At 12:51 11.03.98 -0800, you wrote:
>> Eckhard:
>> Should this bit of code pretty much be mandatory in
>> all games we work on? And could you please explain
>> a little more about what you mean 'the signal might
>> get too weak'? This sounds very strange to me...
>> how does hitting the register more often 'strengthen'
>> the signal?
The STA VBLANK would of course better be positioned at the
end of the display kernel, if it remains turned on until
the start of the display kernel, but the rest of this code
should be used by everyone. All games, that produce rolling
pictures on my TV access the TIA or the RIOT during VSYNC
time. Since taking this code out of the sync routine would
only cost a couple of cycles, I would suggest using the
save sync routine.
If you look at the code again, you will notice, that the only
register, that I access several times in a row is WSYNC. This
only halts the processor until the next scanline starts. That
way the TIA will not do anything besides producing the sync signal.
>Robin,
>
>The video signals produced by the TIA are digital, but these are passed
>through an RC network to produce the analog signal which eventually
>goes to the tv. The issue that Eckhard mentions could be due to a
>lack of current drive ability inside the TIA. If you try to do too
>many things at once, there may not be enough current to properly drive
>the RC network, and your analog voltages will suffer...possibly to the
>point of being unusable.
>
>Does this sound right, Eckhard?
I don't know that much about TV electronics. I was just guessing
about the weak sync signal. But your explanation would at least
fit my experiance with games, that produce rolling pictures.
Ciao, Eckhard Stolberg
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