That is an output of the Function Block ModbusMasterRTU example: xIsConnected=> xIsConnected In this line the VAR ModbusMasterRTU.xIsConnected is written to VAR xIsConnected xError=> is writing to nothing here.
That is an output of the Function Block ModbusMasterRTU example: xIsConnected=> xIsConnected In this line the VAR ModbusMasterRTU.xIsConnected is written to VAR xIsConnected