ATMEGA325-16AJ ATMEL [ATMEL Corporation], ATMEGA325-16AJ Datasheet - Page 20

• Manufacturer Part Number: ATMEGA325-16AJ
• Description: 8-bit Microcontroller with In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

The EEPROM Address
Register – EEARH and EEARL
The EEPROM Data Register –
EEDR
The EEPROM Control Register
– EECR
20
ATmega325/3250/645/6450
• Bits 15..11 – Res: Reserved Bits
These bits are reserved bits in the ATmega325/3250/645/6450 and will always read as
zero.
• Bits 10..0 – EEAR10..0: EEPROM Address
The EEPROM Address Registers – EEARH and EEARL specify the EEPROM address
in the 1/2K bytes EEPROM space. The EEPROM data bytes are addressed linearly
between 0 and 1023/2047. The initial value of EEAR is undefined. A proper value must
be written before the EEPROM may be accessed.
Note:
• 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 oper-
ation, the EEDR contains the data read out from the EEPROM at the address given by
EEAR.
• Bits 7..4 – Res: Reserved Bits
These bits are reserved bits in the ATmega325/3250/645/6450 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 interrupt 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 description of the EEWE bit for an EEPROM write procedure.
• Bit 1 – EEWE: EEPROM Write Enable
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
EEAR10 is only valid for ATmega645 and ATmega6450.
EEAR7
MSB
R/W
R/W
15
R
–
7
0
X
7
0
7
–
R
0
EEAR6
R/W
R/W
14
R
R
–
6
0
X
6
0
6
–
0
EEAR5
R/W
R/W
13
R
X
R
–
5
0
5
0
5
–
0
EEAR4
R/W
R/W
12
R
X
R
–
4
0
4
0
4
–
0
EEAR3
EERIE
R/W
R/W
R/W
11
R
0
X
0
0
–
3
3
3
EEAR10
EEMWE
EEAR2
R/W
R/W
R/W
R/W
10
2
X
X
2
0
2
0
EEAR9
EEAR1
EEWE
R/W
R/W
R/W
R/W
X
X
X
9
1
1
0
1
EEAR8
EEAR0
EERE
R/W
R/W
LSB
R/W
R/W
2570A–AVR–09/04
X
X
8
0
0
0
0
0
EEARH
EEARL
EEDR
EECR