CHAPTER 18. Multi-tasking and the real-time operating system
Almost every embedded system has more than one activity that it needs to perform. A program for the Derbot AGV, for example, may need to sense its environment through bump and light sensors, measure the distance it has moved, and hence calculate and implement drive values for its motors. As a system becomes more complicated, it becomes increasingly difficult to balance the needs of the different things it does. Each will compete for CPU time and may therefore cause delays in other areas of the system. The program needs a way of dividing its time ‘fairly’ between the different demands laid upon it.
An important parallel aspect of the need to time-share the CPU is the need to ensure ...

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