wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (02/14/90)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
VLSI/GROUP SEMINAR
-Thursday, February 22, 1990
Mr. Bruce Cockburn, graduate student, Dept. of Comp.
Sci., University of Waterloo will speak on ``The
Detection of Coupling Faults in RAMs''.
TIME: 10:30 a.m.
ROOM: DC 1304
ABSTRACT
The random-access memory (RAM) is a fundamental
integrated circuit (IC) used for rapid-access storage
in virtually all digital systems. Since the
manufactured volume of RAMs is high, it is especially
important to minimize test times without unduly
compromising fault coverage. For the purposes of
designing and analyzing functional tests, the effects
of physical defects on the logical behaviour of a
digital IC are modelled using mathematical abstractions
called faults. This talk presents results concerning
the problem of detecting coupling faults in one-bit-
per-address RAMSs. Good and faulty memories are
represented as Mealy automata using the formal
framework for sequential machine testing developed by
Brzozowski and Jurgensen. A precise description of the
coupling fault is used to define various fault models
including ``general coupling'', which is the set of all
possible multiple coupling faults, and ``general
toggling'', which is a subset of general coupling. A
lower bound of 2n +n is presented on the length of any
- --
test that detects general toggling in an n cell memory;
-
a test by Marinescu is thereby shown to be optimal for
2
this fault model. A lower bound of 2n +3n is derived
- - -
on the length of any test that detects general
2
coupling, and a corresponding test of length 2n +4n is
- - -
described. Recent lower bound results and tests for
other subsets of general coupling will also be
discussed.