Find the addresses of the two input devices shown in Figure 7.21 and write a program to read
data from each of these ports and move it to some other registers.
Solution
Two sets of 8 switches Si)
0
to S
7
are connected to the data bus through two tri-state buff ers
and this setup functions as two input ports.
e address of the ports are 8-bit, as only address lines Aii)
0
to A
7
have been considered for
decoding. e address of the fi rst port is 7EH and that of the second is 3EH.
e address on the address bus decides which of the input ports get selected. e tri-state iii)
buff er ensures that the port which ...
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