jblkiller Posted April 15, 2014 Report Share Posted April 15, 2014 I have a M91 into a box. I would like to have a acces to the RS232 port for troubleshooting whithout open the box. I connect the cable to a coupler like that: (http://www.digikey.ca/product-search/en?x=0&y=0〈=en&site=ca&KeyWords=a34359-nd) but the plc don't want communicate. I check the continuity for both cables and is ok. I there a maximum length for rs232? When I plug the plc direct to the pc with one cable is ok. When I connect two cable with the coupler don't work. Thanks Quote Link to comment Share on other sites More sharing options...
MVP 2021 Flex727 Posted April 15, 2014 MVP 2021 Report Share Posted April 15, 2014 The typical RJ-11 cable (like used for phones and like what comes with the PLC) is a crossover cable. If you add an additional cable between the PLC and the coupler it must be a straight-thru cable like this one: http://www.monoprice.com/Product?c_id=102&cp_id=10222&cs_id=1022201&p_id=928&seq=1&format=2 You are probably doing a double crossover which will not work. Two crossover cables WILL only work if the coupler is also a crossover. Where I work we do exactly what you are trying to do and encountered the same issue you are having. A straight-thru cable inside the box works perfectly. 1 Quote Link to comment Share on other sites More sharing options...
jblkiller Posted April 15, 2014 Author Report Share Posted April 15, 2014 Thanks you for the explanation! Quote Link to comment Share on other sites More sharing options...
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