Modbus/TCP

[StefanA]

Found a free software on the web called Advanced Hmi (some kind of software HMI)  which I try use together with my nano-10 trough Modbus/TCP. I can display and write values (holding register) back and forth but I can't control any outputs or internal relays from the software. Toggle a relay in the plc and make a lamp symbol blink on the screen works fine but I can't use a switch symbol to toggle a relay or output in the plc.  Asked Advanced Hmi support about my problem and they did a successful test with a slave simulator and the address 00258 (nano output 2 if I'm not mistaken). Any suggestions about what I doing wrong?  

[support]

Is the HMI program using Modbus function 05 to write to coil 258? Only function 01, 02, 03, 04, 05, 06, 16 are supported.

I tried using a Modbus Poll master to send to output coil 258 and output #2 is turned ON.

Also ensure that the coil or relay are not already controlled by your PLC program. Otherwise what you manage to do is to change it for one program scan time (which may be < 1ms) and then your PLC program change it back to what the ladder logic or TBASIC decides the coil status should be.

The best way of testing is to put a blank program into the PLC and then try using your HMI to toggle a coil and see if it works with the PLC.