PIC16F877A-HITECHC Part-2 UART & EEPROM

SERIAL COMMUNICATION

UART

Transmission

#include<pic.h>
#define _XTAL_FREQ 16000000
void main() {
    SPEN = 1;          // enables serial port
    SYNC = 0;          // setting in asynchronous mode
    BRGH = 0;          // selects low speed baud rate
    SPBRG = 25;        // setting baud rate @ 9600
    TXEN = 1;          // enables transmission
    TX9 = 0;           // sets transmission in 8-bit mode
    while (1) {
        if (TRMT == 1) // check status of transmit shift register for empty
        {
            TXREG = 'A'; // writes ascii value of letter A
        }
    }
}

Reception

Note– i have used PORTB to see incoming ascii value

#include<pic.h>
#define _XTAL_FREQ 16000000
void main()
{
    SPEN = 1;          // enables serial port
    SYNC = 0;          // setting in asynchronous mode
    BRGH = 0;          // selects low speed baud rate
    SPBRG = 25;        // setting baud rate @ 9600
    CREN = 1;          // enables reception
    RX9 = 0;           // sets reception in 8-bit mode
    TRISB = 0;
    PORTB = 0;
    while (1)
    {
        PORTB = (RCREG - 0x30); // writes ascii value of letter A
    }
}

See software UART at http://jimmyjosep.blogspot.in/2013/11/under-standing-uartsoft.html

EEPROM

Steps to Read

1. Specify the memory location in EEADR (EEADR=4;)
2. Clear the EEPGD bit (EEPGD=0 😉
3. Read the value from EEDATA register (unsigned short int a =EEDATA 😉

Steps to Write

1. Specify the memory location in EEADR (EEADR=4;)
2. Write the value to EEDATA register (EEDATA=7;)
3. Set WREN (WREN=1;)
4. Clear the EEPGD bit (EEPGD=0 😉
5. Write 55h to EECON2 (EECON2=0x55;)
6. Write AAh to EECON2 (EECON2=0xAA;)
7. Set the WR bit (WR=1;)

#include<pic.h>
#define _XTAL_FREQ 16000000
__CONFIG(0x3f7a);
unsigned short int eeread();
eewrite(unsigned short int , unsigned short int );
main()
{
    eewrite(4,'1');
    unsigned short int a = eeread(); // data from eeprom
    TRISB = 0;
    PORTB = a;
    while(1) ;
}
unsigned short int eeread()
{
    EEADR = 4;
    EEPGD = 0;
    unsigned short int z = EEDATA;
    return z;
}
eewrite(unsigned short int x, unsigned short int y)
{
    EEADR = x;
    EEDATA = y;
    WREN = 1;
    EEPGD = 0 ;
    EECON2 = 0x55;
    EECON2 = 0xAA;
    WR = 1;
}