How to implement TDR in software?
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Posted by Dmitri(Cabling-Design.com on August 31, 2005, 6:07 pm
Please log in for more thread options NANewbie wrote: > Does a standard NIC allow itself to be configured to send an electrical
> signal down a cable? Is there a standard way to trigger an NIC > (regardless of brand) to send a signal? I was thinking, if it's > possible > to write a program to achieve 1) and it's guaranteed that the signal > would > get reflected either at a fault or end of cable, then the rest would > not > be a problem. Well, not a *REGULAR* 10/100 Ethernet NIC card. It sends signal down one pair and receives it from another. So, you are so out of luck if you would have tried to implement it on a *regular* NIC. In any case, I seriously doubt you will have access to such low level of programming on the chipset. Gigabit NICs are different: they transmit and receive on the same pair (all four of them). As such, they are much better suited for experiments like that (Marvell chipset is one example) although I have a feeling that you still can't get thru to such low level programming on any chipset that's other than the elusive Marvell Alaska. -- Dmitri Abaimov, RCDD http://www.cabling-design.com Cabling Forum, color codes, pinouts and other useful resources for premises cabling users and pros http://www.cabling-design.com/homecabling Residential Cabling Guide ------------------------------------- ##-----------------------------------------------## Article posted with Cabling-Design.com Newsgroup Archive http://www.cabling-design.com/forums no-spam read and post WWW interface to your favorite newsgroup - comp.dcom.cabling - 2381 messages and counting! ##-----------------------------------------------## | |||||||||||||||||||||||||||||||||||||
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Posted by Mark Evans on September 9, 2005, 9:30 am
Please log in for more thread options > NANewbie wrote:
> > As we know the whole TDR concept involves 1) sending a signal down a
> > cable, 2) waiting for its return, > > 3) taking the time difference, 4) and calculating the distance. > > Does a standard NIC allow itself to be configured to send an electrical
> > signal down a cable? Is there a standard way to trigger an NIC > > (regardless of brand) to send a signal? I was thinking, if it's > > possible > > to write a program to achieve 1) and it's guaranteed that the signal > > would > > get reflected either at a fault or end of cable, then the rest would > > not > > be a problem. > Well, not a *REGULAR* 10/100 Ethernet NIC card. It sends signal down one
> pair and receives it from another. So, you are so out of luck if you would > have tried to implement it on a *regular* NIC. In any case, I seriously I'm aware of at least one 10M chipset which supported such a feature. > doubt you will have access to such low level of programming on the chipset.
> Gigabit NICs are different: they transmit and receive on the same pair
> (all four of them). As such, they are much better suited for experiments > like that (Marvell chipset is one example) although I have a feeling that > you still can't get thru to such low level programming on any chipset > that's other than the elusive Marvell Alaska. You would need the data *book* for starters. As well as knowing how the chipset is plugged into the BUS. This is really a driver programming issue. -- Mark Evans St. Peter's CofE Aided School Phone: +44 1392 204764 X109 Fax: +44 1392 204763 | |||||||||||||||||||||||||||||||||||||
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Posted by Mark Evans on September 9, 2005, 9:24 am
Please log in for more thread options
> Hi!
> I wonder if anyone can help me understand something. I've just read the
> whitepaper about the VCT Technology by Marvell and the TDR technique used. > I was just wondering, how did they implemented TDR in software? Did they > manufacture the NIC in such a way that it acts as a reflectometer or did > they program it? If it's the latter, how is that possible? It's undoubtedly the former. -- Mark Evans St. Peter's CofE Aided School Phone: +44 1392 204764 X109 Fax: +44 1392 204763 | |||||||||||||||||||||||||||||||||||||
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> cable, 2) waiting for its return,
> 3) taking the time difference, 4) and calculating the distance.