CPE 100L LOGIC DESIGN I
CPE 100L
LOGIC DESIGN I
LABORATORY 7:
2-BIT ALU AND 7-SEGMENT DISPLAY
BY GRZEGORZ CHMAJ
DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
UNIVERSITY OF NEVADA, LAS VEGAS
GOALS:
Design a 1-Bit and 2-Bit arithmetic logic units and implement the circuits on the DE0 board. Learn
how to use DE0’s 7-segment display.
BACKGROUND:
ARITHMETIC-LOGIC UNIT (ALU)
Arithmetic logic unit is the most important element of microprocessor which performs both math
and logic functions. An ALU loads data from input registers, an external Control Unit then tells the
ALU what operation to perform on that data, and then the ALU stores its result into an output
register. ALU takes many operands as input data, then depending on the operation which is
currently programmed in operation selector, it performs this operation on input operand and
produces the result. The result is presented on the ALU’s output.
Figure 1. Block schematic of ALU
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CPE 100L LOGIC DESIGN I
a)
logic operation
b) arithmetic operation
Figure 2. Logic and arithmetic operation in ALU
In this lab, we will be working on ALU which performs three functions:
 logical AND:
y = ab
 logical OR:
y = a+b
 arithmetic addition:
y = a+b
Figure 3. Implementation of 1-bit ALU
While 1-bit ALU, takes 1-bit numbers as arguments (each operand contains 1-bit number), the 2-bit
ALU takes two 2-bit operands as inputs. Let’s take the following notation:
 a0 – first (less significant) bit of first argument
 a1 – second (most significant) bit of first argument
 b0 – first (less significant) bit of second argument
 b1 – second (most significant) bit of second argument
 y0 – first (less significant) bit of the output result
 y1 – second (most significant) bit of the output result
Then the operations could be expressed as:
 logic AND – bitwise operation:
o y0 = a0 AND b0
o y1 = a1 AND b1
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CPE 100L LOGIC DESIGN I


logic OR – bitwise operation:
o y0 = a0 OR b0
o y1 = a1 OR b1
arithmetic add:
o a1a0 + b1b0 = y1y0
(x1x0 are 2-bit binary numbers)
7-SEGMENT DISPLAY
Binary coded decimal (BCD) numbers are often displayed on seven segment display using BCD to
seven segment decoder such as 7447, which we use in this lab. Figure 6-3 illustrates BCD to seven
segment display circuit.
a) 7-segment display segments
b) photo of 7-segment display
Figure 4. 7-segment display
Truth table of BCD to seven segment display decoder is as follows:
Table 1. 7-segment display truth table
Inputs
b3 b2 b1 b0
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
Outputs
abcdefg
0000001
1001111
0010010
0000110
1001100
0100100
0100000
0001111
0000000
0000100
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CPE 100L LOGIC DESIGN I
Inputs representing BCD numbers from 10 to 15 are don’t cares.
There are 2 types of 7-segment display: common anode (logical 0 lights up the segment) and
common cathode (logical 1 lights up the segment). The schematic of common-anode 7-segment is
shown in Fig. 5.
Figure 5. Common anode 7-segment display circuit
BCD to 7-segment display decoder is the circuit that converts BCD number into its 7-bit
representation. We can say, that decoder realizes the truth table shown above. The examples of
such decoder are: 7447, 7449. The example circuit of converting BCD into 7-segment is shown in
Fig. 5.
Figure 6. Example of decoding BCD number using 7447 IC.
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CPE 100L LOGIC DESIGN I
LAB DELIVERIES:
PRELAB:
1. 7-segment display
1. Apply the rules of K-map to find the expression of the each of the seven outputs.
2. 1-bit ALU:
1. Create 1-bit ALU schematic in Quartus (Figure 3).
2. Perform functional simulation
3. 2-bit ALU:
1. Based on 1-bit ALU, design 2-bit ALU
2. Draw the schematic in Quartus
3. Perform functional simulation
Prelab deliveries
Include in the report document:
1. Schematics created in Quartus
2. Simulation waveform generated by Quartus
3. Answer the question: what is bitwise operation? Give an example.
LAB EXPERIMENTS:
1. Experiment 1: 7-segment display
1. Implement the circuit, which represents 3-bit BCD number on DE0’s board 7-segment
display
a. Connect 3 bits of a number to switches SW0, SW1, SW2
b. Use HEX0 to display the number
a0
a1
decoder
a2
2. Demonstrate the circuit to the TA
2. Experiment 2: 1-bit ALU
1. Implement your 1-bit ALU on the DE0 board
a. Connect input a to KEY3
b. Connect input b to KEY2
c. Connect selectors to the switches SWx of your choice
d. Connect outputs to LEDs of your choice
2. Demonstrate the circuit to the TA
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CPE 100L LOGIC DESIGN I
3. Experiment 3: 2-bit ALU
1. Implement your design of 2-bit ALU on the DE0 board
a. Connect input a1 to KEY3
b. Connect input a0 to KEY2
c. Connect input b1 to KEY1
d. Connect input b0 to KEY0
e. Connect selectors to the switches SW0 and SW1
f. Connect outputs to LEDs of your choice.
2. Extra credit: represent the state of pushbuttons and switches on neighboring LEDs.
3. Demonstrate the circuit to the TA
4. Experiment 4: 2-bit ALU and 7-segment display
4. Use circuits from experiments 3 and 1, and represent the result of 2-bit ALU on 7-segment
display.
POSTLAB REPORT:
Include the following elements in the report document:
Section
1
Element
Theory of operation
Include a brief description of every element and phenomenon that appears during the experiments.
2
3
4
5
Prelab report
Results of the experiments
Experiment
Experiment Results
a. Schematic of the circuit doing translation of BCD to 7-segment
1
b. Picture of the 7-segment displaying a number of your choice
a. Schematic from Quartus
2
b. Simulation waveforms
a. Schematic from Quartus
3
b. Simulation waveforms
4
a. Schematic from Quartus
Answer the questions
Question no.
Question
1
Does Table 1. represent common anode or common cathode display?
2
Pick two simple ALU chips and list their most important functions.
3
What is LED?
Conclusions
Write down your conclusions, things learned, problems encountered during the lab and how they were
solved, etc.
6
Attachments
Zip your projects. Send through email as attachments, or provide link to the zip file on Google Drive /
Dropbox, etc.
List of attachments to deliver:
1. Quartus project for experiment 4
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CPE 100L LOGIC DESIGN I
References:
1. DE0 pin table: http://faculty.unlv.edu/eelabs/docs/guides/DE0_Pin_Table.pdf
2. Altera DE0 Introduction / User Manual
http://faculty.unlv.edu/eelabs/docs/guides/DE0_CV_User_Manual.pdf
3. Altera DE0 Computer System
http://faculty.unlv.edu/eelabs/docs/guides/DE0_CV_Computer.pdf
4. Simulating Design in Quartus 13.1
http://faculty.unlv.edu/eelabs/docs/guides/Simulating_Design_in_Quartus_13_1.pdf
5. Datasheets of 7400 series chips:
http://faculty.unlv.edu/eelabs/index.html?navi=main_icdatasheets
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