I have bought a new JHD204A lcd display which is a 20×4 lcd. When i have interfaced it without a contrast control resistor(pot) it displayed the character clearly. How it is possible. I have seen many interfacing circuits provided with a pot for controlling contrast but in this case it is set automatically. Then i have connected a 10K pot to 3rd pin of lcd w.r.t GND and varied it but no change in contrast it is set to a value is it possible?