TSC , 8254, and such

["daniel sheltraw" <l5gibson@hotmail.com>]

Paolo

Let me see if I got oneshot mode straight. Does it go something like this:

set up one-shot mode for 8254

loop
  get time from TSC
  compute time until next oneshot task scheduled
  program 8254 with this time
  {which generates interrupt from counter 0 after count down}
end loop

Q: What if the time computed until next task is greater than 2^16/frequency 
(8254 hits turns over)? Who is that interval timed?



>From: Paolo Mantegazza <mantegazza@aero.polimi.it>
>To: daniel sheltraw <l5gibson@hotmail.com>, rtl@rtlinux.org
>Subject: Re: [rtl] TSC and 8254 interaction
>Date: Mon, 10 Jul 2000 19:43:28 +0200
>
>daniel sheltraw wrote:
> >
> > Sorry Paolo
> >
> > I still do not understand the interaction between the TSC and 8254 for
> > oneshot scheduling. Is there any documentation on this (besides the 
>source)?
>
>To program a oneshot you need a time base to decide the next time to be
>interrupted, that's the TSC, and a device to interrupt after the next
>shot is expired, under UP that's the 8254.
>
>Since there are not many ways to do such a thing, tell me how you would
>program it and I'll place TSC and 8254 in due places, for you. Maybe in
>that way you'll understand.
>
>Ciao, Paolo.

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