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???
01/20/09 13:17
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 		 #161637 - No negative Tx supply
Responding to: ???'s previous message
Hi Bing!
Rx section will work. But Tx section needs at least -6V in low side of R19, as RS232 protocol is "bipolar": "1" is a negative voltage of a minimum of -8V aprox. But probably +/-6V will work with almost all PC serial port. I would use a MAX232 or similar IC.

Also you did not draw the reset circuitry for AT89C4051.

Best regards

Daniel

List of 34 messages in thread
TopicAuthorDate
Serial Communication Problems            01/01/70 00:00      
   standards have a purpose            01/01/70 00:00      
      Serial Communication Problem            01/01/70 00:00      
         OH, how often            01/01/70 00:00      
   No negative Tx supply            01/01/70 00:00      
      Serial Communication Problem            01/01/70 00:00      
   Software or documentation bug            01/01/70 00:00      
      I am so new sorry            01/01/70 00:00      
         Reset            01/01/70 00:00      
   I found this Image at google            01/01/70 00:00      
      Read datasheets to better understand            01/01/70 00:00      
      which derivative            01/01/70 00:00      
      It will meet the RS232 requirements            01/01/70 00:00      
         Are You sure?            01/01/70 00:00      
            are you saying "PC" when you say "mother board"            01/01/70 00:00      
               You are right , Eric,            01/01/70 00:00      
                  because            01/01/70 00:00      
                     cheap is paradigm today, so            01/01/70 00:00      
                        That's odd ... I've never seen one ...            01/01/70 00:00      
                           odd, but real .            01/01/70 00:00      
                              Explaining to beginners            01/01/70 00:00      
                                 agree            01/01/70 00:00      
                           look for a copy of the EIA standard and read it            01/01/70 00:00      
                           right, but not the issue            01/01/70 00:00      
            RS-232 transceiver in PC            01/01/70 00:00      
   Basics            01/01/70 00:00      
      MAX232 vs DS275            01/01/70 00:00      
         It is not that simple            01/01/70 00:00      
            I bought the required componentss            01/01/70 00:00      
               It worked! Yahoo!!!!Googlooo!!!            01/01/70 00:00      
   Circuit Design            01/01/70 00:00      
      May need to have pullup resistors            01/01/70 00:00      
         It worked, thanks!            01/01/70 00:00      
            It destroyed though my red led            01/01/70 00:00      

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