Masking circuit removing unknown bit from cell in scan chain

摘要

Electronic scan circuitry includes a decompressor (510), a plurality of scan chains (520.i) fed by the decompressor (510), a scan circuit (502, 504) coupled to the plurality of scan chains (520.i) to scan them in and out, a masking circuit (590) fed by the scan chains (520.i), and a scannable masking qualification circuit (550, 560, 580) coupled to the masking circuit (590), the masking qualification circuit (550, 560, 580) scannable by scan-in of bits by the decompressor (510) along with scan-in of the scan chains (520.i), and the scannable masking qualification circuit (550, 560, 580) operable to hold such scanned-in bits upon scan-out of the scan chains through the masking circuit (590). Other scan circuitry, processes, circuits, devices and systems are also disclosed.

主权项

1. Electronic scan circuitry comprising:
a decompressor; a plurality of scan chains fed by the decompressor; a scan circuit coupled to the plurality of scan chains to scan them in and out; a masking circuit fed by the scan chains; a scannable masking qualification circuit coupled to the masking circuit, the masking qualification circuit scannable by scan-in of scan chain cell qualifying bits by the decompressor along with scan-in of the scan chains, and the scannable masking qualification circuit operable to hold such scanned-in scan chain cell qualifying bits upon scan-out of the scan chains through the masking circuit; and the masking circuit is, in response to the scan chain cell qualifying bits, for removing an unknown bit from a single cell in a single scan chain in the plurality of scan chains.