To generate the event on value change of the boolean indicator

[RBCHAVAN_77]

We need to store the faults sensed by the Digital Input Module in a file. We need to generate the event on fault occurrence or value change of the indicator(Boolean) so that we can save the fault status. We tried using the Value signalling property of the indicator but it generates the event even if there is no change in the value and we need to generate the event only during the value change of the Boolean indicator.

Thanks

[crossrulz]

Very common issue.  You have a few options. 

1. You could use a feedback node to hold the previous value, if the values are different then you use the Value (Signaling) property.  Otherwise you don't even write.

2. The other way to handle this is in the event structure where you compare the new and old values to see if it really did change and react accordingly.

I recommend the first option.