First public commit.

lenser/atari/viewer/gr15.s

@@ -0,0 +1,50 @@
+; lenser -- Atari GR.15 (ANTIC mode E) viewer, self-booting
+;
+; 160x192, 4 colours chosen globally (no per-cell limit).  Boots from sector 1:
+; the OS loads this blob to $2000 and JSRs $2006.  Appended data (from $4000):
+;   $4000  bitmap lines 0-101   (4080 bytes)
+;   $5000  bitmap lines 102-191 (3600 bytes)   [split at the 4K ANTIC boundary]
+;   $6000  4 colour register values (value 0..3)
+;
+; assembled by atari/viewer/assemble.py via xa
+
+        * = $2000
+boot:
+        .byte 0                 ; flags
+        .byte 0                 ; sector count (patched by the ATR writer)
+        .word $2000             ; load address
+        .word binit             ; init address (DOSINI)
+
+cont:                           ; $2006 -- OS JSRs here after loading
+        lda #$22
+        sta $22f                ; SDMCTL = normal playfield + DL DMA
+        lda #<dlist
+        sta $230                ; SDLSTL
+        lda #>dlist
+        sta $231                ; SDLSTH
+        lda #$00
+        sta $26f                ; GPRIOR = 0 (no GTIA mode)
+        ; copy the 4 colour registers from $6000
+        lda $6000
+        sta $2c8                ; COLBAK  (pixel value 0)
+        lda $6001
+        sta $2c4                ; COLPF0  (value 1)
+        lda $6002
+        sta $2c5                ; COLPF1  (value 2)
+        lda $6003
+        sta $2c6                ; COLPF2  (value 3)
+#include "awyt.i"
+
+binit:
+        rts
+
+dlist:
+        .byte $70,$70,$70       ; 24 blank scan lines
+        .byte $4e               ; LMS + mode E
+        .word $4000
+        .dsb 101,$0e            ; 101 more mode E lines (102 total from $4000)
+        .byte $4e               ; LMS + mode E
+        .word $5000
+        .dsb 89,$0e             ; 89 more mode E lines (90 total from $5000)
+        .byte $41               ; JVB
+        .word dlist