◆ What is an embedded system?
The embedded system refers to the operating system and function software integrated into the computer hardware system. Simply put is the system
Application software and system hardware integration, similar to BIOS work. Has small software code, high automation
, Response speed is fast. It is especially suitable for real-time and multitasking systems.
◆ Embedded real-time multi-task operating system
Real Time Operating System is based on the operating characteristics of the operating system
of. Real time refers to the real time of the physical process. Real-time operating system refers to real-time, supporting real-time control
Working operating system. The primary task is to schedule all available resources to complete real-time control tasks, followed by
Important to improve the efficiency of the computer system, the important feature is to meet the limitations and requirements for time.
◆ Real-time multi-task operating system and minute multitasking operating system
They have obvious differences. Specifically, for the time-time operating system, the implementation of the software in time is not
Strict, time errors generally do not cause catastrophic consequences. For real-time operating systems, the main task is
Real-time processing on events, although events may arrive at the moment that cannot be predicted, but the software must be in the event
A response can be responded within a strict time limit when the occurrence occurs, even in the spike load,
Therefore, the timeout of the system time response means deadly failure. In addition, the important feature of real-time operating systems is
The system's deterministic, that is, the system can make an accurate estimate of the best and worst of the operation.
◆ Important concepts in real-time operating systems
System Response Time system issues a process requirement to give the system to give a response signal.
Task turn-switch time is the time used by the task switching between tasks.
Interrupt Latency is a computer receiving interrupt signal to the operating system to make a response, and complete
Change the time to the interrupt service program.
Real-time operating systems should have the following functions:
1) Task management (multitasking and priority-based task scheduling)
2) Synchronization and communication between tasks (semaphoex)
3) Memory optimization management (including ROM management)
4) Real-time clock service
5) Interrupt Management Service
◆ Work characteristics of real-time operating systems
The task in the real-time operating system (task) is equivalent to the process of process in the time-time operating system. In the system
There are four states of the task: Executing, Ready, Suspend, Hibut (Doormant).
Run: Get the CPU control.
Ready: Enter the task waiting for the queue. The scheduling is converted to the operating state.
Hang up: Task occurs, remove task waiting queue, waiting for system real-time events to wake up. Thereby
Woke or run.
Hibernation: Task for clearance or error. It is also considered to be tasks that do not exist in the system.
There can only be one task in the system in the system. Each task has obtained access to the CPU through the level of time by time.
