I am using an FMD88-10 and Weintek HMI MT8050iE in an oven application. I have the HMI programmed so the operator can monitor and change the SetPoint Temperature, Actual Temperature, conveyor speed and the condition of various fans. Changing those values from the HMI is relatively easy since I'm only dealing with integer and Data Memory variables. But, I have 3 heating elements that operate for different times. They all turn on together, but turn off at different times. Currently I use the TimerSV that is assigned to each Timer when it's created in i-Trilogi.
I want to have the ability to change the TimerSV from the HMI. I assume I need to use the SetTimerSV function. However, according to the TL6 Reference Manual "the new S.V. are only stored on RAM-shadowed CPU flash memory and is normally volatile unless..." OK, requires an extra step to write the data to CPU flash memory. No big deal. However, I get a bit nervous when I read things like "Programmer should therefore use this command sparingly".
On the HMI I would also like to have a "CANCEL" and "SAVE" button to give the operator the option to save the new S.V. values or abort the action. Pressing the "SAVE" button could trigger a Special Function in the PLC to write new values to the TimerSV. Can the "CANCEL" feature be implemented entirely in the HMI?
Is there and easier (better?) way to change the SV of a timer from the HMI than using the SetTimerSV function? According to the Comments in Section 12.73 of the TL6 Reference Manual a "TBASIC custom function can start a timer by setting it's TIMERPV[] variable to any integer value between -1 (reset timer) and 9999 so it is not necessary to change the timer S.V." Really? How does that work? Examples?
