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01/10/08 17:32
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 		 #149245 - Are there don't-care situations?
Responding to: ???'s previous message
Brett said:
I would say case 4 does not do what DA says it will do in the description provided in the bible, but conforms to what DA should do. If the idea is to make the result be a valid number BCD from a previous BCD addition. If 0x07 is in A this is a valid BCD number, whereas 7 + 6 = 13 or 0x0D is not.

Ah--maybe you are on to something. If we assume that the only use for DA A is to adjust the accumulator following a BCD addition, then the only cases it would have to handle would be those that could result from a previous, valid BCD addition.

It could be that the cases where the chip appears to act in a non-biblical fashion will never actually be realized in the "normal" use of DA A. I'll check this out after lunch. In the meantime, it's still bothersome that the bible says one thing and the chip appears to do something else.

-- Russ


List of 34 messages in thread
TopicAuthorDate
DAA Misunderstanding            01/01/70 00:00      
   could this be it?            01/01/70 00:00      
      Maybe ... nope            01/01/70 00:00      
   a double negative ???            01/01/70 00:00      
      ... or an exclusive OR            01/01/70 00:00      
      Case 4            01/01/70 00:00      
         Are there don't-care situations?            01/01/70 00:00      
            I think this is the case            01/01/70 00:00      
               Not quite ...            01/01/70 00:00      
                  no            01/01/70 00:00      
            True to bible            01/01/70 00:00      
   e-mail to SILabs sent just now            01/01/70 00:00      
   Operands must consist of two packed BCD digits!            01/01/70 00:00      
      OK, but what does a packed 07 look like            01/01/70 00:00      
         Correct            01/01/70 00:00      
            if case 4 is a biblical catastrophe            01/01/70 00:00      
               Not true            01/01/70 00:00      
                  more to this            01/01/70 00:00      
                     Same as Case 1            01/01/70 00:00      
   reply from SILabs            01/01/70 00:00      
      I'm happy now            01/01/70 00:00      
      I am willing to try...            01/01/70 00:00      
         DA A test program            01/01/70 00:00      
            the results...            01/01/70 00:00      
               DS89C450 is strictly "biblical", too...            01/01/70 00:00      
                  The DAA instruction is so specific...            01/01/70 00:00      
                     point of view            01/01/70 00:00      
                        Agreed!            01/01/70 00:00      
               the last hope gone... XC866 is DAA-biblical too            01/01/70 00:00      
                  no "pick and choose" eitherThe Bible or "the bible            01/01/70 00:00      
                     don't take it too literally, please...            01/01/70 00:00      
      DAA on other Architectures            01/01/70 00:00      
         this is how it happened            01/01/70 00:00      
         Thanks for the link!            01/01/70 00:00      

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