A special case of B-logic is a partition that includes a linear-feedback shift register (LFSR) that performs signature analysis for compression of output error data. Table B-XVI lists penalty values for different LFSR degrees. If the LFSR implements a primitive GF(2) polynomial of degree "k", where there is at least one flip-flop stage between inputs to a multiple-input LFSR, then the following procedure shall be used in order to determine a lower bound on the established fault coverage of the logic partition:
Step 1: Excluding the LFSR, but including any stimulus generation logic considered to be part of the logic partition, determine the fault coverage of the logic partition by fault simulation without signature analysis; denote this fault coverage by C.
Step 2: Reference Table B-XVI. For a given degree "k" obtain the penalty value "p". The established fault coverage of the logic partition using a LFSR of degree "k" shall be reported as (1-p)C. That is, a penalty of (100p) percent is incurred in assessing the effectiveness of signature analysis if the actual effectiveness is not determined.
Table B-XVI - Penalty Values, P, for LFSR Signature Analyzers Implementing Primitive Polynomial of Degree k
k |
p |
k < 8 |
1.0 |
k = (8 . . . 15) |
0.05 |
k = (16 . . . 23) |
0.01 |
k > 23 |
0.0 |