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HOMEWORK
V
CS2204
DIGITAL LOGIC & STATE MACHINE DESIGN
FALL 2009
Polytechnic Institute of NYU
Page 1
of
26
Handout No : 16
November 5, 2009
DUE :
November 19, 2009
READ :
Related portions of Chapters III, IV, VI, VII and VIII
ASSIGNMENT :
There are seven
questions.
Solve all homework and exam problems as shown in class and past exam solutions.
1)
Consider the vending machine controller digital system designed in class.
Assume that it is
modified so that it accepts
quarters
:
Modify the following in order to accept quarters :
i)
The operation diagram.
ii)
The highlevel state diagram.
iii)
The datapath.
2)
Develop a
nonpriority
10to4 encoder shown below.
“Nonpriority” means that it is guaran
teed that at any time either all inputs are 0 or only one input is 1.
Provide an output named
“valid” which is 1, when an encoder input is 1. The valid output is 0, when all 10 inputs are 0.
Q
DG
clock
DC
RetDime
D
N
G
14
Amount
Inputs
Q
: Quarter is input
D
: Dime is input
N
: Nickel is input
G
: Gum is selected
C
: Chips is selected
Outputs
Amount
: Value of gum and chips (35 cents) or the
coin input so far shown on two 7segment displays
DG
: Deliver Gum
DC
: Deliver chips
RetDime
: Return 10 cents
RetNickel
: Return 5 cents
Textual Input/Output Relationship
After receiving the necessary amount (35 cents to 50 cents) and the selection is
made deliver a gum or chips and return 5 or 10 or 25 cents if necessary
C
RetNickel
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Page 2
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26
CS2204
Handout No : 16
November 5, 2009
Students can take a look at the implementation of the
74LS147
TTL MSI chip which is a 10to4
priority
encoder with activelow inputs, activelow data outputs and
no
valid output.
3)
Consider Question 4 of Homework 4 where a complex combinational circuit is analyzed.
Implement the two blocks (the ADDer and comparator) in the figure, by using
minimum
number
of TTL LS chips.
Draw the full schematic by hand, showing all the connections.
By using a
green
pen, outline the
two blocks in your schematic.
4)
Consider the black box view and input/output relationship of a
BCD
ADDer, a combinational
circuit, shown below :
Implement
the BCD ADDer on a PCB.
That is, implement the BCD ADDer with chips.
Use the
following notes as you implement the BCD ADDer :
i)
The circuit is a combinational circuit !
The
Digital Product Development
handout indicates that
first the precise input/output relationship must be obtained : the truth table !
This is impractical
for the BCD ADDer since there are
nine
inputs !
Therefore, we have to obtain the
operation
table
.
Then, we would proceed with the implementation step below.
10to4
Encoder
I0
I1
I2
I3
Y0
I4
I5
I6
I7
I8
I9
Y1
Y2
Y3
valid
msb
First, show the operation table of the encoder, which is a
simplified
truthtable since at any time no more than one
input is 1.
From the operation table, you will derive the
minimal equations.
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