M68ICS08GR datasheet(163/408 Pages) FREESCALE

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Flash Memory

FLASH Block Protection

MC68HC908GR8 — Rev 4.0

Technical Data

MOTOROLA

Flash Memory

163

NOTE:

Programming and erasing of FLASH locations cannot be performed by

code being executed from the FLASH memory. While these operations

must be performed in the order shown, other unrelated operations may

occur between the steps. Do not exceed tPROG maximum. See Memory

Characteristics.

11.8 FLASH Block Protection

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

a block of memory from unintentional erase or program operations due

to system malfunction. This protection is done by using 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 at the bottom of

the FLASH memory ($FFFF). When the memory is protected, the HVEN

bit cannot be set in either ERASE or PROGRAM operations.

NOTE:

In performing a program or erase operation, the FLASH block protect

asserting the HVEN bit

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 with address ranges as shown in FLASH Block Protect

any erase or program of the FLBPR or the protected block of FLASH

memory is prohibited. 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.

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