19
7734Q–AVR–02/12
AT90PWM81/161
4.3.2
EEARH and EEARL - EEPROM Address Registers
Bits 15..9 – Reserved Bits
These bits are reserved bits in the AT90PWM81/161 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
512 bytes 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.
4.3.3
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.
4.3.4
EECR - EEPROM Control Register
Bits 7 – NVMBSY: Non-volatile memory busy
The NVMBSY bit is a status bit that indicates that the NVM memory (FLASH, EEPROM, Lock-
bits) is busy programming. Once a program operation is started, the bit will be set and it remains
set until the program operation is completed.
Bits 6 – EEPAGE: EEPROM page access (multiple bytes access mode)
Writing EEPAGE to one enables the multiple bytes access mode. That means that several bytes
can be programmed simultaneously into the EEPROM. When the EEPAGE bit has been written
to one, the EEPAGE bit remains set until an EEPROM program operation is completed. Alterna-
tively the bit is cleared when the temporary EEPROM buffer is flushed in software (see EEPMn
bits description). Any write to EEPAGE while EEPE is one will be ignored. See
data into the temporary EEPROM page and the usage of the EEPAGE bit.
Bit
1514
1312
11
10
9
8
––
–
EEAR8
EEARH
EEAR7
EEAR6
EEAR5
EEAR4
EEAR3
EEAR2
EEAR1
EEAR0
EEARL
76
54
3
2
1
0
Read/Write
R
R/W
Initial Value
0
X
XX
X
Bit
76543210
EEDR7
EEDR6
EEDR5
EEDR4
EEDR3
EEDR2
EEDR1
EEDR0
EEDR
Read/Write
R/W
Initial Value
00000000
Bit
7
65
43
2
1
0
NVMBSY
EEPAGE
EEPM1
EEPM0
EERIE
EEMWE
EEWE
EERE
EECR
Read/Write
R/W
Initial Value
X
0
X
0