Working Python version for Commodore.

c64view/viewer/multicolor.s

@@ -0,0 +1,98 @@
+; c64view -- multicolor (Koala) bitmap viewer (self-contained)
+;
+; The picture data is appended to this program by the exporter and loads in one
+; pass, so no second disk access is needed.  Fixed memory layout after load:
+;   $0801 this program  (BASIC stub + ML, padded up to $2000)
+;   $2000 bitmap 8000   (VIC reads here directly)
+;   $3F40 screen 1000   (copied to $0400)
+;   $4328 colram 1000   (copied to $D800)
+;   $4710 background 1
+;
+; assembled by viewer/assemble.py via xa
+
+        ; BASIC autostart, SYS 2061
+        * = $0801
+        .word basicend
+        .word 10
+        .byte $9e
+        .byte "2061"
+        .byte 0
+basicend:
+        .word 0                   ; ML begins at $080D
+
+SRC = $fb
+DST = $fd
+
+start:
+        lda #$0b
+        sta $d011                 ; blank screen during setup
+
+        ; copy screen RAM  $3F40 -> $0400
+        lda #$40
+        sta SRC
+        lda #$3f
+        sta SRC+1
+        lda #$00
+        sta DST
+        lda #$04
+        sta DST+1
+        jsr copy1024
+
+        ; copy colour RAM  $4328 -> $D800
+        lda #$28
+        sta SRC
+        lda #$43
+        sta SRC+1
+        lda #$00
+        sta DST
+        lda #$d8
+        sta DST+1
+        jsr copy1024
+
+        ; program the VIC-II
+        lda $dd00
+        ora #$03
+        sta $dd00                 ; VIC bank 0 ($0000-$3FFF)
+        lda $4710
+        sta $d021                 ; background colour
+        lda #$00
+        sta $d020                 ; border black
+        lda #$18
+        sta $d018                 ; screen $0400, bitmap $2000
+        lda #$d8
+        sta $d016                 ; multicolor mode on
+        lda #$3b
+        sta $d011                 ; bitmap mode, display on
+        lda #$ff
+        sta $cc                   ; disable cursor blink
+
+waitkey:
+        jsr $ffe4                 ; GETIN
+        beq waitkey
+
+        ; restore text mode and return to BASIC
+        lda #$1b
+        sta $d011
+        lda #$c8
+        sta $d016
+        lda #$15
+        sta $d018
+        lda #$00
+        sta $cc
+        jsr $e544                 ; clear screen
+        rts
+
+; copy 1024 bytes from (SRC) to (DST)
+copy1024:
+        ldx #4
+        ldy #0
+cploop:
+        lda (SRC),y
+        sta (DST),y
+        iny
+        bne cploop
+        inc SRC+1
+        inc DST+1
+        dex
+        bne cploop
+        rts