Hello, everybody.

I have a task to visualize remaining time on HMI screen. The project is created in Step7 v5.6 and based on S7-300 PLC. The timer we use in the project is SFB4 TON. At the input "PT" there is a preset time value - 129 seconds MD305 in msec (declared as TIME data type). At the "ET" output there is an elapsed time value - MD315 in msec (also declared as TIME). In the next step (network) I try to substract "Elapsed Time" value from the inintial "Preset Time" with the "SUB_I" block and see the strange thing at the output (see the attachment), even when the elapsed time is 0, the output value has some "initial" value and is equal to 65535 or about 66 seconds (in the attachment there is a bit less value). So what I do wrong?