Processor : 89c51rd2 + 6Mhz crystal @ 6 clock mode
LCD : HD44780 driving a 2x16 jumbo display having a display area of 148 x 31mm

This code works for the normal ( small LCD displays) but does not work with the above LCD - it does not even initialize as only the first row is just fully black.

The code is this :

LCDCOM: MOV P2, #ADD_H
MOV R0, #LCD_C
MOVX @R0, A
DELAY: MOV R3, #200 ; 400 Micro delay for each write
DLOOP: DJNZ R3, DLOOP
RET

The RS pin of the LCD is connected to the Bit4 of the 74573 address latch. The R/W pin of LCD is connected directly to the /W pin of MCU. The Enable pin of LCD is connected to one of the outputs of 74138 after inversion. This is also activated by the /W pin of MCU.

In this setup the time between Data Valid to Enable is 58 nS and the Enable Pulse width is 398 nS.

Instead of scratching the head, just rigged up a small direct bit driven setup and tried. The Jumbo LCD works beautifully :

WR_INST:CLR P3.0 ; Select Command register
CLR P3.1 ; Select write mode
CLR P3.2 ; Pull enable low
MOV P1, A ; Move data to LCD
SETB P3.2 ; Pull Enable high
NOP ; Delay of 1 Microsecond
CLR P3.2 ; Pull Enable low
CALL DLY500m ; 500 micro delay
RET

In the memory mapped set up, I dont think there is any way of bringing in the sequence and delays as in the direct bit driven mode.

But somehow I need to use that method only - any tips?

Raghu