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???
12/21/06 23:41
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 		 #129960 - The timing issue was the delay ....
Responding to: ???'s previous message
... between the falling edge of /wr or /rd and the leading edge of the next /wr or /rd. If i recall, the parameter is called out as "tRV".

The later i8255 data sheets warned about this characteristic as did the i8085 application handbook.

The original IBM "AT" was notorious for delays in the BIOS to accomodate this timing issue.

For all the screaming, i think you'll find a '8255 able to implement with contemporary processors a popular design.

regards,
p


List of 29 messages in thread
TopicAuthorDate
The 8255A is stronger and faster than reported.            01/01/70 00:00      
   The Data Sheet rules            01/01/70 00:00      
      How can we rely on that specification?            01/01/70 00:00      
   Not proven!            01/01/70 00:00      
   who give s hoot what you have 'found'            01/01/70 00:00      
      Data sheets don' rule in reverse engineering            01/01/70 00:00      
         Does that mean...            01/01/70 00:00      
            I'm a chip provider, not a user            01/01/70 00:00      
               then do notstate "The 8255A is stronger and fast"            01/01/70 00:00      
                  8255 statements            01/01/70 00:00      
         They do determine what you have to deliver ...            01/01/70 00:00      
            What I Did            01/01/70 00:00      
               Hmmmm ...            01/01/70 00:00      
                  Measuring output DC parameters            01/01/70 00:00      
                     What did you really test?            01/01/70 00:00      
                        DC measurements            01/01/70 00:00      
                           That's why measurements are quick and automatic            01/01/70 00:00      
                              My paycheck?            01/01/70 00:00      
   No!            01/01/70 00:00      
   How?            01/01/70 00:00      
      Measuring Specs            01/01/70 00:00      
   Population v sample sigma            01/01/70 00:00      
      Should know better            01/01/70 00:00      
         Dangerous extrapolations            01/01/70 00:00      
      The other side of the looking glass            01/01/70 00:00      
   The timing issue was the delay ....            01/01/70 00:00      
      Thanks for the tip            01/01/70 00:00      
      8255            01/01/70 00:00      
         do these two things            01/01/70 00:00      

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