Книга: Microsoft Windows Embedded CE 6.0 Exam Preparation Kit

Lesson Summary

Lesson Summary

Windows Embedded CE 6.0 R2 provides a default Power Manager implementation with a set of power-management APIs that you can use to manage the power state of the system and its devices. It also provides the OEMIdle function, which it executes when the system does not have any threads scheduled in order to provide original equipment manufacturers (OEMs) a chance to put the system into a low power idle state for a specified period of time.

Power Manager is a kernel component that exposes a notification interface, an application interface, and a device interface. It acts as a mediator between kernel and OAL on one side and device drivers and applications on the other side. Applications and device drivers can use the DevicePowerNotify function to control the power state of peripheral devices at five different power levels. Device power states may also associate with default and custom system power states to keep system and devices synchronized. Based on activity times and corresponding events, Power Manger can automatically perform system state transitions. The four default system power states are On, UserIdle, SystemIdle, and Suspend. Customizations for system-state-to- device-state mapping take place in the registry settings of individual devices and device classes.

In addition to Power Manager, the kernel supports power management by means of the OEMIdle function. Switching the processor into idle state reduces power consumption to the lowest possible level while retaining the ability to return from the idle state quickly. The processor will return to non-idle state periodically or when interrupts occur, as when it responds to user input or when a device requests access to memory for data transfer.

You can significantly reduce the power consumption of a device if you implement power management properly using Power Manager and OEMIdle, thereby increasing battery life, decreasing operating costs, and extending device lifetime.

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