Hello Everyone...

Brief Description..

I have some* 16 x 2 LCD's connected to port0 (with 4k7 pullups)of a 89c52b,LCD driven in 4 bit bus mode..
The lcd driver checks the busy flag ,and also a timer count...
Line 1 is used to show the time ,and my company name..
Line 2 is used to show five sensor values (and the setpoints),in a 4 second loop (not scrolled,but overwritten).

some*= When I use my test rig,using a trident 16x2 , everything runs as expected..


The Problem..

In the product I want to use a large character Optrex 16x2 (with a genuine HD44780 controller).
When I write to line 1 , the HD44780 does not lower the busy flag after an internal operation (this would trigger a reset by the external max1232 watchdog if allowed to timeout(600ms)),but as I also use a timer count(71ms) ,the display write continues...
Annoyingly , the correct data is written , but slowly due to the delay.

On Line 2 ,the busy flag works as it should do , and line 2 is re-written instantly...

I have observed the busy flag on my DSO , and it does not work on a line1 write , but does on line2 ..
And there's little slewing of the control signals.

All of the Optrex displays I have exhibit this behavior (so are they all faulty?)
Why do my other LCD's (HD44780 clones) work ,but the genuine HD44780 will not?.
Has anyone seen this behavior before?...