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10/03/07 21:14
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 		 #145343 - Invalid conclusion
Responding to: ???'s previous message
Mahmood Elnasser said:
My first AT89S8252 design 7 years ago had RC reset circuit as per datasheet.
As an outsider to the 8052 I noticed the following:
1. At first power up, the microcontroller works fine.
2. If I toggle the power supply on and off few times quickly, the microcontroller hangs up.

A common situation leading to a common misconception! You have to allow Vcc to reach < Vss + 0.2 Volts before turning the PSU back on. If you don't, you won't get enough "kick" to start the oscillator, and you won't get an effective reset.

3. If I turn the power supply off for over 5 seconds and turn it back on the circuit works fine.

That's consistent with what I stated above.

4. If I press the reset switch multiple times, I noticed not all of the presses produce reset to the microcontroller, and some times it hangs up.

If you have too long a time constant in your RC it can behave in this way. Presumably you used the values recommended by your MCU manufacturer, right?

So I concluded that the RC reset is very unreliable and might work fine in normal power supply conditions (with no interruptions or brownouts) and if no manual reset is needed.

I haven't tried a reset supervisor for lack of such devices in here, I switched to PICs and dsPICs for they have internal reset supervisors and they are more available in local shops in this part of the world.

Yes, and they cost less than the popular supervisors, don't they?

