ADuC831,电子系统设计——基于RTX51实时操作系统程序设.ppt

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1、电子系统设计基于RTX51实时操作系统程序设计基础实时操作系统概述DACCON.7DACCON.6DACCON.5DACCON.4DACCON.3DACCON.2DACCON.1DACCON.0MODERNG1RNG0CLR1CLR0SYNC*PD1*PD0一、实时操作系统概述操作系统操作系统是一种管理计算机硬件的程序，为应用程序提供了基本的运行条件，在计算机用户和计算机硬件之间扮演着中介的角色。The operating system(OS)is the main program that controls how your computer system functions.The OS

2、manages the computers hardware,including the processor,memory,and storage devices,as well as peripheral devices.It is responsible for the management,scheduling,and interaction of tasks.Your first interaction with the OS is the user interface.Four categories:Real-Time(RTOS)Single-User,Single-TaskSing

3、le-User,MultitaskMultiuserWHAT THE OS DOESProvides user interfaceManages the CPUManages memory and storageManages hardware and peripheral devicesCoordinates application software with the CPUThe operating systems provides a way for the user to interact with the computer,manages the processor(CPU),man

4、ages the memory and storage,manages the computer systems hardware and peripheral devices,and provides a consistent means for software applications to work with the CPU.THE USER INTERFACEEnables you to interact with the computerTypes of interfaces:Command-driven interfaceMenu-driven interfaceGraphica

5、l user interface(GUI)PROCESSOR MANAGEMENTControls the timing of events the processor works onInterruptsInterrupt handlerInterrupt tableStack MEMORY AND STORAGE MANAGEMENTThe operating system allocates space in RAM for instructions and dataHARDWARE AND PERIPHERAL DEVICE MANAGEMENTDevice driversProgra

6、ms that enable the operating system to communicate with peripheral devicesProvided by the manufacturer of the device Plug and PlayHardware and software standardFacilitates the installation of new hardwareFILE MANAGEMENTThe operating system provides an organizational structure for the computers conte

7、ntsHierarchical structure of directoriesDrivesFoldersvSubfoldersFilesREAL-TIME OPERATING SYSTEMSREAL-TIME OPERATING SYSTEMS实时系统指系统的计算正确性不仅取决于计算的逻辑正确性，还取决于产生结果的时间。一个实时操作系统面对外界环境发生的变化（包括时间的消逝）时，必须确定性地保证在满足时间要求的情况下予以正确的反应处理。Multiple events handled by a single processor Events may occur simultaneously P

8、rocessor must handle multiple,often competing events Wide range of RTOS systemsSystems with a specific purpose and a certain resultUses include:Industrial machinesRobotic equipmentAutomobilesVideo game consolesHome appliancesREAL-TIME OPERATING SYSTEMSREAL-TIME OPERATING SYSTEMSA task is a program r

9、unning on the CPU core of a microcontroller.1、TaskA real-time operating system allows the execution of multiple tasks on a single CPU.All tasks execute as if they completely owned the entire CPU.Without a multitasking kernel(an RTOS),only one task can be executed by the CPU at a time.This is called

10、a single-task system.REAL-TIME OPERATING SYSTEMSa、Single-task systems(superloop)A superloop application is basically a program that runs in an endless loop,calling OS functions to execute theappropriate operations(task level).No real-time kernel is used,so interrupt service routines(ISRs)must be use

11、d for real-time parts of the software or critical operations(interrupt level).This type of system is typically used in small,uncomplex systems or if real-time behavior is not critical.REAL-TIME OPERATING SYSTEMSvoid main(void)int counter=0;while(1)/*repeat forever*/check_serial_io();/*check for seri

12、al input*/process_serial_cmds();/*process serial input*/check_kbd_io();/*check for keyboard input*/process_kbd_cmds();/*process keyboard input*/adjust_ctrlr_parms();/*adjust the controller*/counter+;/*increment counter*/b、COOPERATIVE MULTITASKINGREAL-TIME OPERATING SYSTEMSCooperative multitasking ex

13、pects cooperation of all tasks.Tasks can only be suspended by calling a function of the operating system.If they do not,the system“hangs”,which means that other tasks have no chance of being executed by the CPU while the first task is being carried out.REAL-TIME OPERATING SYSTEMSREAL-TIME OPERATING

14、SYSTEMSc、PREEMPTIVES MULTITASKINGA real-time operating system needs a regular timer-interrupt to interrupt tasks at defined times and to perform task-switches if necessary.The highestprioritytask in the READY state is therefore always executed,whether it is an interrupted task or not.If an ISR makes

15、a higher priority task ready,a task switch will occur and the task will be executed before the interrupted task is returned to.REAL-TIME OPERATING SYSTEMSREAL-TIME OPERATING SYSTEMS1、SchedulingThere are different algorithms that determine which task to execute,called schedulers.All schedulers have o

