mirror of https://github.com/a2-4am/4cade.git
188 lines
4.9 KiB
Plaintext
188 lines
4.9 KiB
Plaintext
;license:MIT
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;(c) 2021 by 4am
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!cpu 6502
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!to "build/FX.INDEXED/SHR.FADEIN",plain
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*=$A000
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color = $F7 ; byte
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fracv = $F8 ; byte
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fracv_hi = $F9
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incv = $FA ; byte
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src = $FC ; word
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dst = $FE ; word
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palettes = $BC00 ; $200 bytes
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!source "src/fx/macros.a"
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sta $C005
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ldy #0 ; copy pixel data
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sty src
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sty dst
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lda #$20
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sta src+1
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ldx #$7D
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- lda (src), y
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sta (src), y
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iny
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bne -
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inc src+1
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dex
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bne -
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;Y=0
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- lda $9D00, y ; copy SCB
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sta $9D00, y
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iny
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bne -
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sta $C004
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- lda $9E00, y ; Back up palettes to alternate location in main memory.
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sta palettes, y ; The CPU in a 64K Apple ][+/][e w/VidHD ignores STA $C004/5
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lda $9F00, y ; but VidHD respects them, so we can't clear the palettes
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sta palettes+$100, y ; in auxmem until we copy them in mainmem. Whee.
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iny
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bne -
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sta $C005
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lda #0
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- sta $9E00, y ; now clear the palettes
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sta $9F00, y
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iny
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bne -
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sta $C004
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lda #>palettes
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sta src+1
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ldx #$0F ; palette counter ($0F -> $00, not used as index)
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rb_palette_loop
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ldy #$00 ; byte offset within palette (00 -> 1F, used as index)
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rb_color_loop
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lda #$00
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sta fracv
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sta fracv_hi
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sta color
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lda src
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sta dst
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lda src+1
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sec
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sbc #>(palettes-$4000)
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sta dst+1
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lda (src), y ; get final Red or Blue value for this color in this palette
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asl ; Red or Blue value is bits 0-3, shift them into bits 4-7
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asl
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asl
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asl
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sta incv
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rb_step_loop
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lda fracv
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clc
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adc incv
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sta fracv
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bcc +
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lda fracv_hi
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eor #$01
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sta fracv_hi
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bne +
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inc color
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+ lda color
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sta (dst), y
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inc dst+1
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inc dst+1
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bpl rb_step_loop
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iny
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cpy #$20
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bcc rb_color_loop
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lda src
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clc
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adc #$20
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sta src
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bcc +
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inc src+1
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+ dex
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bpl rb_palette_loop
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lda #>palettes
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sta src+1
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ldx #$0F ; palette counter ($0F -> $00, not used as index)
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g_palette_loop
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ldy #$00 ; byte offset within palette (00 -> 1E by 2, used as index)
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g_color_loop
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lda #$00
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sta fracv
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sta fracv_hi
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sta color
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lda src
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sta dst
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lda src+1
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sec
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sbc #>(palettes-$4000)
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sta dst+1
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lda (src), y ; get final Green value for this color in this palette
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and #$F0 ; Green value is bits 4-7, mask out other bits
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sta incv
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g_step_loop
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lda fracv
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clc
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adc incv
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sta fracv
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bcc +
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lda fracv_hi
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eor #$01
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sta fracv_hi
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bne +
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lda color
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clc
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adc #$10
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sta color
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+ lda color
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ora (dst), y ; keep existing Blue value in bits 0-3
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sta (dst), y
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inc dst+1
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inc dst+1
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bpl g_step_loop
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iny
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iny ; high nibble of second color byte is always 0 so skip it
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cpy #$20
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bcc g_color_loop
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lda src
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clc
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adc #$20
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sta src
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bcc +
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inc src+1
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+ dex
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bpl g_palette_loop
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ldx #$44
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stx copy1+2
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inx
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stx copy2+2
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lda #$40
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sta incv
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ldx #$1D
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ldy #$00
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copyloop jsr WaitForVBL
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sta $C005
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copy1 lda $4400, y ; SMC
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sta $9E00, y
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copy2 lda $4500, y ; SMC
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sta $9F00, y
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iny
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bne copy1
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sta $C004
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inc copy1+2
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inc copy1+2
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inc copy2+2
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inc copy2+2
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lda incv
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jsr WaitForKeyWithTimeout
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bmi exit
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dec incv
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dec incv
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dex
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bpl copyloop
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exit jmp UnwaitForVBL
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!source "src/wait.a"
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