23
7647H–AVR–03/12
Atmel ATmega16/32/64/M1/C1
4.3.2 The EEPROM Address Registers – EEARH and EEARL
• Bits 15.11 – Reserved Bits
These bits are reserved bits in the ATmega16/32/64/M1/C1 and will always read as zero.
• Bits 9..0 – EEAR10..0: EEPROM Address
The EEPROM Address Registers – EEARH and EEARL specify the EEPROM address in the
512/1024/2048 bytes EEPROM space. The EEPROM data bytes are addressed linearly
between 0 and 511/1023/2047. The initial value of EEAR is undefined. A proper value must be
written before the EEPROM may be accessed.
4.3.3 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.
4.3.4 The EEPROM Control Register – EECR
• Bits 7..6 – Reserved Bits
These bits are reserved bits in the ATmega16/32/64/M1/C1 and will always read as zero.
• Bits 5..4 – EEPM1 and EEPM0: EEPROM Programming Mode Bits
The EEPROM Programming mode bit setting defines which programming action that will be trig-
gered when writing EEWE. It is possible to program data in one atomic operation (erase the old
value and program the new value) or to split the Erase and Write operations in two different
operations. The Programming times for the different modes are shown in Table 4-1 on page 24.
Bit 15141312 11 10 9 8
– – – – – EEAR10 EEAR9 EEAR8 EEARH
EEAR7 EEAR6 EEAR5 EEAR4 EEAR3 EEAR2 EEAR1 EEAR0 EEARL
76543 2 10
Read/Write R R R R R R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 X X X
XXXX X X XX
Bit 76543210
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 Value00000000
Bit 76543210
– – EEPM1 EEPM0 EERIE EEMWE EEWE 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
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