X-Git-Url: http://git.joshuawise.com/fpgaboy.git/blobdiff_plain/f6fa1d6e1393de5d18302b8674ed1616afdfcefb..39a68cde9f2a76dabfcc9d7654f212ad1d7b356a:/diag.asm

diff --git a/diag.asm b/diag.asm
index 8e09874..7f06de0 100644
--- 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