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Message
From: tomko81@h...
Date: Fri, 7 Nov 2003 04:17:39 +0100
Subject: [usb] question on the PHY with transciever
Dear Rudolf,
1. In the truth table of the datasheet of PDIUSBP11 , it like this one:
----------------
VP, VM => Result
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0, 0 => SE0
0, 1 => Low Speed (1.5Mb/s)
1, 0 => High Speed (12Mb/s)
1, 1 => Error
----------------
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?
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.
Actually the sync packet we recieve should be "01010100"
or "10101011" for full speed mode?
Can Rudolf or any other people can give me an answer to this?
Thank you very much for your kindly help
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