Transcript Combinational Logic

Combinational Logic
Weiqiang Sun
A brief review
 Logic gates
 AND, OR, NOT
 NAND, NOR, XOR, XNOR
 Boolean algebra
 Rules and axioms
 Analysis of logic circuits
 DeMorgan’s Theorem
 Standard forms of Boolean expressions
 K-Map
A brief review –
continued…
 Functions of combinational logic
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Adders
Comparators
Decoders
Encoders
Code converters
Multiplexers
Parity Generator/checkers
Problem
 With logic gates, design a logic circuit to check whether
the blood plasma type of the donor is compatible with
that of the recipient.
 Repeat the previous problem with the blood
compatibility table below.
Problem
 Implement a full subtractor with logic gates.
Problem
 Repeat the problem with 3-line to 8-line decoders and
NAND gates.
Problem
 Design a logic circuit that converts BCD to excess-3
codes
Problem
 Repeat the previous problem with a 4-line to 16-line
decoder and necessary gates
Problem
 Repeat the problem with 1-out-of-16 multiplexers
(data selector).
Problem
 Repeat the problem with 1-out-of-8 multiplexers
(data selector).
Homework
1. Design a 5-line to 32-line decoder with 74LS138
and 74LS139.
2. Implement the following logic function with
74LS138 and NAND gate
a.
b.
F=ΣX,Y,Z(2,4,7),
F=ΣA,B,C,D(2,4,6,14)
3. Repeat problem 2 with 74X151