Once a task has been executed for the specified time period, the kernel suspends that task and allows another task with the same priority to run for its configured time period (on WinCE this time period is called Quantum). Regarding rule number two, when several tasks run at the same priority, the system will run each task for a time period of 100ms (this time period can be configured according to the Thread Quantum). Guidance on the usage of priorities can be found in the following article: Real-Time Priority System Levels (Windows Embedded CE 6.0). Tasks with the same priority level should be executed according to a Round Robin with a timeslice of 100ms (or as defined in the Task Quantum).įor rule number one, the WinCE has 256 priority levels, higher values mean lower priority, and lower values mean higher priorities.Higher priority tasks should be executed first.Every 1ms the scheduler looks at the existing task in the system and decides which task will run based on the rules mentioned below: Hence, one of the first things we must understand is how does its task scheduler work? WinCE follows two simple rules while scheduling tasks. The Windows Embedded Compact is able to behave in accordance with the definition above. Real-time does not necessarily mean fast processing capabilities. Thus, a real-time system executes the code to produce a precise answer and it does that within a prescribed time constraint otherwise, this may lead to a system failure. Real-Time System Design and Analysis (Phillip A. "A real-time system is a system that must satisfy explicit (bounded) response-time constraints or risk severe consequences, including failure." It is always nice to remember the meaning of real-time in the engineering context, which is why I have transcribed below my favorite definition, found in the book “Real-Time System Design and Analysis”, written by Phillip A. This is a very important feature to consider when developing embedded systems. A key distinguishing feature that makes the Windows Embedded Compact different from all other versions of Windows is its real-time scheduler.
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