can operate at 80 mhz and 160 mhz but the scan chains can only operate at 10 mhz by using an ate automatic test equipment the system 100 includes an ate 101 and a circuit under test cut 102 the cut 102 contains two clock domains cd 1 103 and cd 2 104 as well as a crossing clock domain ccd 105 scan cells in cd 1 103 are connected into scan chains 106 107 the i o pads for these scan chains can operate at 80 mhz while the scan chains can only operate at 10 mhz in addition scan cells in cd 2 104 are connected into scan chains 108 109 the i o pads for these scan chains can operate at 160 mhz while the scan chains can only operate at 10 mhz in general since i o pads are designed for use in functional mode they can operate at very high frequencies ranging from a few hundred mhz to a few ghz on the other hand since scan chains are used in test mode they usually only operate at much lower frequencies ranging from 10 mhz to 100 mhz this is because operating scan chains at high frequencies not only has huge design impact but also may damage a chip due to too much peak power consumption during test during test the ate 101 applies test stimuli stimuli 1 121 and stimuli 2 122 to their respective scan chains 106 107 and 108 109 of the cut 102 via the i o pads connected to the scan based integrated circuit first a shift operation is conducted when.