CSE 2341                         LABORATORY ASSIGNMENT 6                     SPRING 1999

A SIMPLE ARITHMETIC LOGIC UNIT (ALU)

(150 POINTS)

PURPOSE: To design, implement, and test a simple ALU.

EQUIPMENT NEEDED: IDL-800 Digital Lab trainer, wire.

PARTS NEEDED: SN7483, SN74157 and others (do not use an SN7482).
 

BACKGROUND:

In this lab you will design a very simple ALU consisting of an adder-subtractor circuit, a logical OR circuit, and an output select circuit. The block diagram of the whole circuit and its function table are shown below:


 
 
 

S1 S0 Function
0 0 Add (A + B)
1 0 Subtract (A - B)
X 1 Logical OR (A OR B)

 

PRELAB (50 points):

    1. Design the ALU specified above before coming to your laboratory session. Use an SN7483 as the basic component of the design. Assume that negative numbers are represented by 2's complements. All of the necessary information is available in your text (see section 4.8). Capture and verify your design using LogicWorks3.
    2. Design a circuit for detecting arithmetic overflow in the above ALU. Capture and verify your design using LogicWorks3.
    3. Design a circuit for detecting a zero result in the above ALU. Capture and verify your design using LogicWorks3.
    4. Design a circuit for detecting a negative result in the above ALU. Capture and verify your design using LogicWorks3.
PROCEDURE:

Have your lab instructor check your work after each part.

Part 1 (50 Points):

Construct the 4-bit adder-subtractor section of your ALU. Test the adder/subtractor with the following additions and subtractions. Record your results.

3 + 4 = ? 6 + 6 = ? 7 - 5 = ?

5 - (-4) = ? (-2) + (-4) = ? (-2) - (-4) = ?

(-4) - (-2) = ? (-5) - 6 = ? (-5) - (-5) = ?

Examine your results. Even if you built your circuit correctly some of your results will not be correct. Explain why the circuit does not always produce the correct answer.
 
 

Part 2 (50 Points):

Incorporate your logical OR circuit and output select circuit with the adder-subtractor circuit you built above. Test the OR and select circuit with the same input patterns given in part 1. Record your results.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

CSE 2341 - Lab Number 6 Compliance Form
 
 
 
 
 
 

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Student's Name                                                 Student's ID Number
 

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Student's signature
 
 

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Lab Assistant's approval (Part 1)
 

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Lab Assistant's approval (Part 2)