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???
07/18/06 15:04
Modified:
  07/18/06 15:04
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 		 #120485 - 8255 main drawback
Responding to: ???'s previous message
The main drawback of the 8255 was, that it cost tons of µc port lines, additional adress latches, decoders and many time to route your pcb.

Thus I use always 74HC165/74HC595 shiftregisters, which need only 5 port lines at all, independent, how many expanders are needed.

Its also possible to build a 9 input + 9 output expander with a single 24 pin CPLD (ATF750) but its a little more expensive as the 74HCs.

Also power shift registers like TPIC6B595 can drive loads of 50V/150mA directly.

Furthermore most today 8051 derivates have internal SPI, which make unsing shiftregisters very easy and very fast.


Peter


List of 30 messages in thread
TopicAuthorDate
can P0 of c51input/output at same time            01/01/70 00:00      
   Why the 8255 ?            01/01/70 00:00      
      how to interface 8155            01/01/70 00:00      
         what does that have to do with this thread ?            01/01/70 00:00      
         Clearly, you should read the datasheet(s)            01/01/70 00:00      
   input/output            01/01/70 00:00      
      That's a very good put it!            01/01/70 00:00      
   Hints...            01/01/70 00:00      
      is 8255 really a bad idea???            01/01/70 00:00      
         Maybe            01/01/70 00:00      
            possibilities            01/01/70 00:00      
         Depends on your actual needs            01/01/70 00:00      
         Have you really considered the economics?            01/01/70 00:00      
            not all of us            01/01/70 00:00      
               the REAL question is ...            01/01/70 00:00      
                  answers            01/01/70 00:00      
                  8255 main drawback            01/01/70 00:00      
      Sorry, wrong link!            01/01/70 00:00      
      74HC595            01/01/70 00:00      
         As long as we must guess...            01/01/70 00:00      
            a little correction kai            01/01/70 00:00      
   Serial I/O Expanders            01/01/70 00:00      
      laser diodes/ldr sensors            01/01/70 00:00      
         Inductive loops            01/01/70 00:00      
            need little more info on inductive loop            01/01/70 00:00      
               Inductive loop            01/01/70 00:00      
                  basically an inductive loop is the same            01/01/70 00:00      
   I2C I/O expander            01/01/70 00:00      
      echo            01/01/70 00:00      
   60LEDs: MAX7219            01/01/70 00:00      

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