##單個定時器

#include <reg52.h>
#include <intrins.h>

unsigned char PWM_COUNT;    //計數
unsigned int HUXI_COUNT;    //佔空比更新時間
unsigned char PWM_VLAUE;    //佔空比比對值
bit direc_flag;							//佔空比更新方向


void Enable_138(unsigned char ch)
{
	P2 = (P2 & 0x1f ) | (ch << 5);
	_nop_();
	_nop_();
	P2 &= 0x1f;
}


void timer0_init()
{
    TMOD=0x02;          //模式設定，定時器0，工作於模式2（M1=1，M0=0）
    TH0=0x47;               //定時器溢位值設定，每隔200us發起一次中斷。
    TL0=0X47;
    TR0=1;                  //定時器0開始計時
    ET0=1;                  //開定時器0中斷
    EA=1;                       //開總中斷
    PWM_COUNT =0;
}
void time0() interrupt 1
{   

    PWM_COUNT++;
    HUXI_COUNT++;
    if(PWM_COUNT == PWM_VLAUE)      //判斷是否到了點亮LED的時候
		{
			P0 = 0xef;
			Enable_138(4);
		}																	//點亮LED
    if(PWM_COUNT == 10)             //當前週期結束
    {
        P0 = 0xff;
				Enable_138(4);			//熄滅LED
        PWM_COUNT = 0;              //重新計時
    }
    if((HUXI_COUNT == 600) && (direc_flag == 0))
    {                               //佔空比增加10%
        HUXI_COUNT = 0;
        PWM_VLAUE++;
        if(PWM_VLAUE == 9)          //佔空比更改方向
            direc_flag = 1; 
    }
    if((HUXI_COUNT == 600) && (direc_flag == 1))
    {                               //佔空比減少10%
        HUXI_COUNT = 0;
        PWM_VLAUE--;
        if(PWM_VLAUE == 1)          //佔空比更改方向
            direc_flag = 0; 
    }   
}
void main()
{
		P0 = 0x00;
		Enable_138(5);
		P0 = 0x00;
		Enable_138(6);
    HUXI_COUNT = 0;
    PWM_COUNT = 0;
    PWM_VLAUE = 5;
    direc_flag = 0;
	
    P0 = 0xff;           
		Enable_138(4);
    timer0_init();      //定時器0初始化
    while(1);
}