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Christoph Franck
02/20/12 14:13
Read: 473 times
Sindelfingen
Germany


 
#186078 - Slow but critical.
Responding to: Per Westermark's previous message
Per Westermark said:
And that the processor can detect if the watchdog clock doesn't work (a watchdog run from internal RC oscillator would often allow a timer or similar to also run from same oscillator) and force a reset.


The problem here would be that after being zapped with enough ESD to flip that one bit that switches from internal RC to external crystal or clock, the processor is in no state to perform that clock test anymore. (Yes, being zapped with lots of ESD is part of our application, and while it's fine for the device to cease working while being zapped, it's not acceptable to keep playing dead after the zapping has stopped)

Oh, yeah, and the reset controller runs off said slow clock, too. Even if you could detect a loss of the slow clock, the reset controller would be stopped, too. Or it would start to reset and hang as soon as it tries to use the slow clock (for timing the power-on reset pulse or similar), since switching back to internal RC as the clock source requires a power cycle, not just a reset.

List of 44 messages in thread
TopicAuthorDate
Pointless watchdog?      Christoph Franck      02/18/12 12:27      
   Sounds Like From What You Said...      Michael Karas      02/18/12 15:00      
      Didn't want to point fingers.      Christoph Franck      02/19/12 02:33      
         A?      JecksonS Ben      02/19/12 04:50      
            Don't forget AVR      Andy Neil      02/19/12 05:44      
               One more argument ...      Christoph Franck      02/20/12 06:14      
                  Independently testable      Per Westermark      02/20/12 11:00      
                     Slow but critical.      Christoph Franck      02/20/12 14:13      
                        Yes      Per Westermark      02/20/12 17:59      
                           ESD      Kai Klaas      02/21/12 05:38      
                               You can't      Per Westermark      02/21/12 06:04      
                                 You can...      Kai Klaas      02/21/12 06:27      
                                    But emi-filter, overvoltage protection etc may not be enough      Per Westermark      02/21/12 06:46      
                                       ESD ...      Kai Klaas      02/21/12 07:51      
                                          It's not just ESD, it's "the works"      Christoph Franck      02/21/12 08:47      
                                             I do not trust the watchdog...      Kai Klaas      02/21/12 09:44      
                                                The simpler, the more trustworthy.      Christoph Franck      02/21/12 11:08      
                                                   Less complex does not mean less probable to fail!      Kai Klaas      02/22/12 06:48      
                                                   WDT and debug breadcrumbs      Oliver Sedlacek      02/23/12 06:14      
                                                Lightning strikes      Kalpak Dabir      02/22/12 04:33      
                                                   A watchdog should never be needed - but should be there      Per Westermark      02/22/12 05:55      
                                                   A watchdog isn't a fuse...      Kai Klaas      02/22/12 07:19      
                                                      correction      Erik Malund      02/22/12 07:35      
                                                      I just can not agree with that reasoning      Per Westermark      02/22/12 08:02      
                                                         Oh please, don't...      Kai Klaas      02/22/12 17:04      
                                                            so?      Per Westermark      02/22/12 17:26      
                                                Why you need a watchdog      Oliver Sedlacek      02/23/12 04:07      
                                                   And even if you had perfect software and hardware ...      Christoph Franck      02/23/12 05:03      
                                                      Reset versus power cycle      Kai Klaas      02/23/12 05:34      
                                                         Mars Pathfinder      Christoph Franck      02/23/12 06:27      
                                                         many modern chips      Erik Malund      02/23/12 07:05      
                                                            The problem with bidirectional reset pins.      Christoph Franck      02/23/12 07:26      
                                                               The uC in question      Erik Malund      02/23/12 08:07      
                                                            Latchup      Per Westermark      02/23/12 07:29      
                                                               ONLY clocked circuits?      Erik Malund      02/23/12 08:15      
                                                                  That kitchen exhaust fan ...      Christoph Franck      02/23/12 08:42      
                                                            link...      Kai Klaas      02/24/12 05:01      
                                                               Sales talk      Per Westermark      02/24/12 05:55      
                                                   certified applications      Erik Malund      02/23/12 07:00      
                  Using external watchdog      Oliver Sedlacek      02/21/12 03:11      
                     It's a feature, actually.      Christoph Franck      02/21/12 04:16      
               Wet      JecksonS Ben      02/24/12 01:04      
   Featuritis...      Kalpak Dabir      02/20/12 19:14      
   Looking at it from another perspective      Jez Smith      02/23/12 22:38      

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