//===================================================================================
//PCA工作在8位脈寬調(diào)制器工作方式，在PWM引腳輸出一個占空比為0<-->0xfe的PWM
//信號且重復輸出，可用示波器觀察占空比變化。

//實驗時短接J12的1,2引腳.
//-----------------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------------

#include <c8051f310.h>                 // SFR declarations
#include <INTRINS.H>
#include <stdio.h>

//------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------
void PORT_Init (void);
void PCA_Init (void);
void PCA_ISR (void);
//------------------------------------------------------------------------------------
// MAIN Routine
//------------------------------------------------------------------------------------
void main (void)
{	
	unsigned long b;
	 
   /*關(guān)看門狗*/
   PCA0MD &= ~0x40; // WDTE = 0 (watchdog timer enable bit)
   OSCICN |= 0x03; // Set internal oscillator to highest
                   // setting (24500000)
	
   	PORT_Init ();			/*初始化I/O口*/
   	PCA_Init ();				/*PCA初始化成8位脈寬調(diào)置方式*/
    EIE1= 0x10;
	EA=1;
	PCA0CPH0=0x20;
   	while (1)      
	{
		
		for(b=0;b>0xffffffff;b++)//延時
		{
			_nop_();
		}	
	}
}
//配置I/O端口
void PORT_Init (void)
{  P0SKIP =0xff;
   P1SKIP = 0x3f;
   XBR1 = 0x42;			/*CEX0-->P1.6*/

   P1MDOUT |= 0x40;     /*使能P1.6腳推挽輸出*/
}
//配置PCA的CEX0輸出8位PWM信號
void PCA_Init (void)
{
    PCA0CN    = 0x40;
    PCA0CPM0  = 0x42;	//pwm-8模式
    PCA0CPL0  = 0x00;
    PCA0CPH0  = 0x00;
	//PCA0CPL4  = 0x00;
	//PCA0MD   &= 0x40;
	PCA0MD    = 0x01;  //pca計數(shù)器/定時器溢出中斷允許
}
//-------------------------------
void PCA_ISR (void) interrupt 11
{     unsigned char a ;
      bit	PWM_PAC;
      CF = 0;
      if(PWM_PAC==0)			//占空比由0	>>0xfe
		{
			PCA0CPH0=a;
		 	a++;
		 	if(a==0xfe){PWM_PAC=1;}
		}
		else					//占空比由0xfe	>>0
		{
			PCA0CPH0=a;
		 	a--;
		 	if(a==0){PWM_PAC=0;}
		}
}