Datasheet

FLASH Memory (FLASH)
FLASH Protection
MC68HC908QY4•MC68HC908QT4•MC68HC908QY2•MC68HC908QT2•MC68HC908QY1•MC68HC908QT1
MOTOROLA FLASH Memory (FLASH) 51
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4.8 FLASH 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
blocks 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: 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.
When the FLBPR is programmed with all 0 s, the entire memory is
protected from being programmed and erased. When all the bits are
erased (all 1’s), the entire memory is accessible for program and erase.
When bits within the FLBPR are programmed, they lock a block of
memory. The address ranges are shown in 4.9 FLASH Block Protect
Register. Once the FLBPR is programmed with a value other than $FF,
any erase or program of the FLBPR or the protected block of FLASH
memory is prohibited. Mass erase is disabled whenever any block is
protected (FLBPR does not equal $FF). The FLBPR itself can be erased
or programmed only with an external voltage, V
TST
, present on the IRQ
pin. This voltage also allows entry from reset into the monitor mode.