An apparatus comprising a plurality of flip-flops each comprising (i) a first
input, (ii) a second input and (iii) an output, where (a) each of the outputs are
coupled to the first input of a subsequent flip-flop to form a chain, (b) the first
input of a first of the flip-flops receives a pattern signal, (c) each of the second
inputs receives a respective first logic signal, and (d) each of the outputs presents
a respective second logic signal in response to the signals received at the first
and second inputs, a pattern generator configured to generate the pattern signal,
and a checking circuit configured to generate a check signal in response to the
second logic signal of a last of the flip-flops. The pattern signal and the first
logic signals are generally selected to influence a behavior of the apparatus.
