dither4/dither4.s

SAVMSC = $58
SDMCTL = $22F
SDLSTL = $230
SDLSTH = $231
COLPF0 = $D016
COLPF1 = $D017
COLPF2 = $D018
COLPF3 = $D019
COLBK = $D01A

WSYNC = $D40A
VCOUNT = $D40B
NMIEN = $D40E

.data

.import palette1
.import palette2
.import palette3
.import framebuffer

displaylist:
    ; @fixme resolve the line counts
    .repeat 3
        .byte $70 ; 8 blank lines
    .endrep
    ; Note the framebuffer cannot cross a 4KiB boundary
    ; so this is split in half
    ; ANTIC mode e (160px 2bpp, 1 scan line per line)
    .byte $4e
    .addr framebuffer
    .repeat 95
        .byte $0e
    .endrep
    .byte $4e
    .addr framebuffer + 96*40
    .repeat 95
        .byte $0e
    .endrep
    .byte $41 ; jump and blank
    .addr displaylist


.code

.export start

.proc start
    ; Disable display DMA
    lda #$00
    sta SDMCTL
    ; Set up the display list
    lda #.lobyte(displaylist)
    sta SDLSTL
    lda #.hibyte(displaylist)
    sta SDLSTH

    ; Turn off interrupts except reset button
    ;lda #$20
    ;sta NMIEN

    ; Manually wait for first scan line
wait_vblank:
    lda VCOUNT
    bne wait_vblank

    ; Re-enable display DMA
    lda #$22
    sta SDMCTL

wait_start:
    lda VCOUNT
    cmp #12
    bne wait_start
    ldy #0

each_scanline:
    tya
    pha

    lda palette1,y
    pha
    ldx palette2,y
    lda palette3,y
    tay
    pla

    ; Wait for horizontal blank
    sta WSYNC

    ; Update color registers as fast as possible
    sta COLPF0
    stx COLPF1
    sty COLPF2

    pla
    tay
    iny
    cpy #192
    bne each_scanline

    jmp wait_start    

.endproc

; Loop through scan lines updating the palette
.proc update_palette
    rts
.endproc
initial atari tests (not with image) and dither improvements palette selection now biases to matches on the bright side of the RGB color cube, since black is always available for dithering does better but still not perfect atari binary just writes some test data to text framebuffer but builds and runs 2022-11-20 23:43:34 +00:00			`SAVMSC = $58`
work in progress 2022-11-25 19:51:27 +00:00			`SDMCTL = $22F`
			`SDLSTL = $230`
			`SDLSTH = $231`
			`COLPF0 = $D016`
			`COLPF1 = $D017`
			`COLPF2 = $D018`
			`COLPF3 = $D019`
			`COLBK = $D01A`

			`WSYNC = $D40A`
			`VCOUNT = $D40B`
			`NMIEN = $D40E`

			`.data`

			`.import palette1`
			`.import palette2`
			`.import palette3`
			`.import framebuffer`

			`displaylist:`
closer 2022-11-26 03:17:34 +00:00			`; @fixme resolve the line counts`
work in progress 2022-11-25 19:51:27 +00:00			`.repeat 3`
			`.byte $70 ; 8 blank lines`
			`.endrep`
closer 2022-11-26 03:17:34 +00:00			`; Note the framebuffer cannot cross a 4KiB boundary`
			`; so this is split in half`
			`; ANTIC mode e (160px 2bpp, 1 scan line per line)`
			`.byte $4e`
work in progress 2022-11-25 19:51:27 +00:00			`.addr framebuffer`
closer 2022-11-26 03:17:34 +00:00			`.repeat 95`
			`.byte $0e`
			`.endrep`
			`.byte $4e`
			`.addr framebuffer + 96*40`
			`.repeat 95`
work in progress 2022-11-25 19:51:27 +00:00			`.byte $0e`
			`.endrep`
			`.byte $41 ; jump and blank`
			`.addr displaylist`

initial atari tests (not with image) and dither improvements palette selection now biases to matches on the bright side of the RGB color cube, since black is always available for dithering does better but still not perfect atari binary just writes some test data to text framebuffer but builds and runs 2022-11-20 23:43:34 +00:00
			`.code`

			`.export start`

			`.proc start`
work in progress 2022-11-25 19:51:27 +00:00			`; Disable display DMA`
			`lda #$00`
			`sta SDMCTL`
			`; Set up the display list`
partly producing output 2022-11-26 01:35:10 +00:00			`lda #.lobyte(displaylist)`
work in progress 2022-11-25 19:51:27 +00:00			`sta SDLSTL`
partly producing output 2022-11-26 01:35:10 +00:00			`lda #.hibyte(displaylist)`
work in progress 2022-11-25 19:51:27 +00:00			`sta SDLSTH`

			`; Turn off interrupts except reset button`
closer 2022-11-26 03:17:34 +00:00			`;lda #$20`
			`;sta NMIEN`
work in progress 2022-11-25 19:51:27 +00:00
			`; Manually wait for first scan line`
			`wait_vblank:`
			`lda VCOUNT`
partly producing output 2022-11-26 01:35:10 +00:00			`bne wait_vblank`
work in progress 2022-11-25 19:51:27 +00:00
			`; Re-enable display DMA`
			`lda #$22`
			`sta SDMCTL`

closer 2022-11-26 03:17:34 +00:00			`wait_start:`
			`lda VCOUNT`
			`cmp #12`
			`bne wait_start`
			`ldy #0`

			`each_scanline:`
			`tya`
			`pha`
work in progress 2022-11-25 19:51:27 +00:00
closer 2022-11-26 03:17:34 +00:00			`lda palette1,y`
			`pha`
			`ldx palette2,y`
			`lda palette3,y`
			`tay`
			`pla`

			`; Wait for horizontal blank`
			`sta WSYNC`

			`; Update color registers as fast as possible`
			`sta COLPF0`
			`stx COLPF1`
			`sty COLPF2`

			`pla`
			`tay`
initial atari tests (not with image) and dither improvements palette selection now biases to matches on the bright side of the RGB color cube, since black is always available for dithering does better but still not perfect atari binary just writes some test data to text framebuffer but builds and runs 2022-11-20 23:43:34 +00:00			`iny`
closer 2022-11-26 03:17:34 +00:00			`cpy #192`
			`bne each_scanline`

			`jmp wait_start`
work in progress 2022-11-25 19:51:27 +00:00
initial atari tests (not with image) and dither improvements palette selection now biases to matches on the bright side of the RGB color cube, since black is always available for dithering does better but still not perfect atari binary just writes some test data to text framebuffer but builds and runs 2022-11-20 23:43:34 +00:00			`.endproc`
closer 2022-11-26 03:17:34 +00:00
			`; Loop through scan lines updating the palette`
			`.proc update_palette`
			`rts`
			`.endproc`