Moar stuff

starfield/main.asm

@@ -5,6 +5,7 @@ org $7530
 tv_flag     EQU $5c3c   ; TV flags
 last_k      EQU $5c08   ; Last pressed key
 clr_screen  EQU $0daf   ; ROM routine to clear the screen
+frames      EQU $5c78
 
 ; Video RAM
 LINHA9      EQU $4820
@@ -21,20 +22,31 @@ 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
+    xor a
+    ld (tv_flag), a
+    push bc
 
     call clear_screen
     ;call INITIALIZE_STARS
-
-    ld hl, LINHA9+$FF
+    ld c, 32
+main
+    ld de, frames
+    ld a, (de)
+    ld d, 0
+    ld e, a
+    ld hl, LINHA9
+    add hl, de
     ld a, (hl)
     set 0,a
     ld (hl), a
 
-    pop bc                  ; Get BC out of the stack
-    ret                     ; Exit to BASIC
+    halt
+    
+    dec c
+    jr nz, main
+    
+    pop bc
+    ret
 
 PROC
 INITIALIZE_STARS
@@ -56,6 +68,38 @@ INITIALIZE_STARS_LOOP
     ret
 ENDP
 
+PROC
+; Get screen address
+; B = Y pixel position
+; C = X pixel position
+; Returns address in HL
+Get_Pixel_Address
+    ld a,b          ; Calculate Y2,Y1,Y0
+    and %00000111   ; Mask out unwanted bits
+    or %01000000    ; Set base address of screen
+    ld h, a         ; Store in H
+    ld a, b         ; Calculate Y7,Y6
+    rra             ; Shift to position
+    rra
+    rra
+    and %00011000   ; Mask out unwanted bits
+    or h            ; OR with Y2,Y1,Y0
+    ld h, a         ; Store in H
+    ld a, b         ; Calculate Y5,Y4,Y3
+    rla             ; Shift to position
+    rla
+    and %11100000   ; Mask out unwanted bits
+    ld l, a         ; Store in L
+    ld a, c         ; Calculate X4,X3,X2,X1,X0
+    rra             ; Shift into position
+    rra
+    rra
+    and %00011111   ; Mask out unwanted bits
+    or l            ; OR with Y5,Y4,Y3
+    ld l, a         ; Store in L
+    ret
+ENDP
+
 PROC
 INCLUDE "clear.asm"
 ENDP