Книга: Microsoft Windows Embedded CE 6.0 Exam Preparation Kit

System Timer

System Timer

The system timer is a hardware timer that generates system ticks at a frequency of one tick per millisecond. The system scheduler uses this timer to determine which threads should run at what time on the system. A thread is the smallest executable unit within a process that is allocated processor time to execute instructions in the operating system. You can stop a thread for an amount of time by using the Sleep function. The minimum value that you can pass to the Sleep function is 1 (Sleep(1)), which stops the thread for approximately 1 millisecond. However, the sleep time is not exactly 1 millisecond because the sleep time includes the current system timer tick plus the remainder of the previous tick. The sleep time is also linked to the priority of the thread. The thread priority determines the order in which the operating system schedules the threads to run on the processor. For those reasons, you should not use the Sleep function if you need accurate timers for real-time applications. Use dedicated timers with interrupts or multimedia timers for real-time purposes.

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