1. An implantable medical device (IMD) comprising: a controller adapted to execute instructions included in firmware; a programmable neural therapy source adapted to provide programmable electrical neural stimulation therapy to at least one neural stimulation electrode; and a state machine separate from the controller and included in hardware circuitry coupled to the programmable neural therapy source, the state machine configured to implement a duty cycle of neural therapy including to automatically apply circuit power to the neural therapy source when neural therapy is initiated by a controller firmware instruction and automatically remove circuit power from the neural therapy source when neural therapy is terminated by a controller firmware instruction.