An apparatus comprising a circuit configured to be tested and a plurality
of test blocks within the circuit. Each of the test blocks generally
comprises (i) a plurality of sequential elements and (ii) a plurality of
logic elements. Each of the test blocks are configured to operate (a) in
a first mode comprising a shift mode and (b) a second mode comprising a
capture mode. The shift mode generally operates with multiple scan clocks
that are clocked simultaneously. The capture mode generally operates with
multiple scan clocks, but only one of which is toggled at a time.