Text - KFUPM - King Fahd University of Petroleum and Minerals

application time and data volume to be greatly reduced, besides over 99% power
reduction. However, it shows that this method compromises the test cost with a high
hardware overhead and the practicality of RAS architecture implementation were
not addressed. A modified RAS scheme has been described by Arslan and Orailoglu
[30] in which the captured response of the previous patterns in the flip-flops is used
as a template and modified by a circular shift for subsequent pattern. Mudlapur et
al. presents a unique RAS cell architecture [31, 32] that aims to minimize the routing
complexity. Another novel scan architecture called Progressive Random Access Scan
(PRAS) [33] and the associated test application methods have been proposed. It
has a structure similar to static random access memory. Test vector ordering and
Hamming distance reduction are proposed to minimize the total number of write
operations for a given test set [33, 34]. Partitioned Grid Random Access Scan
[35] method uses multiple PRAS grids with partitioning. This method achieves
much greater test application time reductions compared to multiple serial scans
with additional test pins. A test compaction technique has also been used with
RAS. In parallel random access virtual scan (PRAVS) architecture [36]. Along with
a X-tolerant compactor, PRAVS, achieves greater test data/time reductions than
conventional RAS.
Recently, compression schemes utilizing RAS architecture have been proposed.
Cocktail Scan [37], a hybrid method unlike the LFSR-based hybrid BIST, adopts a
two-phase approach to perform scan test in which all test data are supplied from the
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