avoid graphics glitch

1 files changed, 12 insertions, 0 deletions

diff --git a/newtitle.s b/newtitle.s
index d62a40a..ae54481 100644
--- a/newtitle.s
+++ b/newtitle.s
@@ -28,6 +28,9 @@ start:
  lda #0
  sta SDMCTL
 
+ ; wait for the next frame, to avoid graphics glitching
+ jsr wait1jiffy
+
  ; setup our display list
  lda SDLSTL
  sta FR0
@@ -64,12 +67,21 @@ wait4key:
  lda FR0+1
  sta SDLSTH
 
+ jsr wait1jiffy
+
  ; switch to normal playfield, enable screen
  lda #$22
  sta SDMCTL
 
  rts ; return to DOS
 
+wait1jiffy:
+ lda RTCLOK+2
+wait:
+ cmp RTCLOK+2
+ beq wait
+ rts
+
  ; display list here
 dlist:
  .byte $70 ; 24 scanlines of blanks