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???
05/17/06 09:42
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 		 #116360 - Another gem? Well explained!
Responding to: ???'s previous message
Richard Erlacher said:
If it says that, you have to take it in context. If the input is NOT LOW, which 1 volt certainly isn't, then it tolerates a 1 volt level. If the input is NOT HIGH, which 1.25 volts isn't, then it tolerates 1.25.

Try putting this datasheet's schematic in your favorite SPICE program and see how it behaves with a 1 KHz sine wave from +5 to -5.

I repeat, not that I should have to do so, correctly receiving RS-232 signal doesn't require a negative supply. It only requires the logic level supply. You can build the same circuit as is in the datasheet and get just as good a noise immunity as you're willing to work for. It might take a bit of bypass work, but I bet you can do better than the MAX-series if you try. With different biasing, that same circuit should work fine with 3.3 volt Vcc.

RE





TG


List of 68 messages in thread
TopicAuthorDate
hardware setup of AT89C51ED2            01/01/70 00:00      
   RTFM            01/01/70 00:00      
   board's setup            01/01/70 00:00      
   has been discussed            01/01/70 00:00      
   AT89C51ED2 in ISP            01/01/70 00:00      
      no 'unique' schematc needed            01/01/70 00:00      
      thanks joel            01/01/70 00:00      
    I sent for your email the schematic!            01/01/70 00:00      
   FLIP            01/01/70 00:00      
      sample code            01/01/70 00:00      
         program in assembly?            01/01/70 00:00      
            sample code in c            01/01/70 00:00      
   ISP without MAX232            01/01/70 00:00      
      that old gem again            01/01/70 00:00      
         A gem is always a gem            01/01/70 00:00      
            it does not help that you respond s..t a            01/01/70 00:00      
      Re: ISP without MAX232            01/01/70 00:00      
         To stop an urban legend ... seems imposs            01/01/70 00:00      
            just for the sake of argument ...            01/01/70 00:00      
               very clearly stated            01/01/70 00:00      
                  That's GREEN cheese!            01/01/70 00:00      
            from old time...            01/01/70 00:00      
               there you go            01/01/70 00:00      
               How about the 1488/1489?            01/01/70 00:00      
                  this all started with            01/01/70 00:00      
                     well, I read that, but ...            01/01/70 00:00      
                        but            01/01/70 00:00      
                           the standard still deserves a look            01/01/70 00:00      
            reminds me of the burden cap argument.            01/01/70 00:00      
         RS232 without -V explained            01/01/70 00:00      
            There is two ways to do things: by desig            01/01/70 00:00      
            Do never do            01/01/70 00:00      
               Answer in shematic of your post            01/01/70 00:00      
            I wouldn't rely on that ...            01/01/70 00:00      
               true, if you have no noise margin worrie            01/01/70 00:00      
                  What??? You imply the 1489 won't work?            01/01/70 00:00      
                     what is a 1489? and what is the issue            01/01/70 00:00      
                        it's what we used before the Max-xxxx            01/01/70 00:00      
                           who said 'require'?            01/01/70 00:00      
                              I think you're dreaming.            01/01/70 00:00      
                                 yes, I 'dream' noise immunity            01/01/70 00:00      
                                    and you're prepared to show ...            01/01/70 00:00      
                                       I can't            01/01/70 00:00      
                                          Try this link            01/01/70 00:00      
                                             I hope the datasheet is wrong            01/01/70 00:00      
                                                Nope, it isn't wrong ...            01/01/70 00:00      
                                                   Another gem? Well explained!            01/01/70 00:00      
                                                      so, now the crap is "justifued"            01/01/70 00:00      
                                                   hy do you keep beating a desd horse            01/01/70 00:00      
                                                      I'm not the one doing the beating            01/01/70 00:00      
                                                         I never said that            01/01/70 00:00      
                                                            Hysteresis, ... sure ...            01/01/70 00:00      
      Interesting ...            01/01/70 00:00      
          Just wait, next time it may very            01/01/70 00:00      
   you keep hammering 'needed'            01/01/70 00:00      
      No, in fact you haven't            01/01/70 00:00      
         standard            01/01/70 00:00      
            Of course I adhere to standards            01/01/70 00:00      
               I did not make the standard            01/01/70 00:00      
                  As long as you're arguing with me ...            01/01/70 00:00      
                     I directly quoted you, so who started th            01/01/70 00:00      
                        Erik, you need some practice            01/01/70 00:00      
                           That should settle it, you get your chip            01/01/70 00:00      
                        Chill brothers            01/01/70 00:00      
                           Time for a rendezvous            01/01/70 00:00      
                           to the two above            01/01/70 00:00      
                              Where's the science?            01/01/70 00:00      
                                 science            01/01/70 00:00      

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