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???
10/08/06 20:17
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 		 #126018 - a few quick tests
Responding to: ???'s previous message
Looks fine...

- is the 7805 unexpectedly hot? (it is sometimes when it oscillates - I'd definitively won't spare down a couple of 100nFs directly onto its terminals)
- measure VCC directly on the mcu's pins
- ditto for RESET
- ditto for /EA

You might try to measure also voltage across the crystal, although that yields no definitive result (a scope would be fine...).

I assume a DMM is always at hand.

Jan Waclawek


PS. Have you tried a lower frequency crystal? 11.0592MHz, perhaps?

List of 52 messages in thread
TopicAuthorDate
AT89S8252-24PI            01/01/70 00:00      
   Questions            01/01/70 00:00      
      Better answer            01/01/70 00:00      
         The newer they are, the faster they become...            01/01/70 00:00      
            Pictures            01/01/70 00:00      
               try a reset cct            01/01/70 00:00      
                  Reset Generator            01/01/70 00:00      
                     read the reset spec's for your part            01/01/70 00:00      
                        RC-reset circuitry is always critical!            01/01/70 00:00      
                           Doing the math            01/01/70 00:00      
                              a confusion            01/01/70 00:00      
                           I don't like 'em, but it's built into the DS89C4x0            01/01/70 00:00      
                              Power-on problem reported for DS89C440!            01/01/70 00:00      
                                 They're discontinuing the '440 anyway ...            01/01/70 00:00      
                              Trouble with inproper reset circuits            01/01/70 00:00      
                                 Interesting ...            01/01/70 00:00      
                                    This is why....            01/01/70 00:00      
                                       why heresy            01/01/70 00:00      
                              already comented in other thread            01/01/70 00:00      
                                 Still not completely relevant.            01/01/70 00:00      
                                    apples and oranges.            01/01/70 00:00      
                                       Sometimes you feel like a nut. Sometimes you don\'t            01/01/70 00:00      
                                    reset FAQ            01/01/70 00:00      
               Can publish it for you            01/01/70 00:00      
                  Here comes the picture...            01/01/70 00:00      
                     Picture            01/01/70 00:00      
                        Isn't needed at VPP            01/01/70 00:00      
                           Solder side            01/01/70 00:00      
                              Second attempt            01/01/70 00:00      
                                 Ok, last try            01/01/70 00:00      
                                    Hmmm            01/01/70 00:00      
                           Picture of solder side            01/01/70 00:00      
                              a few quick tests            01/01/70 00:00      
                                 bigger cap\'s maybe?            01/01/70 00:00      
                                    Yes Marcia, they do oscillate!            01/01/70 00:00      
                                       Who's Marcia?            01/01/70 00:00      
                                       It's like op-amp's            01/01/70 00:00      
                                 Required equipment            01/01/70 00:00      
                                    it MUST go            01/01/70 00:00      
                                       p0 not a good idea            01/01/70 00:00      
                                          check with a scope AND a pullup, then :-)            01/01/70 00:00      
   Re: questions            01/01/70 00:00      
      programmer            01/01/70 00:00      
   try it with a decent reset IC            01/01/70 00:00      
   Possible solution            01/01/70 00:00      
      Possible solution?            01/01/70 00:00      
      "Increase your org?" What does that mean?            01/01/70 00:00      
         Sorry Russ,            01/01/70 00:00      
            no it has not            01/01/70 00:00      
               what he means is ...            01/01/70 00:00      
                  ORG. $25??            01/01/70 00:00      
                     aren't you fortunate            01/01/70 00:00      

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