CIS 351

Project 3: Build an ALU

Fall 2018

Build an ALU using JLS

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

Name your inputs InputA, InputB, and Op.
Name your outputs Output and Overflow.
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. For this project, you need to design your ALU so that your comparator uses your Adder/Subtractor.

Hints and shortcuts

You may find this starter file useful. It has the input and output pins set and also contains an example of using the "group bits" feature of the unbundler.
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. It is in your best interest to start early in case problems arise. Also, please e-mail me with any bugs you find or feature requests you have. If JLS crashes, please e-mail me the JLSerror file.

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 2 points for each buggy submission (-3 if the submission contains too few tests).

Deliverables

To submit your project:

Add a text box to your jls files that includes
- your name,
- the file name,
- the assignment name, and
- the assignment due date.
Either
- Attach all relevant .jls files, bug reports, and test scripts using Assignment Manager. (Attaching your test scripts allows me to determine how well you tested your code, and assess partial credit if necessary.)
- Add me (kurmasz) as a collaborator to your private GitHub or BitBucket project and send me a pull request.

Updated Wednesday, 17 October 2018, 3:14 PM