Datasheet
Memory
MC68HC908GP32 Data Sheet, Rev. 10
44 Freescale Semiconductor
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, address ranges as shown in
2.6.6.1 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 presence of a V
TST
on the
IRQ pin will bypass the block protection so that all of the memory included in the block protect register is
open for program and erase operations.
NOTE
The FLASH block protect register is not protected with special hardware or
software. Therefore, if this page is not protected by FLBPR the register is
erased by either a page or mass erase operation.
2.6.6.1 FLASH Block Protect Register
The FLASH block protect register (FLBPR) is implemented as a byte within the FLASH memory, and
therefore can only be written during a programming sequence of the FLASH memory. The value in this
register determines the starting location of the protected range within the FLASH memory.
BPR[7:0] — FLASH Block Protect Bits
These eight bits represent bits [14:7] of a 16-bit memory address.
Bit-15 is 1 and bits [6:0] are 0s.
The resultant 16-bit address is used for specifying the start address of the FLASH memory for block
protection. The FLASH is protected from this start address to the end of FLASH memory, at $FFFF.
With this mechanism, the protect start address can be XX00 and XX80 (128 bytes page boundaries)
within the FLASH memory.
Figure 2-6. FLASH Block Protect Start Address
Address: $FF7E
Bit 7654321Bit 0
Read:
BPR7 BPR6 BPR5 BPR4 BPR3 BPR2 BPR1 BPR0
Write:
Reset:UUUUUUUU
U = Unaffected by reset. Initial value from factory is 1.
Write to this register is by a programming sequence to the FLASH memory.
Figure 2-5. FLASH Block Protect Register (FLBPR)
1
FLBPR value
16-bit memory address
0000000
Start address of FLASH block protect