This document discusses combinational logic circuits. It defines a combinational logic circuit as one where the output is dependent on the current input combinations, with no storage elements. The analysis procedure for combinational circuits is outlined as labeling gate outputs, determining boolean functions up the circuit to the outputs. Examples of combinational circuits are provided. The design procedure is also summarized as defining the problem, inputs/outputs, deriving the truth table, obtaining boolean expressions, and creating the logic diagram.

1. CS8351
DIGITAL PRINCIPLES
AND SYSTEM DESIGN
BY
E. VINOTH, AP/ECE
MOOKAMBIGAI COLLEGE OF ENGINEERING

2. UNIT 2
COMBINATIONAL LOGIC

3. INTRODUCTION
 When logic gates are connected together to produce a specified
output for certain specified combinations of input variables, with no
storage involved, the resulting circuit is called combinational logic
circuit.
 In combinational logic circuit, the output variables are at all times
dependent on the combination of input variables.

4. ANALYSIS PROCEDURE
1. First make sure that the given circuit is combinational circuit and
not the sequential circuit. The combinational circuit has logic gates
with no feedback path or memory elements.
2. Label all gate outputs that are a function of input variables with
arbitrary symbols, and determine the Boolean functions for each
gate output.

5. ANALYSIS PROCEDURE
(Cont.,)
3. Label the gates that are a function of input variables and
previously labeled gates and determine the Boolean function for
them.
4. Repeat the step 3 until the Boolean function for outputs of the
circuit are obtained.
5. Finally, substituting previously defined Boolean functions, obtain
the output Boolean functions in terms of input variables

6. EXAMPLES

7. EXAMPLES (Cont.,)

8. EXAMPLES (Cont.,)

9. EXAMPLES (Cont.,)

10. EXAMPLES (Cont.,)

11. EXAMPLES (Cont.,)

12. EXAMPLES (Cont.,)

13. DESIGN PROCEDURE
1. The problem definition.
2. The determination of number of available input variables and
required output variables.
3. Assigning letter symbols to input and output variables.
4. The derivation of truth table indicating the relationships between
input and output variables.
5. Obtain simplified Boolean expression for each output.
6. Obtain the logic diagram.

14. EXAMPLES

15. EXAMPLES (Cont.,)

16. EXAMPLES (Cont.,)

17. EXAMPLES (Cont.,)

18. THANK YOU