MC68HC908AZ60 Datasheet, PDF (59/480 Pages) Motorola, Inc – HCMOS Microcontroller Unit

FLASH-2 Memory
FLASH Program/Margin Read Operation
FLASH Program/Margin Read Operation
NOTE:
After a total of 8 program operations have been applied to a row, the row
must be erased before further programming in order to avoid program
disturb. An erased byte will read $00.
Programming of the FLASH memory is done on a page basis. A page
consists of eight consecutive bytes starting from address $XXX0 or
$XXX8. The purpose of the margin read mode is to ensure that data has
been programmed with sufficient margin for long-term data retention.
While performing a margin read the operation is the same as for ordinary
read mode except that a built-in counter stretches the data access for an
additional eight cycles to allow sensing of the lower cell current. Margin
read mode imposes a more stringent read condition on the bitcell to
insure the bitcell is programmed with enough margin for long-term data
retention. During these eight cycles the COP counter continues to run.
The user must account for these extra cycles within COP feed loops. A
margin read cycle can only follow a page programming operation. To
program and margin read the FLASH memory, use the following
algorithm. Memory Characteristics on page 445 has a detailed
description of the times used in this algorithm.
1. Set the PGM bit. This configures the memory for program
operation and enables the latching of address and data for
programming.
2. Read from the block protect register.
3. Write data to the eight bytes of the page being programmed. This
requires eight separate write operations.
4. Set the HVEN bit.
5. Wait for time, t_PROG.
6. Clear the HVEN bit.
7. Wait for time, t_HVTV.
8. Set the MARGIN bit.
9. Wait for time, t_VTP.
10. Clear the PGM bit.
11. Wait for time, t_HVD.
7-flash-2
MOTOROLA
FLASH-2 Memory
MC68HC908AZ60 — Rev 2.0
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