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

Subject: Re: [stella] the B. Watson's problem...
From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx>
Date: Fri, 24 Aug 2001 16:34:41 +0200
> 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
> That is what is meant my "overflow register".  This is in fact the way the
> VCS works.

I think you are right. I must have misunderstood that. It's
just that the 6532 information, I have, lists different addresses
for reading the timer, the timer overflow and the timer interrupt.
But I ran a little test program with these addresses and I was
only able to get the timer overflow and the timer interrupt, so
you must be right about the overflow. The address they gave for
reading the timer only got me the interrupt register. Maybe I just
mixed up the bits when I tried to transfer their address information
to the VCS.

According to the data sheet:

read and clear interrupt flag: RS-, R/W, A2, A0 = 1

read interval timer: RS-, A4, A2, R/W, A0 = 1

read interval timer overflow: RS-, A4, A2, R/W = 1; A0 = 0

RS- = pin 36
R/W = pin 35
A4 = 3
A2 = 5
A0 = 7

Ciao, Eckhard Stolberg

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