Today's content is mainly trying to understand some concepts in the timer! Good Xuan! ! Is the author Xuzhen? !
Continued yesterday, my understanding is: here uses similar to the elves task, i.e., use two parts, existing in the context of the ISR and tasks, respectively. But the target is different. The elves task is to prevent the ISR from occupying system resources to make the task in hungry state, and taken. And here is to prevent ISR from being too long, generating the heat of the system time or even lost. At the same time, you can also manage several soft timer tasks with a Timer (here, it should be called Worker Task), which is connected to a counter as part of the system timer ISR. Reduce the number of installed ISR timers can improve the performance of this system.
[SIZE = 4] Possible processing delay [/ size]
The first delay is a time-driven task scheduling delay. The entire delay process: After the timer INT has occurred and the soft counter arrives, the ISR service is completed, and then the task is scheduled, and finally the worker task is ready. The second delay is based on prioritization task scheduling delay. The entire delay process: After the Worker Task is ready, a time fragment is ready, the high-priority task happens to be executed, and it is always waiting for the high priority task to complete the time, Worker Task starts running.
[SIZE = 4] Realization [/ size] Multiple Soft Timer Facilities can be organized in a two-way chain team, the advantage is startup and inserting a Timer speed is the fastest, but you can find and delete can only take one by one. ! The form of linear form is organized, and if an ordered method is not used, it is the worst form. It is usually sorted in ascending order in ascending order, which is usually sequenced. Timer Bookkeeping. The benefit is that the timer installation requires search and insert, and the deletion is actually positioned in use. I don't know if my understanding is accurate.
[size = 5] time slice rotation [/ size]
Timing Wheel This section makes me believe that the author is a Taoist! ! From Xuanzhen! ! Look at the dizziness! ! Is the author Li Qing can't use it easier to let others understand the way? I really admire him! ! I understand that the schedule mode of the time slice of time is this: use the Timer bookkeeping described in the previous item to record the "slot" where all tasks are located, then after INT generated in a timer, at the same time, at the same time, then go to run The task arrived at the same time. It's so loop! I think I understand Li Qing's ideas, he may have to cry! ! I don't know if it is right! !
In the last section of this chapter, some soft timers are provided and the object-related objects related to the soft timer can be recorded to my data dictionary. (If you use it!) Mainly divided into three groups, 1, underlying hardware related operations. 2, soft timer related operations. 3. Access to real-time clock or system clock memory.
[SIZE = 6] I / O subsystem [/ size]
Some I / O forms of operations are included in all embedded systems. In fact, communication with the device, the programming initialization I / O request, the actual data transfer between the device and the system, and the completion of comrades requesters.
[size = 5] Basic I / O Concept [/ size]
