mc68hc908mr24 Freescale Semiconductor, Inc, mc68hc908mr24 Datasheet - Page 65

• Manufacturer Part Number: mc68hc908mr24
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

4.8 FLASH Block Protection
MC68HC908MR24 — Rev. 4.1
Freescale Semiconductor
NOTE:
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.
Due to the ability of the on-board charge pump to erase and program the
FLASH memory in the target application, provision is made for protecting
blocks of memory from unintentional erase or program operations due to
system malfunction. This protection is done by reserving a location in the
memory for block protect information and requiring that this location be
read to enable setting of the HVEN bit. When the block protect register
is read, its contents are latched by the FLASH control logic. If the
address range for an erase or program operation includes a protected
block, the PGM or ERASE bit is cleared which prevents the HVEN bit in
the FLASH control register from being set so that no high voltage is
allowed in the array.
When the block protect register is erased (all 0s), the entire memory is
accessible for program and erase. When bits within the register are
programmed, they lock blocks of memory address ranges as shown in
4.9 FLASH Block Protect
be erased or programmed only with an external voltage, V
the IRQ pin. This voltage also allows entry from reset into the monitor
mode.
FLASH Memory
Register. The block protect register itself can
Advance Information
HI
FLASH Memory
, present on
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