MC908QT4MPE datasheet(36/184 Pages) FREESCALE

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Memory

MC68HC908QY/QT Family Data Sheet, Rev. 5

Freescale Semiconductor

Wait for time, tPROG (minimum 30 µs).

Repeat step 7 and 8 until all desired bytes within the row are programmed.

10.

Clear the PGM bit(1).

11.

Wait for time, tNVH (minimum 5 µs).

12.

Clear the HVEN bit.

13.

After time, tRCV (typical 1 µs), the memory can be accessed in read mode again.

NOTE

The COP register at location $FFFF should not be written between

steps 5–12, when the HVEN bit is set. Since this register is located at a

valid FLASH address, unpredictable behavior may occur if this location is

written while HVEN is set.

This program sequence is repeated throughout the memory until all data is programmed.

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 16.16

Memory Characteristics.

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, 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.

NOTE

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

asserting the HVEN bit.

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 2.6.6 FLASH Block Protect Register. Once 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.

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