16F877A有三个定时器，中断方式都调试出来了，想把它们整合到一块同时工作，可搞了半天，就是不干。最后整明白了，PIC16系列单片机的中断入口中有一个。PIC的功能是很强大，外围模块也多，速度也较快，但PIC的这个中断方案不好，应该改进。以下是三个定时中断同时工作的调试代码。

#include<pic.h>
#define uchar unsigned char
#define uint  unsigned int
__CONFIG(0x3B31);
void init();
uint Timer0Num,Timer1Num,Timer2Num;//
void timer0();
void timer1();
void timer2();
void main()
{
 init();
 while(1)
 {
  if(Timer0Num>=20)
  {
   Timer0Num = 0;
   RD0 = ~RD0;
  }
  if(Timer1Num >= 4)
  {
   Timer1Num = 0;
   RD2 = !RD2;
  }
  if(Timer2Num >= 50)
  {
   Timer2Num = 0;
   RD4 = !RD4;
  }
 }
}
void init(void)
{
 TRISD = 0;
 PORTD = 0;
 OPTION = 0x07;//256分频
 TMR0 = 56;
 PIE1 |= 0x01 | 0x02;
 TMR1H = (65536-50000)/256;
 TMR1L = (65536-50000)%256;
 T1CON = 0x21;//4分频
 TMR2 = 0;
 PR2 = 100;
 T2CON = 0x1D;
 INTCON = 0xE0;
}
void interrupt Ints()
{
 if(T0IE&&T0IF)    timer0();
 if(TMR1IE&&TMR1IF) timer1();
 if(TMR2IE&&TMR2IF) timer2();
}
void timer0()
{
 T0IF = 0;
 TMR0 = 56;
 Timer0Num++;
}
void timer1()
{
 TMR1IF = 0;
 TMR1H = (65536-50000)/256;
 TMR1L = (65536-50000)%256;
 Timer1Num++;
}
void  timer2()
{
 TMR2IF = 0;
 TMR2 = 0;
 PR2 = 200;
 Timer2Num++;
}