Modbus TCP app - Single coil operation doesn't work/exist

[Vaaclav]

Hello community,

I've got Modbus TCP App v.1.20.2 installed and trying remotely control power supply. There are multiple read/write holding registers for voltage/current reading, which works fine. But then there is single coil access, which I absolutely need to switch power supply to remote control. I was not able to read single coil with FC1 and FC5 for writing single coil doesn't even exist.

 

I tried the communication with Modbus Master tool and everything works as expected. FC1 read succesful, FC5 write successful:

What can do with that? Is there some configuration or workaround I can set or use?

The FC5 single coil write command doesn't really exist on Modbus TCP app? Without that, I'm not even able to set power supply to listen remote command...

Many thanks

[jagz]

Hello @Vaaclav 

Instead of FC5 did you try using FC15(write multiple coils) with quantity 1?

[Vaaclav]

Hi @jagz,

unfortunately it doesn't work. The power supply accepts only specified functions, i.e. FC1, FC3, FC5, FC6, FC16 as you can see on the screenshot above.

[CodeShepherd]

In the official online documentation for the Modbus TCP V1 app (https://docs.automation.boschrexroth.com/doc/4288575786/supported-function-codes/3-03/en/) is FC2 not mentioned. So I guess it is simply not available.

See in comparison the documentation of version 2 https://docs.automation.boschrexroth.com/doc/1973345983/supported-function-codes/latest/en/