TRANSITIONS BETWEEN LOW POWER MODES IN A PROCESSING SYSTEM

Processing circuitry includes a selectively powered domain having a communications interface to communicate with power management circuitry via a bus in accordance with a bus protocol, and a processing core to control the communications interface, wherein the selectively powered domain is not powered when the processing circuitry is operating in any one of multiple low power modes. The processing circuitry also includes an always on power domain having a set of pins to communicate a set of handshake signals with the power management circuitry and a power management sequencer to control power mode transitions of the processing circuitry. When the processing circuitry is operating in one of the multiple low power modes such that the communications interface and the processing core are not powered, the power management sequencer generates a signature on the set of handshake signals to control power mode transitions from one of the multiple low power modes.