MC68HC08AS32 Datasheet, PDF (39/280 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

and applies it to the user EEPROM array. When the EEPGM bit is
cleared, the erase voltage is removed from the array and the internal
charge pump is turned off.
c. Any attempt to clear both EEPGM and EELAT bits with a single
instruction will clear only EEPGM to allow time for removal of high
voltage from the EEPROM array.
In general, all bits should be erased before being programmed. However, if
program/erase cycling is of concern, the following procedure can be used to
minimize bit cycling in each EEPROM byte. If any bit in a byte must be changed
from a 0 to a 1, the byte needs to be erased before programming. Table 2-2
summarizes the conditions for erasing before programming.
Table 2-2. EEPROM Program/Erase Cycling Reduction
EEPROM Data
To Be Programmed
0
0
1
1
EEPROM Data
Before Programming
0
1
0
1
Erase
Before Programming?
No
No
Yes
No
2.5.1.3 EEPROM Block Protection
The 512 bytes of EEPROM are divided into four 128-byte blocks. Each of these
blocks can be protected separately by the EEBPx bit. Any attempt to program or
erase memory locations within the protected block will not allow the program/erase
voltage to be applied to the array. Table 2-3 shows the address ranges within the
blocks.
Table 2-3. EEPROM Array Address Blocks
Block Number (EEBPx)
EEBP0
EEBP1
EEBP2
EEBP3
Address Range
$0800–$087F
$0880–$08FF
$0900–$097F
$0980–$09FF
If the EEBPx bit is set, that corresponding address block is protected. These bits
are effective after a reset or a read to the EENVR register. The block protect
configuration can be modified by erasing/ programming the corresponding bits in
the EENVR register and then reading the EENVR register.
In redundant mode, EEBP3 and EEBP2 will have no meaning.
MC68HC08AS32 — Rev. 4.1
Freescale Semiconductor
Data Sheet
39