#include <pic18.h>#include "usart.h"#include <stdio.h>void interrupt ISR(void){	if((RBIE)&&(RBIF))	{															if(USART_RC)		RCIE=1;//!RCIE;					/*turn USART receive interrupt on and off*/		else		RCIE=0;		if(USART_TX)		TX_INT=1;//!TX_INT;			/*use other variable rather than TXIE, so that printf() routine can be used by the program*/		else		TX_INT=0;									/*TXIE is set only when keyboard input is expected*/		RBIF=0;		UPDATE_REQUIRED=1;	}	if((RCIE)&&(RCIF))										/*receive interrupt routine*/	{		DATA=RCREG;		DATA_RECEIVED=1;								/*indicate that some data has been received*/	}		if((TXIE)&&(TXIF))										/*transmit interrupt routine*/	{		TXREG=DATA;		TXIE=0;	}	}