[00:00] This historical transaction group that I have configured is logging data to my database at a one-second rate and has a read only Boolean tag that I want to use as a trigger to control the execution of the group. From the groups trigger tab I can require it to only execute on a trigger and then point my trigger item to my Boolean tag using this dropdown. I want this group to execute if and only if my Boolean trigger has a value not equal to zero or a true value so I can use this trigger condition here. I want to also toggle this setting. Reset trigger after execution. This means that each time the group evaluates and my trigger has a value of true. My trigger condition will be met and the group will automatically reset my trigger by writing a false back to it upon successful execution. I will enable my transaction group and save my changes to test it out.

[01:07] You notice that every time I talk with my trigger bit to true. It automatically gets reset by the transaction group. Once it executes successfully. And my tag data reaches my database. If I were to change my trigger condition to be equal to zero, meaning only execute my transaction. If my bullying trigger has a value of false. I also see that with every successful execution my trigger gets reset, but now to a value of true or the opposite of what I defined the active trigger condition to be this mechanism has many useful applications. I can write a true value to my trigger tag from say a button script to trigger my groups execution for example, I can have pretty much any part of the ignition ecosystem trigger my group's execution just as long as it can write to this trigger tag. Another common situation is to have what's known as a PLC watchdog, where the PLC is setting this bit high and the group is automatically resetting it in order to prove that the group is still running.

[02:11] This can also be used for flow control. As the PLC may load data into registers, set this bit high and then only load new data. When it sees that the group has executed successfully indicated by the trigger reset. Another way to accomplish this could be the success handshake, but we'll cover that in a future lesson.