[atari7800] Re: Paddle controllers??

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On Sat, 19 Feb 2005, Dennis Debro wrote:
> > Are we talking about timing problems during video DMA from the maria?
> 
> That's what I was thinking. I re-read the programming doc again and it
> states that no time would be stolen when a DLI occurred. Is this true? What
> if the DLI lasts too long? Wouldn't this affect the next line?

I wasn't really concerned with the stack at all.

I'm not really a 7800 programmer (heck I barely hold my own on the 2600)
but here's how I _think_ it works on the 2600.

You discharge a capacitor, then measure the amount of time it takes
for them to charge back up again.  This time varies with the variable
resistance of the pot (potentiometer in the paddle controller).

If the MARIA is constantly and randomly halting the CPU to do video DMA,
there's no way the CPU can keep accurate time to determine the paddle
position.

- -- 
adam@xxxxxxxxxxxxxxxx        http://cuddlepuddle.org/~adam
KG6GZR                       http://cuddlepuddle.org/~adam/resume.html

"Feminist?  Why would I want to alienate half the population?  I'm an 
egalitarian."

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