Memory
FLASH Memory (FLASH)
MC68HLC908QY/QT Family — Rev. 2
Data Sheet
MOTOROLA
Memory
37
When the FLBPR is programmed with all 0s, the entire memory is protected from
being programmed and erased. When all the bits are erased (all 1s), the entire
memory is accessible for program and erase.
When bits within the FLBPR are programmed, they lock a block of memory. 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
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.
2.6.6 FLASH Block Protect Register
The FLASH block protect register 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 address of the
protected range within the FLASH memory.
BPR[7:0] — FLASH Protection Register Bits [7:0]
These eight bits in FLBPR represent bits [13:6] of a 16-bit memory address. Bits
[15:14] 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, or XXC0 within the FLASH
Figure 2-6. FLASH Block Protect Start Address
Address:
$FFBE
Bit 7
654321
Bit 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)
0
1
FLBPR VALUE
START ADDRESS OF
16-BIT MEMORY ADDRESS
FLASH BLOCK PROTECT
0