LFSR The aim of this exercise is to study the LFSR presented in section 14.5.

1. First of aB, it is used as a generator of pseudo-random sequences.

Analyze its behavior when its initial state is (111), then (010).

2. The basic LFSR circuit is modified as shown in Figure 14.31: the D input of the first D flip-flop receives the XOR of bits Q2 and Q3. Does this circuit still behave as a LFSR?

3. We will now analyze the compaction circuit of Figure 14.26 (Example 14.7). Check the compacting sequence given in Table 14.2.

4. Still for the PSA circuit, find several non-detectable errors.

5. What do you think about the use of LFSR and of the BIST techniques by signature analysis?

Transcribed Image Text:

Clk C Q1 C D Q D 20 Q2 Q3 C D Q Figure 14.31. Modified LFSR circuit