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From: arc@leland.Stanford.EDU (Andrew Richard Conway)
Subject: Re: Pulse Width Modulation
Message-ID: <1993Nov3.221740.7663@leland.Stanford.EDU>
Sender: news@leland.Stanford.EDU (Mr News)
Organization: DSG, Stanford University, CA 94305, USA
References: <wgpp3ee00iV1AIDy5z@andrew.cmu.edu>
Date: Wed, 3 Nov 93 22:17:40 GMT
Lines: 25

Christopher Kristof <ck3i+@andrew.cmu.edu> writes:
>    I'm looking for a chip to do pulse width modulation.  I'd like
>something that is easily interfacable to an HC11 and which requires a
>minimum of extra parts.  Also, the ability to do more than 1 channel per
>chip would be great.  Can anyone recommend a chip?  I was given the
>number of a Nat'l Semiconductor part (LM3524N-ND / LM3524DN-ND) but know
>nothing else about it.  Information on it would also be appreciated.

A 68HC11 can do 4 PWM channels itself very easily using its timers.
(and also have 4 PWM inputs). If you want slow PWM (eg for motors)
rather than high speed (eg for servos), you could get a basically
unlimited number with clever use of one timer channel. (Ie, use lots
of output lines. Use one timer to interrupt when you need to change
state. It will be a little late. _Store_ this lateness, and use it
to compensate for next time, and on average you will be fine. You
should be able to do this fast enough that averaging will be fine).

					Andrew.



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Andrew Conway    arc@leland.stanford.edu  Phone: USA 415 497 1094

