UCR EE/CS 120B   Digital Systems   Spring 1998  Professor Frank Vahid

Homework 1  Due: Tuesday, 4/14, BEFORE lecture.  You can turn it
in before lecture begins at 11:10, or put it under the door of
A207 before 11:00.  You must complete the following using two sides of 
only ONE sheet of 8x11 paper (no perforated edges from spiral notebooks),
with no attachments (no staples, clips, etc.).  Don't forget the required 
statement of originality at the top of the page.  SHOW YOUR WORK for every 
problem.

1. Design a NOR gate using CMOS transistors.

2. Design a 5x1 multiplexor using AND, OR, and INVERT gates.
   Include a truth table representing its functionality.
   Make use of don't cares if possible.

3. (a) Design a sprinkler controller that reads a 3-bit binary
   input, and asserts (sets to 1) exactly one output that would
   turn on one of 8 sprinklers.  Make sure to show a truth
   table as well as a circuit. (b) What common combinational
   component does the circuit represent?

4. Design an ALU that can perform add, subtract, increment,
   AND, and OR operations.  Use a table to indicate the operation
   for each combination of the ALU's control lines.
   
5. Design a 3-bit carry-lookahead adder

6. Design a 1-bit magnitude comparator (compares two 1-bit inputs)
   with three outputs: less-than, equal-to, and greater-than.
   Demonstrate whether or not you can connect N of these comparators
   to form an N-bit comparator without using any additional logic.