MB Ethernet single port multiple connections

[Anagha.G]

Hie,

I am trying to communicate Siemens with PLC S71200 through Labview 11 using Modbus TCP/IP Protocol. Initially I suceed to communicate PLC using single port single connection. But now when there are mutiple connections, I am facing issues in communication. I don't get any error codes but still no outputs are driven through my program.

I am using a standard Modbus TCP IP Library for this communication. I could not find any sample program for such type of communication.

If anyone is having solution for it please let me know.

Thanks,

Anagha

[K C]

Hi,

Assuming that you are using the 'NI MODBUS Library 1.2.1' 

I tried to use this but it didn't work for my devices. I found that this lib does not send the slave address to the device. Although the device does not send the slave address back it needs the slave address to be present within the data transmitted to the device.

So I ended up building my own Serial/TCP ModBus program to test my devices which also have dedicated commands.

Could it be that this slave address is given you trouble. If so I will look for the simple test VI I used.

Kees