12

7766DS–AVR–01/09

ATmega16U4/ATmega32U4

Note:

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 reg-

isters, 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 regis-

ters as data space using LD and ST instructions, $20 must be added to these addresses. The ATmega16U4/ATmega32U4 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 - $1FF in SRAM, only the ST/STS/STD and LD/LDS/LDD

instructions can be used.

0x1B (0x3B)

PCIFR

-

-

-

-

-

-

-PCIF0

0x1A (0x3A)

Reserved

-

-

-

-

-

-

-

-

0x19 (0x39)

TIFR4

OCF4D

OCF4A

OCF4B

-

-TOV4

-

-

0x18 (0x38)

TIFR3

-

-

ICF3

-

OCF3C

OCF3B

OCF3A

TOV3

0x17 (0x37)

Reserved

-

-

-

-

-

-

-

-

0x16 (0x36)

TIFR1

-

-

ICF1

-

OCF1C

OCF1B

OCF1A

TOV1

0x15 (0x35)

TIFR0

-

-

-

-

-

OCF0B

OCF0A

TOV0

0x14 (0x34)

Reserved

-

-

-

-

-

-

-

-

0x13 (0x33)

Reserved

-

-

-

-

-

-

-

-

0x12 (0x32)

Reserved

-

-

-

-

-

-

-

-

0x11 (0x31)

PORTF

PORTF7

PORTF6

PORTF5

PORTF4

-

-

PORTF1

PORTF0

0x10 (0x30)

DDRF

DDF7

DDF6

DDF5

DDF4

-

-

DDF1

DDF0

0x0F (0x2F)

PINF

PINF7

PINF6

PINF5

PINF4

-

-

PINF1

PINF0

0x0E (0x2E)

PORTE

-

PORTE6

-

-

-

PORTE2

-

-

0x0D (0x2D)

DDRE

-

DDE6

-

-

-

DDE2

-

-

0x0C (0x2C)

PINE

-

PINE6

-

-

-

PINE2

-

-

0x0B (0x2B)

PORTD

PORTD7

PORTD6

PORTD5

PORTD4

PORTD3

PORTD2

PORTD1

PORTD0

0x0A (0x2A)

DDRD

DDD7

DDD6

DDD5

DDD4

DDD3

DDD2

DDD1

DDD0

0x09 (0x29)

PIND

PIND7

PIND6

PIND5

PIND4

PIND3

PIND2

PIND1

PIND0

0x08 (0x28)

PORTC

PORTC7

PORTC6

-

-

-

-

-

-

0x07 (0x27)

DDRC

DDC7

DDC6

-

-

-

-

-

-

0x06 (0x26)

PINC

PINC7

PINC6

-

-

-

-

-

-

0x05 (0x25)

PORTB

PORTB7

PORTB6

PORTB5

PORTB4

PORTB3

PORTB2

PORTB1

PORTB0

0x04 (0x24)

DDRB

DDB7

DDB6

DDB5

DDB4

DDB3

DDB2

DDB1

DDB0

0x03 (0x23)

PINB

PINB7

PINB6

PINB5

PINB4

PINB3

PINB2

PINB1

PINB0

0x02 (0x22)

Reserved

-

-

-

-

-

-

-

-

0x01 (0x21)

Reserved

-

-

-

-

-

-

-

-

0x00 (0x20)

Reserved

-

-

-

-

-

-

-

-

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

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