Altering bit sequences to contain predetermined patterns
First Claim
1. A method implemented in an electronic circuit, the method comprising:
- (a) generating a pseudorandom binary sequence of bit subsequences;
(b) producing from the bit subsequences a set of ternary sequences, wherein the ternary sequences comprise bit elements deterministically produced from the bit subsequences;
(c) deterministically altering the bit subsequences in accordance with the ternary sequences to produce altered bit sequences containing predetermined bit patterns; and
(d) applying the altered bit sequences to a circuit under test, wherein the ternary sequences are selected such that the altered bit sequences detect faults in the circuit under test.
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Abstract
A low-overhead scheme for built-in self-test of digital designs incorporating scan allows for complete (100%) fault coverage without modifying the function logic and without degrading system performance (beyond using scan). By altering a pseudo-random bit sequence with bit-fixing logic at an LFSR'"'"'s serial output, deterministic test cubes that detect random pattern-resistant faults are generated. A procedure for synthesizing the bit-fixing logic allows for complete fault coverage with low hardware overhead. Also, the present approach permits the use of small LFSR'"'"'s for generating the pseudo-random bit sequence. The faults that are not detected because of linear dependencies in the LFSR can be detected by generating more deterministic cubes at the expense of additional bit-fixing logic.
91 Citations
19 Claims
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1. A method implemented in an electronic circuit, the method comprising:
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(a) generating a pseudorandom binary sequence of bit subsequences; (b) producing from the bit subsequences a set of ternary sequences, wherein the ternary sequences comprise bit elements deterministically produced from the bit subsequences; (c) deterministically altering the bit subsequences in accordance with the ternary sequences to produce altered bit sequences containing predetermined bit patterns; and (d) applying the altered bit sequences to a circuit under test, wherein the ternary sequences are selected such that the altered bit sequences detect faults in the circuit under test. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An electronic circuit comprising:
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(a) means for generating a pseudorandom binary sequence of bit subsequences; (b) means for producing ternary sequences in response to the means for generating the binary sequence, wherein the ternary sequences comprise bit elements deterministically produced from the bit subsequences; (c) means for deterministically altering the bit subsequences in accordance with the ternary sequences, resulting in an altered bit sequence containing predetermined bit patterns; and (d) means for applying the altered bit subsequences to a circuit under test, wherein the ternary sequences are produced to detect faults in the circuit under test by the applied altered sequence. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification