//******************************************************************************************
//  PIC16F877 Sample Program
//   Project      :
//   Program Name :
//   Programer    :
//   Create date  :  
//   History      :
//   Laungage     :  XC8 C Laungage Version 2.20
//******************************************************************************************
//   Description
//******************************************************************************************
//
#include <xc.h>
#pragma config FOSC = HS, WDTE = OFF, PWRTE = OFF, CP = OFF, BOREN = OFF, LVP = OFF, CPD = OFF, WRT = OFF, DEBUG = OFF  //For 16F877
//#pragma config FOSC = HS, WDTE = OFF, PWRTE = OFF, BOREN = OFF, LVP = OFF, CPD = OFF, WRT = OFF, DEBUG = OFF, CP = OFF  //For 16F877A
#define PI_TIM_LP         1000
#define PI_ON             1
#define PI_OFF            2

volatile unsigned int     G_TIMER;
volatile unsigned int     G_cnt;  

void Init_Timer(void);
void Timer_05mS_sub(void);
void Timer_1mS(unsigned int);

void main()
{

// *************************
//   1.Initialize 
// *************************
// (1)TRIS Register
    TRISA=0xff;   
    TRISB=0xff;
    TRISC=0x00;   
    TRISD=0xff;
//  TRISE=0xff;   
    
// (2)PORT Register
    PORTA=0x00;
    PORTB=0x00;
    PORTC=0x00;
    PORTD=0x00;
    PORTE=0x00;
    
// (3)Initialize value
    G_cnt    = 0;
    G_TIMER  = PI_OFF;

// (4)Initialize timer
    Init_Timer();

    while(1){    
        if(G_TIMER == PI_ON ){
            PORTC = 0xff;
            Timer_1mS(1000);
            PORTC = 0x00;
            G_TIMER = PI_OFF;
            G_cnt=0;
        } 
    }

}
        
//******************************************************************************************
//  Function Name : Timer_1mS
//  Title         : Wait function (1mS) * Number (argument)
//  Input         :
//  Output        :
//******************************************************************************************
void Timer_1mS(unsigned int Number)
{
    unsigned int lp;
    unsigned int chk_wdt = 0;

    Number = Number *2;

    for(lp=0;lp<Number;lp++){
        if(chk_wdt > 1000){
            CLRWDT();
            chk_wdt = 0;
        } 
        chk_wdt++;
        Timer_05mS_sub(); 
    }    
}  

//******************************************************************************************
//  Function Name : Timer_05mS_sub
//  Title         : Wait function (1mS)
//  Input         :
//  Output        :
//******************************************************************************************
void Timer_05mS_sub(void)
{
// ******************************************************************
// 1.Define T1CON: TIMER1 CONTROL REGISTER (ADDRESS 10h)
//    T1CON[7-6] Unimplemented: Read as '0'
//    T1CON[5-4] 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
//    T1CON[3] T1OSCEN: Timer1 Oscillator Enable Control bit
//         1 = Oscillator is enabled
//         0 = Oscillator is shut-off (the oscillator inverter is turned off to eliminate power drain)
//    T1CON[2] 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.
//    T1CON[1] TMR1CS: Timer1 Clock Source Select bit
//        1 = External clock from pin RC0/T1OSO/T1CKI (on the rising edge)
//        0 = Internal clock (FOSC/4)
//    T1CON[0] TMR1ON: Timer1 On bit
//        1 = Enables Timer1
//        0 = Stops Timer1  
//    
// Define T2CON: TIMER2 CONTROL REGISTER (ADDRESS 12h)    
//    T1CON[7]   *Unimplemented: Read as ‘0’
//    T1CON[6-3] TOUTPS3:TOUTPS0: Timer2 Output Postscale Select bits
//         0000 = 1:1 postscale
//         0001 = 1:2 postscale
//         0010 = 1:3 postscale
//            **
//            **
//            **  
//        1111 = 1:16 postscale
//    T1CON[2] TMR2ON: Timer2 On bit
//        1 = Timer2 is on
//        0 = Timer2 is off
//    T1CON[1-0] T2CKPS1:T2CKPS0: Timer2 Clock Prescale Select bits
//        00 = Prescaler is 1
//        01 = Prescaler is 4
//        1x = Prescaler is 16
//*****************************************************************  
    
//  T1CON = 0b00000101;     //Since timer1 is used as an interrupt timer, it is changed to timer2.
    T2CON = 0b00000110;
    
