Initial commit of starfield

starfield/main.asm

@@ -0,0 +1,50 @@
+; Begin code at $7530
+org $7530
+
+; System variables
+tv_flag     equ $5c3c   ; TV flags
+last_k      equ $5c08   ; Last pressed key
+clr_screen  equ $0daf   ; ROM routine to clear the screen
+
+; Star Structure
+; X - 2 Bytes
+; Y - 1 Byte
+; Z - 1 Byte
+; Color - 1 Byte
+STAR_SIZE   equ $5
+MAX_STARS   equ 10
+STARS       ds STAR_SIZE * MAX_STARS, 0
+
+
+start
+    xor a                   ; a = 0
+    ld (tv_flag), a         ; Enables rst $10 output to the TV
+    push bc                 ; Save BC on the stack
+
+    call INITIALIZE_STARS
+    
+    pop bc                  ; Get BC out of the stack
+    ret                     ; Exit to BASIC
+
+INITIALIZE_STARS
+    push bc
+    ld b, MAX_STARS
+    ld hl, STARS
+INITIALIZE_STARS_LOOP
+    ld a, 10
+    ld (hl),a
+    inc hl
+    ld a, 15
+    ld (hl),a
+    inc hl
+    ld a, 5
+    ld (hl),a
+    inc hl
+    ld a, 1
+    ld (hl),a
+    inc hl
+    djnz INITIALIZE_STARS_LOOP
+    pop bc
+    ret
+
+end start