这个程序基本上可以跑，但是这是我网上找的，一开始的时候电机不转，按键按一下，缓慢转动，再按加速，再按更加加速，再按，慢速，最后按，停止，然后循环·······请大神帮忙解释解释每步的大概意思，或者帮忙给个直流电机的变速代码，谢谢······
#include <AT89X51.H>void delay( unsigned int ms);
#define Key P2_1
#define motor P1_2
unsigned char code set[4]={0,3,6,9}; //PWM　占空比90%，60%，30%
unsigned char code zy[9]={2,4,6,8,9,8,6,4,2}; //自然风
unsigned char tt=0; //档位
unsigned char jj=0;
void delay( unsigned int ms);
void main( void)
{
bit kk=0; //按键
motor = 0; TMOD = 0x01; //定时器T0，工作方式1
TH0 = -1000/256;TL0 = -1000%256; //定时1ms
ET0 = 1;
EA = 1;
TR0 = 1;
while(1)
{
Key =1;
if( Key == 0)
{
delay(10);
Key =1;
if(Key == 0 && kk ==0)
{ tt++;
if(tt>4) tt=0; kk =1;
}
}
Key = 1; if( Key == 1) kk= 0;
}
}
void IT( void ) interrupt 1
{
static unsigned char i = 0;
TH0 = -1000/256;
TL0 = -1000%256; //定时1ms
if(tt<4)
{
if( i < set[tt] ) motor =1;
else
motor = 0; i++;if(i>=10) i=0;
}
else if(tt==4)
{ static unsigned char j = 0;
if(j<zy[jj]) motor=1;
else motor=0;
j++;if (j>=30)
{
j=0; jj++;} if(jj>9) jj=0;
}
}
void delay( unsigned int ms) //延时
{
unsigned char i;
while( ms--)
{
for( i=0 ; i<125 ; i++);
}
}