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???
10/31/03 00:57
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#57547 - RE: serially addressable LCD
Responding to: ???'s previous message
The shift register idea is quite clever. I do see a potential problem however. The use of a 1N914 diode to hold the LCD module E line low whenever the shift register 6Q output is low is compromising the low level noise margin of the E signal. If you look at the web specification for a typical character mode LCD module such as here you can see that the spec for VIL is 0.6V max. It is rather hard to meet this specification with a diode in the path that drops 0.6 volts plus whatever the output VOL of the shift register is.

If the diode must be used I would suggest selecting a low drop Schottky type and then just for a hobby application of the circuit. If the circuit is intended to be used in a production situation or where the cable to the LCD module has any length from the shift register then I would use the "AND" gate as suggested by the referencing WEB page. Here is a convenient type of gate that could do the trick nicely...single gate AND.

Michael Karas


List of 27 messages in thread
TopicAuthorDate
serially addressable LCD            01/01/70 00:00      
   RE: serially addressable LCD            01/01/70 00:00      
      RE: serially addressable LCD            01/01/70 00:00      
         RE: serially addressable LCD            01/01/70 00:00      
   RE: serially addressable LCD            01/01/70 00:00      
   RE: serially addressable LCD            01/01/70 00:00      
   RE: serially addressable LCD            01/01/70 00:00      
   RE: serially addressable LCD            01/01/70 00:00      
      RE: serially addressable LCD            01/01/70 00:00      
         VFD current requirement            01/01/70 00:00      
         RE: serially addressable LCD            01/01/70 00:00      
            RE: serially addressable LCD            01/01/70 00:00      
               RE: serially addressable LCD            01/01/70 00:00      
               RE: serially addressable LCD            01/01/70 00:00      
                  RE: serially addressable LCD            01/01/70 00:00      
                     RE: serially addressable LCD            01/01/70 00:00      
                        RE: serially addressable LCD            01/01/70 00:00      
                           RE: serially addressable LCD            01/01/70 00:00      
                     RE: serially addressable LCD            01/01/70 00:00      
                  BTW: Datasheet            01/01/70 00:00      
                     RE: BTW: Datasheet            01/01/70 00:00      
   RE: serially addressable LCD            01/01/70 00:00      
   RE: serially addressable LCD            01/01/70 00:00      
      RE: serially addressable LCD            01/01/70 00:00      
   RE: serially addressable LCD            01/01/70 00:00      
      RE: serially addressable LCD            01/01/70 00:00      
   RE: National Control Devices            01/01/70 00:00      

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