38 Clocked Scan Cell SCK QSO DI SI DCK Clocked scan cell In the clocked scan

38 clocked scan cell sck qso di si dck clocked scan

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38 Clocked-Scan Cell SCK Q/SO DI SI DCK Clocked-scan cell In the clocked-scan cell, input selection is conducted using two independent clocks, DCK and SCK .
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EE141 VLSI Test Principles and Architectures Ch. 2 - Design for Testability - P. 39 Clocked-Scan Cell Clocked-scan cell design and operation In normal/capture mode, the data clock DCK is used to capture the contents present at the data input DI into the clocked-scan cell. In shift mode, the shift clock SCK is used to shift in new data from the scan input SI into the clocked - scan cell, while the content of the clocked-scan cell is being shifted out.
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EE141 VLSI Test Principles and Architectures Ch. 2 - Design for Testability - P. 40 LSSD Scan Cell +L 2 C D . . . . A I . . . . B +L 1 L 1 L 2 SRL Polarity-hold SRL (shift register latch) An LSSD scan cell is used for level-sensitive latch base designs. This scan cell contains two latches, a master 2- port D latch L 1 and a slave D latch L 2 . Clocks C , A and B are used to select between the data input D and the scan input I to drive +L 1 and +L 2 . In an LSSD design, either +L 1 or +L 2 can be used to drive the combinational logic of the design.
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EE141 VLSI Test Principles and Architectures Ch. 2 - Design for Testability - P. 41 LSSD Scan Cell C D I +L 1 D 1 D 2 D 3 D 4 T 1 T 2 T 3 T 4 D 1 T 3 A B +L 2 T 3 Polarity-hold SRL design and operation In order to guarantee race-free operation, clocks A , B , and C are applied in a non-overlapping manner. The master latch L 1 uses the system clock C to latch system data from the data input D and to output this data onto +L 1 . Clock B is used after clock A to latch the system data from latch L 1 and to output this data onto +L 2 .
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EE141 VLSI Test Principles and Architectures Ch. 2 - Design for Testability - P. 42 Comparing three scan cell designs Increase routing complexity Insert scan into a latch-based design Guarantee to be race-free LSSD Scan Cell Require additional shift clock routing No performance degradation Clocked-Scan Cell Add a multiplexer delay Compatibility to modern designs Comprehensive support provided by existing design automation tools Muxed-D Scan Cell Disadvantages Advantages
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EE141 43 VLSI Test Principles and Architectures Ch. 2 - Design for Testability - P. 43 Scan Architectures Scan Architectures boxshadowdwn Full-Scan Design square4 All or almost all storage element are converted into scan cells and combinational ATPG is used for test generation boxshadowdwn Partial-Scan Design square4 A subset of storage elements are converted into scan cells and sequential ATPG is typically used for test generation boxshadowdwn Random-Access Scan Design square4 A random addressing mechanism, instead of serial scan chains, is used to provide direct access to read or write any scan cell
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EE141 VLSI Test Principles and Architectures Ch. 2 - Design for Testability - P.
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