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10_test_compression_p6

10_test_compression_p6 - Volume of Test Data Grows Linearly...

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1 © K.T. Tim Cheng 10_test_compression, v1.0 Volume of Test Data Grows Linearly With Chip Size Huge size of test data Up to ~1KB test data per gate 1M gate IC requires 1GB test data # of IO grows much slower than that of gate count 2 © K.T. Tim Cheng 10_test_compression, v1.0 1 10 100 1000 10000 1 10 100 1000 10000 Gate count per chip (millions) Estimated test set size (GB) Test Storage and Test Application Time z Huge volume of stored test data z Excessively long test application time 120 3 © K.T. Tim Cheng 10_test_compression, v1.0 0 20 40 60 80 100 0.01 0.1 1 10 Gate count per chip (millions) Test time vs chip size 100MHz ATE for 8 scan channels Test Data Compression z Test data volume and test time reduction z No functional logic modification such as test point insertion z Easy integration into existing design flows and compatibility with current ATE 4 © K.T. Tim Cheng 10_test_compression, v1.0 Ref: J. Rajski, et al., Embedded Deterministic Test, IEEE Trans. on CAD, May 2004 Test Stimulus Compression Techniques 1. Coding - Run-length codes, Golomb codes, LZ77, . Encode the test vectors and decode on-chip 2. LFSR reseeding Compression : Solving of linear equations Decompression : Compress a test cube into a seed, 5 © K.T. Tim Cheng 10_test_compression, v1.0 reproduce the corresponding test cube while clocked for a number of cycles. 3. Continuous flow linear expansion Compression : Solving of linear equations Decompression : Compressed data are supplied in a continuous flow & decompressed by linear network LFSR Reseeding z Periodically reseeding - The LFSR size has to be large enough to achieve low probability (<10 -6 ) of not finding a seed One linear equation per FF Single-polynomial LFSR : > Maximum specified bits (Smax) + 20 » LFSR-Coded Test Patterns for Scan Design , Konemann ETC 91 6 © K.T. Tim Cheng 10_test_compression, v1.0 Multiple-polynomial LFSR : > Smax + 4 » Generation of vectors patterns through reseeding of multiple- polynomial LFSR , S. Hellebrand. et.al, ITC 92 z
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