#include <c8051f020.h>                    // SFR declarations

//------------------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F02x
//------------------------------------------------------------------------------------



//------------------------------------------------------------------------------------
// Global CONSTANTS
//------------------------------------------------------------------------------------

#define SYSCLK 2000000                    // approximate SYSCLK frequency in Hz

sbit  LED = P3^7;                         // green LED: '1' = ON; '0' = OFF

//------------------------------------------------------------------------------------
// Function PROTOTYPES
//------------------------------------------------------------------------------------
void PORT_Init (void);
void Timer3_Init (int counts);
void Timer3_ISR (void);

//------------------------------------------------------------------------------------
// MAIN Routine
//------------------------------------------------------------------------------------
void main (void) {
 
   
   WDTCN = 0xde;
   WDTCN = 0xad;//關閉看門狗
                 //沒有配置時鐘，默認內部2M晶振
	
   PORT_Init ();
   Timer3_Init (SYSCLK / 12 / 10);        // Init Timer3 to generate interrupts
                                          // at a 10Hz rate.

   EA = 1;								  // enable global interrupts

   while (1) {                            // spin forever
   }
}

//------------------------------------------------------------------------------------
// PORT_Init
//------------------------------------------------------------------------------------
//
// Configure the Crossbar and GPIO ports
//
void PORT_Init (void)
{
   XBR2    = 0x40;                     // Enable crossbar and weak pull-ups
   P1MDOUT |= 0x40;                   
   P3MDOUT |= 0x80;                    // enable P3.7 (LED) as push-pull output
}

//------------------------------------------------------------------------------------
// Timer3_Init
//------------------------------------------------------------------------------------
//
// Configure Timer3 to auto-reload and generate an interrupt at interval
// specified by <counts> using SYSCLK/12 as its time base.
//
void Timer3_Init (int counts)
{
   TMR3CN = 0x00;                      // Stop Timer3; Clear TF3;
                                       // use SYSCLK/12 as timebase
   TMR3RLL  = -counts;                  // Init reload values
   TMR3L    = 0xffff;                   // set to reload immediately
   EIE2   |= 0x01;                     // enable Timer3 interrupts
   TMR3CN |= 0x04;                     // start Timer3
}

//------------------------------------------------------------------------------------
// Interrupt Service Routines
//------------------------------------------------------------------------------------

//------------------------------------------------------------------------------------
// Timer3_ISR
//------------------------------------------------------------------------------------
// This routine changes the state of the LED whenever Timer3 overflows.
//
void Timer3_ISR (void) interrupt 14
{
   TMR3CN &= ~(0x80);                     // clear TF3
   LED = ~LED;                            // change state of LED
}