Computer Science 150 Homework Assignment 6
Spring 1997

Due: Thursday, March 20, 5:00 pm

The numbers in brackets [ ] denote the relative marks assigned for each question.


1. A two-button electrical lock will actuate according to the following sequence:

A: 0 1 1 1 1 0 1

B: 0 0 1 0 1 1 1

Z: 0 0 0 0 0 0 1

Z=1 opens the lock and is the circuit output while A and B correspond to the two buttons. A switch being depressed (pushed and held down) corresponds to a 1 and a switch being released (removing one’s finger from the button) corresponds to a zero. Releasing both buttons clears the circuit and only one button may be pressed or released at a time, as is the case in the above sequence.

(a) Obtain a primitive flow table for the circuit. [20]

(b) Obtain a reduced, merged flow table by eliminating any redundant states and by merging equivalent states. Show your merger diagram. [20]


 

(2) Consider the merged flow table shown opposite:

Perform a race-free state-assignment using as few internal state variables as possible. Indicate all required adjacency constraints and list your final state codes. Be very clear in explaining how you arrived at your result. [40]

 

 

 

 


pchong@cory.eecs.berkeley.edu