16、ne thing in common:they distinguish between tasks that are ready to be executed(in the READY state)and the other tasks thatare suspended for any reason(delay,waiting for mailbox,waiting for semaphore,waiting for event,and so on).The scheduler selects one of the tasks in the READY state and activates

17、 it(executes the program of this task).The task which is currently executing is referred to as the active task.REAL-TIME OPERATING SYSTEMSa、ROUND-ROBIN SCHEDULING ALGORITHMWith round-robin scheduling,the scheduler has a list of tasks and,when deactivating the active task,activates the next task that

18、 is in the READY state.Round-robin can be used with either preemptive or cooperative multitasking.It works well if you do not need to guarantee response time,if the response time is not an issue,or if all tasks have the same priority.All tasks are on the same level;the possession of the CPU changes

19、periodically after a predefined execution time.This time is called timeslice,and may be defined individually for every task.REAL-TIME OPERATING SYSTEMSb、PRIORITY-CONTROLLED SCHEDULING ALGORITHMIn real-world applications,different tasks require different response times.For example,in an application t

20、hat controlsa motor,a keyboard,and a display,the motor usually requires faster reaction time than the keyboard and display.While the display is being updated,the motor needs to be controlled.This makes preemptive multitasking a must.Round-robin might work,but because it cannot guarantee a specific r

21、eaction time.In priority-controlled scheduling,every task is assigned a priority.The order of execution depends on this priority.The scheduler activates the task that has the highest priority of all tasks in the READY state.This means that every time a task with higher priority than the active task

22、gets ready,it immediately becomes the active task.REAL-TIME OPERATING SYSTEMSREAL-TIME OPERATING SYSTEMS2、Communication between tasksIn a multitasking(multithreaded)program,multiple tasks work completely separately.Because they all work in the same application,it will sometimes be necessary for them

23、 to exchange information with each other.a、GLOBAL VARIABLESThe easiest way to do this is by using global variables.In certain situations,it can make sense for tasks to communicate via global variables,but most of the time this method has various disadvantages.For example,if you want to synchronize a

24、 task to start when the value of a global variable changes,you have to poll this variable,wasting precious calculation time and power,and the reaction time depends on how often you poll.REAL-TIME OPERATING SYSTEMSb、COMMUNICATION MECHANISMSWhen multiple tasks work with one another,they often have to:

25、exchange data,synchronize with another task,or make sure that a resource is used by no more than one task at a time.a)SignalsSignals represent the simplest and fastest form of task communication.No actual information is exchanged-only a stimulus is activated for a task.These can always be used when

26、a pure task synchronisation is required without data exchange.b)MAILBOXES AND QUEUESA mailbox is basically a data buffer managed by the RTOS and is used for sending a message to a task.A queue works in a similar manner,but handle larger messages than mailboxes,and every message may have a individual

27、 size.REAL-TIME OPERATING SYSTEMSc)SEMAPHORESIn a multi-tasking system there is often competition for resources.When several tasks can use the same portion of memory,the same serial I/O channel or another system resource,you have to find a way to keep the tasks out of each others way.The semaphore i

28、s a protocol mechanism,which is used primarily to control access to shared resources(mutual exclusion).By means of the semaphore concept,resources can be shared free of conflicts between the individual tasks.RTX51 多任务实时操作系统 RTX51 RTX51 是美国是美国Keil Keil 公司开发的一种小型的应用于公司开发的一种小型的应用于MCS51 MCS51 系列系列单片机的实时

29、多任务操作系统，它的使用可以简化比较复杂、单片机的实时多任务操作系统，它的使用可以简化比较复杂、有严格时间限制的软件的设计过程。有严格时间限制的软件的设计过程。RTX51RTX51主要有两个不同的主要有两个不同的可用版本：可用版本：RTX5lFullRTX5lFull版。这里称之为版。这里称之为RTX51RTX51的标准版，既可以以循的标准版，既可以以循环（环（Round Round 一一Robin Robin）方式执行任务，也可以按）方式执行任务，也可以按4 4 级任务优级任务优先级的方式切换不同优先级的任务。标准版以并行方式工先级的方式切换不同优先级的任务。标准版以并行方式工作，支持中断管

30、理，信号和消息可以通过邮箱系统在不同作，支持中断管理，信号和消息可以通过邮箱系统在不同任务之间传递。任务之间传递。RTX5lTinyRTX5lTiny版。这里称之为版。这里称之为RTX5lRTX5l的精简版，是其标准版的精简版，是其标准版的一个子集。它可以很容易地运行在的一个子集。它可以很容易地运行在8051 8051 的单芯片系统而的单芯片系统而不需要任何外部数据存储器。通用性强，系统需求低，但不需要任何外部数据存储器。通用性强，系统需求低，但功能上受到限制。它只支持循环方式和信号方式的任务切功能上受到限制。它只支持循环方式和信号方式的任务切换，而不支持优先级方式的任务切换。换，而不支持优先

