The operating procedure of the scan circuitry is as follows:

1. Enable the scan operation to allow shifting (to initialize scan cells).

2. After loading the scan cells, hold the scan clocks off and then apply stimulus to the primary inputs.

3. Measure the outputs.
4. Pulse the clock to capture new values into scan cells.
5. Enable the scan operation to unload and measure the captured values while simultaneously loading in new values via the shifting procedure (as in step 1).