Книга: Microsoft Windows Embedded CE 6.0 Exam Preparation Kit

Activity Timers

Activity Timers

System state transitions are based on activity timers and corresponding events. If a user is not using the device, a timer eventually expires and raises an inactivity event, which in turn causes Power Manager to transition the system into Suspend power state. When the user returns and interacts with the system again by providing input, an activity event occurs causing Power Manager to transition the system back into an On power state. However, this simplified model does not take into account prolonged periods of user activity without input, such as a user watching a video clip on a personal digital assistant (PDA). This simplified model also does not take into account target devices without any direct user input methods, as in the case of display panels. To support these scenarios, the default Power Manager implementation distinguishes between user activity and system activity and accordingly transitions the system power state, as illustrated in Figure 3-9.

Figure 3-9 Activity timers, events, and system power state transitions

To configure system-activity and user-activity timeouts, use the Power Control Panel applet. You can also implement additional timers and set their timeouts by editing the registry directly. Windows Embedded CE does not limit the number of timers you can create. At startup, Power Manager reads the registry keys, enumerates the activity timers, and creates the associated events. Table 3-16 lists the registry settings for the SystemActivity timer. OEMs can add similar registry keys and configure these values for additional timers.

Table 3-16 Registry settings for activity timers

Оглавление книги