Datasheet

FLASH Memory (FLASH)

MC68HC908GR16A Data Sheet, Rev. 1.0

Freescale Semiconductor 43

2.6.7 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

BPR[7:0] — FLASH Block Protect Bits

These eight bits represent bits [13:6] of a 16-bit memory address.

Bit 15 and Bit 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.

Figure 2-6. FLASH Block Protect Start Address

Address: $FF7E

Bit 7654321Bit 0

Read:

BPR7 BPR6 BPR5 BPR4 BPR3 BPR2 BPR1 BPR0

Write:

Reset: 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)

Table 2-2. Examples of Protect Address Ranges

BPR[7:0] Addresses of Protect Range

$00 The entire FLASH memory is protected.

$01 (0000 0001)$C040 (1100 0000 0100 0000) — $FFFF

$02 (0000 0010)$C080 (1100 0000 1000 0000) — $FFFF

$03 (0000 0011) $C0C0 (1100 0000 1100 0000) — $FFFF

$04 (0000 0100)$C100 (1100 0001 0000 0000) — $FFFF

and so on...

$FC (1111 1100) $FF00 (1111 1111 0000 0000) — FFFF

$FD (1111 1101)

$FF40 (1111 1111 0100 0000) — $FFFF

FLBPR and vectors are protected

$FE (1111 1110)

$FF80 (111 1111 1000 0000) — FFFF

Vectors are protected

$FF The entire FLASH memory is not protected.

FLBPR VALUE

16-BIT MEMORY ADDRESS

000000

START ADDRESS OF FLASH

BLOCK PROTECT