Email: Password: Remember Me | Create Account (Free)

Back to Subject List

Old thread has been locked -- no new posts accepted in this thread
???
07/26/07 14:03
Modified:
  07/26/07 14:05
Read: times


 		 #142345 - even at startup you can get into trouble
Responding to: ???'s previous message
Lynn Reed said:
a Schmitt "type" cell can be designed that cannot ever oscillate. (It is not Schmitt's design, but it does have hysteresis). If the chip designer uses this type of input, then I don't see any problem with using an RC circuit on RESET.

Andy Neil said:

Well, you won't get problems due to slow rise of the RC reset voltage[...]

But you will get problems due to slow rise of VCC, if it is significantly slower than the RC constant, you'll never get a reset!

Andy said:
- but surely you'll still have the brownout problems where the capacitor doesn't discharge enough during the power "event", so the processor keeps running even with the supply out-of-spec...?

I couldn't have said it better.

Lynn, please, please, stop promoting the RC-Schmitt reset. It can and does fail in so many ways, and - please forgive me - it's foolish from the chipmakers to expect the system designers should care about clean and fast up/down of VCC.

It's partially this thinking which brought the '51 on it's decline - look at the competition - all these AVRs and PICs etc. - a good working (maybe fusable) INTERNAL reset circuit (= bangap reference, comparator and timer) is a MUST today in this class of microcontrollers (as is an RC clock source, too).

JW


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      

Back to Subject List