Self-Test Diagnosis Using Parallel Superposition
Original Publication Date: 1985-Jul-01
Included in the Prior Art Database: 2005-Feb-18
This technique allows diagnosis of self-test failures to a failing backtrace cone using reduced signature sets. The multi-chip module structure shown in Fig. 2 allows the application of a high volume of pseudo-random test patterns using a linear feedback shift register (LFSR) 10 and the compression of the test responses into signatures for failure analysis using a multiple input signature register (MISR) 12. Using gates 14 and the principle of signature superposition, a failing module can be diagnosed first to a failing capture chip and then to a failing capture shift-register latch (SRL). This technique shows that the final MISR signature is the same as the sum (modulo 2) of the individual inputs.