// *******************************************************
// 2.Define TMR1 Register
// *******************************************************
//  (1)TMR1 data ( OSC:16MHz, 1:1 Prescale value, 0.001[S];1000Hz )
//     1mS(1000Hz): 16MHz / 4(FOSC/4) / 1000(1000Hz)==> 0d4000(Count) ==> 0x0FA0(Count)
//     TMR1 = 0xFFFF - 0x0FA0 ==> 0xF05F
//  TMR1H = 0xF0;
//  TMR1L = 0x5F;
//
//  (2)TMR1 data ( OSC:20MHz, 1:1 Prescale value, 0.001[S];1000Hz )
//     1mS(1000Hz): 20MHz / 4(FOSC/4) / 1000(1000Hz)==> 0d5000(Count) ==> 0x1338(Count)
//     TMR1 = 0xFFFF - 0x1338 ==> 0xECC7
//
//  (3)TMR2 data ( OSC:20MHz, 1:1 Prescale value, 0.001[S];1000Hz )
//     1mS(1000Hz): 20MHz / 4(FOSC/4) / 16(Prescale) / 500(2000Hz)==> 0d156(Count) ==> 0x9C(Count)
//     TMR1 = 0xFF - 0x9C ==> 0x63

//  TMR1H = 0xEC;   //Since timer1 is used as an interrupt timer, it is changed to timer2.
//  TMR1L = 0xC7;   //Since timer1 is used as an interrupt timer, it is changed to timer2.
    TMR2  = 0x63;

// *******************************************************
// 3.Timer
// *******************************************************
    PIR1bits.TMR2IF = 0;
    while(1){
        if(PIR1bits.TMR2IF != 0 )break;
    }
}

//******************************************************************************************
//  Function Name : Timer_1mS_sub
//  Title         : Wait function (1mS)
//  Input         :
//  Output        :
//******************************************************************************************
void Init_Timer(void)
{
// ******************************************************************
// 1.Define T1CON: TIMER1 CONTROL REGISTER (ADDRESS 10h)
//    T1CON[7-6] Unimplemented: Read as '0'
//    T1CON[5-4] 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
//    T1CON[3] T1OSCEN: Timer1 Oscillator Enable Control bit
//         1 = Oscillator is enabled
//         0 = Oscillator is shut-off (the oscillator inverter is turned off to eliminate power drain)
//    T1CON[2] 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.
//    T1CON[1] TMR1CS: Timer1 Clock Source Select bit
//        1 = External clock from pin RC0/T1OSO/T1CKI (on the rising edge)
//        0 = Internal clock (FOSC/4)
//    T1CON[0] TMR1ON: Timer1 On bit
//        1 = Enables Timer1
//        0 = Stops Timer1  
// ******************************************************************   
    T1CON = 0b00000101;

// *******************************************************
// 2.Define TMR1 Register
// *******************************************************
//  (1)TMR1 data ( OSC:16MHz, 1:1 Prescale value, 0.001[S];1000Hz )
//     1mS(1000Hz): 16MHz / 4(FOSC/4) / 1000(1000Hz)==> 0d4000(Count) ==> 0x0FA0(Count)
//     TMR1 = 0xFFFF - 0x0FA0 ==> 0xF05F
//  TMR1H = 0xF0;
//  TMR1L = 0x5F;
//
//  (2)TMR1 data ( OSC:20MHz, 1:1 Prescale value, 0.001[S];1000Hz )
//     1mS(1000Hz): 20MHz / 4(FOSC/4) / 1000(1000Hz)==> 0d5000(Count) ==> 0x1338(Count)
//     TMR1 = 0xFFFF - 0x1338 ==> 0xECC7
    TMR1H = 0xEC;
    TMR1L = 0xC7;
 
// *******************************************************
// 3.Define Interrupts
// *******************************************************
    PIR1bits.TMR1IF = 0;   //Timer1 Overflow Interrupt Flag bit          
    INTCONbits.GIE  = 1;   //Grobal Interrupt Ebable (->1)               
    INTCONbits.PEIE = 1;   //Peripheral Interrupt Ebable (->1)
    PIE1bits.TMR1IE = 1;   //Timer1 Overflow Interrupt Enable bit(->1)  
    
}

//******************************************************************************************
//  Function Name : Int_tim
//  Title         : Interrupt function
//  Input         :
//  Output        :
//******************************************************************************************
void __interrupt() isr(void)
{
   
// **********************************
//  1.Initiarize    
// ********************************** 
// 1.Stop Interrupt    
    INTCONbits.GIE  = 0 ;      // Grobal Interrupt Disable             (->1)     
    
// **********************************
//  2.Timer 1    
// **********************************  
    if(PIR1bits.TMR1IF){    
//  1.Check Global Counter
        if(G_cnt < PI_TIM_LP ){
            G_cnt++;
        }else{
            G_cnt   =0;
            G_TIMER = PI_ON;
        }
        
//  2.Initialized timer
        Init_Timer();
    }
    
}