Mike,

You should have sent your question to the list, that way 2000+ people get to
learn something!

You should check the spec yourself.

As to the slow speed thing, I did say IIRC, so that indicates I am not 100%
sure (just 95+%).

Not sure why the requirement, but I do remember being surprised by it.

Now that I think of it, maybe it was to limit the _maximum_ length to the
length of the captive cable. The signaling schemes for low-speed and
full-speed are quite different.

I do know that I was surprised myself.

Bob Ammerman
RAm Systems

----- Original Message -----
From: "Michael Kinsner" <kinsnemh@mcmaster.ca>
To: "Bob Ammerman" <rammerman@ADELPHIA.NET>
Sent: Thursday, June 26, 2003 12:07 AM
Subject: Piclist post question


> Hello,
>
> I saw your recent post on the Piclist, and out of interest was wondering
> why you mentioned that slower speed signals would require a minimum
> cable length.  Reflections could be a problem with stability in very
> high speed signals, but with lower speed signals, it isn't clear to me
> why a minimum transmission line length is significant.
>
> To be clear, I'm certainly not suggesting that what you say is
> incorrect.  I'm just wondering if you recall the reason, as it would be
> interesting to know.
>
> Thanks,
> Mike Kinsner
>
>
>
>
>  >The USB standard was defined so that "If you can hook it up, it will
> work".
>  >
>  >That is the reason that an Male A to Male B cable is the only allowed
>  >configuration.
>  >
>  >Also, Female A/Male A and Female B/Male B are 'illegal' because they
> can be
>  >used to create connections that are too long.
>  >
>  >Also, IIRC low speed devices are supposed to have a captive cable
because
>  >low speed requires a minimum cable length.
>  >
>  >Bob Ammerman
>  >RAm Systems
>
>
>
>

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