MC68HC908LB8_05 Datasheet, PDF (39/234 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

FLASH Memory (FLASH)
9. Clear the HVEN bit.
10. After time, t_RCV (typical 1 µs), the memory can be accessed in read mode again.
NOTE
Programming and erasing of FLASH locations cannot be performed by
code being executed from the FLASH memory. While these operations
must be performed in the order as shown, but other unrelated operations
may occur between the steps.
CAUTION
A mass erase will erase the internal oscillator trim value at $FFC0.
2.6.4 FLASH Program/Read Operation
Programming of the FLASH memory is done on a row basis. A row consists of 32 consecutive bytes
starting from addresses $XX00, $XX20, $XX40, $XX60, $XX80, $XXA0, $XXC0, and $XXE0.
During the programming cycle, make sure that all addresses being written to fit within one of the ranges
specified above. Attempts to program addresses in different row ranges in one programming cycle will
fail. Use this step-by-step procedure to program a row of FLASH memory (Figure 2-4 is a flowchart
representation).
NOTE
In order to avoid program disturbs, the row must be erased before any byte
on that row is programmed.
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 FLASH block protect register.
3. Write any data to any FLASH address within the row address range desired.
4. Wait for a time, t_NVS (minimum 10 µs).
5. Set the HVEN bit.
6. Wait for a time, t_PGS (minimum 5 µs).
7. Write data to the FLASH address to be programmed.
8. Wait for a time, t_PROG (minimum 30 µs).
9. Repeat step 7 and 8 until all the bytes within the row are programmed.
10. Clear the PGM bit.⁽¹⁾
11. Wait for a time, t_NVH (minimum 5 µs).
12. Clear the HVEN bit.
13. After time, t_RCV (minimum 1 µs), the memory can be accessed in read mode again.
NOTE
The COP register at location $FFFF should not be written between steps
5-12, when the HVEN bit is set. Since this register is located at a valid
FLASH address, unpredictable behavior may occur if this location is written
while HVEN is set.
This program sequence is repeated throughout the memory until all data is programmed.
1. The time between each FLASH address change, or the time between the last FLASH address programmed to clearing PGM
bit, must not exceed the maximum programming time, t_PROG maximum.
MC68HC908LB8 Data Sheet, Rev. 1
Freescale Semiconductor
39