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???
04/17/07 12:06
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 		 #137365 - gibberish
Responding to: ???'s previous message
on many 8051 microprocessors (and even microcontrollers), Port 0 is normally float.
the '51 IS a microcontroller

It is fine to use them as general purpose data pins, but they really should be tied to a pull-up (or a pull down) resistor as well. 100K for a cmos chip will work well.
no they MUST be pulled up. 100k give a very slow risetime and is too large for many purposes

If you fail to do this, then there is a good chance that port 0 will float when the program is not running and chances are that there may be a problem using your LCD.
who cares what it does "when the program is not running" but it will NEVER go high (not 'float' BUT not go high) if there is no pullup

Erik

List of 78 messages in thread
TopicAuthorDate
LCD Problem            01/01/70 00:00      
   stop shouting - also            01/01/70 00:00      
      Sorry Erik            01/01/70 00:00      
         no need to be 'sorry'            01/01/70 00:00      
            timing            01/01/70 00:00      
               delays aren't necessary if you monitor busy            01/01/70 00:00      
   Pullup resistors on P0            01/01/70 00:00      
      already answered            01/01/70 00:00      
   make sure            01/01/70 00:00      
      Is there any test procedure to test LCD Module?            01/01/70 00:00      
         from the shop            01/01/70 00:00      
   did you try...            01/01/70 00:00      
      tthat is SOME wait            01/01/70 00:00      
         ...            01/01/70 00:00      
            well, maybe is is a good thing            01/01/70 00:00      
               i need a lcd testing procedure            01/01/70 00:00      
                  like this            01/01/70 00:00      
                     lcd testing            01/01/70 00:00      
                        Couple of links            01/01/70 00:00      
                           no datasheet            01/01/70 00:00      
                              Should work the same...            01/01/70 00:00      
                                 +1 for this answer            01/01/70 00:00      
                                    LJMP limits            01/01/70 00:00      
      delays aren't necessary if you monitor busy            01/01/70 00:00      
      May be LCD is damaged!!            01/01/70 00:00      
         Pin 3 may require a negative voltage            01/01/70 00:00      
            PLEASE!!!!            01/01/70 00:00      
               There is a "convention"            01/01/70 00:00      
            to clarify?            01/01/70 00:00      
         two problems with the 'advice' you followed            01/01/70 00:00      
            Only lower line of LCD is showing!            01/01/70 00:00      
               looks like pretty normal behavior to me ...            01/01/70 00:00      
                  'cheap' -5 for a LCD            01/01/70 00:00      
   where is that standard?            01/01/70 00:00      
      It's not an EIA or a DIN standard ...            01/01/70 00:00      
         you said exactly that            01/01/70 00:00      
            We've all told him to read his LCD datasheet            01/01/70 00:00      
               this is getting ridiculous.            01/01/70 00:00      
                  ok, I deserve -1 from before            01/01/70 00:00      
                     why not spell it correctly            01/01/70 00:00      
                  That's why there are datasheets            01/01/70 00:00      
   LCD is workingggg!!!!!!            01/01/70 00:00      
      Now get to work            01/01/70 00:00      
         MISTAKES made            01/01/70 00:00      
   Datasheet, which created a problem.            01/01/70 00:00      
   Can LCD datasheet be uploaded for others referen.?            01/01/70 00:00      
      You have to get the correct datasheet            01/01/70 00:00      
         need lcd testing procedure            01/01/70 00:00      
            You need more data!            01/01/70 00:00      
               addendum to Richards post            01/01/70 00:00      
                  There is a de-facto standard            01/01/70 00:00      
                     lcd problem            01/01/70 00:00      
                        Disconnect d1            01/01/70 00:00      
                        problem with second line of lcd            01/01/70 00:00      
                           program            01/01/70 00:00      
                              your code has a problem?            01/01/70 00:00      
                                 looks like experimenting again ...            01/01/70 00:00      
                                 from hitachi data sheet on HD44780            01/01/70 00:00      
                                    I'm starting to hate these datasheets            01/01/70 00:00      
                                       BULL            01/01/70 00:00      
                                          get it RIGHT before you deviate from spec's            01/01/70 00:00      
                                       OK... I give up...            01/01/70 00:00      
                                    8 bit Initialization            01/01/70 00:00      
                                       lcd problem            01/01/70 00:00      
                                          program i used            01/01/70 00:00      
                                             driving voltage            01/01/70 00:00      
                                                its not the contrast problem            01/01/70 00:00      
                                                   why?            01/01/70 00:00      
                                                   Contrast and Initialization            01/01/70 00:00      
                                             you are, I hope, aware            01/01/70 00:00      
                                       That's the one...thanks            01/01/70 00:00      
   about P0            01/01/70 00:00      
      It shows that you "experiment" instead of reading            01/01/70 00:00      
      gibberish            01/01/70 00:00      
   small correction            01/01/70 00:00      
      thanks a lot            01/01/70 00:00      
         Thanks for informing us.            01/01/70 00:00      
            so, next time            01/01/70 00:00      

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