pwm.c

北京航空航天大学出版社出版的《C8051F系列单片机开发与C语言编程》的附盘程序。

/////////PCA CEX0为PWM 输出模式//////////////
/////////PWM.c//////////////////////////
#include <C8051F040.h>
typedef unsigned int uint;
typedef unsigned char uchar;
typedef unsigned long ulong;
sfr16 RCAP2=0xca;
sfr16 RCAP3=0xca;
sfr16 RCAP4=0xca;
sfr16 TMR4=0xcc;
sfr16 TMR3=0xcc;
sfr16 TMR2=0xcc;
sfr16 PCA0CP0=0xfb;
sfr16 PCA0CP1=0xfd;
sfr16 PCA0CP2=0xe9;
sfr16 PCA0CP3=0xeb;
sfr16 PCA0CP4=0xed;
sfr16 PCA0CP5=0xe1;
uchar temppage;
void delay1ms(uint time){//延迟1ms
	uint i;
	uint j;
	for (i=0;i<time;i++){
		for(j=0;j<300;j++);
	}
}	
void pca0ini(){//CEX0为8bit PWM输出模式
	SFRPAGE = 0x00;
	PCA0CPM0=0X42;
}
void PWM0_set(uchar low){//占空比设置，高电平占空比为(256-low)/256
	SFRPAGE = 0x00;
	PCA0CPH0=low;
}
void pcaini(){
	SFRPAGE=0x00;
	PCA0MD=0x08;//PCA采用系统时钟，且PCA溢出中断禁止
	PCA0CN=0x40;//启动PCA计数器
	//EIE1|=0x08;//将此代码屏蔽，禁止PCA中断
}
void config(){
//看门狗禁止
	WDTCN = 0x07;	
    WDTCN = 0xDE;   
   	WDTCN = 0xAD;
	SFRPAGE = 0x0F;
//交叉开关配置，CEX0-CEX5配置到P0.0-P0.5
	XBR0 = 0x30;	
	XBR1 = 0x00;	
	XBR2 = 0x40;
 	XBR3 = 0x00;   
//管脚输出配置，P0口为开漏输出，其中P0.6接上拉电阻，P0为数字输入口
 	SFRPAGE = 0x0F;
 	P0MDOUT = 0x00; 
 	P1MDIN = 0xFF;  
//晶振配置，采用内部晶振8分频
	SFRPAGE = 0x0F;
 	CLKSEL = 0x00;  
	OSCXCN = 0x00;	
	OSCICN = 0x84;	
}
void main(void){
	xdata uchar lowset;
	config();
	pcaini();
	pca0ini();
	lowset=0;
	PWM0_set(lowset);
	while(1){
		delay1ms(1000);
		lowset+=10;
		PWM0_set(lowset);
	}

}