Freescale Semiconductor, Inc.
EEPROM-2
Functional Description
Follow this step-by-step procedure to program a byte of EEPROM:
1. Clear EERAS1 and EERAS0 and set EELAT in the EECTL. Set
value of tEEPGM. (See notes a and b.)
2. Write the desired data to any user EEPROM address.
3. Set the EEPGM bit. (See note c.)
4. Wait for a time, tEEPGM, to program the byte.
5. Clear EEPGM bit.
6. Wait for a time, tEEFPV, for the programming voltage 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 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 EECR2
will be allowed only 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 on-board 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.
MC68HC908AS60 — Rev. 1.0
Technical Data
EEPROM-2
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