Northwestern University Nov 22, 2011
Electrical Engineering and Computer Science Handout #12
EECS303: Advanced Digital Design, Fall 11 Due: Nov 29
Prof. Hai Zhou
Homework 5
You may discuss the assignments with your classmates but need to write down your solutions
independently. Be careful with your handwriting. Unclear solutions will be assumed wrong.
1. (10 pts) What are asynchronous circuits? And what are the benefits of asynchronous
circuits over synchronous circuits?
2. (10 pts) What are static 1-hazard, static 0-hazard, and dynamic hazard? Prove that
there can not be dynamic hazard in two-level logic circuits.
3. (20 pts) Consider whether each of the following two-level logic circuits is hazard-free,
and if not, make it hazard-free.
(a) ¯ac +b¯c+c¯
d
(b) (a+c)(¯
b+ ¯c+¯
d)
4. (20 pts) Derive the transition table for the following asynchronous sequential circuit.
Is it hazard-free? Determine the sequence of internal states for the following sequence
of inputs x1x2: 00, 10, 11, 01, 11, 10, 00.
NAND
NOT
NOT
NAND
NAND
NAND
NAND
x1
x2
Y1
Y2
5. (15 pts) Draw a waveform for using dual-rail encoding and 4-phase handshake to
communicate three 2-bit data (0,0),(1,1),(1,0) between two components.
6. (25 pts) Design an asynchronous FIFO buffer which can store up to two 1-bit data.
