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???
11/08/10 20:41
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 		 #179518 - many pull-ups
Responding to: ???'s previous message
Karan Verma said:
I will use a 10-K-ohm pull up between the C8051F120(3.6 V) and JHD162A(5 V), to make the pins swing till +5V, i will have to define the pins as Open-Drain. For configuring the output state of a pin, it's PnMDOUT should be cleared and corresponding Port data bit set to 0 to tie it to the ground, or set to 1 to put it in high impedence.

1. How would a pin tied to GND or High Impedence affect it's output state when it is open - drain ?
Your software ties it to GND or makes it High Impedance by writing a 0 or a 1. When High Impedance the pull-up can pull it up to 5V. When tied to GND the pull-up loses the fight and it is at 0V.

2. Should a pull up resistor be between, Vcc and input, because if the pin is tied to the GND, how would it work ?
Yes. And it doesn't.

3. Will i have to connect all the 11 lines ( DB0 - DB7 & EN, R/W, RS) to the pull up resistor ?
There is no the pull-up resistor. Each pin needs its own pull-up.


List of 45 messages in thread
TopicAuthorDate
JHD162A lcd            01/01/70 00:00      
   5V LCD            01/01/70 00:00      
      in addition !            01/01/70 00:00      
         Matching output voltages with input requirements            01/01/70 00:00      
         C8051F120 has 5V tolerant Input/Output pins            01/01/70 00:00      
            Yes i have...            01/01/70 00:00      
            careful            01/01/70 00:00      
               what are...            01/01/70 00:00      
                  Powered components            01/01/70 00:00      
                     Thank You            01/01/70 00:00      
                  examples            01/01/70 00:00      
               active level converters            01/01/70 00:00      
                  Resistors not good way to reduce voltage            01/01/70 00:00      
                     Thank You...            01/01/70 00:00      
                     Per forgot one thing            01/01/70 00:00      
                        R*C            01/01/70 00:00      
                           delay            01/01/70 00:00      
            5V and micro and LCD            01/01/70 00:00      
   potentiometer            01/01/70 00:00      
      Film Capacitor??            01/01/70 00:00      
         thank you so much            01/01/70 00:00      
      SIL resistor            01/01/70 00:00      
         new delhi            01/01/70 00:00      
            Actually, it seems that they *do* know!            01/01/70 00:00      
         SIL Residtor *network*            01/01/70 00:00      
            correction...Yes they do know            01/01/70 00:00      
   Port I/O pin voltage            01/01/70 00:00      
      "5V-Tolerant" pins - already answered            01/01/70 00:00      
      5V tolerant, not 5V            01/01/70 00:00      
         Thank You            01/01/70 00:00      
            Maybe you can "get by" with this ...            01/01/70 00:00      
               "Absolute Maximum Limits" are not Operating conditions            01/01/70 00:00      
                  That's true, it's an absolute maximum/minimum            01/01/70 00:00      
                     Agree            01/01/70 00:00      
               3V3 logic runs at "TTL levels"            01/01/70 00:00      
                  The HD44780 claims to respond to TTL levels ... but ...            01/01/70 00:00      
   pull up resistor            01/01/70 00:00      
      do not tie a pin to gnd            01/01/70 00:00      
      many pull-ups            01/01/70 00:00      
         Do you mean...?            01/01/70 00:00      
      one more thing ...            01/01/70 00:00      
   high impedence            01/01/70 00:00      
   lcd EN signal            01/01/70 00:00      
      It is a pre-clear            01/01/70 00:00      
         Thank You            01/01/70 00:00      

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