Thanks for all the replies.

1) The 8-bit data/cmd bus from the lcd is tied to p0, and the read/write goes to the 8051's read/write pins. Enable and chip select goes to p1.0 and p1.1. Using a development board and monitor program, I think using the movx @dptr, a should work. Yes, no ?

2) To simplify debug efforts, I have moved the bus and read/write pins of the lcd to p2 and p1.5/p1.6, so read and write is controlled by code. What I notice now is that the monitor program actually changes the address of lcall after 2 lcalls to WriteDisplayCMD, i.e. the code below executes correctly (I'm using the single-step feature of the monitor program) until the 3rd lcall WriteDisplayCMD. I start the code at 8000h and the code actually has WriteDisplayCMD at 803dh, but after the 3rd lcall, it reflects a WriteDisplayCMD address at 8002h.

DisplayInit:
lcall delay
clr p1.1 ;select LCD
mov a, #reset_display ;reset display
lcall WriteDisplayCMD
mov a, #lcd_bias_1_9 ;set LCD brightness
lcall WriteDisplayCMD
mov a, #adc_select_reverse ;segment driver
lcall WriteDisplayCMD
mov a, #common_output_normal ;set LCDdisplay

WriteDisplayCMD:
clr p1.0 ;a0_bit
clr p1.1 ;cs1_bit
clr p1.6 ;wr_bit
setb p1.5 ;rd_bit
mov p2,a
setb p1.6 ;wr_bit
nop
ret
Delay: mov r0, #02h
Delay1: djnz r0,delay1
ret


Any ideas why it's changing the lcall address after calling it the 3rd time ?

Thanks....