; AUTHOR: SEAN KESSLER                        DATE:01/10/2001
; PROGRAM: EEPROM.ASM
; PLATFORM:M68HC11E2FN
; LANGUAGE:CUSTOM ASSEMBLER
; FUNCTION:TEST EEPROM READ/WRITE

RAM          equ 00000h      ; base of code
RAMSIZE      equ 000FFh      ; extent of RAM
STACK        equ RAM+RAMSIZE ; stack expands down from end of RAM
PORTB        equ 01004h      ; address of PORTB register
EEPROM       equ 0F800h      ; start of EEPROM 
PPROG        equ 0103Bh      ; PPROG register
EEPGM        equ 00003h      ; EEPROM Programming Voltage Enable
EELAT        equ 00002h      ; EEPROM Latch Control
  org RAM                    ; base of code
BEGIN equ *
  lds STACK                  ; initialize the stack
START equ *                  ; start sync address
loop equ *

  ldab 01h                   ; move 1 into register b
  stab [PORTB]               ; light b0
  bsr DELAY100
;  bsr DELAY1K                ; pause

  ldab 02h                   ; move 2 into register b  
  stab [PORTB]               ; light b1
  bsr DELAY100
;  bsr DELAY1K                ; pause

  jmp loop

END equ *                   ; need to figure out how to enable stop
  jmp END                   ; do it forever
; ********************* write data to EEPROM location ******************************
EEPROMW equ *               ; register a contains data, x contains eeprom address
  ldab EELAT                ; move EELAT enable into register b
  stab [PPROG]              ; move EELAT enable into PPROG register
  staa ix,0                 ; store contents of register a into EEPROM address at ix
  ldab EEPGM                ; move EEPGM enable bit into register b
  stab [PPROG]              ; move EEPGM enable bits into PPROG register
  bsr DELAY10               ; allow charge pump to charge
  clr [PPROG]               ; turn off high voltage & set to read mode
  rts
; ********************** DELAY ROUTINES ************************
DELAY10 equ *               ; 10ms delay @ 2.1 mhz
  pshy                      ; save register y
  ldy 0BB8h                 ; load loop counter into y register
DELAY10LOOP equ *           ; loop counter sync address
  dey                       ; decrement counter 
  bne DELAY10LOOP           ; loop until zero in y
  puly                      ; restore register y
  rts                       ; return to caller
DELAY1K equ *               ; 1000ms delay @ 2.1 mhz
  pshy                      ; save register y
  ldy 0Ah                   ; load 10d into register y
DELAY1KLP equ *             ; loop counter sync address
  bsr DELAY100              ; call 100 ms delay
  dey                       ; decrement register y
  bne DELAY1KLP             ; continue
  puly                      ; restore register y
  rts                       ; return to caller
DELAY100 equ *              ; 100 ms @ 2.1 mhz
  pshx                      ; save register x
  ldx 07530h                ; load loop counter into register x
DELAY100LP equ *            ; loop counter sync address
  dex                       ; decrement register x
  bne DELAY100LP            ; continue
  pulx                      ; restore register x
  rts                       ; return to caller