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???
02/23/08 19:22
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 		 #151345 - Speed
Responding to: ???'s previous message
Craig said:
Obviously. But is that just to protect the non-changing element from bad code? Because if it's a constant, by definition it's not really a variable. And the easiest way to make sure it doesn't change is to put it in an area of memory that can't (usually) change: code memory.

All true. But on the 8051, the only way for a program to access code memory is with either MOVC A,@A+PC or MOVC A,@A+DPTR. That's a pretty expensive ordeal when compared with all the speedy variants of MOV that manipulate internal data memory. I think that's why you might want to have a 'const' element that's not in code memory.

-- Russ


List of 54 messages in thread
TopicAuthorDate
Best way to consolidate....out of memory            01/01/70 00:00      
   isn't this the classical gotcha?            01/01/70 00:00      
   There was a hint here....            01/01/70 00:00      
      Not const            01/01/70 00:00      
         Not necessarily            01/01/70 00:00      
            Hmmm...            01/01/70 00:00      
               Hmmm, indeed            01/01/70 00:00      
               Why?            01/01/70 00:00      
                  One reason ... and the prolly the original intent            01/01/70 00:00      
                     Obviously            01/01/70 00:00      
                        Speed            01/01/70 00:00      
                           Rogue programs?            01/01/70 00:00      
                              Yes. And stupid programmers            01/01/70 00:00      
                                 True            01/01/70 00:00      
                           cases            01/01/70 00:00      
                        The Obvious...            01/01/70 00:00      
                           Fair enough            01/01/70 00:00      
                              make sure the developer doesn't do something stupi            01/01/70 00:00      
                              Const to Code EPROM or FLASH,,,            01/01/70 00:00      
                           const and volatile - for optimization            01/01/70 00:00      
                  consts in other than CODE space            01/01/70 00:00      
                     Use the extended keywords            01/01/70 00:00      
                        'const' and 'volatile'            01/01/70 00:00      
   Unreadable code!            01/01/70 00:00      
      It really was all Keils fault....;)            01/01/70 00:00      
   You don't want to start from here!            01/01/70 00:00      
      Previously, on 8052.com...            01/01/70 00:00      
      Array of string            01/01/70 00:00      
         Yes, my mistake            01/01/70 00:00      
   string concatenate            01/01/70 00:00      
      Comments            01/01/70 00:00      
         Wow......LOL            01/01/70 00:00      
            Not a C vs ASM thing            01/01/70 00:00      
               From your perspective, it may make sense            01/01/70 00:00      
      I went this direction....code padding removal?            01/01/70 00:00      
         For but one byte added to the array...            01/01/70 00:00      
         With proper ordering in source file...            01/01/70 00:00      
         Putting it all together            01/01/70 00:00      
            Spectacular Russ.....            01/01/70 00:00      
   THINK            01/01/70 00:00      
      that is surely needed            01/01/70 00:00      
      A bit easier to read?            01/01/70 00:00      
         easy to read???            01/01/70 00:00      
      typedef vs #define            01/01/70 00:00      
      I think not            01/01/70 00:00      
         Tks Russ.            01/01/70 00:00      
            THINK(ing)            01/01/70 00:00      
               ???            01/01/70 00:00      
                  Objectives.            01/01/70 00:00      
                     I beg your pardon?!            01/01/70 00:00      
                     I see            01/01/70 00:00      
   Best way to consolidate....out of memory            01/01/70 00:00      
   Why specify CODE for functions?            01/01/70 00:00      
      there is so much stuff            01/01/70 00:00      

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