Method and apparatus for powder management in a multifunction controller

Abstract

A method and apparatus for providing power management functions in a multifunction controller having an embedded microprocessor. An enter sleep mode indication is received in the microprocessor in the form of, for example, a command generated by a host central processing unit or an interrupt indicating a lack of system activity for a predetermined period of time. The clock input to the microprocessor is switched from a first clock source to a second clock source in response to the enter sleep mode indication. The main system supply may then be powered down by the microprocessor. The first clock source is then turned off after expiration of a first predetermined delay. The second clock is subsequently turned off after a second predetermined delay, to thereby place the system and the microprocessor into a sleep mode. While the system and microprocessor are in the sleep mode, an interrupt-handling portion of the microprocessor and a power control logic circuit remain powered off a low-current standby supply. Upon detection of a wake-up event, the second clock source is automatically started and applied to the microprocessor after a predetermined delay. The microprocessor can then process the wake-up event indicator, and if necessary power up the system and re-connect itself to the first clock source.