MC68HC08AZ32A Datasheet, PDF (43/312 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Electrically Erasable Programmable Read-Only Memory (EEPROM)
2.7.1.3 EEPROM Block Protection
The 512 bytes of EEPROM are divided into four 128-byte blocks. Each of these blocks can be protected
from erase/program operations by setting the EEBPx bit in the EENVR. Table 2-2 shows the address
ranges for the blocks.
Table 2-2. EEPROM Array Address Blocks
Block Number (EEBPx)
EEBP0
EEBP1
EEBP2
EEBP3
Address Range
$0800–$087F
$0880–$08FF
$0900–$097F
$0980–$09FF
These bits are effective after a reset or a upon read of 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. Please see 2.7.3.2 EEPROM Array Configuration Register for more information.
NOTE
Once EEDIVSECD in the EEDIVHNVR is programmed to 0 and after a
system reset, the EEDIV security feature is permanently enabled because
the EEDIVSECD bit in the EEDIVH is always loaded with 0 thereafter. Once
this security feature is armed, erase and program mode are disabled for
EEDIVHNVR and EEDIVLNVR. Modifications to the EEDIVH and EEDIVL
registers are also disabled. Therefore, be cautious when programming a
value into the EEDIVHNVR.
2.7.2 EEPROM Programming and Erasing
The unprogrammed or erase state of an EEPROM bit is a 1. The factory default for all bytes within the
EEPROM array is $FF.
The programming operation changes an EEPROM bit from 1 to 0 (programming cannot change a bit from
0 to 1). In a single programming operation, the minimum EEPROM programming size is one bit; the
maximum is eight bits (one byte).
The erase operation changes an EEPROM bit from 0 to 1. In a single erase operation, the minimum
EEPROM erase size is one byte; the maximum is the entire EEPROM array.
The EEPROM can be programmed such that one or multiple bits are programmed (written to 0) at a time.
However, the user may never program the same bit location more than once before erasing the entire
byte. In other words, the user is not allowed to program a 0 to a bit that is already programmed (bit state
is already 0).
For some applications it might be advantageous to track more than 10K events with a single byte of
EEPROM by programming one bit at a time. For that purpose, a special selective bit programming
technique is available. An example of this technique is illustrated in Table 2-3.
MC68HC08AZ32A Data Sheet, Rev. 2
Freescale Semiconductor
43