Datasheet

FLASH Memory (FLASH)

Technical Data MC68HC908LJ12 — Rev. 2.1

64 FLASH Memory (FLASH) Freescale Semiconductor

4.5 FLASH Page Erase Operation

Use the following procedure to erase a page of FLASH memory. A page

consists of 128 consecutive bytes starting from addresses $xx00 or

$xx80. The 48-byte user interrupt vectors area also forms a page. The

48-byte user interrupt vectors cannot be erased by the page erase

operation because of security reasons. Mass erase is required to erase

this page.

1. Set the ERASE bit and clear the MASS bit in the FLASH control

2. Write any data to any FLASH address within the page address

range desired.

3. Wait for a time, t

nvs

(at least 10µs).

4. Set the HVEN bit.

5. Wait for a time, t

erase

(1ms).

6. Clear the ERASE bit.

7. Wait for a time, t

nvh

(5µs).

8. Clear the HVEN bit.

9. After time, t

rcv

(1µs), the memory can be accessed again in read

mode.

NOTE: Programming and erasing of FLASH locations cannot be performed by

executing code from the FLASH memory; the code must be executed

from RAM. While these operations must be performed in the order as

shown, but other unrelated operations may occur between the steps.