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???
09/01/06 19:13
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#123533 - ALE probably won't help ...
Responding to: ???'s previous message
If the oscillator is not oscillating, it's unlikely the ALE will do anything.

What's at issue is the size of the load capacitors on the X1 and X2 pins. Whether the crystal is parallel- or series-resonant, the oscillation should be on the order of 20 MHz if it is a fundamental mode crystal. The circuit internal to the MCU should look, essentially, like a CMOS inverter with its input on X1 and output on X2 (It may be reversed on an ATMEL part, one never knows, but one pin is an input and the other is an output.) If it's not obvious whether or not it's an inverter, perhaps there's no power on the part (bent Vcc or Vss pin, for example.)

Please answer carefully and completely the following questions. Are the load capacitors of the value specified in the datasheet for the device you're using? Is the supply voltage as specified in the datasheet?

RE


List of 41 messages in thread
TopicAuthorDate
20 MHz osc.            01/01/70 00:00      
   no answer            01/01/70 00:00      
      by oscilloscope probe            01/01/70 00:00      
         WHAT DERIVATIVE? WHAT VOLTAGE            01/01/70 00:00      
            Why Erik is asking            01/01/70 00:00      
               Do standard i8052's work at 20 MHz?            01/01/70 00:00      
                  who c ares            01/01/70 00:00      
                     Maybe he don't know what a "derivative" is??            01/01/70 00:00      
         ALE probably won't help ...            01/01/70 00:00      
            it will            01/01/70 00:00      
               true enough, but he knows it\'s not oscillating            01/01/70 00:00      
                  you never know            01/01/70 00:00      
                     FET buffer is suited to touch the oscillator pins            01/01/70 00:00      
                        Or a FET probe for your 'scope            01/01/70 00:00      
                           Of course, but expensive...            01/01/70 00:00      
                              Yes, but necessary            01/01/70 00:00      
                                 Dont take it too literaly...            01/01/70 00:00      
                                    quite true            01/01/70 00:00      
                                       we'll never know            01/01/70 00:00      
                                 Ah, now I know what you mean!            01/01/70 00:00      
                                 Low capacitance probes.            01/01/70 00:00      
   That would be tricky...            01/01/70 00:00      
      Well            01/01/70 00:00      
   thanks for all replies,            01/01/70 00:00      
      8259            01/01/70 00:00      
      Operating?            01/01/70 00:00      
      Crystal Types            01/01/70 00:00      
         Xtal            01/01/70 00:00      
            ???            01/01/70 00:00      
               SMS reply            01/01/70 00:00      
                  Only NP0 ceramics must be used!            01/01/70 00:00      
                     I'm curious            01/01/70 00:00      
      Some answers...            01/01/70 00:00      
      no thanks            01/01/70 00:00      
      You really SHOULD respond            01/01/70 00:00      
         So many people SHOULD...            01/01/70 00:00      
            if only they WOULD            01/01/70 00:00      
   Use Inductor            01/01/70 00:00      
      Yes, but at the right place!            01/01/70 00:00      
         so why bother            01/01/70 00:00      
   and why bother #2            01/01/70 00:00      

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