Datasheet

22
7701F–AVR–10/12
Atmel ATtiny24/44/84 [Preliminary]
6.5 Register Description
6.5.1 EEARH – EEPROM Address Register
• Bits 7..1 – Res: Reserved Bits
These are reserved bits in the ATtiny24/44/84, and will always read as zero.
• Bit 0 – EEAR8: EEPROM Address
The EEPROM address register, EEARH, specifies the most-significant bit for EEPROM
address in the 512-byte EEPROM space for Tiny84. This bit is reserved in the ATtiny24/44,
and will always read as zero. The initial value of EEAR is undefined. A proper value must be
written before the EEPROM may be accessed.
6.5.2 EEARL – EEPROM Address Register
• Bits 7..0 – EEAR7..0: EEPROM Address
The EEPROM address register, EEARL, specifies the EEPROM address. In the 128-byte
EEPROM space in ATiny24, bit 7 is reserved and will always read as zero. The EEPROM data
bytes are addressed linearly between 0 and 128/256/512. The initial value of EEAR is unde-
fined. A proper value must be written before the EEPROM may be accessed.
6.5.3 EEDR – EEPROM Data Register
• Bits 7..0 – EEDR7..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.
6.5.4 EECR – EEPROM Control Register
Bit 76543210
0x1F (0x3F) –––––––EEAR8EEARH
Read/Write RRRRRRRR/W
Initial Value 0 0 0 0 0 0 0 X
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