单片机里采用定时器+时标的办法
参考 时间触发嵌入式系统设计模式

我现在结构是这样的：
void step0（）
{
    T1(100);
    if(flag_finish)
   {
        step++;
       flag_finish=0;
    }
}
void step1（）
{
    T2(100);
    if(flag_finish1)
   {
        step++;
       flag_finish1=0;
    }
}
......
void T1(uchar i)
{
    if(flag_20ms)
   {
      flag_20ms=0;
     if(++count>=i)
    {
     flag_finish=1;
    counter=0;
    }  
}

T2也是如此，是不是可以这样理解两位老师

用软件实现的话 会被中断的,中断时间短的话 没什么大碍 长一点 你都不行了 ,你1MS输出的东西  说不定2MS才能输出.

it will depend on your chip's hardware capabilities.

with a fast chip, you can simply use one counter and perform numerous test within the isr:

tmr_isr() {
  SysTick+=1; //increment systick counter
  for (i=0; i<TMR_MAX; i++) tmr[i].flag = (SysTick % tmr[i].period)?0:1; //set the flag if overflow
}

in your application, tmr.flag will be set if its period has passed.

Because of the '%' operator, this approach is not workable on a slow mcu to drive lots of software timers.

the 2nd approach would be to increment and test individual timers in the isr:

tmr_isr() {
  for (i=0; i<TMR_MAX; i++) {
    tmr[i].counter+=1; //increment timer;
    tmr[i].flag=(tmr[i].counter == tmr[i].period)?1:0; //set the flag
  }
}

if even the testing is too much, and your main loop is fast enough, you can put the testing portion of it over there.

generally, it will take you about 10 ticks to perform the various steps so if you are talking about 1ms isr period, you can do at most 100 software timers on a 1MIPS mcu, and practically 10 - 20 software timers if you want your mcu to perform other tasks.