Philip,

We have had a lot of LCD discussion on this board so please review these posts they will save you some time.

LCD require different delays between command and data input. Ensure you are providing this. I always look for the longest command (Clear Display Cursor to Home if i remember correctly) and use this as my general delay between writes for LCD's.

Check you RS, E, and WR lines for proper sequencing.

Once this is in place. Read about init'ing the Display. You will find that you have to set the transfer width twice in case it "wakes" in 4 bit mode (assuming you are using 8 bit mode).

Before you attempt to control the display area and cursor. Write Clear to Home preceeding each message

'420 isn't to "fast" for the Display from a signalling standpoint but if you do not delay between writes as the spec indicates don't expect much to happen.

BTW, the '420 is not uniformly single cycle per instructions but is for many, and faster overall than a '320.


regards,
p