You helped me narrow down the problem. I added a 2nd test tag in my PLC of datatype REAL and was able to write 160.5 to it so that gave me a clue as to what happened. I had changed my first tag datatype from DINT to REAL and downloaded earlier today so the gateway must not have recognized it for whatever reason. I restarted the Ignition gateway and the first tag started responding to decimal value writes from Ignition also.