Test Two, CSCI 312, Spring 2005

1. (3 points) For the and operator:
   1. Provide the boolean expression.
   2. Give a truth table.
   3. Draw the logic symbol.
2. (5 points) D flip-flop
   1. Describe the use of this circuit.
   2. Describe the operation of the circuit.
   3. Give a non-trivial timing diagram that demonstrates the behavior of this circuit.
3. (2 points) Describe the basic difference between the circuit in question 1 and the circuit in question 2. (What is the difference between sequential circuits and combinational circuits?)
4. (4 points) For the tristate device:
   1. Provide the boolean expression.
   2. Give a truth table.
   3. Draw the logic symbol.
   4. What is the principle use of a tristate device?
5. (6 points) Multiplexors
   1. Describe the data and control lines for a multiplexor.
   2. Describe the operation of a mux.
   3. Draw a circuit, using only basic gates, that behaves as a 4 input mux. Label all data and control lines.
6. (6 points) Give a truth table, boolean expression, and circuit diagram that takes three inputs, representing votes of members of a committee, and lights a led when at least two members have voted for (or input a 1) a proposal.
7. (6 points) Draw a gate level representation of a 3 bit register. It should have a single control line, 0 = load, 1 = shift right, and a clock. The register should fill with a 0 on shift. Label all data and control lines.
8. (6 points) Adders
   1. Draw the circuit diagram for a full adder.
   2. Draw the circuit diagram for a ripple carry adder (you may use full adders for this task)
   3. Draw the circuit diagram for a ripple carry subtractor.
9. (4 points) Describe how a look ahead carry adder is built. How is this adder superior to a ripple carry adder?
10. (4 points) Describe the data and control lines for a 32x3 memory. Make sure that you describe the bit width of each line.
11. (4 points) Describe the importance of modular design in computer architecture. (Think transistors to CPUs)