//Displaying "YES" on LCD connected to MDE8051 Trainer using 4-bit data connection
//Using 4-bit data line option of LCD can save I/O port pins 
//Modified and tested from Example 12-1 in chapter 12 of the "8051 Microcontroller" textbook by Mazidis & McKinlay 
//P1.7-P1.4 to data line of D7-D4 of LCD
// P2.0 = RS, P2.1 = R/W, and P2.2 = E
#include <reg51.h>
sfr ldata = 0x90;			
sbit rs = P2^0;
sbit rw = P2^1;
sbit en = P2^2;
void lcdcmd4(unsigned char);
void lcddata4(unsigned char);
void MSDelay(unsigned int);
void main()
  {
    MSDelay(250);
    lcdcmd4(0x33);      //needed by 4-bit data LCD
    MSDelay(250);
    lcdcmd4(0x32);		//needed by 4-bit data LCD
    MSDelay(250);
    lcdcmd4(0x28);		//needed by 4-bit data LCD
    MSDelay(250);
    lcdcmd4(0x0E);
    MSDelay(250);
    lcdcmd4(0x01);
    MSDelay(250);
    lcdcmd4(0x06);
    MSDelay(250);
    lcdcmd4(0x86);			
    MSDelay(250);
    lcddata4('Y');       
    MSDelay(250);
    lcddata4('E');       
    MSDelay(250);
    lcddata4('S'); 
    for(;;);       //do it once and stay here       
  }

//------------- command-write 4-bit version
void lcdcmd4(unsigned char value)
  {
    ldata = value & 0xF0;		//mask the lower 4-bits and issue it D7-D4 data line      		
    rs = 0;
    rw = 0;
    en = 1;             		
    MSDelay(1);
    en = 0;
    ldata = (value &0x0F) <<4; //mask the upper 4-bits and issue it D7-D4 data line after shifting left 
 		
    rs = 0;
    rw = 0;
    en = 1;             		
    MSDelay(1);
    en = 0;

    return;
  }
  
//------------- data-write 4-bit version
  
void lcddata4(unsigned char value)
  {
    ldata = value & 0xF0;   		//mask the lower 4-bits and issue it D7-D4 data line 
    rs = 1;
    rw = 0;
    en = 1;           		
    MSDelay(1);
    en = 0;
    ldata = (value &0x0F) <<4;//mask the upper 4-bits and issue it D7-D4 data line after shifting left 
       		
    rs = 1;
    rw = 0;
    en = 1;           		
    MSDelay(1);
    en = 0;

    return;
  }
void MSDelay(unsigned int itime)
  {
    unsigned int i, j;
    for(i=0;i<itime;i++)           //Modify this this delay to see
      for(j=0;j<127;j++);         //the lowest delay acceptable for LCD
  }