In a scannable D master-slave flip-flop circuit with synchronous preset or clear
capability, the output of the slave latch is gated with the scan-enable signal
to form the scan-data-output signal. This output gating of the scan-output data
that allows for considerable simplification of the input logic. This simplification
also provides for the reduction in both the size and the number of transistors
in the input logic. This in turn is multiplied many tens of thousands of times
in a complex processor chip, resulting in a substantial reduction in chip power
and silicon area usage.