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Failure of 204A

I am adding a display to existing PIC based hardware using 11 outputs from SN74HC574 latches for 8 bit data and RS RW EP  but not having much success. 

At first it had been working perfectly with 80 charactor messages being displayed but then it degraded to random charactors scrolling through the display, then to just a solid flashing cursor and then totally blank.

After some investigation and eventual replacement of the 204A with a known good Powertip display I am convinced the 204A has become faulty.  Could this fault be caused by long duration  E pulse ?  Due to hardware restrictions the E pulse is active high for 1,65 micro seconds.

The annoyance was that it failed immediately after I had added a large amount of code to the micro-processor which lead me to think I had somehow corrupted the display handler.

 

Regards

Bernard Green

UK