21
2588F–AVR–06/2013
ATtiny261/461/861
5.5.2
EEARL – EEPROM Address Register
Bit 7 – EEAR7: EEPROM Address
This is the most significant EEPROM address bit of ATtiny461. In devices with less EEPROM,
i.e. ATtiny261, 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 – EEAR6:0: 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. 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 – 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.
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 ATtiny261/461/861. 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 ATtiny261/461/861 and will always read as zero.
Bits 5, 4 – EEPM1 and EEPM0: 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
765
432
10
EEAR7
EEAR6
EEAR5
EEAR4
EEAR3
EEAR2
EEAR1
EEAR0
EEARL
Read/Write
R/W
Initial Value
X/0
X
Bit
7
6
543210
EEDR7
EEDR6
EEDR5
EEDR4
EEDR3
EEDR2
EEDR1
EEDR0
EEDR
Read/Write
R/W
Initial Value
0
000000
Bit
7
6
543210
–
EEPM1
EEPM0
EERIE
EEMPE
EEPE
EERE
EECR
Read/Write
R
R/W
Initial Value
0
X
0
X
0