;
; Initialization routine.  Call once Display List is set up
; Display List should have a blank line with DLI at the top
; and a Mode 2,3 or F line with DLI as it's last display instruction
;
    lda #0
    sta nmien
    ldx #<vblank
    ldy #>vblank
    stx $222
    sty $223
    lda #$40
    sta nmien
;    lda pactl
;    and #$fb
;    sta pactl
;    lda #$80
;    sta porta
;    lda pactl
;    ora #4
;    sta pactl
        rts
    .byte 0,0,0,0; filler
waitvc
    cmp vcount
    bne waitvc
    rts
vblank
    lda #$c0
    sta nmien
    ldx #<dli1
    ldy #>dli1
    stx $200
    sty $201
    lda 20
    lsr a
    bcc vblank2
    jmp vblankend
vblank2
    lda #$88
    jsr waitvc
; *****************************************************************************
; Important - don't modify anything between this comment and the next "Important" comment
; *****************************************************************************
    lda #0
    sta $d017
    sta $d018
    sta $d01a
    sta wsync
    sta porta
    ldy #3
    sta wsync
    sta wsync
; first line of vsync... half line at blanking level, second half at sync level
    nop; 105
    sty dmactl; 109
    ldx #7; 111
; Refresh cycles 26 30 34 38 42 46 50 54 58
vbwait1
    dex
    bne vbwait1; 5*X-1=34=31 (+2 Ref)= 33
    ldx #3; 36 (1)
    nop; 39 (1)
    nop; 41
    nop; 44 (1)
    nop; 47 (1)
    nop; 49
    sta dmactl; 55 (2)
    nop; 57
    stx vscount; 62 (1)
    ldx #7; 63
; Refresh cycles 26 30 34 38 42 46 50 54 58
vbloop1
vbwait3
    dex
    bne vbwait3; 5*X-1 = 34 = 97,
    sty dmactl; 101 get HSync pulses back in normal order
    nop; 103
    nop; 105
    nop; 107
    sta dmactl; 111
    dec vscount; 116 = 2
    beq vsyncend; 4
    ldx #5; 6
vbwait2
    dex
    bne vbwait2; 5*X-1 = 24 (+ 2 Ref) = 32
    ldx #6; 35 (1)
    nop; 37
    nop; 40 (1)
    nop; 43 (1)
    nop; 45
    sty dmactl; 51 (2)
    nop; 53
    sta dmactl; 59 (2)
    nop; 61
    nop; 63
    nop; 65
    jmp vbloop1; 68
; Refresh cycles 26 30 34 38 42 46 50 54 58
vsyncend
    lda #1
    jsr waitvc
vblankend
; *****************************************************************************
; Important - don't modify anything between this and the previous "Important" comment
; *****************************************************************************
    lda sdmctl
    sta savesdmctl
    lda #$20
    sta sdmctl
;    lda #$80
    sta wsync
;    sta porta
; Following NOPs just padding for patches etc. Can be safely removed
    .byte 234,234,234,234
    .byte 234,234,234,234
    .byte 234,234,234,234
    jmp $e45f
savesdmctl .byte 0
; Following zeros just padding
    .word 0,0,0,0,0,0,0,0
dli1
    pha
    lda savesdmctl
    sta sdmctl
    sta wsync
    sta dmactl
    lda #<dli2
    sta $200
    lda #>dli2
    sta $201
    pla
    rti
dli2
    pha
    lda #0
    sta wsync
    sta dmactl
    pla
    rti