I have been trying to write a program for LCD on PIC18f452. I found a library and worked on it and MPLAB XC8 compiled it successfully. I tested it in ISIS and it showed perfect output. However, when I burned the program, the controller hardware refused to display anything. Then I ported the same code in MikroC - only made a slight change of replacing __delay_us and __delay_ms with available delay routines in MikroC. To my surprise, the Proteus as well as hardware worked as a charm.

I am confused that configuration bits are as same for both MPLAB and MikroC. Where does the difference lay? I suspect it has something to do with delay speed or so...

Code for main is as follows because its the thing that i change

#include <xc.h>
#include <p18f452.h>
#include "lcd.h"

#define _XTAL_FREQ 8000000L

#pragma config OSC = HS         // Oscillator Selection bits (HS oscillator)
#pragma config OSCS = OFF       // Oscillator System Clock Switch Enable bit (Oscillator system clock switch option is disabled (main oscillator is source))

#pragma config PWRT = OFF       // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOR = ON         // Brown-out Reset Enable bit (Brown-out Reset enabled)
#pragma config BORV = 20        // Brown-out Reset Voltage bits (VBOR set to 2.0V)

#pragma config WDT = OFF        // Watchdog Timer Enable bit (WDT disabled (control is placed on the SWDTEN bit))
#pragma config WDTPS = 128      // Watchdog Timer Postscale Select bits (1:128)

#pragma config CCP2MUX = ON     // CCP2 Mux bit (CCP2 input/output is multiplexed with RC1)

#pragma config STVR = ON        // Stack Full/Underflow Reset Enable bit (Stack Full/Underflow will cause RESET)
#pragma config LVP = ON         // Low Voltage ICSP Enable bit (Low Voltage ICSP enabled)

#pragma config CP0 = OFF        // Code Protection bit (Block 0 (000200-001FFFh) not code protected)
#pragma config CP1 = OFF        // Code Protection bit (Block 1 (002000-003FFFh) not code protected)
#pragma config CP2 = OFF        // Code Protection bit (Block 2 (004000-005FFFh) not code protected)
#pragma config CP3 = OFF        // Code Protection bit (Block 3 (006000-007FFFh) not code protected)

#pragma config CPB = OFF        // Boot Block Code Protection bit (Boot Block (000000-0001FFh) not code protected)
#pragma config CPD = OFF        // Data EEPROM Code Protection bit (Data EEPROM not code protected)

#pragma config WRT0 = OFF       // Write Protection bit (Block 0 (000200-001FFFh) not write protected)
#pragma config WRT1 = OFF       // Write Protection bit (Block 1 (002000-003FFFh) not write protected)
#pragma config WRT2 = OFF       // Write Protection bit (Block 2 (004000-005FFFh) not write protected)
#pragma config WRT3 = OFF       // Write Protection bit (Block 3 (006000-007FFFh) not write protected)

#pragma config WRTC = OFF       // Configuration Register Write Protection bit (Configuration registers (300000-3000FFh) not write protected)
#pragma config WRTB = OFF       // Boot Block Write Protection bit (Boot Block (000000-0001FFh) not write protected)
#pragma config WRTD = OFF       // Data EEPROM Write Protection bit (Data EEPROM not write protected)

#pragma config EBTR0 = OFF      // Table Read Protection bit (Block 0 (000200-001FFFh) not protected from Table Reads executed in other blocks)
#pragma config EBTR1 = OFF      // Table Read Protection bit (Block 1 (002000-003FFFh) not protected from Table Reads executed in other blocks)
#pragma config EBTR2 = OFF      // Table Read Protection bit (Block 2 (004000-005FFFh) not protected from Table Reads executed in other blocks)
#pragma config EBTR3 = OFF      // Table Read Protection bit (Block 3 (006000-007FFFh) not protected from Table Reads executed in other blocks)

#pragma config EBTRB = OFF      // Boot Block Table Read Protection bit (Boot Block (000000-0001FFh) not protected from Table Reads executed in other blocks)

//Simple Delay Routine
void Wait(unsigned int delay)

void main()
    //Let the Module start up
        PORTD = 0x00;
        TRISD = 0x00;

    //Initialize the LCD Module

    //Clear the Module

    //Write a string at current cursor pos
    LCDWriteString("F**k Yeh!!");


    //Now Clear the display

    LCDWriteString("God Bless all !!");

    //Goto POS (X=0,Y=1 i.e. Line 2)
    //And Write a string


    //Write Some Numbers
    for(char i=0;i<100;i++)

    LCDWriteString("    The  End    ");

    //Loop Forever
            PORTD = ~PORTD;


Config bits seen by PICkit2 from hex files compiled my MPLAB and MikroC are

enter image description here

  • \$\begingroup\$ Thanks. Is your oscillator 8MHz (and not broken)? \$\endgroup\$ – user17592 May 2 '13 at 8:29
  • \$\begingroup\$ Yes its 8mhz and not broken. If it was broken it would not work for MikroC version. it works for mikroC hex of same code but not for MPLAB version \$\endgroup\$ – Lagrangian May 2 '13 at 15:23

The screenshot you have provided of the configuration bits shows a variance. Config 4 Bit 2 which is the Low Voltage ICSP Enable bit is disabled on the MicroC Screenshot??

I would be more suspect that your delay timings for the LCD screen are causing you the issues your seeing however.

To debug this problem you may want to try the following.

A) Create a simple program to flash an LED light and verify that the frequency of the light flashing is the same. Use the delay routines and verify they work correctly.
B) Carefully read and re-read your LCD datasheet. A delay of 100us compared to 100ms can make a huge difference in terms of getting the LCD to display correctly. In your code you seem to be missing the delay after clearing the display. Also note that when repositioning the cursor delays are also required. The delays are dependent on the LCD you are using but the timings must be strictly adhered to. If not it is common that the LCD will not display correctly.

If you are able to verify that the clocks are running at the same frequency for MicroC and MPLAB XC8 we can eliminate the configuration bits and you will be able to focus more of your efforts on adjusting the LCD code.

Good luck.


Turn off the low voltage programming and reprogram the chip. This should solve the problem

#pragma config LVP = ON


#pragma config LVP = OFF 

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