In addition to the Power Up Diagnostics use of oversized packets
(to detect hardware faults) I/A uses them to download display
files to WP20/3-'s and for Uploads of station images after a
crash (which of course doesn't happen any more :-) ).
warren
>From: "Fred" <[EMAIL PROTECTED]>
>Reply-To: "Foxboro DCS Mail List" <[EMAIL PROTECTED]>
>To: "Foxboro DCS Mail List" <[EMAIL PROTECTED]>
>Subject: Re: NodeBus versus Ethernet
>Date: Fri, 18 May 2001 19:19:59 -0400
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>I believe that the only packets that are greater than the 1536 size (with I
>think is a standard), that I know of have to do with support of diskless
>workstations (WP20 and WP30).
>
>
>----- Original Message -----
>From: James Kahlden <[EMAIL PROTECTED]>
>To: <[EMAIL PROTECTED]>
>Sent: Tuesday, May 15, 2001 3:39 PM
>Subject: Re: NodeBus versus Ethernet
>
>
>I recently attended user group meeting where Craig Ouellette of Foxboro TAC
>spoke to us about nodebus communications. The following is what Craig had
>to say about the nodebus.
>
>"The I/A Nodebus uses redundant cable communications based on the IEEE
>802.3
>standard. Electrically the polarity is reversed from standard Ethernet.
>The characteristic impedance is about 47 ohms instead of 50 ohms. Some of
>the diagnostic messages have larger than standard packet lengths, but
>otherwise it follows Ethernet rules."
>
>Hope this helps.
>
>Jim Kahlden
>[EMAIL PROTECTED]
>
>
> >>> [EMAIL PROTECTED] 05/15/01 12:30PM >>>
>
>
>From: Timothy A. Ruhland
>
>My understanding is that Foxboro reversed the "sense" on the Nodebus, i.e.
>0s are 1s and 1s are 0s, or something like that (AJ will give us the
>straight poop I am sure) to make it so you could not connect a standard
>ethernet device to your nodebus. Given that the nodebus evolved in the late
>80s, this was a very reasonable thing for them to do (IMHO). After all, can
>you imagine the mess if you just used standard out of the box ethernet and
>then had customers plugging any old box onto their nodebus?
>
>
>
>
>
>Corey R Clingo <[EMAIL PROTECTED]> on 05/15/2001 01:40:30 PM
>
>Please respond to "Foxboro DCS Mail List"
> <[EMAIL PROTECTED]>
>
>To: Foxboro DCS Mail List <[EMAIL PROTECTED]>
>cc: (bcc: Timothy A. Ruhland/506538/EKC)
>Subject: Re: NodeBus versus Ethernet
>
>
>
>
>The DNBI/DNBT, among other things, handles the switching between the
>redundant
>nodebus segments. Your DNBI/DNBT actually connects to the AW/WP via an
>ethernet
>card (the DNBI also uses a serial port, I presume for the switching and
>other
>types of data; the DNBT does it all "in-band" over the ethernet
>connection).
>The packets going out le0/hme0 on the AW/WP, through the DNBI/DNBT, and out
>on
>the nodebus, probably conform to 802.3.
>
>Actually, 802.3 is an old standard in itself. It is not used any more on
>modern
>networks, because IIRC, it doesn't allow multiple protocols (e.g., IP and
>IPX)
>to traverse the wire simultaneously. This is not an issue with the
>nodebus,
>obviously.
>
>Corey Clingo
>Sr. Engineer
>BASF Corporation
>
>
>Hi All,
>
>In all Foxboro documentation, there is a differentiation between Ethernet
>and
>NodeBus. However, Foxboro states clearly that NodeBus is according to IEEE
>802.3
>standard. This implies that you can connect AW or WP directly through an
>Ethernet card. so, why using DNBI !!!!. the only difference between old
>Ethernet
>and IEEE 802.3 standard I know is in the "type" field in the frame
>structure and
>all new Ethernet cards are according to IEEE 802.3 Standard. So, what is
>realy
>the difference??.
>
>Regards
>Ashraf Tantawy
>
>
>
>
>
>
>
>
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