Fig. 5: Bit configuration of RCSTA /Receive Status and Control Register in EUSART of PIC Microcontroller

Fig. 6: Bit Configuration of PIR1 /Peripheral Interrupt Request Register of PIC’s EUSART

Fig. 7: Bit configuration of PIE1/ Peripheral Interrupt Enable Register 1of EUSART in PIC Microcontroller

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// Program to depict the configuration of EUSART in PIC18F4550
// This code receives and then transmits the same data back to the PC .. // ..through PC's Serial Port

// Configuration bits
/* _CPUDIV_OSC1_PLL2_1L,  // Divide clock by 2
   _FOSC_HS_1H,           // Select High Speed (HS) oscillator
   _WDT_OFF_2H,           // Watchdog Timer off
   MCLRE_ON_3H            // Master Clear on
*/

void tx_data(unsigned char);

unsigned char rx_data(void);
unsigned char serial_data;
unsigned int i=0;

#define FREQ 12000000    // Frequency = 12MHz
#define baud 9600
#define spbrg_value (((FREQ/64)/baud)-1)    // Refer to the formula for Baud rate calculation in Description tab

void main()
{
    SPBRG=spbrg_value;                                // Fill the SPBRG register to set the Baud Rate
    RCSTA.SPEN=1;                                     // To activate Serial port (TX and RX pins)
    TXSTA.TXEN=1;                                     // To enable transmission
    RCSTA.CREN=1;                                     // To enable continuous reception
    while(1)
    {
        serial_data=rx_data();    // Receive data from PC
        tx_data(serial_data);        // Transmit the same data back to PC
    }


}


void tx_data(unsigned char data1)
{
    TXREG=data1;                                     // Store data in Transmit register
    while(PIR1.TXIF==0);                             // Wait until TXIF gets low
}


unsigned char rx_data(void)
{
    while(PIR1.RCIF==0);                            // Wait until RCIF gets low
    return RCREG;                                   // Retrieve data from reception register
}

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• MAX232
• PIC18F4550