Re: [stella] reset vectors

Subject: Re: [stella] reset vectors
From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 12 May 1998 16:52:27 +0200
At 13:16 12.05.98 +1000, you wrote:
>I haven't seen it in the SPG, I'm wondering just what the 6502 reset vectors
>should look like.  I note that the Playfield demo only includes two vectors,
>yet I seem to recall three - NMI, IRQ, RESET.  I imagine that the IRQ
>doesn't exist on the 2600 - am I right?  That would explain the need for
>only two - yet other code I've seen uses three.

The 6507 is pretty much the same as a 6502, except that it is
missing three address lines and it has no interrupt line. 
Therefore, there is no need to set the IRQ vector in VCS programs.

>One thing that is troubling me is that, having downloaded the stella 2600
>emulator for the PC, I find that my demo - and several other programs from
>this list - do not seem to work.  I imagine this is due to poor
>initialisation (?) but at this stage I'm in the dark.  It appears that the
>Playfield demo doesn't work, either (or I've hacked it so it doesn't)
>Can anybody help me out?

The Stella emulator contains a list of most available BINs
with the corresponding settings, like the bankswitching method.
It calculates a checksum over parts of the BIN file to see
which program is which. Unfortunately smaller programs, with
only very little code, all result in the same checksum, so
the emulator might use the wrong BS method or something. To
avoid this, you can edit the STELLA.VCS file, which lets you
set the settings for programs, that will be recognized by
name and not by checksum. Luckily Bradford has promised to
fix this in the next release.


Ciao, Eckhard Stolberg



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