Patent ID: 7343504

Claim:
A microcontroller unit (MCU) with a stand-alone Real Time Clock (RTC), comprising: a processing circuit for receiving digital information and processing said received digital information; a primary clock circuit for providing the timing for said processing circuit; a power control circuit for controlling the power to said processing circuit and said primary clock circuit to control the operation thereof to operate in at least a full power mode drawing a full power level from a supply voltage input and a reduced power mode drawing less than the full power level from said supply voltage input; and a stand-alone RTC circuit, said stand-alone RTC circuit including: an RTC clock circuit operating independent of said primary clock circuit, a timer for being clocked by said RTC clock circuit to increment a stored time value for output therefrom, said RTC clock circuit having a defined time base, an input/output (I/O) device for allowing access by said processing circuit to the results output by said timer, circuitry for controlling by at least one of two different and separate processes said processing circuit to facilitate changing said processing circuit and said primary clock circuit from operating in an inactive mode or a deep sleep mode to an active mode, said two different processes being configurable and including at least one interrupt process for generating an interrupt to said processing circuit or controlling said primary clock circuit to begin clocking, and power management circuitry for managing the power to said stand-alone RTC circuit, such that said RTC clock circuit, said timer, and said I/O device operate regardless of the power mode of operation of said processing circuitry and said primary clock circuit.