MC68HC908AT32 Datasheet, PDF (58/378 Pages) Freescale Semiconductor, Inc – Microcontrollers

Electrically Erasable Programmable ROM (EEPROM)
5. Clear EEPGM bit.
6. Wait for the programming voltage time, t_EEFPV, to fall.
7. Clear EELAT bits. (See note d.)
8. Repeat steps 1 to 7 for more EEPROM programming.
Notes:
a. EERAS1 and EERAS0 must be cleared for programming. Otherwise, the part will be in erase
mode.
b. Setting EELAT bit configures the address and data buses to latch data for programming the
array. Only data a with valid EEPROM address will be latched. If another consecutive valid
EEPROM write occurs, this address and data will override the previous address and data.
Any attempts to read other EEPROM data will read the latched data. If EELAT is set, other
writes to the EECR will be allowed after a valid EEPROM write.
c. To ensure proper programming sequence, the EEPGM bit cannot be set if the EELAT bit is
cleared and a non-EEPROM write has occurred. When EEPGM is set, the onboard charge
pump generates the program voltage and applies it to the user EEPROM array. When the
EEPGM bit is cleared, the program voltage is removed from the array and the internal charge
pump is turned off.
d. Any attempt to clear both EEPGM and EELAT bits with a single instruction will only clear
EEPGM. This is to allow time for removal of high voltage from the EEPROM array.
5.3.2 EEPROM Erasing
The unprogrammed state is a logic 1. Only the valid EEPROM bytes in the non-protected blocks and
EENVR can be erased. When the array is configured in the redundant mode, erasing the first 256 bytes
also will erase the last 256 bytes.
Using this procedure erases EEPROM:
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, t_EEFPV, to fall.
7. Clear EELAT bits. (See note c.)
8. Repeat steps 1 to 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 can not be erased and bulk erase mode does not apply.
Notes:
a. Setting 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 may be used in step 2. All locations
within this block will be erased. In bulk erase mode, any EEPROM address may be used to
MC68HC908AT32 Data Sheet, Rev. 3.1
58
Freescale Semiconductor