There are a lot of the Factory ISF shaders that have a Reset Time button (a [live.text] in button mode) in their Configure window, which in the device is displayed as regular dial. Crossing over 0.50 in either direction will translate to 0 or 1, where 1 triggers the event. In a custom M4L wrapper you could approach it like this, which is also how the Reset Time button behaves:
I realize now that I only gave half the answer, as you won’t find a Reset Time parameter in any of the ISF shader files, since the parameter is hardcoded in Videosync. To see how it’s handled in the a .fs file, take a look at the Etch-a-Sketch.fs generator shader.