/* --- STC12C5Axx Series MCU PCA module Extended external interrupt */


#include "reg51.h"
#include "intrins.h"

typedef unsigned char BYTE;
typedef unsigned int WORD;

/*Declare SFR associated with the PCA */
sfr CCON        =   0xD8;           //PCA control register
sbit CCF0       =   CCON^0;         //PCA module-0 interrupt flag
sbit CCF1       =   CCON^1;         //PCA module-1 interrupt flag
sbit CR         =   CCON^6;         //PCA timer run control bit
sbit CF         =   CCON^7;         //PCA timer overflow flag
sfr CMOD        =   0xD9;           //PCA mode register
sfr CL          =   0xE9;           //PCA base timer LOW
sfr CH          =   0xF9;           //PCA base timer HIGH
sfr CCAPM0      =   0xDA;           //PCA module-0 mode register
sfr CCAP0L      =   0xEA;           //PCA module-0 capture register LOW
sfr CCAP0H      =   0xFA;           //PCA module-0 capture register HIGH
sfr CCAPM1      =   0xDB;           //PCA module-1 mode register
sfr CCAP1L      =   0xEB;           //PCA module-1 capture register LOW
sfr CCAP1H      =   0xFB;           //PCA module-1 capture register HIGH
sfr PCAPWM0     =   0xf2;
sfr PCAPWM1     =   0xf3;

sbit PCA_LED    =   P1^0;           //PCA test LED

void PCA_isr() interrupt 7 using 1
{
    CCF0 = 0;                       //Clear interrupt flag
    PCA_LED = !PCA_LED;             //toggle the test pin while CEX0(P1.3) have a falling edge
}

void main()
{
    CCON = 0;                       //Initial PCA control register
                                    //PCA timer stop running
                                    //Clear CF flag
                                    //Clear all module interrupt flag
    CL = 0;                         //Reset PCA base timer
    CH = 0;
    CMOD = 0x00;                    //Set PCA timer clock source as Fosc/12
                                    //Disable PCA timer overflow interrupt
    CCAPM0 = 0x11;                  //PCA module-0 capture by a negative tigger on CEX0(P1.3) and enable PCA interrupt
//  CCAPM0 = 0x21;                  //PCA module-0 capture by a rising edge on CEX0(P1.3) and enable PCA interrupt
//  CCAPM0 = 0x31;                  //PCA module-0 capture by a transition (falling/rising edge) on CEX0(P1.3) and enable PCA interrupt

    CR = 1;                         //PCA timer start run
    EA = 1;

    while (1);
}