31、级方式的任务切换。RTX51 多任务实时操作系统Advantages in using a Real-Time Multitasking Executive:A program can be more easily implemented,tested and maintained bybreaking down the problem to be solved into individual,easily comprehensible tasks.The modular approach allows individual tasks to be used in other projects

32、.Since the real-time and multitasking problems which occur are already solved the time required for creating programs and testing is considerably reduced.Advantages of RTX-51：Simple use of RTX-51 by integration in the Keil C51 development system.Complete support of all C51 features such as floating-

33、point operations,reentrant functions and interrupt functions.User-friendly configuration of RTX-51 for all members of the 8051 family.Flexibility-only requires a few system resources and can also be applied fortime-critical applicationsRTX51 多任务实时操作系统ParameterLimitsMaximum Number of Defined Tasks16M

34、aximum Number of Active Tasks16Required CODE Space900 Bytes MaxRequired DATA Space7 BytesRequired STACK Space3 Bytes/TaskRequired XDATA Space0 BytesTimer0System Clock Divisor1,000-65,535Interrupt Latency20 Cycles or LessContext Switch Time100-700 CyclesRTX51Tiny系统资源需求：系统资源需求：RTX-51 requires the foll

35、owing 8051 system resources:CODE Memory:Approx.6 to 8 Kbytes,depending on the function scope used.Internal(DATA and IDATA)RAM:40 to 46 bytes for system data(depending on the selected processor type).20 to 200 bytes for the stack(can be configured by the user).Register bank 0 for standard tasks;regis

36、ter banks 1,2 and 3 for fast tasks orC51 interrupt functions.External(XDATA)RAM:Minimal 450 bytes.Timer 0,1 or 2 for the system clock(can be configured by the user).RTX51 多任务实时操作系统RTX51 多任务实时操作系统RTX-51 recognizes two classes of tasks:Fast tasks with especially short responses and interrupt times.Eac

37、h fast task uses an individual register bank of the 8051 and contains its own stack area.RTX-51 supports a maximum of three fast tasks active at a time.Standard tasks that require somewhat more time for the task switching,therefore less internal memory than the fast tasks.All standard tasks share a

38、register bank and a stack area;during a task change the current contents of registers and the stack are stored in the external RAM.RTX-51 supports a maximum of 16 standard tasks active at a time.Task StatesEach RTX51 Tiny task is always in exactly one state which tells the disposition of the task.St

39、ateDescriptionRUNNINGRUNNINGThe task that is currently running is in the RUNNINGRUNNING State.Only one task at a time may be in this state.The os_running_task_id returns the task number of the currently executing task.READYREADYTasks which are ready to run are in the READYREADY State.Once the Runnin

40、g task has completed processing,RTX51 Tiny selects and starts the next Ready task.A task may be made ready immediately(even if the task is waiting for a timeout or signal)by setting its ready flag using the os_set_ready or isr_set_ready functions.WAITINGWAITINGTasks which are waiting for an event ar

41、e in the WAITINGWAITING State.Once the event occurs,the task is switched to the READYREADY State.The os_wait function is used to place a task in the WAITINGWAITING State.DELETEDDELETEDTasks which have not been started or tasks which have been deleted are in the DELETEDDELETED State.The os_delete_tas

42、k routine places a task that has been started(with os_create_task)into the DELETEDDELETED State.TIME-OUTTIME-OUTTasks which were interrupted by a Round-Robin Time-Out are in the TIME-OUTTIME-OUT State.This state is equivalent to the READYREADY State for Round-Robin programs.void main(void)int counte

43、r=0;while(1)/*repeat forever*/check_serial_io();/*check for serial input*/process_serial_cmds();/*process serial input*/check_kbd_io();/*check for keyboard input*/process_kbd_cmds();/*process keyboard input*/adjust_ctrlr_parms();/*adjust the controller*/counter+;/*increment counter*/RTX51 多任务实时操作系统M

44、ulti-Tasking ProgramsMore sophisticated C programs may implement a pseudo-multitasking scheme where several functions(or tasks)are called in a loop.For example:RTX51 Tiny Programsvoid check_serial_io_task(void)_task_ 1 /*This task checks for serial I/O*/void process_serial_cmds_task(void)_task_ 2 /*

45、This task processes serial commands*/void check_kbd_io_task(void)_task_ 3/*This task checks for keyboard I/O*/void process_kbd_cmds_task(void)_task_ 4 /*This task processes keyboard commands*/void startup_task(void)_task_ 0 os_create_task(1);/*Create serial_io Task*/os_create_task(2);/*Create serial_cmds Task*/os_create_task(3);/*Create kbd_io Task*/os_create_task(4);/*Create kbd_cmds Task*/os_delete_task(0);/*Delete the Startup Task*/