// Copyright 2006 Yamane Akira
//ICC-AVR application builder : 2005/07/24 9:21:20
// Target : M48
// Crystal: 8.0000Mhz
// TWI Slave Mode Test Program
// Programmed by A.Yamane

#include <iom48v.h>
#include <macros.h>

 unsigned char s_addr, rdata;

void port_init(void)
{
 PORTB = 0xFF;
 DDRB  = 0x00;
 PORTC = 0b1001111; //SDA,SCL Low
 DDRC  = 0x00;
 PORTD = 0xFF;
 DDRD  = 0xFF;
}

//TWI initialize
// bit rate:1
void twi_init(void)
{
 TWCR= 0X00; //disable twi
 TWBR= 0x00; //set bit rate as 0
 TWSR= 0x00; //set prescale as 0
 TWAR= 0x00; //set slave address 
 TWCR= 0x04; //enable twi
}

//call this routine to initialize all peripherals
void init_devices(void)
{
 //stop errant interrupts until set up
 CLI(); //disable all interrupts
 port_init();
 twi_init();

 MCUCR = 0x00;
 EICRA = 0x00; //extended ext ints
 EIMSK = 0x00;
 
 TIMSK0 = 0x00; //timer 0 interrupt sources
 TIMSK1 = 0x00; //timer 1 interrupt sources
 TIMSK2 = 0x00; //timer 2 interrupt sources
 
 PCMSK0 = 0x00; //pin change mask 0 
 PCMSK1 = 0x00; //pin change mask 1 
 PCMSK2 = 0x00; //pin change mask 2
 PCICR = 0x00; //pin change enable 
 PRR = 0x00; //power controller
 SEI(); //re-enable interrupts
 //all peripherals are now initialized
}

void ERROR(unsigned char edata)
    {
	PORTD= ~edata;
	//while(1);
	}
	
	
unsigned char SlaveReceive(void)
    {
	 TWAMR = 0x00;  // No address Mask
	 TWAR = ((s_addr <<1) | 0);   // Slave Address
	 TWCR = (1 << TWEA) | (1 << TWEN);  // Ack Enable
	   while (!(TWCR & (1 << TWINT)))  // Wait TWINT Flag
	         ;		 
	  if ((TWSR & 0xF8) != 0x60)   // Own Address Packet has received 
		  ERROR(3);
	 TWCR = (1 << TWINT) | (1 << TWEA) | (1 << TWEN);  // Data will be received
	                                                   // & Ack will be returned
	    while (!(TWCR & (1 << TWINT)))  // Wait TWINT Flag
		    ;
	
      if ((TWSR & 0xF8) != 0x080) // Previous addressed Data has been received
		  ERROR(4);	
    	 rdata = TWDR;	          // Read received DATA 
	 TWCR = (1 << TWINT) | (1 << TWEN); // Ack return
	 	while (!(TWCR & (1 << TWINT)))  // Wait TWINT
		    ;
		  if ((TWSR & 0xF8) != 0x0A0)   // STOP condition has been received
		    ERROR(5);
	 TWCR = (1 << TWINT) | (1 << TWEN)	// Switched to the not addressed
	         | (1 << TWEA);           // Slave Mode; own SLA will be recognized
			 return rdata;		 
	}

//
void main(void)
{
 init_devices();
    s_addr = 0x10;   
    PORTD =0xAA;

    while(1)
	  {
	    PORTD = ~SlaveReceive();
	  }
}