This is a reply for the beginning designer.  I had one of our 
     designers hardware designers look at your question.  His reply is 
     below.
     
     John Gulley


I think he's on the right track.  A parallel termination at both ends will 
probably work best.  Some experimentation may be required.  RS-423 uses 
this approach, but is a balanced signal.  For RS-423 the termination goes 
from the positive leg to the negative leg.  With single ended signals 
assume the other leg is ground.  By this I mean that the termination goes 
from the signal leg to ground.
     
I hope this helps.
Rob
     
     
     
     
______________________________ Reply Separator _________________________________
Subject: DES:I/O Terminations
Author:  John Gulley at inet8
Date:    6/19/97 9:13 AM
     
     
     Think you can help him along.
     
     john
     
     
______________________________ Forward Header __________________________________
Subject: DES:I/O Terminations
Author:  [log in to unmask] (Andreas Olofsson) at Internet 
Date:    6/18/97 6:50 PM
     
     
     
Hi,
     
  With the risk of being flamed I will pose a rather simple question here 
(although I certainly don't know the answer). I am kind of new to board 
level design, and I have tried for days to figure out how to terminate 
tranmission lines with I/O devices connected to them.  Assuming CMOS I/Os, 
and rise times of 1 ns, any interconnects longer than about an inch could 
have serious problems with ringing.  I am fairly clear on how to terminate 
lines with a driver and a receiver.  However, I can't figure out how to 
terminate when you have two I/O pins separated by a transmission line.  
Would you do parallel termination on both ends?
     
  Any thoughts?
     
  Thanks,
     
     
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