Re: 1351 mouse

From: Hársfalvi Levente (
Date: 2002-02-11 11:57:31

Hi Nick!, wrote:

> Whilst the 5717 chip is waiting to read the "sync" going low, what is it
> doing with the line that is connect to the same POTX via the resistor? Is it
> being driven low, hi or held in the MOS equivalent of O/C?

I couldn't measure this myself since I never had a 1351 (Frank Kontros
did some measurements for me instead :-) ). The patent document must
have had something about this.

(As I noticed, Delphion has dropped providing free download service, so
the 1351 patents aren't freely available anymore :-/. I have the patents
somewhere -- I've saved them onto a CD, should I post them tomorrow?).

I'd say the outputs are left floating.

At the end of the 512 cycles long process, in cycle #480, the 5717 stops
driving both POT outputs (I clearly remember this, I even noted it
somewhere in the mouse interface document). Will it sometimes still
drive the outputs? I don't know but the patent didn't mention anything
like that.

(I'm sure you're thinking about the first startup of the circuit -- how
on Earth will the process start, if the POT line is constantly at low
level -- or, how will it rise to +5v if nothing pulls it up. I don't
know. I remember setting both POT outputs to drive the lines in my
design, to ensure startup).

Best regards,


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