AC800M Modbus TCP Slave ID issue
Hi Stefan,
I am currently working a project that is using an AC800M communicating Modbus TCPIP. It has a number of Modbus Slaves attached to the network however there is a device that communicates through a MOXA Gateway MB3180 (485/TCPIP). This device has a slave id, therefore I have the the PLC communication network for this device to a gateway, then to a modbus serial slave.
The specs are:
IP = 192.168.1.78
Slave ID = 78
When I have downloaded the software to the controller it can see the network is established, however I am unsure how to specifically talk to that slave ID through the PLC.
I am unsure how to tie the Partner and Slave ID to my POU's, my POU's see a connection valid using the Modbus TCP library but can't read the data. I get the error code -7006 which i beleive indicates "no response from slave".
We have used the software "MGate" to confirm physical connectivity.
Kind Regards
Sam
Answers
Hi, Sam
Try with a Modbus Simulator from your laptop !!!!!!
Check the connection 485: Gateway<->Modbus slave harware, If is a two wires, then try to change the wires: A->B and B->A.
Regards
Further to my question, here are a few screenshots
This is my set up, at this point I have a device sent from a 485/TCP device with a slave id of 100.
I get a connection valid however the PLC is looking for a 0xFF (255) slave ID, which I beleive is the modbus standard. This screenshot proves my point.
When I change the Modbus TCP Slave to a gateway then set up a serial slave of 100, the PLC requests the correct function code from the correct Unit ID however I lose a connection valid on the Modbus TCP connect block.
Do I need to change the ModbusTCPConnect block to suite a serial slave?
I am not experienced with this software so apolagies if this is a silly question.
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