A power management PC expansion card controller that includes power on
reset circuitry to reset power management enable registers during a reset
period, thereby ensuring that the PME registers correctly identify the
power management capabilities of the controller. Once the PME registers
are reset, an instruction may be provided to change the state of the
registers from a default reset state to a state that supports advanced
power management capabilities, for example wake-up functions.
Additionally, the controller includes blocking circuitry to block
conventional reset signals from resetting the power management and
proprietary registers if the PME register is instructed to change states,
thereby preserving the data contained in the power management and
proprietary registers against future reset events. The controller of the
present invention supports advanced power management specifications
without requiring additional pinout arrangement or reassignment of pin
functionality, so that the controller of the present invention can be
implemented in current computer system without a the need for retooling
or re-layout of system board circuitry and wiring diagrams.