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

Subject: Re: [stella] the B. Watson's problem...
From: Chris Wilkson <ecwilkso@xxxxxxx>
Date: Thu, 23 Aug 2001 12:45:09 -0400 (EDT)
On Thu, 23 Aug 2001, Eckhard Stolberg wrote:

> On a note to Chris:
> are you sure that your RIOT map is correct. I have a data sheet
> for it that says that reading from address $294 (RS-, A$, A2, R/W = 1,
> A0 = 0) would get you the timer overflow register. I'm not quite sure
> what it does, and I'm not sure if the VCS really has it, though.


According to my databook (Rockwell, 1985) it is correct.

Before the timer has expired, INTIM holds the current value of the timer.
After the timer expires, INTIM decrements once per clock cycle, regardless
of if you're using TIM1T, TIM8T, TIM64T, or TIM1024T.  This auto decrement
allows you to know how many clock cycles have passed since the timer expired.
That is what is meant my "overflow register".  This is in fact the way the
VCS works.

Can you post the relevant section of my map, just so I'm sure of what you're
referring to?

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