CP1E Modbus RTU Help!

[andreik 0]

Good day, I have a problem with Modbus-RTU. I'm using Omron "CP1E-N60DT-D" connecting to Oriental Motor "ARD-KD". I've understood how to Read/Write data one at a time during my tests. However, in application, I need to Read(03h) and Write(06h) at the same time (like our usual PLC I/O's) but I can't imagine how to do it. By the way I'm using "CP1W-CIF11". I've read something about the built-in RS232C port capable for Modbus-RTU but I'd never found any technical data regarding this or is it possible to use 2 ports at the same time. I'd appreciate any help I can get. Please see attached. Thank you very much. Sincerely, Andrei K. CP1E_taModbus Compatibility Mode.pdf Edited 13 Apr 2012 by andreik

[lostcontrol 23]

the CIF11 is for RS485 media, the most common for Modbus comms. The CIF01 is the RS232C version. For Modbus, it does not care what board you use, just that everything matches up electrically...

[andreik 0]

I'd like to try to use the built-in RS232C but I can't find a manual for this unlike the CIF11. Hmmh, but wait. I need to use a terminating resistor for this because it doesn't have a dip switch right? Thank you very much.

[lostcontrol 23]

Does the CP1E have built in RS232C? Or are you referring to the CIF01 that clips into the same place as the CIF11? if you are going to use RS232C, then the Inverter will have to support RS232 also. In my experience, almost all Modbus Slave devices provide a RS485 port for Serial comms like this, not RS232. You may have to use a Protocol Convertor.

[andreik 0]

I'm using a built-in RS232C. Thanks a lot.

[lostcontrol 23]

So you only have a single device, then there is no problem with update rates.. What code are you using to do the Modbus function? Have you created your own, or using a template from here?

[andreik 0]

I'm creating my own program. Actually, I'm already getting dizzy with the bytes and bit thing but I can handle at least. :D

[PMCR 66]

andreik The complexity of implementing a Modbus RTU application with many reads / writes was the driving factor behind the Modbus RTU Master that I wrote for CP1L / CP1H. http://forums.mrplc.com/index.php?app=downloads&showfile=867 Unfortunately because the CP1E has a greatly reduced instruction set, and no IR / DR indirect addressing capability, I was not able to migrate the code for CP1E. I know that it is too late for your application, but I normally recommend CP1L for Modbus RTU master applications, because the code is already written for you. PMCR

[lostcontrol 23]

andreik, Does the Oriental Motor utilise RS232 or RS485? This is the 1st most important step to get this working. My advice would be to use RS485. You cannot put RS232C & RS485 onto the same 2-wire Bus, they are just not comaptible. Do you have a list of the functions you need to read/write from the drive? This will help in determining what you need to do & how easy it will be to implement.. Are you using the Servo for positioning or speed control?

[andreik 0]

OK, understood. Thank you very much.

[andreik 0]

Actually, I've already decided to use basic signals to control the Motor and Modbus RTU for Monitoring (2 sets; regular status and position feedback). The application is for positioning. Thanks a lot.