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Communication Issue

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Hello all, We have an old PLC driven steam generator. PLC is a Allen Bradley SLC 5/04 with a Allen Bradley DTAM Operatar Interface that is connected from the RS232 port on the SLC to the OIT. Yesterday I attempted to hook up my laptop using a PCMK card, and RSLinx didnt see it the processor. PCMK card is good, and RSLinx configured properly. What could it be? any ideas? Thanks John Bourg

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where did you physically connect the cable from the PCMK card? ... how is the card set up in RSLinx? ... have you used the same PCMK card and cable to successfully connect to other processors? ... lately? ...

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PCMK was connected to the DH+ or DH 485 port. DTAM is connected to the RS232 port The PCMK is configured under "configured drivers" in Rslinx.. but the Network setup for the PCMK card is currently set up for "DH+". I wonder if i have the option to set to DH485? In fact I did notice that the DH+ LED on the SLC was just flickering on/off..not solid like I'm used to seeing on other processors. Could it be something in the communication setup in the RSlogix 500 controller properties I used the PCMK Card / cable on another PLC just before I hooked up to this one so I know (well think) that that part is ok Edited by ICTechs.com

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if it's an SLC-5/04 then you can forget about DH-485 while using the PCMK card ... SLC-5/04 is pure DH+ on the top two ports ... the DH+ LED is supposed to flash once every two or three seconds ... it's trying to communicate with someone else on the Data Highway ... once it has someone else to "talk" to, the LED will go solid green ... it's a slow day ... call me up if you like ... I'll be available for about 30 more minutes ... till about 3:00 Eastern time ...

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If you didn't reach Ron - it sounds like your PC and SLC are using the same node number. Change the DH+ node number of your PC and see what happens.

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John reached me by phone - but wasn't able to try anything while we were still talking (he wasn't in the same building with the system) ... anyway ... his PCMK card was set for node 77 - so PROBABLY that was OK ... I suggested that he try another baud rate for the PCMK - or connect through the Channel 0 port - trying DF1 ... he said he'd get back to us soon and let us know how things went ... my best GUESS: the baud rates are different between the PCMK and the SLC's DH+ port ...

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