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???
10/28/08 09:56
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#159395 - naaaah... see bible
Responding to: ???'s previous message
Russell Bull said:
P0 and P2 contents will be related to the previous memory accces.

After an external memory cycle, P0 is set to 0FFh (i.e. all pins floating - it's an open collector in that moment), and P2 regains its previous state (as having been written to the P2 SFR).

Russell said:
/WR & /RD will be high.
Yes, if the corresponding bits in P3 SFR are 1.

With such a "mixed" mode, while possible, a mild caveat also might be, that while in the "true" external memory cycles both P2 and P0 are driven strongly to both 0 and 1; in the "port mode" P0 is open collector only, and P2 has that intel-ish quasi-bidirectional property.

JW


List of 8 messages in thread
TopicAuthorDate
is it possible to mix direct connect & mem. mapped            01/01/70 00:00      
   Probably,,,            01/01/70 00:00      
      naaaah... see bible            01/01/70 00:00      
         If your code is internal ...            01/01/70 00:00      
            It seems feasible...            01/01/70 00:00      
               I wouldn't presume to tell you what to do ...            01/01/70 00:00      
                  ALE off SFR            01/01/70 00:00      
                     I don't know what YOUR MCU does, but ...            01/01/70 00:00      

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