Mahmood





List of 189 messages in thread
TopicAuthorDate
Reset Accuracy            01/01/70 00:00      
   Read This            01/01/70 00:00      
   throw it away!            01/01/70 00:00      
   That is the nature of RC resets!            01/01/70 00:00      
   Inhereted design            01/01/70 00:00      
   1st Lesson            01/01/70 00:00      
      P.S. Welcome            01/01/70 00:00      
      is IS an iteresting question, isn't it?            01/01/70 00:00      
         more on supervisor            01/01/70 00:00      
            same thing            01/01/70 00:00      
            Extendec ASCII Characters            01/01/70 00:00      
               That's cool Joe            01/01/70 00:00      
               Not ASCII            01/01/70 00:00      
               Beware - Your results may vary            01/01/70 00:00      
         Thoughts on RC Resets            01/01/70 00:00      
            Schmitt leaves problems?            01/01/70 00:00      
               even at startup you can get into trouble            01/01/70 00:00      
                  the decline and f.. naah rise of the \'51            01/01/70 00:00      
                     the lpc9xx is the glaring BAD example...            01/01/70 00:00      
                        it's not about NXP, though I woldn't forgive them            01/01/70 00:00      
                           it's far past that time...            01/01/70 00:00      
                     only partially so            01/01/70 00:00      
            not quite            01/01/70 00:00      
            Lynn ... can you see anything wrong with ...            01/01/70 00:00      
               how about shooting a sparrow with a RPG?            01/01/70 00:00      
                  You've got to ask yourself ...            01/01/70 00:00      
                     Which manufacturers?            01/01/70 00:00      
                        everybody is            01/01/70 00:00      
                           errare humanum est...            01/01/70 00:00      
                        It's up to us to see that they fix it!            01/01/70 00:00      
                  What's the point?            01/01/70 00:00      
                     I do noy 'believe' I KNOW.            01/01/70 00:00      
                        You can't prove a negative ...            01/01/70 00:00      
                           when it's been gone for 100,000 "unit hours"            01/01/70 00:00      
                              correction            01/01/70 00:00      
                                 How do you monitor this?            01/01/70 00:00      
                                    how stupid can you be            01/01/70 00:00      
                                       so YOU really haven't ever looked at any of them?            01/01/70 00:00      
                                          sure I did            01/01/70 00:00      
                                             it's just as I said ... YOU guess and ship ...            01/01/70 00:00      
                                                Same question            01/01/70 00:00      
                                                   You force them in your test fixture            01/01/70 00:00      
                                                that I do not want to do my job is an insult            01/01/70 00:00      
                                                   It's always about your ego, isn't it, Erik?            01/01/70 00:00      
                                                      adding insult to injury            01/01/70 00:00      
         make it opposite            01/01/70 00:00      
            Answer is wrong            01/01/70 00:00      
               No, is not!            01/01/70 00:00      
                  RE: No, is not!            01/01/70 00:00      
                     Oops.            01/01/70 00:00      
                        the "small embedded printf"...            01/01/70 00:00      
                           LED blinking            01/01/70 00:00      
                              LCD init delay            01/01/70 00:00      
            possibly (most likely) incorrect post            01/01/70 00:00      
      supervisor IC            01/01/70 00:00      
   Check reset Schematic and capacitor .            01/01/70 00:00      
      not necessarily            01/01/70 00:00      
   RC time            01/01/70 00:00      
      crystal frequency is a negligible problem            01/01/70 00:00      
      who cares            01/01/70 00:00      
         Not so fast, there, Pilgrim ...            01/01/70 00:00      
            reset toujours            01/01/70 00:00      
               correction            01/01/70 00:00      
                  I didn\'t know this is the price of a bit...            01/01/70 00:00      
                     the origin of the \'bit\'            01/01/70 00:00      
                        Almost but not quite ...            01/01/70 00:00      
                           wasn't that a gold coin?            01/01/70 00:00      
                  So you assert that that's the one that works?            01/01/70 00:00      
               What is this "reset problem" solved by supervisor            01/01/70 00:00      
                  the final effect is on peripherals not the micro            01/01/70 00:00      
                  not, "this" but all            01/01/70 00:00      
                     What did you mean to say, Erik?            01/01/70 00:00      
                        proof? many ways, here is an example            01/01/70 00:00      
                           I don't doubt any of that, but ...            01/01/70 00:00      
                              the skinny            01/01/70 00:00      
                                 just another reset-related story            01/01/70 00:00      
                        true reset-related stories            01/01/70 00:00      
                           Relevance?            01/01/70 00:00      
                              yes, relevance.            01/01/70 00:00      
                                 the second example ...            01/01/70 00:00      
                                    I gave you two SOLID examples            01/01/70 00:00      
                                       I agree with Erik and Jan            01/01/70 00:00      
                                          Start at the end ...            01/01/70 00:00      
                                          I just think you're all fooling yourselves ...            01/01/70 00:00      
                                       Vexing, perhaps. Solid? Not in the least!            01/01/70 00:00      
                                       What\'s so \"solid\" about an anecdote?            01/01/70 00:00      
                                          Who gives a hoot            01/01/70 00:00      
                                    let\'s put it in another way            01/01/70 00:00      
                                       Here\'s what I want from you ...            01/01/70 00:00      
                                          A particular experience            01/01/70 00:00      
                                 Just consider THIS thread ...            01/01/70 00:00      
                                    well, what about this            01/01/70 00:00      
                                       there's a difference between a fake and a fix            01/01/70 00:00      
                                          I believe you are the only one with that opinion            01/01/70 00:00      
                                             So, who has actually tested their product?            01/01/70 00:00      
                                                incoirrecrt            01/01/70 00:00      
                                    my experience with RC reset            01/01/70 00:00      
                                       Invalid conclusion            01/01/70 00:00      
