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???
12/25/04 18:47
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 		 #83852 - Address decoding
Responding to: ???'s previous message
In order to decode the address lines A2..A15 to deliver appropriate ChipSelect signal to the 8255 and 28F512, What do you sujjest except for using GALs?

If not a GAL/PLD then you are left with the choice of some glue logic.

I could not figure out anything but five 74HC138s with A2 through A15 connected to their input pins.

With 5 x HC138, you can generate CS for as many as 40 devices. The 3 to 8 decoder is a good choice where your devices are distributed evenly in the memory map like 8 RAM chips of 8 KBytes each.

Just putting "Address decoding" in Google, I got several good links like this one.

http://research.cs.tamu.edu/prism/lec...sd_l16.pdf

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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