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???
12/05/07 08:36
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 		 #147897 - There must be room for doubt ...
Responding to: ???'s previous message
I got to thinking about that, and find that the CMOS and FAST logic versions seem to lack the schmidt inputs, but the LS versions of 240, 241, 242, 243, 244, and 245 form Motorola and National, as well as Signetics, (can't find the '72 TI TTL book ) seem to have the hysteresis inputs.

Apparently the hysteresis slows things down enough that, in going to the HCMOS, ACMOS, etc. versions, they left it out.

That may explain the problems of which some people have complained when substituting LS 244's for HC244's in those ISP programming interfaces.

RE


List of 30 messages in thread
TopicAuthorDate
... ahem .... Has anyone used EPP mode lately?            01/01/70 00:00      
   EPP for what ? programming 8051            01/01/70 00:00      
      for ANYTHING at all            01/01/70 00:00      
         Its fast            01/01/70 00:00      
            Maybe, but ...            01/01/70 00:00      
   Scanners?            01/01/70 00:00      
      did you build the scanner?            01/01/70 00:00      
         Oh, I see            01/01/70 00:00      
   we've used it in the miniLA project            01/01/70 00:00      
      perhaps you've underestimated it            01/01/70 00:00      
         What's your PC programming environment?            01/01/70 00:00      
            I don't trust Windows ...            01/01/70 00:00      
               good idea - if ...            01/01/70 00:00      
                  With LPT in EPP mode ...            01/01/70 00:00      
                     that's not quite the case            01/01/70 00:00      
                  Windows doesn't like direct I/O            01/01/70 00:00      
                     there are ways...            01/01/70 00:00      
                        That's one of many pages ...            01/01/70 00:00      
                        inpout32.dll            01/01/70 00:00      
                           Really?            01/01/70 00:00      
                              It\'s moot, since I don\'t use Windows for that            01/01/70 00:00      
            Too much hassle            01/01/70 00:00      
               If only USB were fast enough ...            01/01/70 00:00      
               the workhorse            01/01/70 00:00      
   Only I can tell is, ...            01/01/70 00:00      
      Interesting ...            01/01/70 00:00      
         Believe me, I was also surprised!            01/01/70 00:00      
            '245's are schmidt triggered, aren't they?            01/01/70 00:00      
               schmitt trigger on '245?            01/01/70 00:00      
                  There must be room for doubt ...            01/01/70 00:00      

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