Hardware Reference
In-Depth Information
Tabl e 5. 1
The ten possible
static bridge types
f
a
.b/
f
b
.a/
Bridge type
0
0
Fault free
0
1
a dominates b
0
a
a AND-dominates b
0
a
a OR-dominates b
1
1
a and b swap values (4-way bridge)
1
a
b dominates a & a AND-dominates b
1
a
b dominates a & a OR-dominates b
b
a
wired-AND
b
a
b AND-dominates a & a OR-dominates b
b
a
wired-OR
All common bridge fault models are present in this table. There are also three
more exotic bridges described which are not widely used. These are combinations
of different dominations from a to b and from b to a.
5.4
Logic Diagnosis
In this section, we apply the CLF calculus to logic diagnosis. The method presented
below identifies possible faulty regions in a combinational circuit based on its in-
put/output behavior and independent of a fault model. The approach combines a
flexible and powerful effect-cause pattern analysis algorithm with high-resolution
AT P G .
5.4.1
Effect Cause and Cause Effect
The classic diagnosis algorithms follow two different paradigms: Effect-cause anal-
ysis looks at the failing outputs and starts reasoning using the logic structure of
the circuits (
Abramovici and Breuer
1980
;
Waicukauski and Lindbloom
1989
)
. One
example of effect-cause analysis is the 'Single Location At a Time' (SLAT) tech-
nique introduced in
Bartenstein et al.
(
2001
). A diagnostic test pattern has the SLAT
property, if there is at least one observable stuck-at fault which produces a response
on that pattern identical with the response of the device under diagnosis (DUD).
In SLAT diagnosis, the explaining stuck-at faults for all available SLAT patterns
are combined to form possible explanations for the erroneous behavior of the DUD
as a whole. Cause-effect analysis is based on a fault model. For each fault of the
model, fault simulation is performed, and the behavior is matched with the outcome
of the DUD.
Standard debug and diagnosis algorithms usually work in two passes. First, a fast
effect-cause analysis is performed to constrain the circuits region where possible
