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???
12/15/06 19:16
Modified:
  12/15/06 19:31
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 		 #129573 - Not yet, my friend ... but you\'re onto something
Responding to: ???'s previous message
The circuit is wired in accordance with the original datasheet for the 1979 version of the 8751.

The more comprehensive datasheet, repackaged in '94 to incorporate all of Intel's variants, shows different hookups for the oscillator in various verisons. The original circuit shows XTAL1 (pin 19) driven by an external gate and XTAL2 (pin 18) left unconnected. This is consistent with the connection scheme recommended for the DS89C4x0 family.

The Intel connection diagram for the HMOS version, however, suggests that one should drive XTAL2 with an external gate and attach XTAL1 to GND, yet their CHMOS devices want us to drive XTAL1 and leave XTAL2 open in one document, and they want an inverter between the two in another document.

This all seems reasonable enough, BUT, since the part is supposed to be totally static, it shouldn't go into meltdown with a .001 Hz clock, should it?

BTW, I've found that another very similar circuit causes the HMOS parts to behave in the same way, though they use a crystal rather than an external oscillator.

I'll give this a look, just to put this matter to bed.

RE


List of 45 messages in thread
TopicAuthorDate
Why would the OLD part get hot?            01/01/70 00:00      
   Could be            01/01/70 00:00      
      just to focus ...            01/01/70 00:00      
         Current consumption?            01/01/70 00:00      
      HMOS            01/01/70 00:00      
         Yes, they were warm ...            01/01/70 00:00      
            some special mode?            01/01/70 00:00      
               I know            01/01/70 00:00      
               I doubt there\'s a special mode involved            01/01/70 00:00      
                  BI NGO!            01/01/70 00:00      
                     Not yet, my friend ... but you\'re onto something            01/01/70 00:00      
                        doen memory lane            01/01/70 00:00      
                           it's all pretty confusing            01/01/70 00:00      
                              they all did            01/01/70 00:00      
   well ... the REAL question is ...            01/01/70 00:00      
   Have you tried using slow SRAM...            01/01/70 00:00      
      How about....            01/01/70 00:00      
         I'm not sure what that will tell me.            01/01/70 00:00      
      What do you believe that would do?            01/01/70 00:00      
         Step Back            01/01/70 00:00      
            Well, that's how it is ...            01/01/70 00:00      
   Some hints            01/01/70 00:00      
      Yes, that\'s so ...            01/01/70 00:00      
         Maybe            01/01/70 00:00      
            Intel doesn\'t care ...            01/01/70 00:00      
            O.K. ... so here\'s what I\'ve found ...            01/01/70 00:00      
               do you want to be stylish?            01/01/70 00:00      
                  Bipolar logic? Maybe            01/01/70 00:00      
                     Back in the day            01/01/70 00:00      
                        Pull-ups            01/01/70 00:00      
                           Dynamic logic may be the reason for the hot part            01/01/70 00:00      
                           That's what I find confusing            01/01/70 00:00      
                              pullups HCT and LS            01/01/70 00:00      
                                 74HCTMOS does not contain internal pull-ups            01/01/70 00:00      
                                 emitters vs resistors            01/01/70 00:00      
                           So, Kai, How did you arrive at 10K-ohms?            01/01/70 00:00      
                              No calculations, just a compromise            01/01/70 00:00      
                                 I haven't tried it with LS parts ... yet ...            01/01/70 00:00      
                                    throw away that databook :-)            01/01/70 00:00      
                                       Well, it's the old TTL book from TI ...            01/01/70 00:00      
                                          just a thought re LS pullup            01/01/70 00:00      
                                             That's the HCTLS from Samsung            01/01/70 00:00      
                        re: back in the day            01/01/70 00:00      
                           What about P2?            01/01/70 00:00      
                              No Just P0            01/01/70 00:00      

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