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Steve G

RS232 Controllogix to SLC

9 posts in this topic

Good morning to you all, I am in the middle of a project were I need to send and receive some data, to and from a SLC PLC and a Contrologix PLC via the serial post. I am having some issues setting this up and am unable to get the right data sent and received. My question is can I use MSG instruction with the serial ports of the two PLC's or will I have to Use ASCII read and rights to accomplish this. If I have to use serial read and write commands what is the best way to do this. Thanks will all the help.

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You will not be able to explicit message data using the controllers serial ports; you could transfer data between the CPUs using ASCII commands. What type SLC processor are you using and what are the existing ControLogix implemented communications (if any)?

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I do messaging over ethernet between ML1100's and CLX boxes all the time. Does the SLC have an ethernet port?

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Of course you can use MSG instructions to transfer data to and from SLC and ControlLogix serial ports. I recommend using the SLC Typed Read and SLC Typed Write functions and using the ControlLogix to implement the messaging. Post some details on what you have tried. Quick tips: 0. Use DF1 Full Duplex mode. 1. Use CRC error checking; it's default on the SLC and selectable on the Logix. 2. Use a null modem cable between the ports. 3. Create an INT[x] array tag or two in the ControlLogix to hold the SLC data.

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Thanks Ken I currently have a SLC 504 and Compact Logix L23, I guess one of my problem has been the serial setting. I will change them to what you have told me they need to be and then give it a try. When I tried the SLC type Read and write functions I have received the error not such register in target device, or something to that nature. I have also tryed to use acii string read and write to accomplish this but with no luck Thanks again and will post the outcome after I try your settings

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The "invalid register" error is a good sign; it suggests that your physical wiring and port configurations are correct. Be sure the data files you are requesting actually exist; try 1 register, then several. Exactly what are the data registers you are trying to read and write in the SLC ?

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Thanks for all the help with this, I was able to get it working. I messed up at had the wrong communication path set. I was using 1,0 and it should have been 2,1. This is the address for the serial port on the L23 PLC. Thanks again

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Thank you for posting the followup ! The CIP Path "1, 0" sends the message back to the CompactLogix CPU itself, so it makes sense that it gave an "invalid register" error.

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