MC908QL4 FREESCALE [Freescale Semiconductor, Inc], MC908QL4 Datasheet - Page 40

• Manufacturer Part Number: MC908QL4
• Description: M68HC08 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Memory
2.6.5 FLASH Protection
Due to the ability of the on-board charge pump to erase and program the FLASH memory in the target
application, a provision is made to protect blocks of memory from unintentional erase or program
operations due to system malfunction. This protection is done by use of a FLASH block protect register
(FLBPR). The FLBPR determines the range of the FLASH memory which is to be protected. The range
of the protected area starts from a location defined by FLBPR and ends to the bottom of the FLASH
memory ($FFFF). When the memory is protected, the HVEN bit cannot be set in either erase or program
operations.
When the FLBPR is programmed 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. The address ranges are
shown in
$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, V
allows entry from reset into 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]
40
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 memory. See
2.6.6 FLASH Block Protect
Write to this register is by a programming sequence to the FLASH memory.
Reset:
Read:
Write:
In performing a program or erase operation, the FLASH block protect
register must be read after setting the PGM or ERASE bit and before
asserting the HVEN bit.
BPR7
Bit 7
Figure 2-5. FLASH Block Protect Register (FLBPR)
Figure 2-6
BPR6
6
and
MC68HC908QL4 Data Sheet, Rev. 7
Register. Once the FLBPR is programmed with a value other than
Unaffected by reset. Initial value from factory is $FF.
BPR5
Table
5
2-2.
BPR4
NOTE
4
TST
BPR3
, present on the IRQ pin. This voltage also
3
BPR2
2
BPR1
1
Freescale Semiconductor
BPR0
Bit 0