AC scan diagnostic method
First Claim
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1. An apparatus for performing AC scan chain built-in self test and diagnostics of an integrated circuit, comprising:
- a reconfigurable linear feedback shift register (LFSR) having an input and a plurality of output lines, the LFSR generating a bit pattern;
a plurality of scan chains having a plurality of latches, the scan chains interconnected to the LFSR, each scan chain serially receiving at a respective input the bit pattern output by the LFSR, and each scan chain propagating the bit pattern from the respective input to a respective output of each scan chain;
a multiple input signature register (MISR), the MISR receiving the bit patterns output by the respective scan chains;
the MISR generating a signature in accordance with the bit patterns input from the scan chains;
a comparison circuit for comparing the signature with an expected signature based upon the pattern input to the plurality of scan chains, wherein when the signature is equal to the expected signature, the scan chains are functioning correctly; and
a controller for reconfiguring the LFSR to vary the bit patterns output by the LFSR and for varying a timing sequence of operation of the LFSR, the plurality of scan chains, the MISR, and the comparison circuit.
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Abstract
Disclosed is an alternating current (AC) scan diagnostic system in which one or a plurality of scan chains are tested by serially propagating predetermined bit patterns through the scan chain and comparing the output against an expected result. The system comprises identification phase, verifications and localization, and a characterization phases. The system is adaptable for use with on-board diagnostics and is adaptable for use with on-product clock generation systems.
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Citations
16 Claims
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1. An apparatus for performing AC scan chain built-in self test and diagnostics of an integrated circuit, comprising:
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a reconfigurable linear feedback shift register (LFSR) having an input and a plurality of output lines, the LFSR generating a bit pattern;
a plurality of scan chains having a plurality of latches, the scan chains interconnected to the LFSR, each scan chain serially receiving at a respective input the bit pattern output by the LFSR, and each scan chain propagating the bit pattern from the respective input to a respective output of each scan chain;
a multiple input signature register (MISR), the MISR receiving the bit patterns output by the respective scan chains;
the MISR generating a signature in accordance with the bit patterns input from the scan chains;
a comparison circuit for comparing the signature with an expected signature based upon the pattern input to the plurality of scan chains, wherein when the signature is equal to the expected signature, the scan chains are functioning correctly; and
a controller for reconfiguring the LFSR to vary the bit patterns output by the LFSR and for varying a timing sequence of operation of the LFSR, the plurality of scan chains, the MISR, and the comparison circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for performing AC scan chain built-in self test and diagnostics of an integrated circuit, comprising:
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a reconfigurable linear feedback shift register (LFSR) having an input and a plurality of output lines, the LFSR generating a bit pattern;
a plurality of scan chains having a plurality of latches, the scan chains interconnected to the LFSR, each scan chain serially receiving at a respective input the bit pattern output by the LFSR, and each scan chain propagating the bit pattern from the respective input to a respective output of each scan chain;
a multiple input signature register (MISR), the MISR receiving the bit patterns output by the respective scan chains, the MISR generating a signature in accordance with the bit patterns input from the scan chains;
a comparison circuit for comparing the signature with an expected signature based upon the pattern input to the plurality of scan chains, wherein when the signature is equal to the expected signature, the scan chains are functioning correctly; and
an on-product clock generator (OPCG) to generate clock signals to synchronize operation of the LSFR, the plurality of scan chains, and the MISR. - View Dependent Claims (9, 10, 11)
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12. An apparatus for performing AC scan chain built-in self test and diagnostics of an integrated circuit, comprising:
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a reconfigurable linear feedback shift register (LFSR) having an input and a plurality of output lines, the LFSR generating a bit pattern;
a plurality of scan chains having a plurality of latches, the scan chains interconnected to the LFSR, each scan chain serially receiving at a respective input the bit pattern output by the LFSR, and each scan chain propagating the bit pattern from the respective input to a respective output of each scan chain;
a multiple input signature register (MISR), the MISR receiving the bit patterns output by the respective scan chains, the MISR generating a signature in accordance with the bit patterns input from the scan chains;
a comparison circuit for comparing the signature with an expected signature based upon the pattern input to the plurality of scan chains, wherein when the signature is equal to the expected signature, the scan chains are functioning correctly;
an on-product clock generator (OPCG) to generate clock signals to synchronize operation of the LSFR, the plurality of scan chains, and the MISR; and
a logic built-in self test (LBIST) controller for controlling operation of the OPCG, the LSFR, the plurality of scan chains, and the MISR, wherein the LBIST varies generation of predetermined bit patterns input to the respective scan chains in predetermined timing sets. - View Dependent Claims (13, 14, 15, 16)
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Specification