I connected two 8255 ppi to 8051 to accessing keypad and lcd and other modules are connected in that.
I attached here my schematic diagram and embedded c programming for that.
while i simulating that i cant find out error.
Can anyone findout?

I connected lcd data port with port a of 8255 ppi1
I connected lcd control signal(wr,rd,cr) port with port b of 8255 ppi1(4000H)
I connected keypad(4*3) row pins with port c(pc0,pc1,pc2,pc3) of 8255 ppi1(8000H)
I connected keypad(4*3) column pins with port b(pb4,pb5,pb6) of 8255 ppi1

BElow is embedded c program for that,

Thanks in advance..

__________

#include<reg51.h>
#define sec 100     
char xdata lcdctr _at_ 0x4001;
char xdata dataport _at_ 0x4000;
char xdata keyr _at_ 0x4002;
char xdata keyc _at_ 0x8001;
xdata cw[4003]=0x88;
xdata cw2[8003]=0x92;

void delay(unsigned int msec) //Time delay function
{
int i,j ;
for(i=0;i<msec;i++)
  for(j=0;j<1275;j++);
}

void lcd_cmd(unsigned char item)  //Function to send command to LCD
{
dataport = item;
lcdctr=0x04;
delay(1);
lcdctr=0x00;
return;
}

void lcd_data(unsigned char item) //Function to send data to LCD
{
dataport = item;
lcdctr=0x05;

delay(1);
lcdctr=0x01;
return;
}



void lcd_data_string(unsigned char *str) // Function to send string on LCD
{
int i=0;
while(str!='\0')
{
  lcd_data(str);
  i++;
  delay(10);
}
return;
}

void lcd(unsigned char str[16])  // Funtion to Initialize LCD
{
lcd_cmd(0x38);
lcd_cmd(0x0e);
//delay(sec);
lcd_cmd(0x01);
//delay(sec);
lcd_cmd(0x82);
//delay(sec);
lcd_data_string(str);
}  

void display(int a) //Display functon for LCD

{
switch(a)
{
  case 1:lcd("one 1");
    break;
  case 2:lcd("two 2");
    break;
  case 3:lcd("three 3");
    break;
  case 4:lcd("four 4");
    break;
  case 5:lcd("five 5");
    break;
  case 6:lcd("six 6");
    break;
  case 7:lcd("seven 7");
    break;
  case 8:lcd("EIGHT 8");
    break;
  case 9:lcd("NINE 9");
    break;
  case 0:lcd("ZERO 0");
    break;
  case 11:lcd("*");
    break;
  case 12:lcd("#");
    break;
    
}
}

void check_col1() //Function for checking column one
{
int temp;//row1=row2=row3=row4=1;
keyr=0xff;

keyr=0xfe;//row1=0;
   temp=0x10&keyc;
  if(temp==0x00)//if(col1==0)
{display(1);return;}

//row1=1;
keyr=0xfd;//row2=0;
 temp=0x10&keyc;//keyc*=0x10;
  if(temp==0x00)//if(col1==0)
display(4);
//row2=1;
keyr=0xfb;//row3=0;
 temp=0x10&keyc;//keyc*=0x10;
  if(temp==0x00)//if(col1==0)
display(7);
keyr=0xf7;
//row3=1;
//row4=0;
 temp=0x10&keyc;//keyc*=0x10;
  if(temp==0x00)//if(col1==0)
display(11); 
keyr=0xff;//row4=1;
}

void check_col2() //Function for checking column two
{
int temp;
keyr=0xff;

keyr=0xfe;//row1=0;
   temp=0x20&keyc;//keyc*=0x20;
  if(temp==0x00)//if(col1==0)
display(1);
//row1=1;
keyr=0xfd;//row2=0;
 temp=0x20&keyc;//keyc*=0x20;
  if(temp==0x00)//if(col1==0)
display(4);
//row2=1;
keyr=0xfb;//row3=0;
 temp=0x20&keyc;//keyc*=0x20;
  if(temp==0x00)//if(col1==0)
display(7);
keyr=0xf7;
//row3=1;
//row4=0;
 temp=0x20&keyc;//keyc*=0x20;
  if(temp==0x00)//if(col1==0)
display(11); 
keyr=0xff;
}

void check_col3() //Function for checking column three
{
int temp;
keyr=0xff;

keyr=0xfe;//row1=0;
   temp=0x40&keyc;//keyc*=0x40;
  if(temp==0x00)//if(col1==0)
display(1);
//row1=1;
keyr=0xfd;//row2=0;
 temp=0x40&keyc;//keyc*=0x40;
  if(temp==0x00)//if(col1==0)
display(4);
//row2=1;
keyr=0xfb;//row3=0;
 temp=0x40&keyc;//keyc*=0x40;
  if(temp==0x00)//if(col1==0)
display(7);
keyr=0xf7;
//row3=1;
//row4=0;
 temp=0x40&keyc;//keyc*=0x40;
  if(temp==0x00)//if(col1==0)
display(11); 
keyr=0xff;
}

void main()
{
//display(13);
//col1=col2=col3=1;  //Input Port
while(1)
{
int temp;
  keyr=0x00;//row1=row2=row3=row4=0;
  temp=0x10&keyc;//keyc*=0x10;
  if(temp==0x00)
  check_col1();
  else
  {
  temp=0x20&keyc;//keyc*=0x20;
   if(temp==0x00)
   check_col2();
   else
   {
   temp=0x40&keyc;//keyc*=0x40;
    if(temp==0x00)
    check_col3();
     }
   }
}

}

 

C, there is our problem

 

If you have connected A0 to the RS pin of the LCD then the Control is at 4000 and the data is on address 4001

RS = high data, low command

 

I connected two 8255 ppi to 8051 to accessing keypad and lcd and other modules are connected in that.
I attached here my schematic diagram and embedded c programming for that.

I dont see any schematic....or are you unable to attach it to your post?

Allen

 

I connected keypad(4*3) row pins with port c(pc0,pc1,pc2,pc3) of 8255 ppi1(8000H)
I connected keypad(4*3) column pins with port b(pb4,pb5,pb6) of 8255 ppi1

You can actually combine the 3x4 keyboard onto port c. The directions of upper & lower nibble can be set separately. There was an example on 8085 addressing the keypad using 8255 not long ago.

Allen