MC68HC908LB8_05 Datasheet, PDF (42/234 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Memory
2.6.6 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.
Address: $FF7E
Bit 7
6
5
4
3
2
Read:
Write:
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
Reset: U
U
U
U
U
U
U = Unaffected by reset. Initial value from factory is 1.
Write to this register is by a programming sequence to the FLASH memory.
1
BPR1
U
Figure 2-5. FLASH Block Protect Register (FLBPR)
Bit 0
BPR0
U
BPR[7:0] — FLASH Block Protect Bits
These eight bits represent bits [13:6] of a 16-bit memory address. Bit 15 and 14 are 1s and bits [5:0]
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, $XX40, $XX80, and $XXC0 (64 bytes
page boundaries) within the FLASH memory.
START ADDRESS OF FLASH
BLOCK PROTECT
1
1
16-BIT MEMORY ADDRESS
FLBPR VALUE
000000
Figure 2-6. FLASH Block Protect Start Address
Table 2-2. Examples of Protect Address Ranges
BPR[7:0]
$00–$78
$79 (0111 1001)
$7A (0111 1010)
$7B (0111 1011)
$7C (0111 1100)
$FC (1111 1100)
$FD (1111 1101)
$FE (1111 1110)
$FF
Addresses of Protect Range
The entire FLASH memory is protected.
$DE40 (1101 1110 0100 0000) — $FFFF
$DE80 (1101 1110 1000 0000) — $FFFF
$DEC0 (1101 1110 1100 0000) — $FFFF
$DF00 (1101 1111 0000 0000) — $FFFF
and so on...
$FF00 (1111 1111 0000 0000) — FFFF
$FF40 (1111 1111 0100 0000) — $FFFF
FLBPR and vectors are protected
$FF80 (1111 1111 1000 0000) — FFFF
Vectors are protected
The entire FLASH memory is not protected.
MC68HC908LB8 Data Sheet, Rev. 1
42
Freescale Semiconductor