// File : m21_port.c 

#include <gc89c520_tq32i.h>

void init_port()
{
	//
	// don't select adc channel
	//
	
	ADCSEL |= 0xF0;
	ADCSELH = 0xFF;	
	ADCHH = 0xFF;
	ADCHL = 0xFF;
	
	//
	// Push-pull output
	//
	
	P0TYPE = 0x00;
	P1TYPE = 0x00;
	P2TYPE = 0x00;
	P3TYPE &= 0xC0;
	
	//
	// Output
	//
	
	P0DIR = 0x00;
	P1DIR = 0x00;	
	P2DIR = 0x00;
	P3DIR = 0xC0;
	
	//
	// pull-up on	
	//
	
	P0SEL = 0x00;
	P1SEL = 0x00;
	P2SEL = 0x00;
	P3SEL = 0xC0;
	
	//
	// XTAL PORT SET TO I/O PORT
	//
	
	ALTSEL |= 0x80;
	
	//
	// XTAL AMPLIFIER OFF
	//
	
	PMR |= 0x08;
	
	//
	// RESET PORT SET TO I/O PORT 
	//
	
	ALTSEL |= 0x40;
}

void main()
{
	init_port();
	while(1)
	{
		P0_0 = 1;
		P0_0 = 0;
	};
}