MC912DG128A Motorola, MC912DG128A Datasheet - Page 102

• Manufacturer Part Number: MC912DG128A
• Description: Microcontrollers
• Manufacturer: Motorola

EEPROM Selective Write More Zeros
EEPROM
MC68HC912DT128A Rev 2.0
102
The EEPROM can be programmed such that one or multiple bits are
programmed (written to a logic “0”) at a time. However, the user should
may never program one bit more than once before erasing the entire
byte. In other words, the user is not allowed to over write a logic “0” with
another “0’.
For some applications it may 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 is shown here.
Original state of byte = binary 1111:1111 (erased)
First event is recorded by programming bit position 0
Program write = binary 1111:1110;
Second event is recorded by programming bit position 1
Program write = binary 1111:1101;
Third event is recorded by programming bit position 2
Program write = binary 1111:1011;
Fourth event is recorded by programming bit position 3
Program write = binary 1111:0111;
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 writes (up to eight) to a unique location followed by a single
erase sequence.
EEPROM
Result = binary 1111:1100
Result = binary 1111:1000
Result = binary 1111:0000
Result = binary 1111:1110
MOTOROLA
2--eeprom