can not read data from ks0108 lcd

[abbas1707]

i was playing with ks0108 lcd on proteus using 89c51. i am able to write data,fonts and images to lcd . but i cant read data from display RAM.
here is code for reading data from lcd

Code:

#include <reg51.h>

sbit rs=P3^3;
sbit rw=P3^2;
sbit en=P3^1;
sbit cs1=P3^5;
sbit cs2=P3^4;

void delay()
{
   int k,l;
   for(k=0;k<3;k++)
      for(l=0;l<50;l++);
}
void sendCommand(unsigned char val)
{
   P1=val;
   rs=0;
   rw=0;
   en=1;
   en=0;
}
void sendByte(unsigned char dat)
{

   P1=dat;
   rs=1;
   rw=0;
   en=1;
   en=0;
}
void readByte()
{
   
   P1=0xff;
   rs=1;
   rw=1;
   delay();
   en=1;
   delay();
   en=0;
   P2=P1;
}

void main()
{
     while(1)
     {
      cs1=0;
      sendCommand(0x40);
      sendCommand(0xb8);
      sendByte(0xf4);
      sendCommand(0x40);
      sendCommand(0xb8);
      readByte();
      readByte();
   }
}

please help me solving this problem

[sam_des]

Hello abbas,

Try this,

Code:

// Using definitions from your code....

#define CON_LEFT    0
#define CON_RIGHT  1

unsigned char Ks_readbyte( unsigned char con )
{
  unsigned char rd_byte;

  rs = 1;               // we're not sending command
  P1 = 0xff;          // as input(float lines)
  rw = 1;              // we're reading

  // Assuming non-inverted CS
  if( con == CON_LEFT ) {  // reading from left controller
    cs1 = 1;         
    cs2 = 0;
  } else {                        // reading from right controller
    cs1 = 0;
    cs2 = 1;
  }

  en = 1;
  _nop_();
  rd_byte = P1;                // read while en=1 !
  en = 0;
 
  cs1 = cs2 = 0; // de-select both controllers 
  P1 = 0x00;      // as output

  return rd_byte;
}

Hope you can work that out now. If you still have any problem, I can post isis sample.

BTW, how are able to put text, images on LCD when you're having problems with read 
My code for putting pixel on LCD involves call to readbyte() function 
How did you managed to do that

regards,
sam_des

[abbas1707]

Thanx again. its working....
when we have to put text or image on blank lcd then there is no need of read()...thats y i was able to write text,images.
Anyway
now im going to make methods like
setPixel()
clearPixel()
goto(x,y)
etc...

[sam_des]

Hello abbas,

Glad to hear that you got it working !

when we have to put text or image on blank lcd then there is no need of read()...thats y i was able to write text,images.

That's true. But we never know the contents of LCD on power-up. So it is safer to assume that it is not blank, unless we expilcitly do it.

BTW, I am posting a proteus sample for Ks0108 with 8051 as attchement.

regards,
sam_des

[cjq_sh]

Change the readByte() like this:
void readByte()
{
   P1=0xff;
   rs=1;
   rw=1;
   delay();
   en=1;
   delay();
   P2=P1;
   en=0;
  }