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Digital Logic and LogicWorks #2
The seven-segment display
Introduction
In this lab, you will use the “7 segment display -red” (or whatever color you wish to
choose) found in the library window to the right of the screen. (Be sure the window says
“ALL LIBRARIES” when you hunt for this element.) Use a binary switch to experiment
with the different inputs on the display to determine which input lights up which segment
of the display. For example, see the diagram in Figure 1. Make a careful note of those
data.
Figure 1, A “7-segment display-dot.” Each input controls
one segment of the displayed character.
In the table below, sketch all of the 16 hexadecimal digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, b,
C, d, E, F in the digital clock style displayed by the 7-segment display. Notice that b and
d are written as lower case.
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Truth tables and Karnaugh maps
Next, for all of the segments, fill in the following table. Place a 1 in any cell where
your segment is lit up by the hexadecimal digit to the left:
Hexadecimal
In binary
a
b
c
d
e
f
digit
0
0000
1
0001
2
0010
3
0011
4
0100
5
0101
6
0110
7
0111
8
1000
9
1001
A
1010
b
1011
C
1100
d
1101
E
1110
F
1111
g
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Karnaugh Maps
cd
ab
F=
00
cd
ab
F=
00
00
cd
ab
F=
00
00
00
4
cd
ab
F=
00
cd
ab
F=
00
00
cd
ab
F=
00
00
00
5
cd
ab
F=
00
00
Circle any 1x2, 1x4, 2x2, 2x4, or 4x4 collections of adjacent ones and write the resulting
logical expressions, one from each of your segment diagrams.
Circuits
Construct a circuit diagram in Logicworks using AND, OR, and NOT for any three of the
expressions. Build the first circuit with the input supplied by the hex keyboard and the
output going to the 7-segment display to light up your first segment. Then, and only
then, build the second circuit right below the first and run the input from the same
keyboard and the output to the same 7-segment display. Finally, build the third circuit.
The whole design has three circuits with one input keyboard and one output 7-segment
display.
You will find that IF you label each of the AND gates in the circuits, it will be much
easier to track down any errors in your formulae or in your circuits.
Test the circuits, fix any errors, show the working circuit to the instructor to initial here:
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