beater6502/lcd2.s at master · RunnerScrab/beater6502 · GitHub

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HOME = $02
CLEAR = $01
ENTRY = $06
SETDDRADDR = $80
FUNCSET = $2F
DISPON = $0f

	org $8000

reset:
	lda #$ff		; Set data direction bits for port B to output
	sta $6002		; Port B's data direction register address
	lda #$00		; Write 0 to Port B pins
	sta $6000
main:
	jsr initlcd

	ldx #"S"
	jsr writelcddata

	ldx #$81
	jsr writelcdcmd

	ldx #"h"
	jsr writelcddata

	ldx #$82
	jsr writelcdcmd

	ldx #"i"
	jsr writelcddata

	ldx #$83
	jsr writelcdcmd

	ldx #"t"
	jsr writelcddata


end:
	nop
	nop
	nop
	nop
	jmp end

initlcd:
	pha
	txa
	pha
	php

	ldx #$02
	jsr writelcdcmd

	ldx #$2f
	jsr writelcdcmd

	ldx #$0f
	jsr writelcdcmd

	ldx #$01
	jsr writelcdcmd

	ldx #$80
	jsr writelcdcmd

	plp
	pla
	tax
	pla
	rts

writelcdcmd:
	;; opcode passed in X

	lda #%01000000		; E = 1
	sta $6000

	txa
	lsr
	lsr
	lsr
	lsr
	ora #$40
	sta $6000


	lda #%00000000		; E = 0
	sta $6000
	lda #%01000000		; E = 1
	sta $6000

	txa
	and #$0f
	ora #$40
	sta $6000

	lda #%00000000		; E = 0
	sta $6000
	jsr delay
	rts

writelcddata:
	;; data passed in X

	lda #%01100000		; E = 1, RS = 1
	sta $6000

	txa
	lsr
	lsr
	lsr
	lsr
	ora #$60
	sta $6000

	lda #%00000000		; E = 0
	sta $6000
	lda #%01000000		; E = 1
	sta $6000

	txa
	and #$0f
	ora #$60
	sta $6000

	lda #%00000000		; E = 0
	sta $6000

	jsr delay

	rts

delay:
	pha
	php
	lda #0
delayloop:
	sec
	adc #0
	cmp 128
	bne delayloop
	plp
	pla
	rts

nmi:

	rti
irq:

	inc $0200 		; Increment counter
	lda $6001
	rti

	org $FFFA
	word nmi
	word reset
	word irq