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An Arithmetic Structure for Test DatAn Arithmetic Structure for Test Data Horizontal Compressiona Horizontal Compression
Marie-Lise FLOTTES, Regis POIRIER, Bruno ROUZEYRE Marie-Lise FLOTTES, Regis POIRIER, Bruno ROUZEYRE Laboratoire d’Informatique, de Robotique et de MicroelectroniLaboratoire d’Informatique, de Robotique et de Microelectroni
que de Montpellier, Franceque de Montpellier, FranceDATE ‘04DATE ‘04
Laboratory of Reliable ComputingDepartment of Electrical EngineeringNational Tsing Hua UniversityHsinchu, Taiwan
2
ReferenceReference An Arithmetic Structure for Test Data Horizontal C
ompressionMarie-Lise FLOTTES, Regis POIRIER, Bruno ROUZEYRE
DATE ‘04
Test Data Compression Using Dictionaries with Fixed-Length Indices
Lei Li and Krishnendu ChakrabartyVTS ‘03
An Efficient Test Vector Compression Scheme Using Selective Huffman Coding
Abhijit Jas, Jayabrata Ghosh-Dastidar, Mon-Eng Ng and Nur A. Touba IEEE Transaction on CAD of IC and System, June 2003
Improving compression ratio, area overhead, and test application time for SOC test data compression / decompression
P. T. Gonciari, B. Al-Hashimi and N.Nicolici DAT ‘02
3
OutlineOutline
Instruction
Lossless Compression algorithm
Compression principle and De-compressor Architecture
Main Issue Compression Issue Timing Issue
Experimental Result
Compare & Conclusion
4
Why need compression ?Why need compression ?
Higher circuit densities and a large number of embedded cores will lead the increase of test data volume, which in turn leads to an increase in testing time.
Transmitting test patterns and handshaking between cores and ATE will waste a lot testing time.
5
How to reduce testing cost ?How to reduce testing cost ? ATE has limited pin counts and testing time is
equal to the testing cost.
More patterns transmit to core, more testing time
Reduce testing cost
a. Reduce testing time
- compaction
b. Reduce testing pin counts
- compressionn
m
Channel
n < m
6
Compression MethodCompression Method
(1) Easy compression → Hard decompression (2) Hard compression → Easy decompression Compression Method
Lossless Lossy
Compression can be executed through software, therefore the dominate area overhead is the circuit of decompression.
7
Lossless Compression AlgorithmLossless Compression Algorithm
Run-Length Coding
Frequency-Directed Run-Length (FDR)
& Extend FDR
Huffman
Dictionary Based
Main idea of above algorithms More common data, shorter bits to represent
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Run-Length CodingRun-Length Coding First bit represents the
data is ‘1’ or ‘0’.
Next m bits represent the runs of ‘1’ or ‘0’.
16 2
24 3
111111000000011111100000
m=3
1110011111100011
101010
m=3
100100011001000110010001
Compression Ratio :24
46
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FDR & EFDRFDR & EFDR
Source : VTS ‘99
10
Example of Huffman TreeExample of Huffman Tree
Source : VTS ‘99
11
Simplified Huffman TreeSimplified Huffman Tree
Source : vlsitsa ‘01
12
Variable-Length Input Variable-Length Input Huffman CompressionHuffman Compression
Source :DAT ‘02
13
ExampleExample
12
14
8
1 3 7
1115 4
52
13
16 10
9 6
Source : VTS ‘03
11100011
01000110
14
Example(1/2)Example(1/2)
1 3 7
111512 4
528
14 13
16 10
9 6
11
52
13
16
9 6
maximum degree
Sub graph
52
13
16
9 6
5
13
16
6
Clique
15
Example(2/2)Example(2/2)
1 3 7
111512 4
528
14 13
16 10
9 6
5
13
16
6
More this clique
1 3 7
111512 4
28
14
10
9
New Graph
16
Example ResultExample Result
Obtain 4 cliques : {5,6,13,16} , {2,8,14} , {3,4,7} , {1,11} 12 words are encoded, and there are else 4 diffe
rent words un-coded. So total need transmit (1+2)*12+(1+8)*4=72 bits. If no compression, we need transmit 8*16=128
bits. Therefore, after compression, reducing about 43.75% bits needed to transmit to core.
