What about 100base/T? Same wiring?

Steve Keller


-----Original Message-----
From:   pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU] On
Behalf Of Ake Hedman, eurosource
Sent:   Tuesday, October 13, 1998 2:00 PM
To:     PICLIST@MITVMA.MIT.EDU
Subject:        Re: [OT] Ethernet electrical characteristics

While on it. What does it mean (Electrically) when the link lamp comes on?
Is there any cheap circuits available to support Ethernet in embedded
systems?

/Ake

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Lee Jones
> Sent: Tuesday, October 13, 1998 8:41 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [OT] Ethernet electrical characteristics
>
>
> > Does anybody know what the electrical characteristics of
> > Ethernet (10base-T) are?  I'm using an RJ-45 plug in my PIC
> > device because I need 7 conductors and they're cheap and
> > durable, and I want to choose which wires go to what such
> > that if Mr. Curious plugs an ethernet network into my box
> > it won't let the magic smoke out.
>
> I don't have the exact specs handy.  You can get it from
> IEEE under the 802.3 series.
>
> > I found a cabling diagram that tells me which pins carry data,
> > but I have no idea what the voltages are.
>
> Each pair (TX, RX) uses differential signaling of about +/- 5V.
>
> Transmit (TX, pins 1 & 2) is transmitting from a remote station
> to a hub.  Receive pair (RX, pins 3 & 6) is transmitting from a
> hub to a remote station.
>
> So if you think your PIC device looks like a hub, expect to
> see voltage on pins 1 & 2.  If your PIC device looks like a
> desktop unit (where someone will cable it up to a hub), you
> can expect to see voltage on pins 3 & 6.
>
> > It also seems there should be a signal ground and perhaps a
> > power pin in there somewhere, but the cabling diagram showed
> > only 4 data signals (Tx +/- and Rx +/-).
>
> No signal ground.  No power.  10base-T only used 4 lines for
> differential signaling; pins 1, 2, 3, & 6.  Sometimes 10base-T
> patch cables are made with only 4 wires; they work fine.
>
> Enclosed below is an ASCII art drawing of 10base-T UTP wiring.
>
>                                                 Lee Jones
>
>
>
> 10base-T wiring on RJ-45 jacks/plugs (view with monospaced font)
> ====================================
>
>                     RJ-45 jack
>         ,---------------------------------,
>         !  V   V   V   V   V   V   V   V  !
>         !                                 !
>         !  1   2   3   4   5   6   7   8  !
>         !                                 !
>         !                                 !
>         !                                 !
>         !                                 !
>         '---------,            ,----------'
>                   !            !
>                   '------------'
>
>
>                RJ-45 plug (top view)
>         ,---------------------------------,
>         !                                 !
>         !  !   !   !   !   !   !   !   !  !
>         !  !   !   !   !   !   !   !   !  !
>         !  !   !   !   !   !   !   !   !  !
>         !  !   !   !   !   !   !   !   !  !
>         !  !   !   !   !   !   !   !   !  !
>         !  !   !   !   !   !   !   !   !  !
>         !                                 !
>         !  1   2   3   4   5   6   7   8  !
>         !                                 !
>         ! TX+ TX- RX+         RX-         !
>         !                                 !
>         !                                 !
>         !                                 !
>         !                                 !
>         !                                 !
>         '---------------------------------'
>                  !               !
>                  !     cable     !
>                  !               !
>                  !               !
>                  !               !
>                  !               !
>
>
> 10base-T is predicated on the use of twisted pairs (i.e. UTP or
> unshielded twisted pair) in the cable.  Pins 1 & 2 must be a pair.
> Pins 3 & 6 must be a pair.  Normal color coding is:
>
>      pin  EIA T568A      EIA T568B
>      1    white/green    white/orange
>      2    green/white    orange/white
>      3    white/orange   white/green
>      4    blue/white     blue/white
>      5    white/blue     white/blue
>      6    orange/whit    green/white
>      7    white/brown    white/brown
>      8    brown/white    brown/white
>
>
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> Jones Computer Communications             lee@frumble.claremont.edu
> 509 Black Hills Dr, Claremont, CA 91711         voice: 909-621-9008
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