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Message
From: Rudolf Usselmann <rudi@a...>
Date: Fri, 07 Nov 2003 12:12:37 +0700
Subject: Re: [usb] question on the PHY with transciever
On Fri, 2003-11-07 at 10:17, tomko81@h... wrote:
> Dear Rudolf,
>
> 1. In the truth table of the datasheet of PDIUSBP11 , it like this one:
> ----------------
> VP, VM => Result
> ----------------
> 0, 0 => SE0
> 0, 1 => Low Speed (1.5Mb/s)
> 1, 0 => High Speed (12Mb/s)
> 1, 1 => Error
> ----------------
Read the text that is above the table in the Philips specification.
Or better yet study the USB specification from www.usb.org in great
detail. I think the Philips spec is somewhat confusing.
(Also when you copy text you should copy it carefully, there is
no "high speed" mode in the Philips transceiver, nor in my PHY).
> It is mean that when the USB are working in a High Speed mode, VP and
> VM will keep unchange to '1' and '0' no matter the transmitting data are
> logic '1' or logic '0'. Can i deduce the data from VP and VM pin?
> If yes , why do we still need a RCV pin ?
> If no , according to the PHY core, you are checking the sync packet by
> watching the signal rxdp(VP) and rxdn(VM), why don't you check it with
> rxd (RCV) signal?
because rxd can only detect two levels: '0' or '1', whereas using
dp and dn I can also detect 'se0'. If I detect se0 I must abort
syncing, in that case neither 'k' or 'j' will be active.
>
> So from this it can be seen that VP and VM are used to tell the physical
> layer what speed the device is. This is my understanding. I could be
> wrong.
Thats ONE of many uses.
> Actually the sync packet we recieve should be "01010100"
> or "10101011" for full speed mode?
Read the USB spec ...
> Can Rudolf or any other people can give me an answer to this?
> Thank you very much for your kindly help
> --
Regards,
rudi
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