Re: [stella] Weird timing bug, I!

Subject: Re: [stella] Weird timing bug, I!
From: Thomas Jentzsch <tjentzsch@xxxxxx>
Date: Sat, 20 Apr 2002 19:58:38 +0200
At 20.04.2002, 19:11, Adam Thornton wrote:
> And I ran to plug it in...and....

> The text is unreadable.  It's doing this weird sort of
> horizontal-wrapping thing, and some text is appearing in the overscan
> area, and in general it looks like I'm just taking too many cycles per
> scan line.  And the colors are weird and fadey.

I don't know why it works on SC, but I think there is a problem with
VSYNC. Your code (@Manuel: availabe at AtariAge :-) looks like this:

    lda #2          ;bit 1 needs to be 1 to start retrace
    sta VSYNC       ;start retrace
    sta WSYNC       ;wait a few lines
    sta WSYNC
    lda #44         ;prepare timer to exit blank period
    sta TIM64T      ;turn it on
    sta WSYNC       ;wait one more
    sta VSYNC       ;done with retrace, write 0 to bit 1

The problem might be, that you don't do 3 full lines of VSYNC. The first
WSYNC happens (according to z26) after about 1/3 of the line. Then you
are doing two more WSYNCs. So you only do 2 2/3 lines of VSYNC, but you
should do at least 3 full lines. Adding one more WSYNC might solve that
problem. But I'm not 100% sure.

Did you change that part of code or is that original Dark Mage code? If
it's original code, then does Dark Mage work on your TV?

Have fun!
Thomas Jentzsch         | *** Every bit is sacred ! ***
tjentzsch at web dot de |

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