MC68HC08AZ32A Datasheet, PDF (63/456 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
EEPROM
Functional Description
The erase operation changes an EEPROM bit from logic 0 to logic 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 a logic 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 logic 0 to a bit
that is already programmed (bit state is already logic 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 5-2.
Table 5-2. Example Selective Bit Programming Description
Description
Program Data Result
in Binary
in Binary
Original state of byte (erased)
n/a
1111:1111
First event is recorded by programming bit position 0
1111:1110
1111:1110
Second event is recorded by programming bit position 1
1111:1101 1111:1100
Third event is recorded by programming bit position 2
1111:1011 1111:1000
Fourth event is recorded by programming bit position 3
1111:0111 1111:0000
Events five through eight are recorded in a similar fashion
Note that none of the bit locations are actually programmed more than
once although the byte was programmed eight times.
When this technique is utilized, a program/erase cycle is defined as
multiple program sequences (up to eight) to a unique location followed
by a single erase operation.
MC68HC08AZ32A — Rev 1.0
MOTOROLA
EEPROM
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Technical Data
63