METHOD AND APPARATUS FOR SHIFTING AT-SPEED SCAN PATTERNS IN A SCAN-BASED INTEGRATED CIRCUIT

摘要

A method and apparatus for time-division demultiplexing and decompressing a compressed input stimulus (421), provided at a selected data-rate R1 (421), into a decompressed stimulus (424, 426, 433, 435), driven at a selected data-rate R2 (442), for driving selected scan chains in a scan-based integrated circuit (401). The scan-based integrated circuit (401) contains a high-speed clock CK1 (443), a low-speed clock CK2 (442), a plurality of scan chains (411), ..., (418), each scan chain comprising multiple scan cells coupled in series. The method and apparatus comprises using a plurality of time-division demultiplexors (TDDMs) (402, 403) and time-division multiplexors (TDMs) (408, 409) for shifting stimuli (421) and test responses (444) in and out of high-speed I/O pads. When applied to the scan-based integrated circuit (401) embedded with one or more pairs of decompressors (404, 405) and compressors (406-407), it can further reduce the circuit's test time, test cost, and scan pin count. A synthesis method is also proposed for synthesizing the time-division demultiplexors (TDDMs) (402, 403), decompressors (404, 405), compressors (406, 407), and time-division multiplexors (TDMs) (408, 409).