Title:PIC16F877A TIMER1计数操作 
Author:hnrain 
Date:2010-12-28

使用前置分频器 
T1CKPS1  T1CKPS1   
   0        0        1  分频  TMR1时钟为晶振时钟/(4*1) 
   0        1        2  分频  TMR1时钟为晶振时钟/(4*2) 
   1        0        4  分频  TMR1时钟为晶振时钟/(4*4) 
   1        1        8  分频  TMR1时钟为晶振时钟/(4*8) 
   TMR1是16位宽度的TMR1由2个8位的可读写的寄存器TMR1H和TMR1L组成。

TMR1有专门的启停控制位TMR1ON，通过软件可以任意启动或暂停TMR1计数功能。

T1CON:TIMER1 CONTROL REGISTER

bit7-6 unimplemented :Read as ‘0’

bit5-4 T1CKPS1:T1CKPS0:Timer1 input Clock Prescale Select bits

          11=1:8 prescale value

          10=1:4 prescale value

          01=1:2 prescale value

          00=1:1 prescale value

bit3   T1OSCEN:Timer1 Oscillator Enable Control bit

         1 = Oscillator is enable

         0 = Oscillator is shut-off

bit2 T1SYNC:Timer1 External Clock Input Synchronization Control bit

        when TMR1CS = 1

        1= Do not synchronize external clock input

        0= Synchronize external clock input

        when TMR1CS = 0

        This bit is ignored .Timer1 uses the internal clock when TMR1CS = 0.

bit1 TMR1CS:Timer1 Clock Source Select bit

       1 = External clock from pin RC0/T1OSO/T1CKI

       0 = Internal clock

bit0 TMR1ON:Timer1 on bit

     1 = enables timer1

     0 = stops timer1 
说明：作用在TMR1的计数状态，计数信号从RC0/T1CKI输入， 
当来一个上升沿时，采集到一个有效的信号，计数到TMR1L,TMR1H中。 
当计满时就会产生中断信号。 
***********************/ 
#include  
#include "../head/config.h"

__CONFIG(HS&WDTDIS&LVPDIS&PWRTEN);

void main(void) 
{ 
    T1CKPS0 = 0; 
    T1CKPS1 = 0;//不分频

    TMR1L = (65536 - 1)%256;//TMR1L,TMR1H赋初值 
    TMR1H = (65536 - 1)/256; 
    T1SYNC = 1;//TMR1异步计数器 
    TMR1CS = 1; 
    GIE = 1;//打开全局中断 
    PEIE = 1;//打开外部中断 
    TMR1IE = 1;//TMR1中断打开 
    TMR1ON = 1; 
    PORTD = 0x00; 
    TRISD = 0x00; 
    while(1){} 
}

void interrupt ISR(void) 
{ 
    TMR1L = (65536 - 1)%256;//重新赋值 
    TMR1H = (65536 - 1)/256; 
    if(TMR1IE && TMR1IF) 
    { 
        TMR1IF = 0; 
        PORTD = ~PORTD; 
    }    
}