A microprocessor simulation method, which is built upon the underlying
hardware design of the microprocessor, stop normal functions of a
simulation testcase, start the scan clocks, and record a first "snap
shot" of the scan ring data at an initial time. The hardware logic then
rotates (shifts) the scan ring using the current scan data, and when the
scan clock stops (where the stop of the scan clock is controlled based on
the number of latches on the scan ring), another "snap shot" of scan ring
data is taken. The "snap shots" are compared and if both of the "snap
shots" are identical the functional scan is successful. But if the
functional scan verification fails to rotate the scan chain correctly,
that is, if some of the latches do not match in the two "snap shots," it
becomes necessary to locate the broken spot within the large number of
scan latches.