
FLASH Memory
MC68HC908GP32 MC68HC08GP32 Data Sheet, Rev. 7
112
Freescale Semiconductor
When the FLBPR is program 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
erase or program of the FLBPR or the protected block of FLASH memory is prohibited. The FLBPR itself
can be erased or programmed only with an external voltage, VTST, present on the IRQ pin. This voltage
also allows entry from reset into the monitor mode.
11.7.1 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 logic 1 and bits [6:0] are logic 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 11-4. FLASH Block Protect Start Address
Examples of protect start address:
Address:
$FF7E
Bit 7
654321
Bit 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 11-3. FLASH Block Protect Register (FLBPR)
BPR[7:0]
Start of Address of Protect Range
$00
The entire FLASH memory is protected.
$01 (0000 0001)
$8080 (1000 0000 1000 0000)
$02 (0000 0010)
$8100 (1000 0001 0000 0000)
and so on...
$FE (1111 1110)$FF00 (1111 1111 0000 0000)
$FF
The entire FLASH memory is not protected.
Note: The end address of the protected range is always $FFFF.
1
FLBPR value
16-bit memory address
0
000
Start address of FLASH block protect