PIC16F877A TIMER1計數操作

Title:PIC16F877A TIMER1計數操作
Author:hnrain
Date:2010-12-28

使用前置分頻器
T1CKPS1 T1CKPS1
0 0 1 分頻 TMR1時(shí)鐘為晶振時(shí)鐘/(4*1)
0 1 2 分頻 TMR1時(shí)鐘為晶振時(shí)鐘/(4*2)
1 0 4 分頻 TMR1時(shí)鐘為晶振時(shí)鐘/(4*4)
1 1 8 分頻 TMR1時(shí)鐘為晶振時(shí)鐘/(4*8)
TMR1是16位寬度的TMR1由2個(gè)8位的可讀寫(xiě)的寄存器TMR1H和TMR1L組成。

TMR1有專(zhuān)門(mén)的啟?？刂莆籘MR1ON，通過(guò)軟件可以任意啟動(dòng)或暫停TMR1計數功能。

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
說(shuō)明：作用在TMR1的計數狀態(tài)，計數信號從RC0/T1CKI輸入，
當來(lái)一個(gè)上升沿時(shí)，采集到一個(gè)有效的信號，計數到TMR1L,TMR1H中。
當計滿(mǎn)時(shí)就會(huì )產(chǎn)生中斷信號。
***********************/
#include
#include "../head/config.h"

__CONFIG(HS&WDTDIS&LVPDIS&PWRTEN);

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

TMR1L = (65536 - 1)%256;//TMR1L,TMR1H賦初值
TMR1H = (65536 - 1)/256;
T1SYNC = 1;//TMR1異步計數器
TMR1CS = 1;
GIE = 1;//打開(kāi)全局中斷
PEIE = 1;//打開(kāi)外部中斷
TMR1IE = 1;//TMR1中斷打開(kāi)
TMR1ON = 1;
PORTD = 0x00;
TRISD = 0x00;
while(1){}
}

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