Some basic concepts of embedded operating system

What is embedded system.

Embedded system refers to the integration of operating system and functional software into the computer hardware system. Simply put, the system's application software and system hardware integration, similar to the way the BIOS works. It has the characteristics of small software code, high automation, fast response and so on. Especially suitable for real-time and multitasking systems.

Embedded real-time multitasking operating system

Real-time multitasking operating systems (Realtimeoperatingsystem) are based on the operating system's operational characteristics. Real time refers to the real timing of the physical process. Real-time operating system is the operating system that can support real-time control system work. The first task is to dispatch all available resources to complete the real-time control tasks, and then focus on improving the use of computer systems, the important feature is to meet the time constraints and requirements.

Real-time multitask operating system and time-sharing multi-task operating system

There is a clear difference between them. Specifically, for time-sharing operating system, software implementation in time requirements, not strict, time errors, generally will not cause disastrous consequences. For real-time operating systems, the main task is to deal with the event in real time, although the event may arrive at an unpredictable time, but the software must be able to respond to the event in a strict time frame within the time of the response (System response times), even under the peak load, it should be so, The timeout of the system time response means a fatal failure. In addition, the important feature of the real-time operating system is the certainty of the system, that is, the system can make a precise estimate of the best and worst situation of the operation.

Important concepts in real-time operating systems

The system response Time (Systemresponsetime) system emits the processing request to the system to give the response signal time.

Task Lane Time (Context-switchingtime) is the time that is used to switch between tasks.

Interrupt Latency (interruptlatency) is the time when the computer receives an interrupt signal to the operating system to respond and completes the lane change into the interrupt service.

The real-time operating system should have the following features:

1 task management (multitasking and priority-based task scheduling)

2 synchronization and communication between tasks (semaphores and mailboxes, etc.)

3 storage optimization management (including ROM management)

4) Real Time clock service

5) Interrupt Management Service

Working characteristics of real-time operating systems

Tasks in a real-time operating system are equivalent to the concepts of processes (process) in a time-sharing operating system. The tasks in the system are four states: run (executing), Ready (Ready), suspend (suspended), Hibernate (dormant).

Run: Gain CPU control.

Ready: Enter the task wait queue. To a running state by scheduling.

Suspend: The task is blocked, the task waits for the queue, waits for the system real-time event to wake up. To be ready or run.

Hibernation: A task that is cleared for reasons such as task completion or error. It can also be considered a task that does not exist in the system.

There can be only one task running in the system. Each task obtains access to the CPU by level of the time slice respectively.

This article is reproduced to 51testing software test network