MC68HC908AS32A Datasheet, PDF (54/280 Pages) Freescale Semiconductor, Inc – Microcontrollers

Memory
2.9.3 FLASH Page Erase Operation
Use this step-by-step procedure to erase a page (128 bytes) of FLASH memory to read as a 1:
1. Set the ERASE bit and clear the MASS bit in the FLASH control register.
2. Read the FLASH block protect register.
3. Write any data to any FLASH location within the address range of the block to be erased.
4. Wait for a time, t_NVS (minimum 10 µs).
5. Set the HVEN bit.
6. Wait for a time, t_Erase (minimum 1 ms or 4 ms).
7. Clear the ERASE bit.
8. Wait for a time, t_NVH (minimum 5 µs).
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 page erase of the vector page will erase the internal oscillator trim value at $FFC0.
In applications that require more than 1000 program/erase cycles, use the 4 ms page erase specification
to get improved long-term reliability. Any application can use this 4 ms page erase specification. However,
in applications where a FLASH location will be erased and reprogrammed less than 1000 times, and
speed is important, use the 1 ms page erase specification to get a shorter cycle time.
MC68HC908AS32A Data Sheet, Rev. 2.0
54
Freescale Semiconductor