M68HC08 datasheet(38/188 Pages) FREESCALE

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Memory

Data Sheet

MC68HC908RF2 — Rev. 4.0

Memory

MOTOROLA

This routine erases the block of FLASH defined by H:X and CTLBYTE. The

algorithm defined in 2.5.3 FLASH 2TS Erase Operation is used.

Preserves the contents of H:X (address passed)

2.5.8.4 REDPROG Routine

Name:

REDPROG

Purpose:

This routine will use a range of multiple rows in the FLASH array to emulate

increased write/erase cycling capability of one row.

Entry conditions:

H:X

Contains the address of the first row in the range. This address must

be the first address of a row (multiple of eight bytes)

LADDR

Address of last row in the range; must be the first address of a row

(multiple of eight bytes)

DATA

Data to program in the row (bit 7 of DATA + 0 is used internally and

will be overwritten). Routine will always use 8 bytes starting at DATA

BUMPS

Contains the maximum allowable number of programming bumps to

use

CPUSPD

Contains the bus frequency times 4 in MHz

DERASE

Contains the erase delay time in

µs/24

Exit conditions:

C bit

Set if successful program; cleared otherwise

I bit

Set, masking interrupts

This routine uses a range of the FLASH array containing multiple rows to emulate

increased write/erase cycling capability for data storage. The routine will write data

to each row of the FLASH array (in the range defined) upon subsequent calls. The

number of rows is the difference between the value in H:X and LADDR, divided

by 8.

A row is the minimum range that can be programmed with the REDPROG routine.

All rows in the range will be programmed once before any are programmed again.

This approach is taken to ensure that all rows reach the end of lifetime at

approximately the same time.

A special bit will be maintained by the routine, called a cycling bit, in each row. This

bit is used to ensure that the data is programmed to all the rows defined in the

range. This is the high bit of the first byte in each row. This bit cannot be used to

store user data. It will be modified by the REDPROG routine. This is at bit 7 of the

byte at address DATA+0.

To determine which row to program, the algorithm will step from the first to the last

row in a range looking for the first row whose cycling bit is different from the first. If

all rows contain the same cycling bit, then the first row will be used.

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