Post on 22-Dec-2015
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Forging new generations of engineers
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DESIGN EXAMPLE“Date of Birth Problem”
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Combinational Logic Application
Date of Birth
7-Segment Display
Driver Logic Circuit
abcdefg
X
Y
Z
Design a combinational logic circuit that has three inputs and seven outputs. As the inputs count from 000 to 111, the seven outputs will generate the required logic to display your date of birth on a seven segment display.
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X Y Z
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
-
-
Example:
If your date of birth is July 23, 1961, the circuit will display the output shown to the right 07 23 61. There are dashes between numbers.
Circuit Inputs
Display
Common AnodeLED Display
+5 V
Logic ForSegment A
270 - 330
0 Segment Is ON !1 Segment Is OFF !
X Y Z
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
a b c d e f g
a
g
f b
d
e c
0 0 0 0 0 0 1 a
g
f b
d
e c
a
g
f b
d
e c
0 0 0 1 1 1 1
1 0 0 1 1 1 1
a
g
f b
d
e c
0 0 0 0 0 0 1
0 0 0 1 1 1 1
0 0 1 0 0 1 0
0 0 0 0 1 1 0
0 1 0 0 0 0 0
Display
-
-
1 1 1 1 1 1 0
1 1 1 1 1 1 0
X X
Y Z
Y Z
Y Z
Y Z
Logic ForSegment “a”
0
0
0
1
0
1
1
0
a = XZ+X’YZ’
X Z
X Y Z
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
a b c d e f g
1 0 0 1 1 1 1
0 0 0 0 0 0 1
0 0 0 1 1 1 1
0 0 1 0 0 1 0
0 0 0 0 1 1 0
0 1 0 0 0 0 0
Display
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-
1 1 1 1 1 1 0
1 1 1 1 1 1 0 X’YZ’
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Create Boolean Equations for all 7 Segments
a = XZ+X’YZ’
e =
f =
c =
b =
d =
g =
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DOB 7-Segment Display Driver Circuit
7404Inverters
7432OR Gates
7408AND Gates
7408
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7-Segment LED Display
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Assignment
– Design a Date-of-Birth 7-Segment Display Driver Circuit for your birth date. Include the truth table, K-Maps & logic design.
– Simulate your design using circuit design software.
– Breadboard and test your design.