getting closer

dither-image.js

@@ -741,9 +741,11 @@ ${byte2byte(frames[1].bitmap.slice(half))}
 .align 1024
 displaylist:
     ; 40 lines overscan
-    .repeat 5
+    .repeat 4
         .byte $70 ; 8 blank lines
     .endrep
+    ; include a DLI to mark us as frame 0
+    .byte $f0 ; 8 blank lines
 
     ; 160 lines graphics
     ; ANTIC mode e (160px 2bpp, 1 scan line per line)

dither4.s

@@ -1,4 +1,7 @@
 SAVMSC = $58
+VDSLST = $200
+VDSLSTL = $200
+VDSLSTH = $201
 COLPF0 = $D016
 COLPF1 = $D017
 COLPF2 = $D018
@@ -24,6 +27,7 @@ sample_ptrh = $85
 sample_ptr = sample_ptrl
 scanline = $86
 audiotemp = $87
+frame_counter = $89
 
 height = 160
 bytes_per_line = 40
@@ -99,6 +103,16 @@ audio_high_byte:
     lda #.hibyte(displaylist)
     sta DLISTH
 
+    ; Set up the DLI handler
+    lda #.lobyte(dli_handler)
+    sta VDSLSTL
+    lda #.hibyte(dli_handler)
+    sta VDSLSTH
+
+    ; Disable VBI but allow Reset and DLI
+    lda #$a0
+    sta NMIEN
+
     ; Manually wait for first scan line
 wait_vblank:
     sta WSYNC
@@ -113,25 +127,28 @@ wait_start:
     ; Wait for the vblank
     ; Resynchronize the scanline counter
 wait_loop:
-    lda VCOUNT
-    tay ; save for audio lookup
+    ldy VCOUNT
     bne wait_loop
-    lda #(256 - scanline_offset)
-    sta scanline
 
-each_scanline:
     .macro audio_prep
         ; Y is VCOUNT at entry
         lda (sample_ptr),y ; 5/6 cyc
         sta audiotemp ; 3 cyc
     .endmacro
 
-    .macro inner_scanline frame_base
+    .macro inner_scanline palette1, palette2, palette3
         ; it'll fire on unused lines, but harmlessly
         ldy scanline ; 3 cyc
         inc scanline ; 5 cyc
 
         ; Leisurely memory fetches
+     ;   lda palette1,y ; 5 @FIXME alternate
+    ;    pha                   ; ...3?
+   ;     ldx palette2,y ; 5
+  ;      lda palette3,y ; 5
+ ;       tay
+;        pla
+
         lda frame1_palette1,y ; 5 @FIXME alternate
         pha                   ; ...3?
         ldx frame1_palette2,y ; 5
@@ -186,57 +203,37 @@ each_scanline:
         audio_cont:
     .endmacro
 
-    ;audio_prep
-    inner_scanline
-    ;audio_play_lo
-    inner_scanline
-    ;audio_play_hi
+    .macro run_frame palette1, palette2, palette3
+    .scope
+    each_scanline:
+        ;audio_prep
+        inner_scanline palette1, palette2, palette3
+        ;audio_play_lo
+        inner_scanline palette1, palette2, palette3
+        ;audio_play_hi
 
-    lda VCOUNT
-    tay ; save for audio lookup
-    cmp #130 ;#130
-    bne each_scanline
-    audio_inc
-    jmp wait_start
+        ldy VCOUNT ; save for audio lookup
+        cpy #130
+        bne each_scanline
+        ;audio_inc
+        inc frame_counter
+        jmp wait_start
+    .endscope
+    .endmacro
+
+    lda #(256 - scanline_offset)
+    sta scanline
+    lda frame_counter
+    bne run_frame2
+    run_frame frame1_palette1, frame1_palette2, frame1_palette3
+run_frame2:
+    run_frame frame2_palette1, frame2_palette2, frame2_palette3
 
 .endproc
 
-; temp1 contains source address
-; temp2 contains dest address
-; clobbers a/x/y
-; incremepts temp1 and temp2 to the end of their regions
-.proc copy_half_frame
-    ldx #0
 
-copy_loop_lines:
-    ldy #00
-
-copy_loop_bytes:
-    lda (temp1),y
-    sta (temp2),y
-    iny
-    cpy #bytes_per_line
-    bne copy_loop_bytes
-
-    clc
-    lda temp1l
-    adc #bytes_per_line
-    sta temp1l
-    lda temp1h
-    adc #00
-    sta temp1h
-
-    clc
-    lda temp2l
-    adc #bytes_per_line
-    sta temp2l
-    lda temp2h
-    adc #00
-    sta temp2h
-
-    inx
-    cpx #(height / 2)
-    bne copy_loop_lines
-
-    rts
+.proc dli_handler
+    lda #0
+    sta frame_counter
+    rti
 .endproc