Set IA is an action that allows you to automatically turn one or more IA buttons on or off. This makes it possible to create complex interactions between buttons. For example, you could program a button that turns on a fuzz pedal to turn off all buttons that control overdrives. Or, turn on a delay whenever you activate any overdrive (but not have the delay button affect the overdrives).
Set IA works on any button that has Type set to IA. IA buttons have an IA ID parameter - this is how you identify and refer to buttons. IA IDs can range from 0 to 255. Setting the ID to 0 means that the button will never be affected by Set IA actions. Any other value allows it to be controlled by Set IA.
Once you have IA IDs assigned, you can use a System / Set IA action to control those buttons. Here's an example:
System / Set IA #4 off:ON on:OFF
Putting this action on an IA button will make it control any IA buttons that have IA ID #4. When this button is turned on, it will turn off all buttons with IA ID #4. When this button is turned off, it will turn on all buttons with IA ID #4.
The Mastermind will only allow a button to be switched once during a Set IA action, and it won't allow a button to control itself. This prevents the Mastermind from being stuck in an infinite loop.