Re: [stella] supercharger good; busted code bad

Subject: Re: [stella] supercharger good; busted code bad
From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx>
Date: Sun, 14 Jul 2002 14:29:52 +0200
> One last mystery though...
> my Sprites are refelcted opposite on the 2600  relative to
> all 3 emus!  the code below is 'correct' on the supercharged
> atari, backwards everywhere else...

I think Nicolás is right. You seem to have forgotten the #
in front of your binary constants that you put into REFP0
and REFP1. One question though: are you by any chance using
your Supercharger in an Atari 7800 console?

The reason I'm asking is because if that were the case, it
would explain the different behaviour between the emulators
and your console. For the TIA read registers (which you are
reading from, if you leave out the #) only the two topmost
bits are defined. For the other six bits the programmers
guide doesn't give a defined state. On a 2600 these bits will
stay at whatever data has been on the data bus last. Since
this usually is the address byte of the register, the results
are the same for the lower six bits between reading $01 and
reading #$01. On the 7800 Atari changed the state of the undefined
bits. They now seem to always be zero. This is why your code fails
on your Supercharger.

> How foolish will I sound if I say "there's a dasm manual?"

Yes there is. But I think it was only included with the
DASM source code distribution. So you'd need to find a copy
of that, if you want to have a look at the manual.

Ciao, Eckhard Stolberg

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