FactoryTalk View Studio ME

studentplc1

Member
Join Date
Feb 2010
Location
Canada
Posts
29
Hi,

I have a HMI program in FactoryTalk View Studio ME and was looking through how the Numeric Input Cursor Point is used. Under the connections tab in properties, how come you have to edit BOTH the Value and the Indicator. What do each of these mean?

In the program I have both have the same tag assocated with them.

When running, this button has a value and when the operator touches the button, he can change the value through a pop up screen. My only questin is what is the Value vs. Indicator.

Thanks!
 
You can leave the Indicator blank and it will show the result of the Value connection.

If you want to ensure that your communication is working correctly, you could choose a unique value for the Indicator connection, and COPy (or MOVe) the Value tag to the Indicator tag in the PLC.

With both tags set the same, or nothing in the Indicator connection, your HMI will display the last value you entered but there's no guarantee that it was successfully sent to the PLC.
 
is that because, for sure, when the rung with the "move," "copy" command runs, it will get the desired value?

and why is it that if the tag is the same it won't update the PLC? Or may have a chance of not properly getting the value?
 
by the way I just checked what it is doing right now, and it is taking the value from the HMI and moving it to a TIMER.PRESET using the MOV command, through the PLC.

But like you said, it isn't desirable to make it directly the TIMER.PRE value. Why!!!!!!!!?? :)
 
Leaving the Indicator tag blank won't cause any problems, it just might not let you know if there is a problem, whereas using the PLC to move the Value tag to the Indicator tag will show you when there's a problem.

For your second question, it can be risky to write directly to a timer preset in a SLC, because if you accidentally put a negative number in the timer preset, it will cause a math overflow which will result in a major error at the end of the scan, and your CPU will fault, halting your process.

Another reason to do that, is that it will allow you to better organize your tags making communications more efficient. It is better to read/write addresses that are in blocks rather than to read/write addresses that are scattered.
 

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