> I  need to test a series of CAN transceivers on maximum cables lengths for 
> agiven bitrate (250kbs, 500 meters CAT5) to determine the optimum sample 
> point and wonder how I best do this.  My first though  is to use just a RC 
> low pass filter with R equal to the the cable resistans and C equal to the 
> capacitance. This will not take the propagation delay into account and I 
> have no idea on how to simulate that. Will this be to any use at all for 
> me or do I have to think in a completely different way?

If you only want to do this over 500 metres, and the results are important 
to you, then 2 1000 foot boxes of Cat 5 is a small price to pay for testing 
it on the real thing. And you can use it afterwards!

Even for telephony simulating cable is not just a matter of using a single 
lumped equivalent. A real cable is a distributed LCR filter and you would 
need a number of sections to do justice to this. How many to be meaningful 
in your case I don't know, but 500 metres of Cat 5 does a wonderful job of 
simulating itself.


        RM


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