Models in Memory Testing - Models in Hardware Testing - page 174

Tabl e 6. 3 Single-cell linked faults

FFM FPs

TF x ! WDF x <x; w x =x= >!<x; w x = x= >; x 2f0; 1g

WDF x ! WDF x <x; w x = x= >!< x; w x =x= >x2f0; 1g

DRDF x ! WDF x <x;r x = x=x >!< x; w x =x= >; x 2f0; 1g

TF x ! RDF x <x; w x =x= >!<x;r x = x=Nx>;x2f0; 1g

WDF x ! RDF x <x; w x = x= >!< x; r x =x=x >; x 2f0; 1g

DRDF x ! RDF x <x;r x = x=x >!< x; r x =x=x >; x 2f0; 1g

2-coupling FP .LF2 va /.Table 6.4 reports the list of realistic 2-coupling linked
faults where the following notation is used: op 2f r; w g , x 2 D y 1 , x i D y i if

op i D r .

3-coupling linked faults : 3-coupling linked faults are composed of FPs sharing
the same victim cell but having different aggressor cells (a 1 and a 2 ). Considering
the possible mutual positions of a 1; a 2 ,and v , realistic fault models proposed in
[ Hamdioui et al. 2004 ] belong to the following two situations: (i) a 1 < v <a 2 ,
and (ii) a 2 < v <a 1 . Realistic 3-coupling linked faults can be represented by
the same FPs used to represent 2-coupling linked faults.

6.4.7 Fault Models for Specific Technologies and Architectures

The space of fault models defined in the previous sections is far from representing
a complete taxonomy of possible memory faults. It actually focuses on a set of very
high level, technology independent faults that can be easily applied to any type of
memory.
As we start exploring all the dimensions of the multidimensional space intro-
duced in Section 6.2 , several specific functional fault models can be defined, as for
example:

Fault models for multi-port memories ( Hamdioui et al. 2001 )
Fault models for cache memories ( Al-Ars et al. 2008 )
Fault models for DRAMs ( Al-Ars 2005 )
A detailed analysis of all these fault models is out of the scope of this chapter, and,
if interested, the reader should refer to specific publications.

6.5 From Fault Models to Memory Testing

In order to inspect memory devices for possible faulty behaviors, all memory com-
ponents are usually tested at the end of production and sometimes in the field. As
already stated in Section 6.1 , common practice for memory testing is to apply func-
tional test patterns that try to cover FFMs.