.setcpu "65C02"

                        ACIA_DATA       = $7F00
                        ACIA_STATUS     = $7F01
                        ACIA_COMMAND    = $7F02
                        ACIA_CONTROL    = $7F03

                        .segment "VECTORS"

                        .word nmi
                        .word reset
                        .word irq

                        .code

reset:                  jmp main
nmi:                    rti
irq:                    rti

main:
init_acia:              lda #%00001011
                        sta ACIA_COMMAND
                        lda #%00011111
                        sta ACIA_CONTROL

                        lda #0
                        sta $00
                        sta $01

loop:                   jsr print
                        jsr increment
                        bra loop

print:                  lda $00
                        jsr acia_put_hex_byte
                        lda $01
                        jsr acia_put_hex_byte

                        pha
                        lda #$0D
                        jsr acia_put_byte
                        lda #$0A
                        jsr acia_put_byte
                        pla

                        rts

increment:              clc
                        lda $01
                        adc #1
                        sta $01

                        lda $00
                        adc #0
                        sta $00

                        rts

delay:                  pha
                        lda #$FF
:                       nop
                        dec a
                        bne :-
                        rts

acia_put_hex_byte:      pha
                        pha
                        and #$F0
                        lsr
                        lsr
                        lsr
                        lsr
                        tax
                        lda hex_lut,x
                        jsr acia_put_byte
                        pla
                        and #$0F
                        tax
                        lda hex_lut,x
                        jsr acia_put_byte
                        pla
                        rts

acia_put_byte:          pha
:                       lda ACIA_STATUS
                        and #$10
                        beq :-
                        pla
                        sta ACIA_DATA
                        rts

hex_lut:                .byte "0123456789ABCDEF"