#include <iom128v.h>
#include <macros.h>
#pragma interrupt_handler UART0_RX_interrupt:19
void UART0_RX_interrupt( void )           
{  MCURC=(1<<IVCE);
   MCURC=(1<<IVSEL);
   unsigned char Temp;
   Temp=UDR0;
   if(Temp=='b')Buzzer();
}
void Buzzer(void)
{
 	 PORTB&=0xfe;      			//開蜂鳴器
	delay(50);
	PORTB|=0x01;             //關蜂鳴器
}
void delay(int n)
{
 int i,j;
 for(i=0;i<n;i++)
  for(j=0;j<1000;j++) 
    ;
}
void USART_Transmit(char data)
{
 	 while(!(UCSR0A&(1<<UDRE0)))
	 ;
	 UDR0=data;

}
void USART_Init(unsigned int baud)
{
 UBRR0H=(unsigned char)(baud>>8);
 UBRR0L=(unsigned char)baud;
 UCSR0B=(1<<RXCIE0)|(1<<RXEN0)|(1<<TXEN0); //接收終端使能，發送和接受使能
 UCSR0C=(1<<UCSZ00)|(1<<UCSZ01);           //設置字符長度，一個停止位，八位數據
}
main()
{
  DDRB=0xff;
  PORTB=0xff;
  USART_Init(51);
  USART_Transmit('s');
  while(1);
 }