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From: Ted Dennison <dennison@telepath.com>
Newsgroups: comp.lang.ada
Subject: Re: Using "delay until" in real-time
Date: Tue, 12 Dec 2000 20:54:32 GMT
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In article <yec3dfttmnd.fsf@king.cts.com>,
  Keith Thompson <kst@cts.com> wrote:
> Ted Dennison <dennison@telepath.com> writes:
> The value 1.0/60.0 is still not exactly representable; it's going to
> be either 0.166666666 or 0.166666667.

Right, that's the issue. The resolution just dictates how often we get
hosed. We don't want to get hosed at all.

> Is the scheduler intended to be portable?  If the design of the
> scheduler depends on the underlying 240Hz clock tick, perhaps you
> should just bite the bullet and delay for 4 ticks.

It is portable right now. The only system dependancy is that the
executive's clock rate be achieveable exactly. On the OS we are using
(vxWorks) that can be set via a script or compiled into the kernel. I
see no good reason to make it non-portable if I don't have to.

I'm trying out the cycle-counting solution right now. If anyone has any
better ideas, I'd still like to hear them.

--
T.E.D.

http://www.telepath.com/~dennison/Ted/TED.html


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