C8051F单片机PWM输出程序

//PWM输出脚P0.3
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------
#include // SFR declarations
#include 
#include 
//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------
void PORT_Init (void);
void PCA_Init (void);
void PCA_ISR (void);
void SYSCLK_Init (void);
//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------
void main (void)
{ 
unsigned long b;
WDTCN = 0xde; // disable watchdog timer
WDTCN = 0xad;
SYSCLK_Init ();
PORT_Init (); /*初始化I/O口*/
PCA_Init (); /*PCA初始化成8位脉宽调置方式*/
EIE1= 0x08;
EA=1;
PCA0CPH0=0x20;
while (1) 
{ }
}
//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
void PORT_Init (void)
{ 
XBR0 = 0x11; // XBAR0: Initial Reset Value
XBR1 = 0x00; // XBAR1: Initial Reset Value
XBR2 = 0x40; // XBAR2: Initial Reset Value
// Port configuration (1 = Push Pull Output)
PRT0CF = 0x08; // Output configuration for P0 
PRT1CF = 0x00; // Output configuration for P1 
PRT2CF = 0x00; // Output configuration for P2 
PRT3CF = 0x00; // Output configuration for P3 
}
//-----------------------------------------------------------------------------
// SYSCLK_Init
//-----------------------------------------------------------------------------
void SYSCLK_Init (void)
{
unsigned int i; // delaynms counter
OSCXCN = 0x67; // start external oscillator with
for (i=0; i < 256; i++) ; // XTLVLD blanking interval (>1ms)
while (!(OSCXCN & 0x80)) ; // Wait for crystal osc. to settle
OSCICN = 0x88; // select external oscillator as SYSCLK 
}
//-----------------------------------------------------------------------------
// PCA_Init
//-----------------------------------------------------------------------------
void PCA_Init (void)
{ 
// PCA0CPM0 = 0x42; // PCA Capture/Compare Register 0
PCA0CN = 0x40;
PCA0CPM1 = 0x42;
PCA0CPL0 = 0x00;
PCA0CPH0 = 0x00;
// PCA0MD &= 0x40;
PCA0MD = 0x01;
}
//-----------------------------------------------------------------------------
// PCA_ISR
//-----------------------------------------------------------------------------
void PCA_ISR (void) interrupt 9
{ unsigned char a ;
bit PWM_PAC;
CF = 0;
if(PWM_PAC==0) //占空比由0 >>0xfe
{
PCA0CPH1=a;
a++;
if(a==0xfe){PWM_PAC=1;}
}
else //占空比由0xfe >>0
{
PCA0CPH1=a;
a--;
if(a==0){PWM_PAC=0;}
}
}