/**********************************************
*   File: DA_2.C
*   Description: Tri-Angle  
*   Created Date:  2007-10-01
*   Last Modified: 2007-10-01
*   Author: Jeffrey - Schicksal@126.com
*   Notes: None
**********************************************/
#include "Atmel/AT89X51.h"
#include "INTRINS.H"

#define TH0_VALUE 0x00
#define TL0_VALUE 0x08			   // 定時器計數值 2us
#define PWM P2_0                   // PWM輸出引腳

volatile unsigned char time_tick = 0;

// 函數聲明
void TIMER_Start();
void TIMER_Init(void);

/**********************************************
*   Function: delay(unsigned int t)
*   Input Variables: t
*   Return Variables: None
*   Usage: Common Delay Routine, t as the delay time ticks
**********************************************/
void delay(unsigned int t)
{
	for(;t>0;t--);		// 延時循環
}

/**********************************************
*   Function: main()
*   Input Variables: None
*   Return Variables: None
*   Usage: Program Entry
*********************************************/
void main()
{
	unsigned char N = 0;
	unsigned char x = 50;					// 占空比50%
	
	TIMER_Init();
	TIMER_Start();
	while(1)
	{
		PWM = 1;							// PWM輸出引腳高
		while(1)
		{
			time_tick = 0;
			while(!time_tick);				// 等待2us時鐘中斷
			if(N==x)
				PWM = 0;					// PWM輸出引腳低
			if(N==100)
				break;
			N++;
		}
		N = 0;								// 重新計數開始
	}
}

/**********************************************
*	Function: TIMER_Init
*	Input Variables: None
*    Return Variables: None
*    Usage: T0 Initialization
*********************************************/
void TIMER_Init(void)
{
	
	ET0 = 0;					// 關閉T0的中斷
	TMOD = 0x00;				// T0工作在模式0
	TCON = 0x00;				// 暫時未啟動T0
	TL0 = TL0_VALUE;
	TH0 = TH0_VALUE;			// 產生2ms中斷 |24 MHz 晶振
	ET0 = 1;				  	// 打開T0的中斷
	time_tick = 0;
}



/**********************************************
*	Function: timer0_interrupt
*	Input Variables: None
*    Return Variables: None
*    Usage: TIMER_Interrupt Service Routine 
*********************************************/
void timer0_interrupt(void) interrupt 5 using 1 
{		  
	EA = 0;										// 關全局中斷
	TF0 = 0;									// 清中斷標志

	time_tick++;								// 2us
	
	TL0 = TL0_VALUE;							// T0初值裝載
	TH0 = TH0_VALUE;							// 產生2ms中斷 |24 MHz 晶振
    EA = 1;										// 開中斷
}


/**********************************************
*   Function: TIMER_Start
*    Input Variables: None
*    Return Variables: None
*    Usage: Start T0 
*********************************************/
void TIMER_Start()
{
	TR0 = 1;				// 啟動T0
}