任务切换的精华思想

川长思鸟来 2022-06-09 06:47 81阅读 0赞

在21IC论坛上,无意中看到介绍简单OS的实现,感觉不错，抄下来.

#include <reg51.h>  
    
    #define MAX_TASKS 2       //任务槽个数.必须和实际任务数一至  
    #define MAX_TASK_DEP 12   //最大栈深.最低不得少于2个,保守值为12.  
    unsigned char idata task_stack[MAX_TASKS][MAX_TASK_DEP];//任务堆栈.  
    unsigned char task_id;    //当前活动任务号  
    
    
    //任务切换函数(任务调度器)  
    void task_switch(){  
            task_sp[task_id] = SP;  
    
            if(++task_id == MAX_TASKS)  
                    task_id = 0;  
    
            SP = task_sp[task_id];  
    }  
    
    //任务装入函数.将指定的函数(参数1)装入指定(参数2)的任务槽中.如果该槽中原来就有任务,则原任务丢失,但系统本身不会发生错误.  
    void task_load(unsigned int fn, unsigned char tid){  
            task_sp[tid] = task_stack[tid] + 1;  
            task_stack[tid][0] = (unsigned int)fn & 0xff;  
            task_stack[tid][1] = (unsigned int)fn >> 8;  
    }  
    
    //从指定的任务开始运行任务调度.调用该宏后,将永不返回.  
    #define os_start(tid) {task_id = tid,SP = task_sp[tid];return;}  
    
    /*============================以下为测试代码============================*/  
    
    void task1(){  
            static unsigned char i;  
            while(1){  
                    i++;  
                    task_switch();//编译后在这里打上断点  
            }  
    }  
    
    void task2(){  
            static unsigned char j;  
            while(1){  
                    j+=2;  
                    task_switch();//编译后在这里打上断点  
            }  
    }  
    
    void main(){  
            //这里装载了两个任务,因此在定义MAX_TASKS时也必须定义为2  
            task_load(task1, 0);//将task1函数装入0号槽  
            task_load(task2, 1);//将task2函数装入1号槽  
            os_start(0);  
    }

原文地址:[http://bbs.21ic.com/icview-1843574-1-1.html][http_bbs.21ic.com_icview-1843574-1-1.html]

补充资料:[http://blog.csdn.net/fivedoumi/article/details/50395701][http_blog.csdn.net_fivedoumi_article_details_50395701]

[http://www.eeworld.com.cn/mcu/article\_2017010432937.html][http_www.eeworld.com.cn_mcu_article_2017010432937.html]

[http_bbs.21ic.com_icview-1843574-1-1.html]: http://bbs.21ic.com/icview-1843574-1-1.html
[http_blog.csdn.net_fivedoumi_article_details_50395701]: http://blog.csdn.net/fivedoumi/article/details/50395701
[http_www.eeworld.com.cn_mcu_article_2017010432937.html]: http://www.eeworld.com.cn/mcu/article_2017010432937.html