PIC单片机定时器取值

用PIC16F877A,晶振用4M的做了一个实验如下:

实验通过示波器测得LED的高电平是500MS,低电平是500MS.以下为测试图:

#include

#define uint unsigned int

#define uchar unsigned char

uint intnum=0;

void init_system()

{

TRISC=0x00;

PORTC=0;

INTCON=0xc0;

PIE1=0x01;

TMR1L=(65536-63000)%256; //并非很多书上定的取50000

TMR1H=(65536-63000)/256;

T1CON=0x31;

}

void interrupt time0() //定时

{

TMR1IF=0;

TMR1L=(65536-63000)%256;

TMR1H=(65536-63000)/256;

intnum++;

}

void main()

{

init_system();

while(1)

{

if(intnum==1)

{

intnum=0;

PORTC=!PORTC;

}

}

}