MC68HC908AS32A Datasheet, PDF (52/280 Pages) Freescale Semiconductor, Inc – Microcontrollers

Memory
2.9.1.2 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 FLASH programming sequence. The value in this register
determines the starting location of the protected range within the FLASH memory.
Address: $FF80
Bit 7
6
5
4
3
Read:
BPR7
Write:
BPR6
BPR5
BPR4
BPR3
Reset: 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.
2
BPR2
U
1
BPR1
U
Figure 2-12. FLASH Block Protect Register (FLBPR)
Bit 0
BPR0
U
FLBPR[7:0] — Block Protect Register Bits [7:0]
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. 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 byte page boundaries) within
the FLASH array.
START ADDRESS OF _{1 1}
FLASH BLOCK PROTECT
FLBPR VALUE
0 00000
Figure 2-13. FLASH Block Protect Start Address
Decreasing the value in FLBPR 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 $FF00–$FFFF are protected in FLASH. See Table 2-6.
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 (Figure 2-1) and
make sure that the desired locations are protected.
MC68HC908AS32A Data Sheet, Rev. 2.0
52
Freescale Semiconductor