STC11F系列不带PCA PWM输出功能。若需要可以使用12系列。这里提供一个11F系列的解决办法，但是占用一个定时器。废话少说，贴出主要代码：

#include <reg51.h>
#include <string.h>
#define uchar unsigned char
#define uint  unsigned int

sbit SubKey = P3^3; //PWM占空比下调按钮
sbit AddKey = P3^4; //PWM占空比上调按钮
sbit AdjKey = P3^5; //调节幅度按钮

sbit PWM = P1^3;    //PWM输出引脚

unsigned char Total = 0; //总计数
unsigned char zkb =  0;  //占空比
unsigned char tj  =  2;  //控制当前调节键减价幅度
unsigned char Cur =  0;  //当前计数

void initTimer(void)
{
 TMOD=0x1;
 TH0=0xff;
 TL0=0xf7;
}

void Dealy5Ms()
{
    unsigned int Count = 500;
    while(Count --);
}

  
void main(void)
{ 
   PWM = 1;
   initTimer();
    TR0=1;
    ET0=1;
    EA=1;

 while(1)
 {
        if(!AdjKey)
        {
            Dealy5Ms();
             if(!AdjKey)
             {
                if(tj < 10)
                {
                     tj++; 
                }
                else
                {
                   tj =0;
                }
             }
             while(!AdjKey);
        }

        if(!AddKey)
        {
            Dealy5Ms();
             if(!AddKey)
             {
                if(zkb < 101-tj)
                {
                    zkb = zkb + tj;
                   
                }
             }
             while(!AddKey);
        }

        if(!SubKey)
        {
            Dealy5Ms();
             if(!SubKey)
             {
                if(zkb > tj)
                {
                    zkb= zkb - tj;
                }
             }
             while(!SubKey);
        }  //end if    

    } //end while

}//end main

void timer0(void) interrupt 1
{
    if(Cur <101)
        Cur ++;
    else
        Cur = 0;

    if(Cur < zkb)
        PWM = 1;
    else
        PWM = 0; 

 
    TH0=0xff;
    TL0=0xf7;

}

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