----------------------------------------------------------timer 0----------------------------------------------------------

TMR0為8位寬，有一個可選的預(yù)分頻器，用于通用目的，可用于定時和計數(shù)。

TMR1為16位寬，附帶一個可編程的預(yù)分頻器和一個可選的低頻時基振蕩器，適合與CPP模塊配合使用來實現(xiàn)輸入捕扣或輸出比較功能，也可于定時和計數(shù)。

TMR2為8位寬，附帶一個配合使用來實現(xiàn)PWM脈沖寬度調(diào)制信號的產(chǎn)生，只能用于定時。

TMR0用作定時器時，定時器時鐘＝系統(tǒng)時鐘/4；
寫TMR0時，會產(chǎn)生2個周期的的延時，如果不使用前置分頻器，可通過設(shè)置
初值進行補償。
例如 需要定時200個時鐘周期時，TMR0 = 256 -200 + 2= 58

OPTION_REG:

bit5 T0CS:TMR0 Clock Source Select bit

1 = Transition on T0CKI pin

0 = Internal instruction cycle clock(CLKO)

bit 4 T0SE:TMR0 Source Edge Select bit

1 = Increment on high-to-low transition on T0CKI pin

0 = Increment on low-to-high transition on T0CKI pin

bit 3 PSA:Prescaler Assignment bit

1 = Prescaler is assigned to the WDT

0 = Prescaler is assigned to the Timer0 module

bit2-0 PS2:PS0:Prescaler Rate Select bits

任何時候?qū)MR0寄存器進行一次寫操作后，其計數(shù)功能將被禁止2個指令周期。

給大家一個意見：如果想用TMR0實現(xiàn)精確的定時，一旦用了預(yù)分頻器后就不要對TMR0做任何寫操作。

注意：在中斷服務(wù)程序中查詢TMR0中斷時，既要查詢T0IE位，還要查詢T0IF位。

uint16 count = 0;
void main(void)
{
PSA = 1;//prescaler is assigned to the WDT
T0CS = 0;//Internal instruction cycle clock

TMR0 = 58;//timer 200 cycle clock

GIE = 1;//global interrupt enable
T0IE = 1;//TMR0 interrupt enable

PORTD = 0x00;
TRISD = 0x00;

while(1)
{}
}

void interrupt ISR(void)
{
if(T0IE && T0IF)
{
T0IF = 0;
count++;
if(count ==15530) // 大于1s左右，led閃 爍一次。
{
count = 0;
PORTD = ~PORTD;
}
TMR0 = TMR0 + 58;
}
}

---------------------------------------------timer1--------------------------------------

Title:PIC16F877A TIMER1計數(shù)操作
Author:hnrain
Date:2010-12-28

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

TMR1有專門的啟停控制位TMR1ON，通過軟件可以任意啟動或暫停TMR1計數(shù)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
說明：作用在TMR1的計數(shù)狀態(tài)，計數(shù)信號從RC0/T1CKI輸入，
當(dāng)來一個上升沿時，采集到一個有效的信號，計數(shù)到TMR1L,TMR1H中。
當(dāng)計滿時就會產(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(shù)器
TMR1CS = 1;
GIE = 1;//打開全局中斷
PEIE = 1;//打開外部中斷
TMR1IE = 1;//TMR1中斷打開
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;
}
}