18.1 real-time system with front and back office systems
Real-time system
Real-time system RTOS , can run multiple tasks, and according to different tasks for resource management, task scheduling, message management and other work, while RTOS according to the priority of each task to the task scheduling, in order to achieve real-time requirements. RTOS enables CPU utilization to be maximized , and can make the application modular, and in real-time applications, developers can be complex application hierarchy, so the code easier to design and maintenance, more common RTOS such as ucos , VxWorks , FreeRTOS such as , for example, there are relatively more advanced applications on the phone operating system Palm OS , Symbian (Symbian) , Windows Mobile, Linux , Android (Andrews), the iPhone (Apple) OS Figure 18.1-1 , Black Berry (Blackberry) OS 6.
A real-time system is any system that must respond within a specified limited time. In this system, the time plays an important role, the success of the system is not only to see whether the output of the logical correct results, but also depends on whether it is given within the specified time the results.
In accordance with the stringent requirements of the time, real-time system is divided into hard real-time ( Hard Real Time ), solid real-time ( Firm Real Time ) and soft real-time ( Soft Real Time ). Hard real-time system is the system response to the absolute requirements within the specified time range. Soft real-time system, timely response is also very important, but the occasional response is also slow to accept. In the solid real-time system, can not respond in time will cause the service quality decline.
The flight control system of the aircraft is a hard real-time system, because a timely response is likely to cause serious consequences. Data acquisition system is often a soft real-time system, and occasionally unable to respond in a timely manner may cause the collection of data is not accurate, but there is no serious consequences. VCD machine controller if you do not play the screen in time, will not cause any big loss, but the user may lose confidence in product quality, such a system can be counted as solid real time system.
Common real-time system usually by the computer through the sensor input some data, the data processing, and then control some of the physical equipment to respond to the action. Such as the refrigerator's temperature control system needs to read the temperature inside the refrigerator, decide whether to continue or stop the temperature. Since real-time systems are often the core of large projects, the control member is typically embedded in a larger system, a control program is solidified in ROM , so sometimes called embedded systems ( Embedded System ).
The system needs to respond to events in real time can be divided into periodic ( with the Periodic ) and non-periodic ( Aperiodic ) of. For example, the air detection system every 100ms through the sensor to read a data, which is cyclical; and fighter aircraft flight control system needs to face a variety of emergencies, are non-cyclical.
Real-time system has the following characteristics:
To interact with the real world
This is a significant feature of the real-time system that distinguishes it from other systems. It is often necessary to control the external device, so that timely response to external events.
Such as the production workshop of the robot, the parts must be accurately assembled up.
The system is complex and complex
The complexity of real-time systems is not only reflected in the number of lines of code, but also in the diversity of requirements. Due to real-time system and reality
Industry, and the real world is always changing, which will lead to real-time system in the life cycle often face changes in demand, had to make the appropriate changes.
The reliability and safety requirements are very high
Many real-time systems are used in very important places, and some are even related to life safety. Failure of the system can lead to loss of life and property, which requires real-time systems with high reliability and security.
Strong concurrency
Real-time systems often require simultaneous control of many peripherals, for example, the system needs to simultaneously control sensors, conveyors and sensors and other equipment. In most cases, the use of micro-controller time slices assigned to different processes can be simulated in parallel. However, in the case where the response time of the system is very strict, the method of allocating the time slice simulation may not be able to meet the requirements. At this point, you have to consider the use of multi-processor system. This is why the multiprocessor system was the first to flourish in real-time systems.
Using a real-time system simplifies the design of the application:
( 1 ) The mechanism of multitasking and inter-task communication between operating systems allows complex applications to be divided into a series of smaller and more manageable tasks.
( 2 ) the division of the program to make software testing easier, team work decomposition, but also conducive to code reuse.
( 3 ) Complex timings and details of the order of the program can be removed from the application code.
Thanks,
Mintspring
21ic open class, 21ic friends common learning circle! Learn microcontroller , embedded, analog, power ... ... see here http://open.21ic.com move more 21ic exclusive micro class: http://open.21ic.com/list/3/0/0
RTX Real-Time Kernel System
2. Front and back systems
If you do not carry real-time system called front and back system architecture, such as the previous experiments have been done such as GPIO , timer, digital tube experiments are front and back system architecture, the order of the implementation of the order, and the front refers to the interrupt level , The background refers to the main function of the program that is the task level, front and back system is also called the super cycle system, this can be "while (1)" keyword can be learned. In the front and back system, the key time operation must be interrupted by the operation to ensure real-time, because the front and back system tasks are executed sequentially, the interrupt service function provides the information necessary to the background of the process to deal with this information If the number of tasks, the more real-time can not be guaranteed, because the cycle of the execution time is not constant, the program through a specific part of the exact time is not certain. Furthermore, if the program is modified, the timing of the loop is also affected. Many microprocessor-based microcontroller products using front and back office systems design, such as microwave ovens, telephones, toys and so on. In other applications based on micro-controller, from the point of view of power saving, usually the microcontroller in a halt state (halt) , all things rely on interrupt service to complete.
3. Real-time system comparison with front and back systems
The most obvious difference between the implementation of the system and the front and back systems is whether the task is concurrency, Figure 18.1-2 shows the real-time system tasks
State, Figure 18.1-3 shows the status of the front and back system tasks.
Figure 18.1-2 Real-time system execution task status
Figure 18.1-3 Front and Back Systems Perform task status
As can be seen from Figure 18.1-2, the traditional microcontrollers can only perform one task at the same time, but only through the fast task switching , all tasks of the real-time system (task 1 , task 2 and task 3 ) The
As can be seen from Figure 18.1-3 , the front and back systems default to the traditional microcontrollers can only perform a task at the same time, the task of the task 1 , task 2 and task 3 .
Thanks,
Mintspring
If you do not carry real-time system called front and back system architecture, such as the previous experiments have been done such as GPIO , timer, digital tube experiments are front and back system architecture, the order of the implementation of the order, and the front refers to the interrupt level , The background refers to the main function of the program that is the task level, front and back system is also called the super cycle system, this can be "while (1)" keyword can be learned. In the front and back system, the key time operation must be interrupted by the operation to ensure real-time, because the front and back system tasks are executed sequentially, the interrupt service function provides the information necessary to the background of the process to deal with this information If the number of tasks, the more real-time can not be guaranteed, because the cycle of the execution time is not constant, the program through a specific part of the exact time is not certain. Furthermore, if the program is modified, the timing of the loop is also affected. Many microprocessor-based microcontroller products using front and back office systems design, such as microwave ovens, telephones, toys and so on. In other applications based on micro-controller, from the point of view of power saving, usually the microcontroller in a halt state (halt) , all things rely on interrupt service to complete.
3. Real-time system comparison with front and back systems
The most obvious difference between the implementation of the system and the front and back systems is whether the task is concurrency, Figure 18.1-2 shows the real-time system tasks
State, Figure 18.1-3 shows the status of the front and back system tasks.
Figure 18.1-2 Real-time system execution task status
Figure 18.1-3 Front and Back Systems Perform task status
As can be seen from Figure 18.1-2, the traditional microcontrollers can only perform one task at the same time, but only through the fast task switching , all tasks of the real-time system (task 1 , task 2 and task 3 ) The
As can be seen from Figure 18.1-3 , the front and back systems default to the traditional microcontrollers can only perform a task at the same time, the task of the task 1 , task 2 and task 3 .
Thanks,
Mintspring
-
- Information
-
Who is online
Users browsing this forum: No registered users and 5 guests