Help With Modbus

I am using the cj1m cpu from Omron and I am trying to do modbus communications to a Frequency drive that has modbus protocol built in it does any body hkows if the cj1m family of PLC;s sopports the protocolo and how would you do it..

I use Modbus RTU all the time with these PLCs.

The best and easiest way is to install a CJ1W-SCU21 or 41 in the rack and use a CX-Protocol generated code to communicate with the drive. To read there is only one instruction required in the PLC. If you have CX-One, CX-Protocol comes as part of the suite.

Here is a link to the CX-Protocol Modbus RTU file
http://forum.mrplc.com/index.php?act=Downloads&CODE=02&id=259

You could write ladder to communicate through the onboard serial port but I would suggest you do not even go there. The SCU is the way to go. They are inexpensive and the CX-Protocol file is free.

If you use the rs232 port that is on the cpu of the cj1m to do it with what instractions would you use
to do modbus

Here is a link to ladder Modbus RTU slave code that may help. I have absolutely no intention of going up that path as it would take too long. I will always use the SCU and CX-Protocol as it is much quicker. I do not have time to fiddle around with ladder for Modbus.

http://forum.mrplc.com/index.php?act=Downloads&CODE=02&id=512

Hi;

You can use CX Protocol with the onboard serial port and talk modbus RTU. Now everybody can be happy. If it is the cost of CX Protocol that is the issue, you will pay for it in time saving.

Jim

If it is the cost of CX Protocol that is the issue, you will pay for it in time saving.

Click to expand...

What are you talking about Jim Knee? CX-Protocol is included as part of CX-One. CX-One is very inexpensive as compared to the so called majors of the PLC industry.

Bob;

Before CX One was released you had to purchase CX Protocol as a separate producd. I assume you still can. However I do agree with you that Omron software is very reasonably priced and CX One is the way to go.

Personally CX Protocol has been a breath of fresh air in my working life. We were always writing custom protocol in ladder, not any more. Once you get the hang of CX Protocol there is no going back (For us Omron Guys).

Jim

hi guys,
in cp1h manual, it says "easy master - modbus" protocol, but icannot find any example or techical documentation about this topic.
also, does cx-protocol support cp1h onboard rs485.

mrplc.com disappear for a while is there any technical problem??

* http://www.omron.com.au/product_info/CP1H/index.asp

i found informations in cp1h operation manuel (w450.pdf).
thanks