US Patent 9261561 Scan chain latch design that improves testability of integrated circuits

A scan chain latch circuit, a method of operating a latch circuit in a scan chain, and a computer-readable medium having stored thereon a data structure defining a scan chain latch circuit for instantiation on a semiconductor die are disclosed. In an embodiment, the scan chain latch circuit comprises a first latch for holding one data value, a second latch for holding another data value, and a multiplexor. The one data value is applied to a first data input of the multiplexor and the another data value is applied to a second data input of the multiplexor. An alternating clock signal is applied to a select input of the multiplexor to control the output of the multiplexor, wherein the output of the multiplexor toggles between the two data values held in the two latches at a defined frequency.