	US 7,590,905 B2
	Method and apparatus for pipelined scan compression
Khader S. Abdel-Hafez, San Francisco, Calif. (US); Laung-Terng (L.-T.) Wang, Sunnyvale, Calif. (US); Boryau (Jack) Sheu, San Jose, Calif. (US); and Shianling Wu, Princeton Junction, N.J. (US)
Assigned to Syntest Technologies, Inc., Sunnyvale, Calif. (US)
Filed on May 05, 2005, as Appl. No. 11/122,244.
Claims priority of provisional application 60/573341, filed on May 24, 2004.
Prior Publication US 2006/0064614 A1, Mar. 23, 2006
This patent is subject to a terminal disclaimer.
Int. Cl. G01R 31/3177 (2006.01); G01R 31/40 (2006.01)

U.S. Cl. 714—726 [714/729; 714/733]

40 Claims

1. A method for broadcasting compressed scan data patterns driven through N scan chains into decompressed scan data patterns stored in M scan chains, where N<M, using a decompressor, in a scan-based integrated circuit, in a selected scan-test mode or selected self-test mode, the scan-based integrated circuit containing one or more scan chains, each scan chain comprising one or more scan cells coupled in series, one of said scan cells having an output coupled exclusively to the decompressor, the decompressor being a combinational logic network whose inputs are directly taken from N or more selected scan cell outputs of all scan cells in the N scan chains and whose outputs directly drive the M scan chains; said method comprising:

(a) shifting in said decompressed scan data patterns to all said scan cells in said scan-based integrated circuit by broadcasting said compressed scan data patterns driven through said N scan chains into said decompressed scan data patterns stored in said M scan chains using said decompressor during a shift-in operation;

(b) capturing a scan data response to all said scan cells during a selected capture operation; and