20
2486AA–AVR–02/2013
ATmega8(L)
The EEPROM Address
Register – EEARH and
EEARL
Bits 15..9 – Res: Reserved Bits
These bits are reserved bits in the ATmega8 and will always read as zero.
Bits 8..0 – EEAR8..0: EEPROM Address
The EEPROM Address Registers – EEARH and EEARL – specify the EEPROM address in the
512bytes EEPROM space. The EEPROM data bytes are addressed linearly between 0 and 511.
The initial value of EEAR is undefined. A proper value must be written before the EEPROM may
be accessed.
The EEPROM Data
Register – EEDR
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.
The EEPROM Control
Register – EECR
Bits 7..4 – Res: Reserved Bits
These bits are reserved bits in the Atmel
AVR ATmega8 and will always read as zero.
Bit 3 – EERIE: EEPROM Ready Interrupt Enable
Writing EERIE to one enables the EEPROM Ready Interrupt if the I bit in SREG is set. Writing
EERIE to zero disables the interrupt. The EEPROM Ready interrupt generates a constant inter-
rupt when EEWE is cleared.
Bit 2 – EEMWE: EEPROM Master Write Enable
The EEMWE bit determines whether setting EEWE to one causes the EEPROM to be written.
When EEMWE is set, setting EEWE within four clock cycles will write data to the EEPROM at
the selected address If EEMWE is zero, setting EEWE will have no effect. When EEMWE has
been written to one by software, hardware clears the bit to zero after four clock cycles. See the
Bit 1 – EEWE: EEPROM Write Enable
The EEPROM Write Enable Signal EEWE is the write strobe to the EEPROM. When address
and data are correctly set up, the EEWE bit must be written to one to write the value into the
EEPROM. The EEMWE bit must be written to one before a logical one is written to EEWE, oth-
Bit
151413121110
9
8
–––
––––
EEAR8
EEARH
EEAR7
EEAR6
EEAR5
EEAR4
EEAR3
EEAR2
EEAR1
EEAR0
EEARL
765
4321
0
Read/Write
RR
R
RR
R
R/W
Initial Value
000
0000
X
XX
XXX
Bit
765
4321
0
MSB
LSB
EEDR
Read/Write
R/W
Initial Value
000
0000
0
Bit
765
4321
0
–
EERIE
EEMWE
EEWE
EERE
EECR
Read/Write
R
R/W
Initial Value
0
X
0