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???
12/25/04 19:58
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 		 #83857 - Use OR
Responding to: ???'s previous message
You need to distinguish an "0 all" and "any is 1" state - the logical function which does this is called "OR".
However, I doubt you will find this easy to implementing in 74xx series. Rather, consider mapping the 8255 to the highest addresses, enabling to use two 8-input NAND's (7430? I don't have the handbook here) and a quad 2-input NOR to make both CS signals.

But first, consider NOT USING 8255 - you will find plenty of arguments for this in the forum.

Jan Waclawek


List of 31 messages in thread
TopicAuthorDate
Hardware problem            01/01/70 00:00      
   Address decoding            01/01/70 00:00      
   Use OR            01/01/70 00:00      
      Jan Waclawek            01/01/70 00:00      
   Adress decoding            01/01/70 00:00      
   instead of the 8255            01/01/70 00:00      
   Code segment adr space VS Xmem adr space            01/01/70 00:00      
   Why the 8255 ?            01/01/70 00:00      
      Steve M. Taylor            01/01/70 00:00      
         Farnell Distributor in Iran            01/01/70 00:00      
            Disturbutors donot supply many chips            01/01/70 00:00      
               Re: Disturbutors donot supply many chips            01/01/70 00:00      
                  Quite off-topic now            01/01/70 00:00      
         alternatives?            01/01/70 00:00      
   Check for a sinple gate            01/01/70 00:00      
   8254+1            01/01/70 00:00      
      Who ever said the 8255 was for x86?            01/01/70 00:00      
      a rebuttal            01/01/70 00:00      
         rebutal            01/01/70 00:00      
            psd            01/01/70 00:00      
            decoder            01/01/70 00:00      
         Item #2 Rebuttal            01/01/70 00:00      
            not me            01/01/70 00:00      
      Atmel Disturbutor in Iran            01/01/70 00:00      
         Thanx Farshid.            01/01/70 00:00      
            chips            01/01/70 00:00      
               Dear Steve            01/01/70 00:00      
                  How many ?            01/01/70 00:00      
                     AT89C51SND            01/01/70 00:00      
                        SMD soldering iron?            01/01/70 00:00      
                     there is no market in Iran for them            01/01/70 00:00      

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