RE: [stella] 6502 question (was INV+ ... )

Subject: RE: [stella] 6502 question (was INV+ ... )
From: "Lee Fastenau" <stella@xxxxxxxxxxxxxxx>
Date: Wed, 7 Apr 2004 12:31:10 -0500
> Yeah.  Not only would it fail to position the players (since it
> doesn't write to RESPx), it would read from the collision
> registers, including the undefined lower bits, to use as the
> return address for the RTS.  And if the topmost bit of the
> collision register is 0, the PC won't even be pointing to ROM.

Why would the RTS read from the collision registers after a JSR that writes
to RESPx?  The Reset registers don't share memory locations with any other
registers... at least not as far as vcs.h is concerned, so reading from them
would yield totally unexpected results.  Or so I would think.

Is this another undocumented feature (of thousands) of TIA?

> If anyone can make use of *that*, I'll buy a cartridge and eat it. :)

(Stares at discarded gauntlet sitting near Erik's feet.)

> Thanks to everyone for the help and suggestions on the issue :)

Thanks for yet another enlightening thread.

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