Video RAM cut 1 -- on distributed ram
[fpgaboy.git] / diag.asm
index 8e09874..7f06de0 100644 (file)
--- a/diag.asm
+++ b/diag.asm
@@ -32,6 +32,8 @@ main:
        
        ld hl, signon
        call puts
+
+       call putscreen
        
        ei
 
@@ -48,6 +50,25 @@ main:
 signon:
        db $0D,$0A,$1B,"[1mFPGABoy Diagnostic ROM",$1B,"[0m",$0D,$0A,0
 
+putscreen:
+       ld a, $FF               ; Copy two tiles.
+       ld hl, $8000
+       ld [hli], a
+       ld [hli], a
+       xor a
+       ld [hli], a
+       ld [hli], a
+       
+       ld hl, $9800
+.loop: ld a, $FF
+       ld [hli], a
+       xor a
+       ld [hli], a
+       ld a, h
+       cp $9C
+       jp nz,.loop
+       ret
+
 vbl:
        PUSH AF
        PUSH BC
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