
(0x8C) Reserved - - - - - - - -
(0x8B) OCR1BH Timer/Counter1 - Output Compare Register B High Byte 140
(0x8A) OCR1BL Timer/Counter1 - Output Compare Register B Low Byte 140
(0x89) OCR1AH Timer/Counter1 - Output Compare Register A High Byte 140
(0x88) OCR1AL Timer/Counter1 - Output Compare Register A Low Byte 140
(0x87) ICR1H Timer/Counter1 - Input Capture Register High Byte 141
(0x86) ICR1L Timer/Counter1 - Input Capture Register Low Byte 141
(0x85) TCNT1H Timer/Counter1 - Counter Register High Byte 140
(0x84) TCNT1L Timer/Counter1 - Counter Register Low Byte 140
(0x83) Reserved - - - - - - - -
(0x82) TCCR1C FOC1A FOC1B - - - - - - 139
(0x81) TCCR1B ICNC1 ICES1 - WGM13 WGM12 CS12 CS11 CS10 138
(0x80) TCCR1A COM1A1 COM1A0 COM1B1 COM1B0 - - WGM11 WGM10 136
(0x7F) DIDR1 - - - - - - AIN1D AIN0D 242
(0x7E) DIDR0 ADC7D ADC6D ADC5D ADC4D ADC3D ADC2D ADC1D ADC0D 261
(0x7D) Reserved - - - - - - - -
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Page
ATmega164A/PA/324A/PA/644A/PA/1284/P
¤ 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 638
(0x7C) ADMUX REFS1 REFS0 ADLAR MUX4 MUX3 MUX2 MUX1 MUX0 257
(0x7B) ADCSRB - ACME - - - ADTS2 ADTS1 ADTS0 241
(0x7A) ADCSRA ADEN ADSC ADATE ADIF ADIE ADPS2 ADPS1 ADPS0 258
(0x79) ADCH ADC Data Register High byte 259
(0x78) ADCL ADC Data Register Low byte 259
(0x77) Reserved - - - - - - - -
(0x76) Reserved - - - - - - - -
(0x75) Reserved - - - - - - - -
(0x74) Reserved - - - - - - - -
(0x73) PCMSK3 PCINT31 PCINT30 PCINT29 PCINT28 PCINT27 PCINT26 PCINT25 PCINT24 78
(0x72) Reserved - - - - - - - -
(0x71) TIMSK3 - - ICIE3 - - OCIE3B OCIE3A TOIE3 142
(0x70) TIMSK2 - - - - - OCIE2B OCIE2A TOIE2 164
(0x6F) TIMSK1 - - ICIE1 - - OCIE1B OCIE1A TOIE1 142
(0x6E) TIMSK0 - - - - - OCIE0B OCIE0A TOIE0 113
(0x6D) PCMSK2 PCINT23 PCINT22 PCINT21 PCINT20 PCINT19 PCINT18 PCINT17 PCINT16 78
(0x6C) PCMSK1 PCINT15 PCINT14 PCINT13 PCINT12 PCINT11 PCINT10 PCINT9 PCINT8 78
(0x6B) PCMSK0 PCINT7 PCINT6 PCINT5 PCINT4 PCINT3 PCINT2 PCINT1 PCINT0 79
(0x6A) Reserved - - - - - - - -
(0x69) EICRA - - ISC21 ISC20 ISC11 ISC10 ISC01 ISC00 75
(0x68) PCICR - - - - PCIE3 PCIE2 PCIE1 PCIE0 77
(0x67) Reserved - - - - - - - -
(0x66) OSCCAL Oscillator Calibration Register 48
(0x65) PRR1 - - - - - - - --PRTIM3 57
(0x64) PRR0 PRTWI PRTIM2 PRTIM0 PRUSART1 PRTIM1 PRSPI PRUSART0 PRADC 56
(0x63) Reserved - - - - - - - -
(0x62) Reserved - - - - - - - -
(0x61) CLKPR CLKPCE - - - CLKPS3 CLKPS2 CLKPS1 CLKPS0 48
(0x60) WDTCSR WDIF WDIE WDP3 WDCE WDE WDP2 WDP1 WDP0 67
0x3F (0x5F) SREG I T H S V N Z C 19
0x3E (0x5E) SPH SP15 SP14 SP13 SP12 SP11 SP10 SP9 SP8 20
0x3D (0x5D) SPL SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0 20
0x3C (0x5C) Reserved - - - - - - - -
0x3B (0x5B) Reserved - - - - - - - -
0x3A (0x5A) Reserved - - - - - - - -
0x39 (0x59) Reserved - - - - - - - -
0x38 (0x58) Reserved - - - - - - - -
0x37 (0x57) SPMCSR SPMIE RWWSB SIGRD RWWSRE BLBSET PGWRT PGERS SPMEN 293
0x36 (0x56) Reserved - - - - - - - -
0x35 (0x55) MCUCR JTD BODS(6) BODSE(6) PUD - - IVSEL IVCE 97/276
0x34 (0x54) MCUSR - - - JTRF WDRF BORF EXTRF PORF 66/276
0x33 (0x53) SMCR - - - - SM2 SM1 SM0 SE 55
0x32 (0x52) Reserved - - - - - - - -
0x31 (0x51) OCDR On-Chip Debug Register 267
0x30 (0x50) ACSR ACD ACBG ACO ACI ACIE ACIC ACIS1 ACIS0 258
0x2F (0x4F) Reserved - - - - - - - -
0x2E (0x4E) SPDR SPI 0 Data Register 174
0x2D (0x4D) SPSR SPIF0 WCOL0 - - - - - SPI2X0 173
0x2C (0x4C) SPCR SPIE0 SPE0 DORD0 MSTR0 CPOL0 CPHA0 SPR01 SPR00 172
0x2B (0x4B) GPIOR2 General Purpose I/O Register 2 37
0x2A (0x4A) GPIOR1 General Purpose I/O Register 1 37
0x29 (0x49) Reserved - - - - - - - -
0x28 (0x48) OCR0B Timer/Counter0 Output Compare Register B 113
