Книга: Real-Time Concepts for Embedded Systems

8.3 Event Registers

Some kernels provide a special register as part of each task’s control block, as shown in Figure 8.7. This register, called an event register, is an object belonging to a task and consists of a group of binary event flags used to track the occurrence of specific events. Depending on a given kernel’s implementation of this mechanism, an event register can be 8-, 16-, or 32-bits wide, maybe even more. Each bit in the event register is treated like a binary flag (also called an event flag) and can be either set or cleared.

Through the event register, a task can check for the presence of particular events that can control its execution. An external source, such as another task or an ISR, can set bits in the event register to inform the task that a particular event has occurred.

Applications define the event associated with an event flag. This definition must be agreed upon between the event sender and receiver using the event register.


Figure 8.7: Event register.

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