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???
09/09/07 23:14
Modified:
  09/09/07 23:23
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 		 #144185 - Is this >good news< ??
Responding to: ???'s previous message
Rubem said:
I'll try not to be overenthusiastic about it, but I removed the two 33pF caps from pins 4 and 5 to ground in the PCB and... bingo!

That removing the burden caps makes the oscillator work isn't good news. Why burden caps shouldn't be omitted I have explained here:

http://www.8052.com/forum/read.phtml?id=79811

Are the crystal and power supply decoupling connections like shown here

http://www.8052.com/forum/read.phtml?id=74689

http://www.8052.com/forum/read.phtml?id=62391 ?

Please note, that in these example layouts a solid ground plane is used! I would highly recommend you to also use a solid ground plane with your projects!!!

Can you show us your layout?

Kai

List of 125 messages in thread
TopicAuthorDate
89C2051 oscillator does not oscillate (?)            01/01/70 00:00      
   Capacitor value?            01/01/70 00:00      
      20-40pF indeed            01/01/70 00:00      
         it might be the crystal            01/01/70 00:00      
            Probably not            01/01/70 00:00      
               because it\'s crap            01/01/70 00:00      
                  Not same position            01/01/70 00:00      
                     one cap or two makes most probably no difference..            01/01/70 00:00      
                        Not on the pins            01/01/70 00:00      
                           I'd recomend you re-read the spec's ...            01/01/70 00:00      
                           It's the same Vcc            01/01/70 00:00      
                  Hhm...I wouldn't recommend this paralleling            01/01/70 00:00      
                     hummm... really? In what frequency range?            01/01/70 00:00      
                        The inductance of the left resonating with...            01/01/70 00:00      
                           interesting            01/01/70 00:00      
                        Spice models            01/01/70 00:00      
                           Thanks, Kai.            01/01/70 00:00      
                           Numerical calculation, some examples...            01/01/70 00:00      
   Wrong reset scheme!            01/01/70 00:00      
      10µF reset capacitor to Vcc            01/01/70 00:00      
      Isn't that the mfg's recommended circuit?            01/01/70 00:00      
         Which do you mean?            01/01/70 00:00      
            10 uF to Vcc and 8.2K (built-in?) to GND            01/01/70 00:00      
               no, it is not            01/01/70 00:00      
                  If it's in nearly every datasheet ...            01/01/70 00:00      
                     this is your perception of the things, Richard            01/01/70 00:00      
                        Here we go again ...            01/01/70 00:00      
                           ... and again...            01/01/70 00:00      
                              I don't know what to say ...            01/01/70 00:00      
                                 there is NO out of spec power supply            01/01/70 00:00      
                                    Not only...            01/01/70 00:00      
                                       Not allways            01/01/70 00:00      
                                       Have you seen evidence of improvement?            01/01/70 00:00      
                                          Wider spectrum            01/01/70 00:00      
                                             maybe ratio of good/bad crystals is the same...            01/01/70 00:00      
                                                In all the various designs I produced ...            01/01/70 00:00      
                                                   Never had a failure until now            01/01/70 00:00      
                                                   I know of lots of crystal problems...            01/01/70 00:00      
                                                      Could be, but I've never encountered it ...            01/01/70 00:00      
                                                      %$#@! Double-post again ... ...            01/01/70 00:00      
                                       ^%$#@! double-post ...            01/01/70 00:00      
                                    If the datasheet says 1 ms ...            01/01/70 00:00      
                           more about locomotives            01/01/70 00:00      
                              symptoms suggest ...            01/01/70 00:00      
                     steam locomotives            01/01/70 00:00      
                        I like the steam locomotives            01/01/70 00:00      
                           So do I            01/01/70 00:00      
                              me too, said the dog            01/01/70 00:00      
                                 The kids should be smarter than that!            01/01/70 00:00      
                                    kids are kids            01/01/70 00:00      
   It might not be a clock problem            01/01/70 00:00      
      Does not work, sorry            01/01/70 00:00      
   Bad Connections or Crystal ?            01/01/70 00:00      
      A picture may be useful            01/01/70 00:00      
         Breadboards are highly unsuited for micros!!            01/01/70 00:00      
            Makes sense            01/01/70 00:00      
