Hi Benny,

The CE (Chip Enable) and C/D has to be connected.
The C/D line is the Command / Dataline of the display. This line determines if a command or databyte is available on the adres bus.
I've downloaded the datasheet of the Optrex and this display uses a T6963 display controller.
I did some experimenting with this controller on a Toshiba TLX-1741 display. Seems to me even the 20 pins connector has the same layout but double check this, please.
You can find an example circuit and some code at this link.

http://www.grote.net/bascom/bascom-archive.html

The source is in Bascom basic but I think it will help. Also take alook at the PDF file about writing software for T6963 based displays. It was very helpfull.

Note : my display is memorymapped connected to the uC

Peter