> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf
> Of Lennart Augustsson
> Sent: Monday, April 24, 2000 12:48 PM
> To: Brad Hards
> Cc: [EMAIL PROTECTED]
> Subject: Re: [linux-usb] more than 7 ports on a hub?
>
>
> Brad Hards wrote:
>
> > As a secondary issue, would / should this count as two hubs in the
> > maximum topology depth? And can anyone provide a reference for why five
> > is the maximum depth - a quick scan of the USB spec only came up with
> > section 6.4.4 which talks about excessive depth, but doesn't say what is
> > excessive.
>
> Well, the number 5 is in there somewhere.
I'm not sure, but I think I read in my Hub-Documentation somethink about
7?!?
>
> > I thought that it was driven by timing and the 5 metre
> > cables, but that wouldn't seem to apply in this case.
>
> It's mostly driven by the hub timing. With maximum length cables
> and maximum
> hub depth there are only a few nanoseconds to spare in the worst case.
> A design where two hubs are on the same PCB would safe the cable
> propagation
> delay, but this would not be enough for another hub (I've not
> checked the figures,
> I must admit).
> I just had a similar problem with the D-link serial adapter. It
> has a hub in it, with
> just one of the ports used for the actual serial adapter. The
> design is a mystery to me
> since the other ports are unused.
>
>
> --
>
> -- Lennart
>
>
>
>
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