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From: Andrew Smallshaw <andrews@sdf.org>
Newsgroups: sci.electronics.repair
Subject: Re: Re (2): USB functionality.
Date: Tue, 19 Mar 2024 17:59:20 -0000 (UTC)
Organization: A noiseless patient Spider
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On 2024-03-13, Dan Purgert <dan@djph.net> wrote:
> On 2024-03-12, Roger Hayter wrote:
>> On 12 Mar 2024 at 19:27:04 GMT, "Dan Purgert" <dan@djph.net> wrote:
>>> 
>>> There's only one set of pins (well, two sets if you count USB2 / USB3 --
>>> but you can only use one set at a time).
>>> 
>>> USB2 -> D+/D- (Bi-directional / Half Duplex)
>>> USB3 -> TX1+/TX1- and RX2+/RX2- (optionally Full Duplex, IIRC)
>>> 
>>> As I recall the "Tx" pair is "Host Transmit to Peripheral", and "Rx" is
>>> "Host Receive from Peripheral", but it's been a while since I read up on
>>> the USB3 / USB-C implementations.
>>
>> Usbc seems to have about 20 pins, that's why I asked.
>
> Yeah, that's just to allow the connector to be flipped over, and still
> connect to the host / peripheral.  The host/peripheral ports themselves
> only have one orientation.

USB-C supports SuperSpeed which uses two additional pairs on top
of USB2 and also allows for full-duplex.  That is what the additional
contacts on a USB3 A plug are for.

-- 
Andrew Smallshaw
andrews@sdf.org