Demultiplexers as general-purpose logic

• A n:2n demux can implement any function of n variables

  • Apply the variables as select inputs
  • Tie the enable input to a logic 1
  • Sum the appropriate minterms

demultiplexer "decodes"

appropriate minterms

from the control signals

C

A

B

0 A'B'C'1 A'B'C2 A'BC'3 A'BC4 AB'C'5 AB'C6 ABC'7 ABC

S2

3:8

Demux

S1

S0

1

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