Hi Prahalad,

The LCD connections are like this:

Port 1.0 - LCD D0
...
Port 1.7 - LCD D7
Port 0.0 - RS
Port 0.1 - R/W
Port 0.2 - EN

I have also pulled up Port zero using 4.7KOhm resistor network. The Microcontroller is 89c51, @12MHz.

I studied the LCD tutorial in this forum, but I am having a doubt. The initialisation code is given like this:

INIT_LCD:

CLR RS
MOV DATA,#38h
SETB EN
CLR EN
LCALL WAIT_LCD
CLR RS
MOV DATA,#0Eh
SETB EN
CLR EN
LCALL WAIT_LCD
CLR RS
MOV DATA,#06h
SETB EN
CLR EN
LCALL WAIT_LCD
RET

Well, The all these commands are to be written to LCD. If so, should not we bring R/W line low? Even in the whole program given in final paragraphs of the turorial, the program sequence goes like this:

start:

LCALL INIT_LCD
LCALL CLEAR_LCD
(character sending..)

Both INIT_LCD and CLEAR_LCD routines leave RW pin untouched. If so, as they are externally pulled high and ports will FFh upon reset, I reckon RW line will be high while these two routines do their job. Is this procedure correct? ( I am asking this doubt to everyone, not only to Prahalad !!)

I also found something peculiar. I am using demoversion simulator of Frontline-Electronicsfor simulating this program. I copied down the code from lcd tutorial, assembled and simulated. All the initialisation commands go well. I saw the RW pin's status. It is high while these commands took place. But, WRITE_LCD routine was called, LCD status is always busy and the WAIT_LCD routine just locks up there.

Then I included CLR RW instruction in the INIT_LCD routine. This time, I was amazed. Even the first init command, 38h is not getting accepted; I mean, LCD shows busy always. As this many tug-of-wars go in the simulation process itself, I am totally diffident about the Hardware working. About the whole code what I have used for simulation is:

stk_bse equ 30h
DB0 EQU P1.0
DB1 EQU P1.1
DB2 EQU P1.2
DB3 EQU P1.3
DB4 EQU P1.4
DB5 EQU P1.5
DB6 EQU P1.6
DB7 EQU P1.7
EN EQU P0.2
RS EQU P0.0
RW EQU P0.1
DATA EQU P1

org 0000h
boot: ljmp start

org 0003h ;IE0 all interupts are returned
ret

org 000Bh ;TF0
ret

org 0013h ;IE1
ret

org 001Bh ;TF1
ret

org 0023h ;serial
ret

org 0030h
start:
mov IE,#00h
mov SP,#stk_bse
mov r4,#0ah

wait:
lcall delay
djnz r4,wait
lcall wait_lcd
lcall INIT_LCD
LCALL CLEAR_LCD
MOV A,#'H'
LCALL WRITE_TEXT

here: sjmp here

INIT_LCD:
SETB EN
;clr RW this is where I tried
CLR RS
MOV p1,#38h
CLR EN
LCALL WAIT_LCD

SETB EN
CLR RS
MOV p1,#0Eh
CLR EN
LCALL WAIT_LCD

SETB EN
CLR RS
MOV p1,#06h
CLR EN
LCALL WAIT_LCD
RET


WAIT_LCD:

SETB EN ;Start LCD command
CLR RS ;It's a command
SETB RW ;It's a read command
MOV p1,#0FFh ;Set all pins to FF initially
MOV A,p1 ;Read the return value
JB ACC.7,WAIT_LCD ;If bit 7 high, LCD still busy
CLR EN ;Finish the command
CLR RW ;Turn off RW for future commands
RET


CLEAR_LCD:

SETB EN
CLR RS
MOV p1,#01h
CLR EN
LCALL WAIT_LCD
RET


WRITE_TEXT:

SETB EN
clr RW
SETB RS
MOV p1,A
CLR EN
setb EN
LCALL WAIT_LCD
RET


delay:
mov r6,#0ffh

loop1:
mov r5,#0ffh

loop2:
djnz r5,loop2


djnz r6,loop1
ret

end

99% of the above program is from the LCD tutorial in this forum. I have done little patchs for my hardware

Where have I missed it? What might be the problems? I am very sure about my hardware part. Also, as I have bought new LCD module, there is no problem with that also. What keeps me down? I am trying for, literally 6 months to get this LCD to display. Sorry for a lenghtier post.

Thanks for your patience,
Regards,
Vignesh.