                                          here is YOUR misconception            01/01/70 00:00      
                                             You\'ve got it wrong ...            01/01/70 00:00      
                                                I can recreate this            01/01/70 00:00      
                                                   maybe you can ...            01/01/70 00:00      
      IN1232N            01/01/70 00:00      
         something is wrong            01/01/70 00:00      
         MAX1232 is better!            01/01/70 00:00      
   What do you mean by "erratic and random"?            01/01/70 00:00      
   RE: something is wrong            01/01/70 00:00      
      Would you be please so kind...            01/01/70 00:00      
         RE: Would you be please so kind...            01/01/70 00:00      
            Hhm,...            01/01/70 00:00      
      What\'s the power supply doing at power-on?            01/01/70 00:00      
   8051 Family Reset Function            01/01/70 00:00      
      Power ON reset            01/01/70 00:00      
         defined power on            01/01/70 00:00      
            inadequate power supply            01/01/70 00:00      
               what does that have to do with            01/01/70 00:00      
                  it has everything to do with it.            01/01/70 00:00      
                     Reset            01/01/70 00:00      
                        ... and what does it do as Vcc decays?            01/01/70 00:00      
                           Defence            01/01/70 00:00      
                              You needn't defend the party line ...            01/01/70 00:00      
                                 correct if you are NOT using a supervisor            01/01/70 00:00      
                                    bidir reset, if there is an internal supervisor            01/01/70 00:00      
                                       Oh, that's what 'bidirectional' means here            01/01/70 00:00      
                                          how do you call that property?            01/01/70 00:00      
                                          Maybe that's your RESET problem!            01/01/70 00:00      
                                             i do not            01/01/70 00:00      
                                                You don't what?            01/01/70 00:00      
                                                   I am sorry, Richard            01/01/70 00:00      
                                                      You do that often ...            01/01/70 00:00      
                                    lower            01/01/70 00:00      
                                    IF you're using too weak a PSU            01/01/70 00:00      
                                       another red herring            01/01/70 00:00      
                                          Well maybe it's not a red herring after all            01/01/70 00:00      
                              Ricxhard, posted            01/01/70 00:00      
                                 supervisor is irrelevant during Vcc decay            01/01/70 00:00      
                                    BULLSHIT            01/01/70 00:00      
                                       I've observed it, while you haven't even looked            01/01/70 00:00      
                     unpredictible is a strong word            01/01/70 00:00      
                        just how would YOU predict the behavior, Jan?            01/01/70 00:00      
                           CMOS            01/01/70 00:00      
                              Yes, that's fine ... well, maybe ...            01/01/70 00:00      
                     male cow manure            01/01/70 00:00      
                        and what's the value of the internal pulldown?            01/01/70 00:00      
               ... and who\\\'ll pay the bills?            01/01/70 00:00      
                  Not only that, but...            01/01/70 00:00      
                  It's too costly if it doesn't work            01/01/70 00:00      
                     get me a muckraker and a pair of boots            01/01/70 00:00      
                        Well, I've observed it, and you haven't even tried            01/01/70 00:00      
      Flash micros need a different treatment!!!            01/01/70 00:00      
         to Kai KISS            01/01/70 00:00      
            Of course, good alternative!            01/01/70 00:00      
         Why do the manufacturers not say that?            01/01/70 00:00      
            one is one            01/01/70 00:00      
            we have answered this many many times before            01/01/70 00:00      
               we really don't disagree ... at least on this            01/01/70 00:00      
                  sure you can            01/01/70 00:00      
            The same story again and again and again...            01/01/70 00:00      
               Clearly, we see things differently            01/01/70 00:00      
                  We aren't so differently...            01/01/70 00:00      
                     I have pulled every string I have ....            01/01/70 00:00      
                        That would be really awesome!!            01/01/70 00:00      
                     it would be awesome            01/01/70 00:00      
                        then I'll call the whole thing off            01/01/70 00:00      
                           No, that's not it            01/01/70 00:00      
                              Would this solve your problem?            01/01/70 00:00      
                                 What do you mean?            01/01/70 00:00      
                                    more details please            01/01/70 00:00      
                                       Maybe this answers some questions            01/01/70 00:00      
                                          Blocking the BBRAMs            01/01/70 00:00      
                                             Why?            01/01/70 00:00      
                                                certainly            01/01/70 00:00      
                                                You asked for a methode, and I showed you one            01/01/70 00:00      
                                                   I agree, what you suggest might work            01/01/70 00:00      
                                                      slowpoke            01/01/70 00:00      
                                                      Because of the enormous currents?            01/01/70 00:00      
                                                         I considered that ...            01/01/70 00:00      
                                                            Of course!!            01/01/70 00:00      
                                                               I've been looking for simple ways            01/01/70 00:00      
                                                more suspition - and more questions            01/01/70 00:00      
                                                   It wasn't a thorough test            01/01/70 00:00      
                                          more questions...            01/01/70 00:00      
                                             I don't understand the questions ...            01/01/70 00:00      
                                                the questions are intended...            01/01/70 00:00      
                                                   there are a number of forces at work here            01/01/70 00:00      
                        Take care....            01/01/70 00:00      
                           You pointed that out once before ...            01/01/70 00:00      
                        We did, of course!            01/01/70 00:00      
                           That\'s probably an adequate statistical basis            01/01/70 00:00      

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