Gaston,
I"m hardly an expert, having created my first brain yesterday, but I would expect you'd want a brain that monitored the spindle RPM DRO, and whether the spindle is running. Test the spindle RPM, and, if too low, force the program to stop, by sending either a Program Stop or E-Stop button press. I wouild think you could use the "Spindle is Running LED" to know that the spindle is on. You'll also want a delay on the Spindle is Running LED input, to prevent the brain from executing before the spindle has come up to speed.
Regards,
Ray L.