CSCI 2321 (Computer Design), Spring 2020:
Homework 6

Credit:

15 points.

Reading

Be sure you have read, or at least skimmed, all assigned sections of Appendix B.

Problems

Answer the following questions. You may write out your answers by hand and scan them, or you may use a word processor or other program, but please submit a PDF, either directly by e-mail or by putting it in your “graded work” folder on Google Drive, subfolder TurnIn, and sending me e-mail that you've done so (no need to share it with me -- I have access). (You can make my job easier by not just sharing another Google Drive file.) For the e-mail, please use a subject line that mentions the course and the assignment (e.g., “csci 2321 hw 6” or “computer design hw 6”).

1. (15 points) Do problems B.7 and B.8 from the textbook.
   1. For problem B.7, note that the parity functions (odd or even) described in Appendix B (starting on p. B-65) are the same idea as “parity bits” as described in many online sources (the Wikipedia article, for example) but not exactly the same -- a parity function tells you whether the input already has whatever parity it is, while a parity bit is whatever is needed to produce the desired parity.

   2. For problem B.8, “bubbled inputs” means for you to show negated inputs with bubbles, as in Figure B.3.4, rather than with explicit inverters.

2. (Up to 7.5 extra-credit points.) Do problems B.37 and B.38 from the textbook.
   1. For problem B.37, you are to to produce something analogous to the diagram in Figure B.10.2. Note however that in the example this diagram illustrates, changes between states happen based on two inputs, while in this problem changes between states happen every cycle, so you won't really be labeling your edges with names of input signals that control transitions.) Hint: You might need more than three states.

   2. For problem B.38, you are to produce something analogous to the Boolean expressions in the text following Figure B.10.2, except that you will need a separate expression for each bit of the output state, assuming you have more than two, which you almost certainly will. Hint: You could do worse than starting by writing down a truth table, where the inputs are the bits of the current state, and the outputs are the bits of the next state and the three outputs that control the lights.

Honor Code Statement

Include the Honor Code pledge or just the word “pledged”, plus at least one of the following about collaboration and help (as many as apply).¹Text in italics is explanatory or something for you to fill in. For programming assignments, this should go in the body of the e-mail or in a plain-text file honor-code.txt (no word-processor files please).

• This assignment is entirely my own work. (Here, “entirely my own work” means that it's your own work except for anything you got from the assignment itself -- some programming assignments include “starter code”, for example -- or from the course Web site. In particular, for programming assignments you can copy freely from anything on the “sample programs page”.)
• I worked with names of other students on this assignment.
• I got help with this assignment from source of help -- ACM tutoring, another student in the course, the instructor, etc. (Here, “help” means significant help, beyond a little assistance with tools or compiler errors.)
• I got help from outside source -- a book other than the textbook (give title and author), a Web site (give its URL), etc.. (Here too, you only need to mention significant help -- you don't need to tell me that you looked up an error message on the Web, but if you found an algorithm or a code sketch, tell me about that.)
• I provided help to names of students on this assignment. (And here too, you only need to tell me about significant help.)

Essay

Include a brief essay (a sentence or two is fine, though you can write as much as you like) telling me what about the assignment you found interesting, difficult, or otherwise noteworthy. For programming assignments, it should go in the body of the e-mail or in a plain-text file essay.txt (no word-processor files please).

Footnotes

... apply).¹

Credit where credit is due: I based the wording of this list on a posting to a SIGCSE mailing list. SIGCSE is the ACM's Special Interest Group on CS Education.