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Richard Erlacher
12/01/12 20:13
Modified:
  12/01/12 20:14

Read: 921 times
Denver, Co
USA


 
#188939 - All too true ... sadly ...
Responding to: Kai Klaas's previous message
While it's reasonable to presume that a finger will not normally be introduced into the operating environment of a microcontroller system, it does happen from time to time and, if it's at all likely, measures should be taken to prevent the finger, among other things, from contacting the MCU board.

I've done a limited amount of fiddling with the notion of controlling the rise and fall of Vcc, using transistors to pull down Vcc to the MCU whenever RESET goes active, but I've not convinced myself that all the bases are covered when that's done. Given a means to limit the rise and fall times of Vcc to the MCU to a few microseconds, an RC reset to the MCU with a very short time constant, just long enough to meet the minimal requirements of the MCU on startup, and less than 10 microseconds on RESET when Vcc is nearly at its nominal value, would probably be sufficient, IMHO. Maybe a supervisor IC would be cheaper. I doubt that it's a complete solution, though. Many 805x users believe it is, however.

I have an EVK for a cousin of your MCU, but mine's smaller one so I don't know that any experimentation on my board would shed any light on your problem. I have lots of other EVK's, but they're not SiLabs' and not in a modern package.

RE




List of 33 messages in thread
TopicAuthorDate
C8051F231 experiences      Daniel Contarino      11/30/12 14:43      
   another solution      Erik Malund      11/30/12 15:11      
   The probabilities are low...      Daniel Contarino      11/30/12 18:34      
      think about what happens when you add a finger      Richard Erlacher      11/30/12 22:55      
         The point is ...      Daniel Contarino      12/01/12 03:08      
            Yes ... the underlying issue is the flash ...       Richard Erlacher      12/01/12 11:28      
               Out of my office, but...      Daniel Contarino      12/01/12 14:05      
                  Don't think in Vcc, ESD or hum...      Daniel Contarino      12/02/12 09:24      
   Apparently several C8051F2xx parts have the same pinout      Richard Erlacher      12/01/12 14:25      
   Characteristic for in system programmable flash micros...      Kai Klaas      12/01/12 18:25      
      All too true ... sadly ...       Richard Erlacher      12/01/12 20:13      
         Power-on slope rate...      Kai Klaas      12/02/12 05:31      
            Sorry, my post should be here, no up there...      Daniel Contarino      12/02/12 09:58      
            Have you any basis for that rate?      Richard Erlacher      12/02/12 10:15      
               Vdd ramp time      Maarten Brock      12/03/12 06:15      
               Some datasheets show numbers...      Kai Klaas      12/03/12 07:05      
                  Those aren't the "usual" 805x-core MCU's      Richard Erlacher      12/03/12 17:43      
                     There aren't many "usual" 8051-cores anymore...      Kai Klaas      12/03/12 18:13      
                        How dangerous power ups can be...      Kai Klaas      12/04/12 06:20      
                           I believe it      Richard Erlacher      12/04/12 08:59      
                              (dV/dt) examples      Jim Granville      12/04/12 13:14      
                                 They don't know it either...      Kai Klaas      12/04/12 18:49      
                                    dV/dT etc       Jim Granville      12/04/12 21:39      
                                       reset request...      Kai Klaas      12/05/12 06:21      
                                          That's what disturbs me greatly      Richard Erlacher      12/06/12 00:19      
                                             It IS disturbing!      Kai Klaas      12/06/12 08:02      
                                                Where this began ... at least for me ...       Richard Erlacher      12/06/12 09:43      
                                                   So, you took the hard road...      Kai Klaas      12/06/12 10:41      
                                                      We've all had that experience       Richard Erlacher      12/06/12 16:23      
   probable cause      Brent Wilson      02/04/13 20:32      
      Brent, this is very nice      Erik Malund      02/05/13 06:38      
         forum no longer down      Maarten Brock      02/05/13 07:33      
      Thank you!      Daniel Contarino      02/05/13 15:04      

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