lcd in 4 bit mode problem

// Config word
#define _LEGACY_HEADERS
// Define pins
#define _XTAL_FREQ 40000000

#include <htc.h>
// Main function
#define lcd_port PORTB
#define LCD_EN RA1
#define LCD_RS RA0


////////////////////////////////////////////////////////////////////
//void delay();
//void lcd_cmd ();
//void lcd_data (unsigned char dat);
//void lcd_init ();

/////////////////////delay routine///////////////////////////////////


/////////////////////main program///////////////////////////////////////
void delay(unsigned int temp)
{
while(temp!=0)
{
temp--;
}
}

/////////////////////main program///////////////////////////////////////
void lcd_cmd (unsigned char cmd)
{
unsigned char a;
a=cmd;
lcd_port = (cmd & 0xf0);
LCD_RS=0;
LCD_EN=1;
delay(300);
LCD_EN=0;
a=cmd;
lcd_port = ((cmd<<4) & 0xf0);
LCD_RS=0;
LCD_EN=1;
delay(300);
LCD_EN=0;
delay(500);
}

void lcd_data (unsigned char dat)
{
unsigned char a;
a=dat;
lcd_port = (dat & 0xf0);
LCD_RS=1;
LCD_EN=1;
delay(300);
LCD_EN=0;
a=dat;
lcd_port = ((dat<<4) & 0xf0);
LCD_RS=1;
LCD_EN=1;
delay(300);
LCD_EN=0;
delay(500);
delay(500);
}
void lcd_string(unsigned char *str)
{
while(*str)
lcd_data(*str++);
delay(300);
}
void lcd_init ()
{
lcd_cmd (0x28); // 4-bit mode - 2 line - 5x7 font.
lcd_cmd (0x0C); // Display no cursor - no blink.
lcd_cmd (0x06); // Automatic Increment - No Display shift.
lcd_cmd (0x80); // Address DDRAM with 0 offset 80h.
}
void main(void)
{
TRISA=0x00;
TRISB=0x00;
delay(200);
lcd_init ();
lcd_cmd (0x81);
lcd_string("HELLO");
lcd_cmd (0xc1);
lcd_string("NITISH");
// while(1);


}

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Without even looking into code flow, your delays are probably wrong. LCDs are quite slow devices and especially during initialization it is very important they have long enough to digest the bytes you feed them. A simple count down of 200 or 300 to zero is likely to take far shorter than the several mS delays needed. In particular, note how long the LCD needs from powering up to being ready for the start of initializing data, most need around 100mS. It looks like you are using a PIC although you haven't said which type, your present 'delay(200)' probably only lasts around 200uS when you really need several mS.

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