EE 110 Lab
Experiment #10
Fall 2008
NAME: _________________________________
EXPERIMENT 10: Magnitude Comparator (1 week)
The purpose of this laboratory is to design, build, and test a magnitude comparator circuit that compares
2 two-bit numbers using the combinational logic techniques we have learned so far. Students will work
individually.
Background:
The following diagrams illustrate the pinouts of some of the TTL devices we have in stock.
In all cases, pin 7 must connect to GND and pin 14 to the +5V power supply. Without proper power and
ground connections, the device will not function. DO NOT wire these backwards – you will destroy the part!
Magnitude Comparator: Your design should compare 2 two-bit inputs, X1 X0 and Y1 Y0. The
magnitude comparator will have 3 outputs, LT, EQ and GT. Only one of these outputs will be high for any
given input combination. LT will be high when X1 X0 < Y1 Y0 in magnitude. When X1 X0 = Y1 Y0, the
EQ output will be high. When X1 X0 > Y1 Y0 in magnitude, the GT output will be high.
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Pre-lab Procedure:
1) Fill out the truth table below for the magnitude comparator inputs and outputs. A few lines have
been given in advance to help you get started.
X0
X1
Y1
Y0
LT
EQ
GT
0
0
0
0
0
0
0
1
0
1
1
0
0
0
1
1
1
0
0
0
1
2) Design a logic circuit to realize each output of the magnitude comparator. (Minimizing your
design is strongly advised. It will help you complete the construction and testing process more
rapidly.)
Show your work below, including K-maps , Boolean equations, and logic diagrams for each
output LT, EQ and GT. Include part numbers and pinouts.
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Experiment #10
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Lab:
1) In lab, build your LT logic circuit on your proto board. Use 22-gauge wire to make the
connections. Use RED wire only for +5V power, and BLACK wire only for GND. Use switches
S3 and S2 for inputs X1 and X0, switches S1 and S0 for inputs Y1 and Y0. Connect your output
LT to LED 7. Check your work thoroughly before applying power to your circuitry. Now test
the LT logic circuit: Run through all input combinations to be sure that LT matches the values
specified in the truth table. Put a check mark to the right of each truth table row you verify as
working correctly. If your output does not match the expected value, first be certain that your
truth table is correct.
2) Then build your EQ logic circuit on your proto board. Use the same switches as above for your
inputs. Connect your output EQ to LED 6. Again, run through all input combinations to ensure
that EQ matches the values specified in the truth table.
3) Lastly, build your GT logic circuit on your proto board. Again, use switches S3 and S2 for
inputs X1 and X0, switches S1 and S0 for inputs Y1 and Y0. Connect your output GT to LED
5. Test your GT output to ensure it functions according to the truth table.
4) Demonstrate the operation of your magnitude comparator logic circuit to the teaching assistant or
professor. Get their signature and comments regarding the functionality of your circuits.
TA Signature: ______________________________________________________________
5)
a. What results did you obtain in this experiment?
b. What difficulties did you have?
c. What are your conclusions? What did you learn about magnitude comparatores?
6) Once your work is complete, please dismantle your wiring and remove the chips you installed.
(Leave the power bus wiring in place.) Return your chips to the correct places in the parts bin.
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Experiment #10
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