I'm in school, attempting my final project, we are trying to interface a Floboss 103 to a Quantum PLC using Modbus plus. The run time errors we are getting when attempting to communicate are "Device you are trying to communicate to is not online or responding." We have directed the Quantum to the start of a range of registers that measure DP with no success. We are using Concept to program the PLC, and are using the MBP_MSTR and the READREG function blocks. Any help would be greatly appreciated!

 

If your wiring and device address are correct, then the problem is likely with your code. Use one or the other function blocks, my recommendation for Concept/Quantum is the MBP_MSTR function. Common error is in the config of routing register 1. It contains the slot number and first routing number. If you are not going through MBplus bridges then the next four routing addresses will all be 0.

CPU slot number is always 0, Module (NOM) in slot 7 is 0000 0111 for high byte. If address of device is 5 then lower byte is 0000 0101. This gives word of 0000 0111 0000 0101 as binary. 0705 Hex or 1797 decimal

 

Are you sure the Flowboss supports the Modbus Plus Network ???

I did a quick search of the Emerson website and could only find a mention of it supporting the Modbus protocol. This requires configuration ROCLINK 800 Software according to the documentation.

If it is Modbus in lieu of Modbus Plus then you would need to use the XMIT function to perform the communicaiton through the Modicon Quantum's communicaiton port (Port 1).


The Flowboss supports both a RS232 or RS485 physical layer. Typically the Modicon Quantum's serial ports are configured RS232 and would need a RS232 to RS485 converter.

 

Thank you Brian, and thank you Robert, Floboss is indeed Modbus only, we are using a converter and using the XXMT command, we're still getting an error, We're still in the process of determining the error, I will update later today!

 

Another thing about the FB103/FB107 Register conversion codes. If you are configuring IEEE Single Precision floats and you use a conversion code of "0" then the requested number of "registers" will actually be the number of floats returned. On the other hand if you use conversion code 65 (or 66, 67 and 68) then the correct number of registers will be returned. For example requesting 8 registers using conversion code 0 will return 32 data bytes (8 floats x 4). On the other hand, requesting 8 registers using conversion code 65 etc will return 16 data bytes (4 floats x 4).

 

You need ROCLINK Software configuration to set network parameter on FB103, and FB103 doesn't support for Modbus PLUS, you can use Modbus RTU/Ascii RS-232 or 485.