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11/06/07 17:51
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#146691 - Atmel 89 Series and EMI
Hello,

I've been using 89c52 for a long time and I found out that there are rare cases where a strong EMI noise can completely lock the CPU logic in such a way that even a hard-reset won't restart the CPU. I'm note sure if it has changed with 89s52 series or any other advanced x52 series.

I found it totally weird when a CPU does not respond to a Hard-Reset thru pin-9 and the only way to reset is cutting the power. Has anyone ever had a similar experience?

I added Opto-Couplers to my circuit so a CPU port never come to direct contact with an EMI source but even a nearby Relay which switches heavy DC currents can cause severe problems. Many of these Relays are from external devices and I have no control over their design. Unfortunately some designers simply don't use diodes to kill EMI at its source. Considering that EMI can travel in the air and there is no way to guarantee that EMI sources are far enough, what is the best design practice to protect your CPU from EMI?



List of 88 messages in thread
TopicAuthorDate
Atmel 89 Series and EMI            01/01/70 00:00      
   FAQ            01/01/70 00:00      
      Thanks, but...            01/01/70 00:00      
         yes it is            01/01/70 00:00      
            EMI design consideration...            01/01/70 00:00      
               reset pulses?            01/01/70 00:00      
                  Finally a note to the OP            01/01/70 00:00      
                     well, sometimes...            01/01/70 00:00      
                     Fire Extinguisher            01/01/70 00:00      
                        extinguisher            01/01/70 00:00      
                  Latched-up CMOS!            01/01/70 00:00      
                     logic, and beyond            01/01/70 00:00      
                     not a cure            01/01/70 00:00      
   EMI Design            01/01/70 00:00      
      restated in one sentence            01/01/70 00:00      
         Don't jump to the conclusion...            01/01/70 00:00      
            then just say "outside the specs, no can do"            01/01/70 00:00      
      Thanks...            01/01/70 00:00      
   What PCB do you use?            01/01/70 00:00      
      Two Layer            01/01/70 00:00      
         No surprise, then!            01/01/70 00:00      
            Ground...            01/01/70 00:00      
               About naked firefighters...            01/01/70 00:00      
               Absolutely it is fair            01/01/70 00:00      
   Some advice            01/01/70 00:00      
      Yes, it's a bunch of measures...            01/01/70 00:00      
      Good points.            01/01/70 00:00      
         No, no, no,....            01/01/70 00:00      
            Remember            01/01/70 00:00      
         CMOS Latch up            01/01/70 00:00      
         NOPE            01/01/70 00:00      
            You think so...            01/01/70 00:00      
               No, it is not            01/01/70 00:00      
               A proper design would stand it!            01/01/70 00:00      
                  Proper design            01/01/70 00:00      
                     some of my definitions            01/01/70 00:00      
                     Me thinks...            01/01/70 00:00      
                        the real point            01/01/70 00:00      
            More advice            01/01/70 00:00      
               Does that mean, that...            01/01/70 00:00      
                  It's the designers responsibility            01/01/70 00:00      
                     No joke, but...            01/01/70 00:00      
                  EMI and 2 layers            01/01/70 00:00      
                     Yes, for tiny projects...            01/01/70 00:00      
               that something is possible/done succesfully            01/01/70 00:00      
   Show us your design...            01/01/70 00:00      
      Why? You want to make fun of it? :)            01/01/70 00:00      
         Or            01/01/70 00:00      
            You mean...            01/01/70 00:00      
               I do not know what Steve ment            01/01/70 00:00      
               Yes !            01/01/70 00:00      
         how about a schematic            01/01/70 00:00      
            Relays            01/01/70 00:00      
               Even then...            01/01/70 00:00      
         From what I can see            01/01/70 00:00      
            Mostly agree.            01/01/70 00:00      
               Layers, layouts...            01/01/70 00:00      
                  are you serious, or did you forget            01/01/70 00:00      
                     Sorry, I forgot...            01/01/70 00:00      
                     Is it good?            01/01/70 00:00      
                        Just a few points.            01/01/70 00:00      
                           I believe you!            01/01/70 00:00      
                        No harm, usually            01/01/70 00:00      
                  Separate Ground Planes            01/01/70 00:00      
                     Inter-plane coupling            01/01/70 00:00      
                     Cable entry point            01/01/70 00:00      
                        Thanks            01/01/70 00:00      
            what I do ..            01/01/70 00:00      
            half measures            01/01/70 00:00      
            Taking notes...            01/01/70 00:00      
               the downfall of many            01/01/70 00:00      
               Do some tests            01/01/70 00:00      
                  This can be deadly!            01/01/70 00:00      
                     Deadly?            01/01/70 00:00      
                        I'm sorry...            01/01/70 00:00      
         Farshad, I would never make fun of it!            01/01/70 00:00      
            Very Informative            01/01/70 00:00      
               Decoupling            01/01/70 00:00      
                  Thank you!            01/01/70 00:00      
               and not a word about 4 layers            01/01/70 00:00      
   paralelling            01/01/70 00:00      
      Why not using 10µF/10V/X5S ceramics?            01/01/70 00:00      
   more information?            01/01/70 00:00      
      Schematics would not be very "helpfil"            01/01/70 00:00      
      More information            01/01/70 00:00      
      The best stuff I have ever seen is...            01/01/70 00:00      
         Sorry, I forgot, that you must suscribe first...            01/01/70 00:00      
      John, I have seen....            01/01/70 00:00      

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