#include <stc89c51.h>
/****小小调度器开始**********************************************/
#define MAXTASKS 3
volatile unsigned char timers[MAXTASKS];
#define _SS static unsigned char _lc=0; switch(_lc){default:
#define _EE ;}; _lc=0; return 255;
#define WaitX(tickets) do { _lc=(__LINE__%255)+1; return tickets ;case (__LINE__%255)+1:;} while(0);
#define WaitUntil(A) do { while(!A) WaitX(1);} while(0);
#define RunTask(TaskName,TaskID) do { if (timers[TaskID]==0) timers[TaskID]=TaskName(); } while(0);
#define RunTaskA(TaskName,TaskID) do { if (timers[TaskID]==0) {timers[TaskID]=TaskName(); continue;}}while(0); //前面的任务优先保证执行
#define CallSub(SubTaskName) do {unsigned char currdt; _lc=(__LINE__%255)+1; return 0; case (__LINE__%255)+1: currdt=SubTaskName(); if(currdt!=255) return currdt;} while(0);
#define InitTasks() do {unsigned char i; for(i=MAXTASKS;i>0 ;i--) timers[i-1]=0; } while(0);
#define UpdateTimers() do{unsigned char i; for(i=MAXTASKS;i>0 ;i--){if((timers[i-1]!=0)&&(timers[i-1]!=255)) timers[i-1]--;}} while(0);
#define SEM unsigned int
//初始化信号量
#define InitSem(sem) do{sem=0;}while(0);
//等待信号量
#define WaitSem(sem) do{ sem=1; WaitX(0); if (sem>0) return 1;} while(0);
//发送信号量
#define SendSem(sem) do {sem=0;} while(0);
/*****小小调度器结束*******************************************************/
sbit LED1 = P2^1;
sbit LED2 = P2^2;
sbit LED0 = P2^5;
unsigned char task0(){
_SS
while(1){
WaitX(50);
LED0=!LED0;
}
_EE
}
unsigned char task1(){
_SS
while(1){
WaitX(100);
LED1=!LED1;
}
_EE
}
unsigned char task2(){
_SS
while(1){
WaitX(100);
LED2=!LED2;
}
_EE
}
void InitT0()
{
TMOD = 0x21;
IE |= 0x82; // 12t
TL0=0Xff;
TH0=0XDB;
TR0 = 1;
}
void INTT0(void) interrupt 1 using 1
{
TL0=0Xff; //10ms 重装
TH0=0XDB;//b7;
UpdateTimers();
RunTask(task0,0);//任务0具有精确按时获得执行的权限，要求：task0每次执行消耗时间<0.5个 ticket----5ms
}
void main()
{
InitT0();
InitTasks(); //初始化任务，实际上是给timers清零
while(1)
{
// RunTask(task0,0);
RunTaskA(task1,1);//任务1具有比任务2高的运行权限
RunTaskA(task2,2);//任务2具有低的运行权限
}
}
