RE: [stella] the B. Watson's problem...

Subject: RE: [stella] the B. Watson's problem...
From: Nicolás Olhaberry <nolh@xxxxxxxxxxxxx>
Date: Mon, 23 Aug 1993 20:33:27 -0300
----- Original Message -----
From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxx>
To: <stella@xxxxxxxxxxx>
Sent: Tuesday, August 21, 2001 3:50 PM
Subject: Re: [stella] the B. Watson's problem...

> For TIM64T and TIM1T it should be the same as INTIM. For TIM8T and
> TIM1024T you would be reading the 'timer overflow register'. I'm
> not quite sure what it does, but I think it counts how ofter the
> timer has gone from $00 to $FF.

    I see. Has anybody posted on this list all the 6532 PIA registers and
their addresses?

> $29D and $29E are TIM8T and TIM64T with interrupt enabled. The
> 6507 processor in the VCS can't handle interrupts, so this isn't
> really much different from the normal timer registers. However,
> since the RIOT keeps the interrupt flag in an extra register
> $285, I think), you might be able to do a wait for timer loop
> with a BIT instruction, since the timer interrupt flag is at D7.

    Mmm... Could you explain that again? I don´t think that I understood it.
I always thought that $285 was a timer mirror, look what Dragon fire does:

   12DB  2C8502              BIT $0285
   12DE  10FB                  BPL $12DB

> BTW, where did you find these addresses? Are you currently
> working on a disassembly of a VCS game?

   No, I had been working on a VCS emulator for some time, so I had seen a
lot   of strange memory accesses ;-)

   $2A2 is accessed by Marine wars, $29D and $29E by Starfox, but I´ve never
took the time to disassemble them. I can´t get a stable screen with those
games, so I probably will...



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