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Richard Erlacher
07/16/12 03:18
Read: 468 times
Denver, Co

#187949 - one thing to consider ...
Responding to: Per Westermark's previous message
Many years ago, PC's came with a parallel port that was intended to drive parallel signals to a printer. It was driven via exactly that same IC, i.e. 74LS245, and the lines were series-terminated through resistors.

Now, I don't remember what the data line resistor values were, but, clearly, this is a similar case to what you're considering. The IBM-supplied cables were not ribbon cable, but ribbons were often enough used in similar situations. The characteristic impedance of this ribbon cable was considered to be approximately 110 ohms. Just as in your case, IIRC, a single ground wire return was apparently sufficient to make the entire subsystem work.

Perhaps a look at the old, original, IBM PC printer interface would answer most of your questions.


List of 10 messages in thread
74LS245 ouput cable drive distance      Raj Nambiar      07/15/12 23:32      
   what is the termination      Erik Malund      07/16/12 00:31      
   Frequancy?      Per Westermark      07/16/12 00:33      
      not only capacitance      Erik Malund      07/16/12 01:22      
         Thanks for the replies      Raj Nambiar      07/16/12 01:32      
            DC      Per Westermark      07/16/12 01:50      
               one thing to consider ...      Richard Erlacher      07/16/12 03:18      
            "an industrial automation project"      Andy Neil      07/16/12 09:11      
               Industrial environments can be dangerous to electronics      Per Westermark      07/16/12 10:13      
                  optical isolation      Mahmood Elnasser      07/16/12 18:01      

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