OMRON RS232 interfacing

Does anyone have a tutorial on this?

I'm largely a computer science guy but I've been hired by a local manufacturing company to integrate an OMRON PLC with several other devices through custom software. I have a fair understanding of ladder logic but get lost when I think about that in combination with RS232 communications.


I'm looking to update a few registers from the computer ideally through the SCU21-V1 communications module. I have the CX-ONE software suite to work with in creating new protocols or whatever I need but I'm having trouble wrapping my head around it.

Someone recently uploaded a working serial comms program for Omron PLC. I downloaded it for my reference, because serial comms is something I attempted with Omron in the past and it seemed too time consuming to learn from the instruction helps. I could not find any decent comms examples at that time. Now I have one, and so can you. Get it before he takes it down.

http://www.plctalk.net/qanda/showthread.php?t=84324

Be aware that instruction sets differ between PLC flavors, so you may need to make some changes.

strantor said:

Someone recently uploaded a working serial comms program for Omron PLC. I downloaded it for my reference, because serial comms is something I attempted with Omron in the past and it seemed too time consuming to learn from the instruction helps. I could not find any decent comms examples at that time. Now I have one, and so can you. Get it before he takes it down.

http://www.plctalk.net/qanda/showthread.php?t=84324

Be aware that instruction sets differ between PLC flavors, so you may need to make some changes.

Click to expand...

Sorry to make you think we delete everything
I fail to see why we would delete that Post.

I think he might have been talking about the original poster iant.

Strantor, thanks a ton that actually help solidify how it's done. Only two facts elude me in the process:


1) I issue the RCV command (address, control bits, size) does the PLC sit and wait for the incoming buffer to fill to size or pull the size off the top of a running buffer?


I vaguely remember a bit being turned on when the buffer fills... I'll have to get back into the books.


2) How can I choose which port to send the command to? One of the control bits is port 1 or port 2 but then on this PLC there is a few communication modules (SCU21-V1 and 41) and I'd like to use one of them instead of the COM port on the CPU.

iant said:

Sorry to make you think we delete everything
I fail to see why we would delete that Post.

Click to expand...

Sorry, I was referring to the OP. It just seemed likely to me that he would delete it after getting the help he wanted. I carry that sense of paranoia with me from another forum that caters more toward academics; "homework help" type stuff. People there often immediately scrub the evidence in fear of their professors coming across it, or their classmates getting the answers that they "worked so hard for." I suppose that's less applicable here, but in the world of IP, it could still happen.

foreverska said:

2) How can I choose which port to send the command to? One of the control bits is port 1 or port 2 but then on this PLC there is a few communication modules (SCU21-V1 and 41) and I'd like to use one of them instead of the COM port on the CPU.

Click to expand...

I'm not quite sure; as I mentioned, I never got that far. But my intuition says that once a module is fitted, there should be a new port, port 3 I guess. I did get so far as to fit a comms module to my CP1L, and it automatically was shown in the plc config, with its own tab.