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8255 problem
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John Kimball
Nov 19, 2002, 11:38:03 AM11/19/02
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on Sun, 17 Nov 2002 22:46:26 +0100 "Seba" <seb...@o2.pl> in Message id:
<ar937e$jaj$6...@news.tpi.pl>:
<ar937e$jaj$6...@news.tpi.pl>:
>Hello
>
>I have one problem with my circuit,if you can help me i would be very happy
>I connect 8255 D0-D7 lines to 89c51 P0.CS,A0,A1 are connected to P2
>The problem is the 8255 doesn't work.I try to write control register by
>#100000000B and then i write to PA #10101010b (and as I see in the PDF I do
>everything good)
(From memory) This would make all the 8255 ports outputs, and place AAh on
port A, correct?
>but PA is still in low state.Reset is connected to 89c51 RESET signal.
>What can I do 8255 start work
1. What did you connect to the 8255 #I/OR and #I/OW?
2. Are the control outputs of your controller connecting to #CS , #I/OR ,
and #I/OW open collector, and if so, are they pulled up?
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