            breadboards are highly unsuited for ANYTHING!            01/01/70 00:00      
               Not at all!            01/01/70 00:00      
                  If you look at the pictures you can see why.            01/01/70 00:00      
                     Yes, it doesn\'t look properly, but...            01/01/70 00:00      
                        It's too risky!            01/01/70 00:00      
                           What is the purpose of your posts??            01/01/70 00:00      
                              My purpose is to point out that there are flaws            01/01/70 00:00      
         *** THE PICTURES ***            01/01/70 00:00      
            Problem may be breadboard            01/01/70 00:00      
               Breadboard correction            01/01/70 00:00      
                  How I programmed the 2051            01/01/70 00:00      
               Must be continuous            01/01/70 00:00      
               there is a good english word \'IS\"            01/01/70 00:00      
            I have the same thing running on my desk...            01/01/70 00:00      
               really ?            01/01/70 00:00      
                  Sadly, it's a trade name            01/01/70 00:00      
                  yea, but...            01/01/70 00:00      
                     again, replacing one uncertainty with another            01/01/70 00:00      
            I see two points            01/01/70 00:00      
   When you\'re ready to give up ... try this!            01/01/70 00:00      
      wow            01/01/70 00:00      
      use the unbuffered parts            01/01/70 00:00      
         It works fine with S, LS, HC, AC, HCT, ACT, etc            01/01/70 00:00      
            It's not so foolproof            01/01/70 00:00      
               I've had pretty good results ...            01/01/70 00:00      
   Many thanks, I'll try some of your tips...            01/01/70 00:00      
      Maybe your AT89C2051 is just damaged?            01/01/70 00:00      
      Overtone            01/01/70 00:00      
      89S51/52 are much more stable            01/01/70 00:00      
   Can you still (re-) program it            01/01/70 00:00      
      Let's hope that Rubem will come back ...            01/01/70 00:00      
         Hi again, sorry            01/01/70 00:00      
            Even with no breadboard            01/01/70 00:00      
               What has the programmer to do with the oscillator?            01/01/70 00:00      
      The chip is fine            01/01/70 00:00      
         What will that tell you about the oscillator?            01/01/70 00:00      
            It is time to tell the manufacturer, that...            01/01/70 00:00      
               oscillator of 2051?            01/01/70 00:00      
                  Sorry, maybe I was too harsh            01/01/70 00:00      
                     The MCU and crystals are all working for sure            01/01/70 00:00      
                        It was not the 7805            01/01/70 00:00      
                           because you shook/dropped/kicked it            01/01/70 00:00      
                        7805 decoupling            01/01/70 00:00      
                           LM79XX need a different treatment!            01/01/70 00:00      
                        Good news            01/01/70 00:00      
                           Is this >good news< ??            01/01/70 00:00      
                           Have you considered the "breadboard" effect?            01/01/70 00:00      
                              Inductance            01/01/70 00:00      
                                 Hey!            01/01/70 00:00      
                                    So what?            01/01/70 00:00      
                                       specifically            01/01/70 00:00      
                                       Let\'s not go overboard ...            01/01/70 00:00      
                                          This does not make him learn to swim...            01/01/70 00:00      
                                             I have only my own experience ...            01/01/70 00:00      
                                          Not Atmel problem            01/01/70 00:00      
                                          things change            01/01/70 00:00      
                                             looking at the wrong characteristic            01/01/70 00:00      
                                                OT: to Richard            01/01/70 00:00      
                                                   OT: I hadn\'t but I have ... Yes, I\'m interested!            01/01/70 00:00      
                                       You are probably right            01/01/70 00:00      
                        do you have a 10-100nF directly across the            01/01/70 00:00      
                           *** PCB and schematic ***            01/01/70 00:00      
                              I cannot find C1            01/01/70 00:00      
                                 Ahh, it is the supercap! Needs some changes!            01/01/70 00:00      
                                    Surprisingly It works like it is            01/01/70 00:00      
                                       No, no...            01/01/70 00:00      
                              I can't really 'read' your PCB but ...            01/01/70 00:00      
                                 It is connected            01/01/70 00:00      
   Is any old recipe.            01/01/70 00:00      

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