CIS 351

Project 3: Build an ALU

Winter 2021

Combine your adder, adder/subtracter, and comparator from previous projects into a single ALU. Notice that you will not be implementing the ALU described in the textbook. Your ALU will have different operations and op codes.

Your ALU must perform the following 16-bit operations:

Unsigned addition	0
Unsigned subtraction	1
And	2
Or	3
Not	4
Xor	5
lui	6
sltu	7
Signed addition	8
Signed subtraction	9
slt	15

Use this GitHub Classroom link to create a repository for the project.
Use ALU_16bit.jls and don't rename any inputs or outputs.
Set the Overflow output to 0 if overflow doesn't apply to the given operation. Specifically, Overflow should be 0 for all operations except signed addition and signed subtraction. (Interestingly enough, by definition, unsigned addition and unsigned subtraction do not overflow.)
The not operator returns the negation of InputA. Ignore InputB.
lui stands for load upper immediate. Take the lower 8 bits of InputA and place them in the upper 8 bits of the output. Ignore InputB.
slt stands for set if less than. The output should be 1 if InputA is less than InputB and 0 otherwise. slt treats the inputs as signed integers, sltu treats the numbers as unsigned.
Your entire ALU may contain one adder only. Your Adder/Subtractor from the previous project should already follow this design. You may need to slightly modify your comparator circuit so it uses your Adder/Subtractor.

Hints and shortcuts

You may find this sample test script helpful: Sample16BitALUTest.java
Remember, JLS inserts the code for sub-circuits directly into the circuits into which they are imported. Thus, changes to sub-circuits are not seen by the circuits that contain them. If you discover a bug in a sub-circuit, you must delete and re-import that sub-circuit into the parent. (Again, test your subcircuits thoroughly before importing them!)
Remember that no software is perfect. This includes JLS and DLUnit. Commit and push often.

Grading

This assignment will be scored out of 30 points.

Category	Rubric	Maximum Score
Correctness
	Not attempted	0
	Passes some tests	1 point per op
	Passes all tests	17
Date 100% correct
	Two days early	12
	One day early	11
	On time	10
	One day late	8
	(-2 per day)	...
	Five or more days late	0
Presentation
	Documentation and Neatness	3

Penalties

You will loose 6 points for each unnecessary copy of an adder or adder/subtracter.
You will loose 5 points if overflow is incorrect.

Deliverables

To submit your project:

Add a text box to your .jls files containing the names of all team members.
When your circuit passes all of my tests, add [Grade Me] to the commit message.

Updated Monday, 28 December 2020, 6:55 PM