MC68HC08AS20 Datasheet, PDF (62/386 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

6.4.2 EEPROM Erasing
The unprogrammed state is a logic 1. Only the valid EEPROM bytes in
the nonprotected blocks and EENVR can be erased. When the array is
configured in the redundant mode, erasing the first 256 bytes
($0800–$08FF) will also erase the last 256 bytes ($0900–$09FF).
Follow this procedure to erase EEPROM. Refer to 21.6 Control Timing
for timing values.
1. Clear/set EERAS1 and EERAS0 to select byte/block/bulk erase,
and set EELAT in EECTL. Set value of t_EEBYT/t_EEBLOCK/t_EEBULK.
(See Note a.)
2. Write any data to the desired address for byte erase, to any
address in the desired block for block erase, or to any array
address for bulk erase.
3. Set the EEPGM bit. (See Note b.)
4. Wait for a time, t_EEPGM, to program the byte.
5. Clear EEPGM bit.
6. Wait for the erasing voltage time to fall, t_EEFPV.
7. Clear EELAT bits. (See Note c.)
8. Repeat steps 1 through 7 for more EEPROM byte/block erasing.
EEBPx bit must be cleared to erase EEPROM data in the corresponding
block. If any EEBPx is set, the corresponding block cannot be erased
and bulk erase mode does not apply.
NOTES:
a. Setting the EELAT bit configures the address and data buses
to latch data for erasing the array. Only valid EEPROM
addresses with their data will be latched. If another
consecutive valid EEPROM write occurs, this address and
data will override the previous address and data. In block
erase mode, any EEPROM address in the block can be used
in step 2. All locations within this block will be erased. In bulk
erase mode, any EEPROM address can be used to erase the
whole EEPROM. EENVR is not affected with block or bulk
Advance Information
62
MC68HC08AS20 —Rev. 4.1
Freescale Semiconductor