FLASH-2 Memory
Technical Data MC68HC908AZ60A — Rev 2.0
82 FLASH-2 Memory MOTOROLA
Decreasing the value in FL2BPR by one increases the protected range
by one page (128 bytes). However, programming the block protect
register with $FE protects a range twice that size, 256 bytes, in the
corresponding array. $FE means that locations $7F00–$7FFF are
protected in FLASH-2.
The FLASH memory does not exist at some locations. The block
protection range configuration is unaffected if FLASH memory does not
exist in that range. Refer to the memory map and make sure that the
desired locations are protected.
5.5 FLASH-2 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 for protecting
blocks of memory from unintentional erase or program operations due to
system malfunction. This protection is done by using the FLASH-2 Block
Protection Register (FL2BPR). FL2BPR determines the range of the
FLASH-2 memory which is to be protected. The range of the protected
area starts from a location defined by FL2BPR and ends at the bottom
of the FLASH-2 memory ($7FFF). When the memory is protected, the
HVEN bit can not be set in either ERASE or PROGRAM operations.
NOTE: In performing a program or erase operation, the FLASH-2 Block Protect
Register must be read after setting the PGM or ERASE bit and before
asserting the HVEN bit.
When the FLASH-2 Block Protect Register 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 FL2BPR are programmed (logic 0), they lock a block of
memory address ranges as shown in FLASH-2 Block Protect Register
on page 80. If FL2BPR is programmed with any value other than $FF,
the protected block of FLASH memory can not be erased or
programmed.
