AN1950

Sensors

18

Freescale Semiconductor

bclr 4,porta

bclr 5,porta

;LEDs off

rts

;-------- WRITE TO EEPROM Routines ----------------------------------

;

wrflash: burns A into flash at location pointed by H:X

;

-------

wrflash: sthx flshadr

;this is the address in the flash

sta flshbyt

;and the byte we want to put there

tsx

sthx memSP

;store SP in memSP, so it can be temporarily used as a 2nd index register

ldhx #ramfree+1

;SP now points to RAM (remember to add 1 to the address!!!, HC08 quirk)

txs

;SP changed (careful not to push or call subroutines)

ldhx #ersflsh

;H:X points to beginning of flash programming code

doall: lda 0,x

;get 1st byte from flash

sta 0,sp

;copy it into RAM

aix #$0001

;HX:=HX+1

ais #$0001

;SP:=SP+1

cphx #lastbyt

;and continue until we reach the last byte

bne doall

ldhx memSP

;once done, restore the SP

txs

jsr ramfree

;and run the subroutine from RAM, you cannot write the flash while

rts

;running a code in it, so the RAM has to take over for that piece

;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

;*************** THE FOLLOWING CODE WILL BE COPIED INTO AND WILL RUN FROM RAM ******

ersflsh: lda #$02

;textbook way to erase flash

sta flcr

lda flbpr

clra

ldhx flshadr

sta 0,x

bsr delayf

lda #$0A

sta flcr

bsr delayf

lda #$08

sta flcr

bsr delayf

clra

sta flcr

bsr delayf

pgmflsh: lda #$01

;textbook way to program flash

sta flcr

lda flbpr

clra

ldhx flshadr

sta 0,x

bsr delayf

lda #$09

sta flcr

bsr delayf

lda flshbyt

ldhx flshadr

sta 0,x

bsr delayf

lda #$08

sta flcr

bsr delayf

clra

sta flcr