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The minimum power management that a serial port driver can perform is to put the serial port hardware into its lowest power consumption state with the driver's HWPowerOfffunction, and to turn the serial port hardware fully back on with the driver's HWPowerOnfunction. Both of these functions are implemented in the serial port driver's PDD layer. Beyond that minimal processing, a serial port driver can conserve power more effectively by keeping the port powered down unless an application has opened the serial port. Most serial port hardware can support reading the port's input lines even without supplying power to the serial line driver. Consult the documentation for your serial port hardware to determine what parts of the serial port circuitry can be selectively powered on and off, and what parts must be powered for various conditions of use. If there is no need for the driver to detect docking events for removable serial port devices, the driver can go one step further and remove power from the serial port's UART chip, provided that no applications are using the port.
Last updated on Tuesday, July 13, 2004