Power Management in Serial Port Drivers (Windows Embedded CE 6.0)
1/6/2010
The minimum power management that a serial port driver can provide is to put the serial port hardware into its lowest power consumption state with the HWPowerOff function, and to turn the serial port hardware fully back on with the HWPowerOn function. Both of these functions are implemented in the lower layer. Beyond this 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. 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 universal asynchronous receiver-transmitter (UART) chip, if no applications are using the 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.