1
EE 101 Homework 9
Fall ’07
●
Redekopp
Name: _________________________________________
Lecture 9:30 / 11:00 / 2:00
Due:
Tues. Dec. 4
th
in class
Score: ________
Show work to get full credit.
Remember, use on only one side of the paper and staple them together.
Only use a calculator to CHECK your work, not to DO your work.
NOTE:
PLEASE DRAW ALL DIAGRAMS NEATLY.
MAKE SURE TO WRITE
IN THE DEVICE LABELS AND SYSTEM LABELS
1.
(15 pts.) Using (1) 74LS85 comparator and 4 AND gates, design a circuit that
accepts a 4bit unsigned number, X[3:0] and produces a 4bit, unsigned output
Y[3:0] such that
Y =
X, if X < 7
0, otherwise.
2.
(20 pts.) Using (2) 74LS85 comparators along with multiplexers, design a circuit
that takes in (3) 4bit, unsigned numbers, X[3:0], Y[3:0], Z[3:0], and outputs a
single 4bit unsigned number, G[3:0], such that G is the maximum of X, Y, and Z.
If two or more numbers are equal and the maximum, then choose the number to
output based on the following priorities:
X (highest), Y (middle), Z (lowest).
[e.g. if X=Y=Z then they are all the maximum but you should output X].
One comparator and one 2to1, 4bit wide mux are drawn on the attached sheet.
Connect these components appropriately. You may not change the connections
we have already started.
Add the second comparator and add any more muxes
you desire.
You may use 1 or 2 if you wish, as long as it works.
Be sure to show
device labels (inside the building blocks) and system labels (outside the
building blocks).
3.
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 '06
 Redekopp
 Binarycoded decimal, ASCII, building blocks, ModelSim, 4bit cascadable comparator

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