Datasheet

Table Of Contents
34
ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]
2549Q–AVR–02/2014
9.2 Register Description
9.2.1 EEPROM registers
9.2.1.1 EEARH and EEARL – The EEPROM Address Register
Bits 15:12 – Res: Reserved Bits
These bits are reserved bits and will always read as zero.
Bits 11:0 – EEAR8:0: EEPROM Address
The EEPROM Address Registers – EEARH and EEARL specify the EEPROM address in the 4Kbytes EEPROM
space. The EEPROM data bytes are addressed linearly between 0 and 4096. The initial value of EEAR is unde-
fined. A proper value must be written before the EEPROM may be accessed.
9.2.1.2 EEDR – The 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.
9.2.1.3 EECR – The EEPROM Control Register
Bits 7:6 – Res: Reserved Bits
These bits are reserved bits 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 triggered when writing
EEPE. 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 9-1 on page 35. While EEPE is set, any write to EEPMn will be ignored. During reset, the EEPMn
bits will be reset to 0b00 unless the EEPROM is busy programming.
Bit 15141312 11 10 9 8
0x22 (0x42) ––––EEAR11EEAR10EEAR9EEAR8EEARH
0x21 (0x41) EEAR7 EEAR6 EEAR5 EEAR4 EEAR3 EEAR2 EEAR1 EEAR0 EEARL
7654 3 2 10
Read/WriteRRRRR/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value0000 X XXX
XXXX X X XX
Bit 76543210
0x20 (0x40) MSB LSB EEDR
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000
Bit 765432 10
0x1F (0x3F) 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