Omron's CP1E-NA Using Mobus-RTU Easy Master FUnction

Hi,

I am using CP1E-NA PLC, RS-232 to RS-485 converter(Make: BB-Electronics) and one wireless gateway(Make: Banner). I have wired the RS-232 port of PLC to converter and then to RS-485 points of gateway. As per the CP1E CPU Unit Software's User Manual, I have did the port settings, programming and DM area allocation. I am trying to read the holding registers of my gateway using the function code, 03. But in PLC, I am getting the error code of 80 (i.e. response was not received from slave) in A640.02 and didn't get any response data which is starting from DM1254. Also, in CP1E CPU Unit Software's User Manual, they have provided the DM area allocation for command not for response. Can someone please share the information to solve my problem.

Regards,
Chandru

What is the device that you are trying to communicate Modbus RTU?

CP1E-NA - RS232/RS485 Converter - Wireless Gateway - ??

Is the device that you are communicating to have any indication lights to show communication?

Regards,

Hi,

Thanks for your reply.

Here, CP1E-NA is set as Modbus Master and gateway is set as Modbus Slave. For RS-485 conversion, I am using the converter because my CP1E-NA PLC has only RS-232 port. In my gateway, there are DIs & DOs. My gateway is mapped to a wirelesss node through wireless radio communication. I switched on a DO in my gateway. Now I am trying to read that status of DO from Omron PLC by setting it as master through Mobus-RTU Easy Master Function.

Can you remove the wireless and go directly to one of the slave units? If we can establish communication then the problem is with the wireless gateway.

Regards,

Hi Garry,

Thanks for your reply. No, it is working fine as a modbus slave. I have checked my gateway unit from Modscan64 software in PC and this reading the values of modbus holding registers. Also for RS232 port, I have made the wiring correctly as per the CP1E's Hardware Manual. I need the communication data format which is starting at 1203 as well as the response data format which is starting at 1254. Here attached is the image shows DM area's allocation and D640.0 in my program. For this program, I am getting the error code of 80H in 1252.

Can u post yr code?
Have u tested yr code with a simulator/something else?
Something simple, have u tried swapping a/b wires?

I tried exchanging the two wires. If I do so, I am getting the framing error, 82H. I didn't try any simulation for PLC program and now I am working online with my program. Could anyone please tell me do we need to enter slave address, function code, etc., in 1250 to 1299. Also please tell me communication data format which is starting at 1203.

Modbus-RTU Easy Master Function in CP1E-NA PLC

Hi All,*

Here attached are the screenshots of my CP1E-NA PLC’s Modbus program, DM allocation and port settings.*

My Modbus slave device has the Modbus Holding Registers of 40001-16 and 2 wire half-duplex RS485 Pins. I want to read these holding registers from Built-in RS232 Port of CP1E-NA. I am using RS232-RS485 converter for connecting PLC & my Modbus slave device. When I execute my program, I am getting the error code of 80H*(A response was not received from the slave). But*I can successfully read the holding registers of my slave from ModScan64 software in PC through the same RS232-RS485 converter. I have provided the correct RS-232 wiring from CP1E as per the hardware manual. Problem is from CP1E and I don’t know how to solve this. Please help me in this regard.

Following are the details of my slave device:

Slave ID: 1

Function Code: 3

Number of Registers: 16

Starting Address: 40001

Communication: RS485, Half-duplex

Protocol: Modbus RTU

Baud Rate: 19200

Parity: None

Data Bits: 8

Stop Bits: 1

Flow Ctrl: None

Try 40000 instead of 40001 - it may be a direct address - they usually are.

Hi All,

Can I connect and communicate from the*Built-in RS232 Port of CP1E-NA20DR-A PLC to the RS485 pins of Modbus Slave Device through Modbus-RTU Easy Master Protocol???

For RS232 to RS485 conversion I*can use a converter in between PLC & Modbus slave device.*