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Signature analysis usage for fault isolation

  • US 5,652,754 A
  • Filed: 12/27/1995
  • Issued: 07/29/1997
  • Est. Priority Date: 12/27/1995
  • Status: Expired due to Fees
First Claim
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1. A test method for providing fault isolation of digital module circuitry under test that comprises a plurality of test signal inputs for receiving test input signals, a plurality of signal outputs, and a plurality of test points, said test method comprising steps of:

  • recording a fault free signature of a functional digital module that comprises circuitry that is substantially identical to the digital module circuitry under test;

    shorting and opening every node of the functional digital module with test input signals applied to signal inputs thereof;

    applying output signals of the functional digital module to a multiple input shift register and signature analyzer and recording signal outputs from said multiple input shift register and signature analyzer in a memory lookup table, which recorded signal outputs correspond to recorded failure signatures of the functional digital module;

    testing the digital module circuitry under test;

    comparing failure signatures that occur during testing of the digital module circuitry under test with the recorded failure signatures derived from the functional digital module; and

    correlating the failed signatures to a specific node failure to generate a fault isolation output signal for the digital module circuitry under test.

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