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 
				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						for(j=0;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);
					}
				
				}