MC68HC908LJ24 Datasheet, PDF (76/464 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
FLASH Memory (FLASH)
4.8 FLASH Block Protection
Due to the ability of the on-board charge pump to erase and program the
FLASH memory in the target application, provision is made to protect
pages of memory from unintentional erase or program operations due to
system malfunction. This protection is done by use of a FLASH block
protect register (FLBPR). The FLBPR determines the range of the
FLASH memory which is to be protected. The range of the protected
area starts from a location defined by FLBPR and ends to the bottom of
the FLASH memory ($FFFF). When the memory is protected, the HVEN
bit cannot be set in either erase or program operations.
NOTE:
The 48 bytes of user interrupt vectors are always protected, regardless
of the value in the FLASH block protect register. A mass erase is
required to erase the vectors.
When the FLBPR is program with $20, the entire memory is protected
from being programmed and erased. When the FLBPR is erased ($FF),
the entire memory is accessible for program and erase.
Once the FLBPR is programmed with a value other than $FF, the FLBPR
itself is protected. It can only be erased using a mass erase operation.
NOTE:
In performing a program or erase operation, the FLASH block protect
register must be read after setting the PGM or ERASE bit and before
asserting the HVEN bit
Data Sheet
76
MC68HC908LJ24/LK24 — Rev. 2
FLASH Memory (FLASH)
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