1. Combinational Logic Instructor : Nyoman Karna Course Number : FEH2H3
As Taught In : 1st semester
Level : Undergraduate

2. Logic Circuit Logic Circuit Combinational Sequential
Synchronous (clock)
Asynchronous
Fundamental
Pulse mode

3. Combinational Logic BLOCK DIAGRAM :
In combinational logic, the value of the output depends only with the input (no feedback)
Input change  output change (after some delay)
BLOCK DIAGRAM :

4. Combinational Logic ? Analysis
Given the circuit, we can determine the function
Function can be explained using:
Boolean approach
Truth Table approach
Design/Synthesis
Given the function, we can determine the circuit ? ?

5. F’2=(A’+B’)(A’+C’)(B’+C’)
Analysis Procedure
Boolean Approach
T2=ABC
T1=A+B+C
T3=AB'C'+A'BC'+A'B'C
F’2=(A’+B’)(A’+C’)(B’+C’)
F2=AB+AC+BC
F1=AB'C'+A'BC'+A'B'C+ABC
F2=AB+AC+BC

6. Analysis Procedure
Truth Table approach
= 0
A B C F1 F2 1

7. Analysis Procedure Truth Table approach A B C F1 F2 0 0 0 0 0 1 1 0
= 0
= 1 1 1
A B C F1 F2 1 1

8. Analysis Procedure Truth Table approach A B C F1 F2 0 0 0 0 0 1 1
= 0
= 1 1 1
A B C F1 F2 1 1 1

9. Analysis Procedure Truth Table approach A B C F1 F2 0 0 0 0 0 1 1
= 0
= 1 1
A B C F1 F2 1 1

10. Analysis Procedure Truth Table approach A B C F1 F2 0 0 0 0 0 1 1
= 1
= 0 1 1
A B C F1 F2 1 1 1

11. Analysis Procedure Truth Table approach A B C F1 F2 0 0 0 0 0 1 1
= 1
= 0 1
A B C F1 F2 1 1

12. Analysis Procedure Truth Table approach A B C F1 F2 0 0 0 0 0 1 1
= 1
= 0 1
A B C F1 F2 1 1

13. Analysis Procedure Truth Table approach F2=AB+AC+BC
A B C F1 F2 1
= 1 1 1 1 F BC BC 00 01 11 10 00 01 11 10 A A 1 1 1 1
F2=AB+AC+BC
F1=AB'C'+A'BC'+A'B'C+ABC

14. Design Procedure Determine input and output Determine the function
Create Truth Table
Simplify (using Boolean Algebra or K-Map)
Determine the simple function
Create the logical circuit
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15. Half Adder
half adder (HA), add 2 bits A and B to create sum and carry. Carry represent overflow of the addition A B
Carry
Sum 1
Carry
Sum
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16. Full Adder A B Cin Sum Cout 11
Prosedur 1 dan 2 lebih dipertegas/ditayangkan

17. Carry Propagate Addition
Binary Adder
Binary Adder
x3x2x1x y3y2y1y0
S3S2S1S0 C0 Cy
c3 c2 c
+ x3 x2 x1 x0
+ y3 y2 y1 y0
────────
Cy => S3 S2 S1 S0
Carry Propagate Addition
x x x x0
y y y y0 FA FA FA FA
C C C C1
S S S S0

18. Multiplexer
Multiplexer has several inputs, selector, and only 1 output
Multiplexer forward one specific input to output based on the value of the selector

19. Multiplexer
The value of “y” correspond to a specific “x” (x0 ... x7) based on the value of selector (s0 ... s2)

20. Demultiplexer
Is the opposite of multiplexer, has only 1 input, selector, and several outputs
Place the value of input to a specific output, based on the value of the selector

21. Demultiplekser
Input a is placed to a specific “y” (y0 ... y3) based on the selector’s value (s0 and s1)

22. X = (x1, x2, …. xm) , Y = (y1, y2, … yn) ; usually m<n
Decoder
Decoder has input(s) and output(s)
Is to transform a specific input code into a specific output code X Y
X = (x1, x2, …. xm) , Y = (y1, y2, … yn) ; usually m<n

23. Example: Binary Decoder (m to 2m)
Input is read as binary
One specific output is on based on the value of input
Only one output is active at one time

24. X = (x1, x2, …. xm) , Y = (y1, y2, … yn) ; usually m>n
Encoder
Encoder has input(s) and output(s)
Is to transform a specific input code into a specific output code X Y
X = (x1, x2, …. xm) , Y = (y1, y2, … yn) ; usually m>n

25. Example: Binary Encoder (2n ke n)
Binary encoder from one specific input to binary version for the output
Only one input is active at one time

26. LED 7 Segment Every input (a, b, c, d, e, f, g) control only 1 LED
Has 128 combinations but only 10 symbols used ( )

27. 3 State Output Has 3 possiblity output state HIGH Vout ~ 5 volt
LOW Vout ~ 0 volt
OPEN (high impedance) Vout = floating A Y C
Logic 1 Logic 0 Logic ?

28. 3 State Buffer
Input “select” activates all gates

29. Bidirectional 3 State Buffer
Input “direction” determines either: A  B or B  A