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???
03/04/08 13:47
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 		 #151872 - Use the extended keywords
Responding to: ???'s previous message
Andy Neil said:
So how do you get a something to be read-only, but not in CODE space?

I would say by using the proper extended keyword, e.g. code.

SDCC is one such compiler that moves const variables to code memory by default. But if you explicitly put it in xdata that is used instead.

Andy Neil said:
Nothing came immediately to mind when I wrote that, which was why I didn't give any examples!

But, having thought about it, there are several possibilities:

An XDATA memory-mapped read-only port;

Allthough possible I doubt you meant this port to be const. As referenced by Tsuneo the const keyword is to help optimizations. The compiler could choose to read this port on startup and cache it in data memory.

Andy Neil said:
ROM mapped into XDATA space;

If you needd a fast lookup table, where CODE space was too slow (obvisouly, only a small table).


These I think are good examples of const in non-code space.

Maarten

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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