Datasheet

8183F–AVR–06/12

ATtiny24A/44A/84A

5.5.2 EEARL – EEPROM Address Register

• Bit 7 – EEAR7: EEPROM Address

This is the most significant EEPROM address bit of ATtiny44A. In devices with less EEPROM,

i.e. ATtiny24A, this bit is reserved and will always read zero. The initial value of the EEPROM

Address Register (EEAR) is undefined and a proper value must therefore be written before the

EEPROM is accessed.

• Bits 6:0 – EEAR[6:0]: EEPROM Address

These are the (low) bits of the EEPROM Address Register. The EEPROM data bytes are

addressed linearly in the range 0...(128/256/512-1). The initial value of EEAR is undefined and a

proper value must be therefore be written before the EEPROM may be accessed.

5.5.3 EEDR – EEPROM Data Register

• Bits 7:0 – EEDR[7:0]: EEPROM Data

For the EEPROM write operation the EEDR Register contains the data to be written to the

EEPROM in the address given by the EEAR Register. For the EEPROM read operation, the

EEDR contains the data read out from the EEPROM at the address given by EEAR.

5.5.4 EECR – EEPROM Control Register

• Bit 7 – Res: Reserved Bit

This bit is reserved for future use and will always read as 0 in ATtiny24A/44A/84A. For compati-

bility with future AVR devices, always write this bit to zero. After reading, mask out this bit.

• Bit 6 – Res: Reserved Bit

This bit is reserved in the ATtiny24A/44A/84A and will always read as zero.

• Bits 5:4 – EEPM[1:0]: EEPROM Programming Mode Bits

The EEPROM Programming mode bits setting defines which programming action that will be

triggered when writing EEPE. It is possible to program data in one atomic operation (erase the

Bit 76543210

0x1E (0x3E) EEAR7 EEAR6 EEAR5 EEAR4 EEAR3 EEAR2 EEAR1 EEAR0 EEARL

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value X X X X X X X X

Bit 76543210

0x1D (0x3D) EEDR7 EEDR6 EEDR5 EEDR4 EEDR3 EEDR2 EEDR1 EEDR0 EEDR

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value 0 0 0 0 0 0 0 0

Bit 76543210

0x1C (0x3C) – – EEPM1 EEPM0 EERIE EEMPE EEPE EERE EECR

Read/Write R R R/W R/W R/W R/W R/W R/W

Initial Value 0 0 X X 0 0 X 0