17
Parameter DefinitionParameter Definition M : # of ATE channel N : # of scan chains in CUT F : # of FF in each scan chain Initial test sequence { V1, V2, … } Numerous difference Di
Di = Vi+1-Vi
Source : DATE ‘04
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M-to-N Horizontal De-compressorM-to-N Horizontal De-compressor
Source : DATE ‘04
M pins in ATE
N scan chains in CUT
M < N
19
De-compressor StructureDe-compressor Structure
Source : DATE ‘04
Overhead Adder N bits-M SRA Shifts Reg./Accumulator
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SRA Operation ModeSRA Operation Mode Parallel Mode ( Shift =0 )
Parallel data-in from adder Transfer test pattern to scan chains in CUT
Semi-Parallel Mode ( Shift =1 ) Store test pattern from ATE SRA likes many scan chains
21
5bits-3 SRA5bits-3 SRA
Source : DATE ‘04
Test Time Evaluate Parallel mode
One clock cycle Semi-Parallel mode
clock cycleN
M
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Shift-in Test PatternShift-in Test Pattern M test pins in ATE
Max difference is 2M
Compressible pattern & Un-compressible pattern
Compressible pattern shift-in time
Un-compressible pattern shift-in time
NF
M
NF
M
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Compression IssueCompression Issue
2 maxlogM D Reduce Dmax can reduce # of test pins M Importance : MSB > LSB
Source : DATE ‘04
24
Compression Issue with Don’t CareCompression Issue with Don’t Care Don’t care bit (X) can be 1 or 0
More don’t care bits, higher compression ratio
Vk0: 1 0 1 x 0Vk1: 0 x x 1 0Vk2: x x 1 x xVk3: 1 x 0 x xVk4: 0 x 1 x 0
1 4 1 4 2
Vk0: x 0 0 1 1Vk1: 1 x 0 x 0Vk2: x x x 1 xVk3: x x x 0 1Vk4: x x 0 1 0
4 4 2 1 1
Vk0: 1 0 0 1 1Vk1: 1 1 0 1 0Vk2: 1 1 1 1 1Vk3: 0 0 1 0 1Vk4: 0 1 0 1 0
Dk0: 0 0 1 1 1Dk1: 0 0 1 0 1Dk2: 0 0 1 1 0Dk3: 0 0 1 0 1
3 bits
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Timing IssueTiming Issue Test pattern transmit time
Total :
Larger Pcomp, smaller test pattern transmit time
Test pattern transmit time is shorter
uncomp uncomp
NT P F
M
( ) 1comp comp
NT P F
M
uncomp compT T F
0 ( ) 1 ( ) 0all all
N NP F F T P F F
M M
( ) classic
NF T
M
26
Experimental Results (1)Experimental Results (1)
Source : DATE ‘04
ISCAS89 Benchmark
27
Experimental Results (2)Experimental Results (2)
ISCAS89 Benchmark : S9234 Version 1 6 scan chains & Length 42 Version 2 10 scan chains & Length 25 Version 3 10 scan chains & Length 25 6-to-10 compressor
28
Experimental Results (3)Experimental Results (3)
Source : DATE ‘04
29
ConclusionConclusion
A useful & simple method for reducing test pin A low overhead
Adder & Nbits-M SRA No impact the fault coverage
compressible & un-compressible pattern
Problem Not use the don’t care bit adequately
30
Conclusion (cont.)Conclusion (cont.)
Combine the SRA and 1st scan chain
…
Scan chain
SRA…
Scan chain
SRA
31
CombinationCombination
Combine this approach with dictionary based compression
1 3 7
111512 4
528
14 13
16 10
9 6
Dictionary Based Compression
Arithmetic Compression
Grouped pattern
Compressed Pattern
Un-compressed Pattern