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Per Westermark
07/16/12 00:33
Read: 483 times
Sweden


 
#187945 - Frequancy?
Responding to: Raj Nambiar's previous message
Yes, the LS245 can communicate over a 2 meter cable.

But (!) what you do not talk about is the signal speed. There is one thing to handle slow signals over that 2 meter cable. It's a completely different thing if you have many MHz signals on that line.

You have two issues - the cable have capacitance. And it is also an antenna. The capacitances affects how fast a transition can be. And the antenna effect means that one transition on one wire can affect another transition (started at a different time) on a different pin.

Note that IDE cables changed from 40 to 80 pins, as the standard allowed faster transfer rates.. The 40-pin cable had data signals did not have any ground wire between the individual data lines. The 80-wire cable for newer drives have an extra ground wire between each data line to reduce issues with cross-talk at high transfer rates, where the transition times are much more important.

List of 10 messages in thread
TopicAuthorDate
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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