Re: vcs.h (was: Re: [stella] redline problem OK...THANKS!!!!)

Subject: Re: vcs.h (was: Re: [stella] redline problem OK...THANKS!!!!)
From: Chris Wilkson <ecwilkso@xxxxxxx>
Date: Wed, 10 Jul 2002 11:12:47 -0400 (EDT)
On Wed, 10 Jul 2002, Manuel Polik wrote:

> >I'm missing a few timer registers, e.g. some of the disassembled games I
> >saw are using $285 (I call it TIMINT) instead of INTIM.
> And how would DiStella call it?

The following is taken from the memory maps I created.  The full maps can
be found at http://web/ecwilkso/www/VCS_hardware

$0284 = (RIOT $06) - INTIM (read), edge detect control (write)
$0285 = (RIOT $05) - read interrupt flag (read), edge detect control (write)

PA7 of the RIOT can be used to generate an interrupt.  Unfortunately, the
6507 has no interrupt inputs.  So the /INT pin of the RIOT is left unconnected.
But an internal flag is still generated and can be read and cleared normally.
I haven't thought of a specific use for it yet, but I'm sure *someone* would
like to know that player 0 moved the joystick to the right (or stopped) or
pressed the paddle 0 button (or stopped) since the last check.

Maybe we can call address $285 "INTFLG"?


Archives (includes files) at
Unsub & more at

Current Thread