Re: [stella] Platform Game - VSYNC

Subject: Re: [stella] Platform Game - VSYNC
From: Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx (Eckhard Stolberg)
Date: Sat, 11 Oct 1997 14:23:19 +0200
>start_vblank        subroutine
>    ldy    #$02
>    lda    #$00
>    sty    WSYNC
>    sty    VSYNC
>    sty    WSYNC
>    sty    WSYNC
>    sty    WSYNC
>    sta    VSYNC
>    sty    VBLANK
>Which is correct, yes?  What else makes the picture roll?  I know that the
>frame is a few lines to tall - but this wouldn't matter on a PAL television
>would it?

It is almost correct. It seems, that the display has to be turned off
during vsync, for my TV to sync correctely. Therefore you should put
the 'sty VBLANK' after the 'lda #$00'.

I have tried that with your program and it syncronised fine on my TV.

Unfortunately your program seems to gain a scanline in some scrolling
positions. If you do an odd number of lines on PAL systems, the TV
looses the colour information completely. I haven't checked this, but
do you do a 'sta WSYNC' between the last kernel line and the line,
where you setup the timer for overscan? When my programs show this 
problem, it is because I forgot the WSYNC, most of the time.

Ciao, Eckhrd Stolberg

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