Patent attributes
The invention includes a novel scan chain structure for LSSD or GSD IC operation. The scan chain structure includes a first flip-flop (L1) and a second flip-flop (L2) configured to operate the first flip-flop (L1) in normal mode operation, in scan mode operation, in initialization mode and in low leakage power mode operation, wherein each flip-flop within a long scan chain of latches includes a data input, data output, a clock input, a scan-in input and a scan-out output, arranged for normal mode operation. A buffer circuit is electrically connected between the scan-out output of the second flip-flop (L2) and the scan-in input of the first flip-flop (L1) for the next latch in the scan chain, the buffer circuit including a control element that controls the operation the first flip-flop (L1) to scan mode or low power leakage mode. The first flip-flop (L1) is set to a data output value upon exit from low power leakage mode that is the same value that it is set to at initialization during normal mode operation. The switching occurs in only one clock cycle.
