Hi Mark
The moment you move the start switch to off it removes the 28v DC ON signal to the ECU and gives a 28v DC OFF signal instead. The 60 second cool down cycle starts when the switch is put to off.
The ECU removes the ready to load signal
Closes the bleed air valve
Closes the inlet guide vanes
Opens the surge control valve
De energizes the starter generator
Starts the 60 second timer.
The maximum duty cycle for the starter is 3 starts one after the other followed by a 15 minute cool down period.
Regards Gascan