Hi all,

I see a lot of circumstance around connecting LCD like 4 bit mode
or additional shift registers.

The easiest way I found was placing it in the memory space.
If already external memory used, you need no additional pins
only an extra chip select.
Then it can connected as following:
LCD: 8051:
D0 - D7 P0.0 - P0.7
RS A0 (or P2.0 if no address latch used)
WR A1 (or P2.1)

only E need a little logic: E = CS + RD * WR.
If you use a CPLD (e.g. 20V8) as address decoder for several
other memory and IO-devices, it can do it also.
On using TTL-decoder (74LS138) for chip select the equation
for E can be transformed to: E = /( /CS * ( /WR + /RD )).
Since CS, WR, RD already inverted, this can do a half 74LS51
(AND-NOR).

Then you can read and write 8bit wide simple with "MOVX"


Peter