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- how µC/OS-II handles access to critical sections of code,
- what a task is, and how µC/OS-II knows about your tasks,
- how tasks are scheduled,
- how µC/OS-II determines the percent CPU your application is using,
- how to write Interrupt Service Routines (ISRs),
- what a clock tick is and how µC/OS-II handles it,
- how to initialize µC/OS-II, and
- how to start multitasking.
Contents of this Section
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Application Services
This chapter also describes the application services listed in table 3.1. The code for OSSchedLock() and OSSchedUnlock() can be disabled by setting OS_SCHED_LOCK_EN to 0 in OS_CFG.H as shown in table 3.1. You should note that the other services cannot be ‘compiled out’ because they are an integral part of the core services offered by µC/OS-II.
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Figure 3.1 µC/OS-II File Structure.
Contents of this Section
Table of Contents
Critical Sections, OS_ENTER_CRITICAL() and OS_EXIT_CRITICAL()
µC/OS-II, like all real-time kernels, needs to disable interrupts in order to access critical sections of code and to reenable interrupts when done. This allows µC/OS-II to protect critical code from being entered simultaneously from either multiple tasks or ISRs. The interrupt disable time is one of the most important specifications that a real-time kernel vendor can provide because it affects the responsiveness of your system to real-time events. µC/OS-II tries to keep the interrupt disable time to a minimum, but with µC/OS-II, interrupt disable time is largely dependent on the processor architecture and the quality of the code generated by the compiler.
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