ICS580-01

The ICS580-01 is a clock multiplexer (mux)  designed to switch between 2 clock sources with no glitches or short pulses.  The operation of the mux  controlled by an input pin but the part can also be  configured to switch automatically if one of the  input clocks stops.  The part also provides clock  detection by reporting when an input clock has  stopped.

For a clock mux with zero delay and smooth  switching, see either the ICS580-01.