Report for Experiment 8
Name : 20121071 김민우, 20121192 박다환, 20121196 박미진
Date : 2013.03.20
Class : CSE20101
Objectives :
□ Develop the truth table for a BCD invalid code detector.
□ Use a Karnaugh map to simplify the expression.
□ Build and test a circuit that implements the simplified expression.
□ Predict the effect of “faults” in the circuit.
Data and Obsevations:
Table 8-2
Truth table for BCD invalid code detector
Inputs
Output
DCBA
X
0000
0
0001
0
0010
0
0011
0
0100
0
0101
0
0110
0
0111
0
1000
0
1001
0
1010
1
1011
1
1100
1
1101
1
1110
1
1111
1
0
0
1
0
0
0
1
0
0
0
1
1
0
0
1
1
FIGURE 8-3
Karnaugh map of truth table for BCD invalid code detector
Minimum sum-of-products read from map:
X=DC+DB
Factiring D from both product terms gives:
X=D(C+B)
Table 8-3
Truth table for BCD invalid code detector constructed in step 6.
Inputs
output
DCBA
X
0000
1
0001
1
0010
1
0011
1
0100
1
0101
1
0110
1
0111
1
1000
1
1001
1
1010
0
1011
0
1100
0
1101
0
1110
0
1111
0
TABLE 8-4
Problem
Problem
Effect
Number
The pull-up resistor for the D switch
1
There is no effect in TTL.
is open.
The ground to the NAND gate in
2
When we open the ground, NAND gate doesn’t work.
Figure8-4 is open.
A 3.3 ㏀ resistor was accidently
3
used in place of the 3.3 ㏀ resistor
LED’s brightness becomes muddy or LED doesn’t work
If magnetic pole connects inversely, it doesn’t work or heat
4
The LED was inserted backward.
occurs.
5
Switch A is shorted to ground.
There is no effect because there isn’t A section
Results and Conclusion:
This experiment's object is to develop the truth table for a BCD invalid code detector, use a Karnaugh map to simplify the
expression, build and test a circuit that implements the simplified expression, and predict the effect of faults in the circuit.
With combinational logic circuits, the outputs are determined solely by the inputs. For simple combinational circuits, truth
tables are used to summarize all possible inputs and outputs, and the truth table completely describes the desired operation of
the circuit. The circuit may be realized by simplifying the expression for the output function as read from the truth table.
In this experiment, we used Karnaugh mapping method to design a BCD invalid code detector. BCD is a 4-bit binary code
that represents the decimal numbers 0 through 9. The binary numbers 1010 through 1111 are invalid in BCD.
When the pull-up resistor for the D switch is open, if it is TTL, has no effect. When the ground to the NAND gate in Figure
8-4 is opened, NAND gate did not work. If 3.3kΩ resistor is accidently used in place of the 330Ω resister, brightness of LED
will become blurred, or will not be turned on. If the LED was inserted backward, it is possible that LED doesn't work, or
develop a fever. Lastly, when switch A is shorted to ground, simplified equation doesn't have term of A, so it doesn't matter
whether it is shorted or not.
FIGURE 8-4
FIGURE 8-3-1(FIGURE for TABLE 8-3)