ys2-intro/loader/samples/minexample/minexample.s

.feature c_comments
.include "../../build/loadersymbols-c64.inc"

.ZEROPAGE
.org $10
bmp_delay: .res 1
bmp_addr: .res 2
bmp_ptr: .res 2
scr_ptr_lo: .res 1
scr_ptr: .res 2
cram_ptr: .res 2
chr_count: .res 1
vbl: .res 1
frame: .res 1
cur_frame: .res 1
frame_delay: .res 1
frame_until: .res 1

.segment "CODE"

ZP=$e0
offset          = ZP+0
ZX0_src         = ZP+2
ZX0_dst         = ZP+4
bitr            = ZP+6
pntr            = ZP+7


    .org $080d
    jsr install

    sei
    lda #$35
    sta $01

    lda #0
    sta ZX0_dst+0

    ldx #<badguy
    ldy #>badguy
    jsr loadraw

    lda #0
    sta ZX0_src
    lda #$e0
    sta ZX0_src+1
    lda #0
    sta ZX0_dst
    lda #$20
    jsr zx02

    lda #127
    sta $dc0d

    and $d011
    sta $d011

    lda $dc0d
    lda $dd0d

    lda #<irq_badguy
    sta $fffe
    lda #>irq_badguy
    sta $ffff
    
    lda #$1b
    sta $d011
    lda #$80
    sta $d012

    lda #1
    sta $d01a
    sta bmp_delay
    jsr init_bmp

    lda #0
    sta vbl

    cli

    lda #7
    sta frame_until
    jsr wait_frame_until

    lda #50*5
    sta frame_delay
    jsr wait_loop

    lda #$0d
    sta frame_until
    jsr wait_frame_until

    lda #50*5
    sta frame_delay
    jsr wait_loop

    lda #50*5
    sta frame_delay
    jsr wait_loop

    lda #26
    sta frame_until
    jsr wait_frame_until
    jmp *

wait_loop:
loop2:
    lda vbl
    beq loop2

    lda #0
    sta vbl

    jsr sfx_play

    dec frame_delay
    lda frame_delay
    beq :+
    jmp loop2
:
    rts

wait_frame_until:
loop:
    lda vbl
    beq loop

    lda #0
    sta vbl

    lda cur_frame
    cmp #2
    bcc :+
    jsr sfx_play
:

    dec bmp_delay
    bpl :+
    jsr update_bmp
:

    lda cur_frame
    cmp frame_until
    beq :+

    jmp loop
:
    rts

init_bmp:
    lda #$3b
    sta $d011
    lda #$19
    sta $d018
    lda #$d8
    sta $d016

    lda $4710
    lsr
    lsr
    lsr
    lsr
    sta $d020

    lda $4710
    and #$0f
    sta $d021

    lda #0
    sta cur_frame
    sta bmp_delay

    lda #$11
    sta bmp_addr
    lda #$47
    sta bmp_addr+1

    ldx #0
:
    .repeat 4, I
        lda $3f40+(I*250), x
        sta $400+(I*250), x
        lda $4328+(I*250), x
        sta $d800+(I*250), x
    .endrepeat
    inx
    cpx #250
    bne :-
    rts

inc_bmp_addr:
    inc bmp_addr
    bne :+
    inc bmp_addr+1
:
    rts

update_bmp:
    ldy #0
    sty scr_ptr
    sty cram_ptr
    lda (bmp_addr), y
    jsr inc_bmp_addr
    sta chr_count
    cmp #0 ; tfw flags update in inc_bmp_addr
    bne @skip_frame_end
    lda (bmp_addr), y
    jsr inc_bmp_addr
    sta bmp_delay
    inc cur_frame
    lda cur_frame
    cmp #2
    bne :+
    lda #0
    jsr sfx_init
:
    rts    
@skip_frame_end:

    lda (bmp_addr), y   
    sta bmp_ptr
    iny
    lda (bmp_addr), y   
    clc
    adc #$20
    sta bmp_ptr+1

    iny
    lda (bmp_addr), y   
    sta scr_ptr_lo
    iny
    lda (bmp_addr), y   
    clc
    adc #$04
    sta scr_ptr+1
    clc
    adc #$d8-$04
    sta cram_ptr+1

    ldy #0
    lda bmp_addr
    clc 
    adc #4
    sta bmp_addr
    bcc :+
    inc bmp_addr+1
:

    ldx #0
@loop:
    ldy #0
    lda (bmp_addr), y
    sta (bmp_ptr), y
    iny 
    lda (bmp_addr), y
    sta (bmp_ptr), y
    iny 
    lda (bmp_addr), y
    sta (bmp_ptr), y
    iny 
    lda (bmp_addr), y
    sta (bmp_ptr), y
    iny 
    lda (bmp_addr), y
    sta (bmp_ptr), y
    iny 
    lda (bmp_addr), y
    sta (bmp_ptr), y
    iny 
    lda (bmp_addr), y
    sta (bmp_ptr), y
    iny 
    lda (bmp_addr), y
    sta (bmp_ptr), y

    lda bmp_ptr
    clc
    adc #8
    sta bmp_ptr
    bcc :+
    inc bmp_ptr+1
:
    lda bmp_addr
    clc
    adc #8
    sta bmp_addr
    bcc :+
    inc bmp_addr+1
:

    ldy #0
    lda (bmp_addr), y
    ldy scr_ptr_lo
    sta (scr_ptr), y
    
    ldy #1
    lda (bmp_addr), y
    ldy scr_ptr_lo
    sta (cram_ptr), y

    inc scr_ptr_lo
    bne :+
    inc scr_ptr+1
    inc cram_ptr+1
:

    lda bmp_addr
    clc
    adc #2
    sta bmp_addr
    bcc :+
    inc bmp_addr+1
:

    dec chr_count
    ldx chr_count
    bne @loop
    jmp update_bmp

irq_badguy:
	pha
    txa
    pha
    tya
    pha

    inc vbl

    asl $d019
    pla
    tay
    pla
    tax
    pla
    rti

badguy: .byte "badguy",0

.include "sfx.asm"
.include "zx02.asm"

    .res loadraw - *
.incbin "../../build/loader-c64.prg", 2

    .res install - *
.incbin "../../build/install-c64.prg", 2