0x27 (0x47) OCR0A Timer/Counter0 Output Compare Register A 113
0x26 (0x46) TCNT0 Timer/Counter0 (8 Bit) 113
0x25 (0x45) TCCR0B FOC0A FOC0B - - WGM02 CS02 CS01 CS00 112
0x24 (0x44) TCCR0A COM0A1 COM0A0 COM0B1 COM0B0 - - WGM01 WGM00 113
0x23 (0x43) GTCCR TSM - - - - - PSRASY PSRSYNC 165
0x22 (0x42) EEARH - - - - EEPROM Address Register High Byte 32
0x21 (0x41) EEARL EEPROM Address Register Low Byte 32
0x20 (0x40) EEDR EEPROM Data Register 32
0x1F (0x3F) EECR - - EEPM1 EEPM0 EERIE EEMPE EEPE EERE 32
0x1E (0x3E) GPIOR0 General Purpose I/O Register 0 37
0x1D (0x3D) EIMSK - - - - - INT2 INT1 INT0 76
0x1C (0x3C) EIFR - - - - - INTF2 INTF1 INTF0 76
0x1B (0x3B) PCIFR - - - - PCIF3 PCIF2 PCIF1 PCIF0 77
0x1A (0x3A) Reserved - - - - - - - -
0x19 (0x39) Reserved - - - - - - - -
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Page
ATmega164A/PA/324A/PA/644A/PA/1284/P
¤ 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 639
Notes: 1. For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O memory
addresses should never be written.
2. I/O registers within the address range $00 - $1F are directly bit-accessible using the SBI and CBI instructions. In these
registers, the value of single bits can be checked by using the SBIS and SBIC instructions.
3. Some of the status flags are cleared by writing a logical one to them. Note that the CBI and SBI instructions will operate
on all bits in the I/O register, writing a one back into any flag read as set, thus clearing the flag. The CBI and SBI
instructions work with registers 0x00 to 0x1F only.
4. When using the I/O specific commands IN and OUT, the I/O addresses $00 - $3F must be used. When addressing I/O
registers as data space using LD and ST instructions, $20 must be added to these addresses.
The ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P is a complex microcontroller with more peripheral units
than can be supported within the 64 location reserved in Opcode for the IN and OUT instructions. For the Extended I/O
space from $60 - $FF, only the ST/STS/STD and LD/LDS/LDD instructions can be used.
5. USART in SPI Master Mode.
6. Only available in the ATmega164PA/324PA/644PA/1284P.
7. Only available in the ATmega1284/1284P
0x18 (0x38) TIFR3 - - ICF3 - - OCF3B OCF3A TOV3 144
0x17 (0x37) TIFR2 - - - - - OCF2B OCF2A TOV2 164
0x16 (0x36) TIFR1 - - ICF1 - - OCF1B OCF1A TOV1 143
0x15 (0x35) TIFR0 - - - - - OCF0B OCF0A TOV0 114
0x14 (0x34) Reserved - - - - - - - -
0x13 (0x33) Reserved - - - - - - - -
0x12 (0x32) Reserved - - - - - - - -
0x11 (0x31) Reserved - - - - - - - -
0x10 (0x30) Reserved - - - - - - - -
0x0F (0x2F) Reserved - - - - - - - -
0x0E (0x2E) Reserved - - - - - - - -
0x0D (0x2D) Reserved - - - - - - - -
0x0C (0x2C) Reserved - - - - - - - -
0x0B (0x2B) PORTD PORTD7 PORTD6 PORTD5 PORTD4 PORTD3 PORTD2 PORTD1 PORTD0 98
0x0A (0x2A) DDRD DDD7 DDD6 DDD5 DDD4 DDD3 DDD2 DDD1 DDD0 98
0x09 (0x29) PIND PIND7 PIND6 PIND5 PIND4 PIND3 PIND2 PIND1 PIND0 98
0x08 (0x28) PORTC PORTC7 PORTC6 PORTC5 PORTC4 PORTC3 PORTC2 PORTC1 PORTC0 98
0x07 (0x27) DDRC DDC7 DDC6 DDC5 DDC4 DDC3 DDC2 DDC1 DDC0 98
0x06 (0x26) PINC PINC7 PINC6 PINC5 PINC4 PINC3 PINC2 PINC1 PINC0 98
0x05 (0x25) PORTB PORTB7 PORTB6 PORTB5 PORTB4 PORTB3 PORTB2 PORTB1 PORTB0 97
0x04 (0x24) DDRB DDB7 DDB6 DDB5 DDB4 DDB3 DDB2 DDB1 DDB0 97
0x03 (0x23) PINB PINB7 PINB6 PINB5 PINB4 PINB3 PINB2 PINB1 PINB0 98
0x02 (0x22) PORTA PORTA7 PORTA6 PORTA5 PORTA4 PORTA3 PORTA2 PORTA1 PORTA0 97
0x01 (0x21) DDRA DDA7 DDA6 DDA5 DDA4 DDA3 DDA2 DDA1 DDA0 97
0x00 (0x20) PINA PINA7 PINA6 PINA5 PINA4 PINA3 PINA2 PINA1 PINA0 97
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Page