Non-destructive sampling of internal states while operating at normal frequency

摘要

A test system for a digital integrated circuit in which internal states of the integrated circuit are captured non-destructively while the digital circuit is operating at normal clock speed. Cells for capturing states are sequentially connected into shift registers. Once internal states are latched within cells, the captured states are serially shifted out a test port while the integrated circuit continues to operate. State sampling is triggered internally via a software command or externally via an external signal synchronized to an internal clock.