PORTB = $6000
PORTA = $6001
DDRB = $6002
DDRA = $6003

value = $0200 			; 2 bytes
mod10 = $0202			; 2 bytes
message = $0204 		; 6 bytes
	
E  = %10000000
RW = %01000000
RS = %00100000

  .org $8000


	
reset:
  lda #%11111111 ; Set all pins on port B to output
  sta DDRB

  lda #%11100000 ; Set top 3 pins on port A to output
  sta DDRA

  lda #%00111000 ; Set 8-bit mode; 2-line display; 5x8 font
  jsr send_inst
	
  lda #%00001110 ; Display on; cursor on; blink off
  jsr send_inst

  lda #%00000001  ; Reset display
  jsr send_inst

  lda #%00000110 ; Increment and shift cursor; don't shift display
  jsr send_inst


	
	;; division rotate minus

	lda #0
	sta message
	
	;;  initialize value to the conversion number
	lda number
	sta value
	lda number + 1
	sta value + 1
divide:	
	;; initialse remainder to zero
	lda #0
	sta mod10
	sta mod10 + 1
	clc
	
	ldx #16
divloop:	

	;; rotate the quotient
	rol value
	rol value + 1
	rol mod10
	rol mod10 + 1

	;;  a,y = dividend = divisor
	sec
	lda mod10
	sbc #10
	tay 			; save low byte in Y
	lda mod10 + 1
	sbc #0
	bcc ignore_result 	; branch if dividend < divosr

	sty mod10
	sta mod10 + 1
	
ignore_result:	
	dex
	bne divloop
	rol value 		; shift in last bit of quotient
	rol value + 1
	
	lda mod10
	clc
	adc #"0"
	jsr push_char

	;;  if value != 0 continue dividing
	lda value
	ora value + 1
	bne divide 


	  ldx #0
print:
	lda message,x
	beq loop
	jsr send_data 
	inx
	jmp print

	
loop:	
	jmp loop

number:	 .word 65521

	;; add character in A to start of message
push_char:
	pha 			; Push first char on stack
	ldy #0
char_loop:	
	lda message,y 		; get char on string and put in X
	tax
	pla
	sta message,y 		; pull char off stack and add it to the string
	iny
	txa
	pha			; put char from string and put it back
	bne char_loop

	pla
	sta message,y		; Pull null off stack stuff on end of string

	rts

	
lcd_wait:
	pha
	lda #%00000000 ; PORT B to INPUT
	sta DDRB
lcd_busy:	
  lda #RW
  sta PORTA
  lda #(RW | E)
  sta PORTA
  lda PORTB
  and #%10000000
  bne lcd_busy
  
  lda #RW
  sta PORTA
  lda #%11111111 ; PORT B to output
  sta DDRB
  pla
  rts

send_inst:	
  jsr lcd_wait
  sta PORTB
  lda #0         ; Clear RS/RW/E bits	
  sta PORTA
  lda #E         ; Set E bit to send instruction
  sta PORTA
  lda #0         ; Clear RS/RW/E bits
  sta PORTA
  rts

send_data:
  jsr lcd_wait
  sta PORTB
  lda #RS         ; Set RS; Clear RW/E bits
  sta PORTA
  lda #(RS | E)   ; Set E bit to send instruction
  sta PORTA
  lda #RS         ; Clear E bits
  sta PORTA
  rts


  .org $fffc
  .word reset
  .word $0000