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08/16/06 07:26
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 		 #122331 - Example - AT89C51
Responding to: ???'s previous message
Andy Neil said:
I think you'll find that other derivatives will also disable MOVC as part of their "protection" scheme... :-

Example:
Atmel AT89C51 Datasheet said:
MOVC instructions executed from external program memory are disabled from fetching code bytes from internal memory, EA is sampled and latched on reset, and further programming of the Flash is disabled

See the section titled Lock Bit Protection Modes.



List of 38 messages in thread
TopicAuthorDate
Switch/Case and code protection            01/01/70 00:00      
   What does it do?            01/01/70 00:00      
      I activate MOVC Disable.            01/01/70 00:00      
         In that case ...            01/01/70 00:00      
            Can't tell...uses external CCASE routine            01/01/70 00:00      
               Things you can and can't do ...            01/01/70 00:00      
                  it does            01/01/70 00:00      
               (double post, please disregard)            01/01/70 00:00      
   switch can use MOVC instructions            01/01/70 00:00      
      Aha!            01/01/70 00:00      
         protecting LPC chips            01/01/70 00:00      
            protecting LPC chips            01/01/70 00:00      
               Old question            01/01/70 00:00      
                  case            01/01/70 00:00      
                     Errr...            01/01/70 00:00      
                        There is more than just switch/case            01/01/70 00:00      
                           No C without MOVC            01/01/70 00:00      
                              Protection on other derivatives            01/01/70 00:00      
                                 Example - AT89C51            01/01/70 00:00      
                                    AT89C51 can do MOVC internal !            01/01/70 00:00      
                                       nope            01/01/70 00:00      
            LPC Protection            01/01/70 00:00      
               naah, but make it quite a bit more difficult            01/01/70 00:00      
   Compiler Optimisation            01/01/70 00:00      
      sure, but there will still be MOVC            01/01/70 00:00      
         And upgrading the compiler can change the output            01/01/70 00:00      
            the ICEman cometh            01/01/70 00:00      
               I have found no issues with the ICE            01/01/70 00:00      
                  sure it 'works'            01/01/70 00:00      
         The Reason            01/01/70 00:00      
            no, no, no            01/01/70 00:00      
               But you said..            01/01/70 00:00      
                  if you heard what I thought I said            01/01/70 00:00      
                     Confused            01/01/70 00:00      
                        jmp @dptr is not movc            01/01/70 00:00      
                           jmp @dptr is a computed goto not a jump table            01/01/70 00:00      
   what requires a movc???            01/01/70 00:00      
      Jump TABLE            01/01/70 00:00      

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