James D Mcgee

US Patent:

6615377, Sep 2, 2003

Filed:

May 8, 2000

Appl. No.:

09/566367

Inventors:

Victor L. da Cruz - Rochester NY
James R. McGee - San Jose CA

Assignee:

Hewlett-Packard Development Company, L.P. - Houston TX

International Classification:

G01R 3128

US Classification:

714724

Abstract:

An integrated circuit with enhanced testability provides a normal-operation mode of operation with an observability function matching that used in a test-drive mode. Specifically, in both normal-operation mode and test-drive mode, captured signal vectors from captured-signal nodes are stored in a signal-vector queue. Thus, the local storage of signal vectors during test-drive mode does not represent a deviation from normal operation that could otherwise impair test validity. Moreover, since captured-signal vectors are stored during normal-operation mode, they are available for readout when normal operation is halted. These captured-normal-signal vectors reflect normal operation without any distortion due to testingâso data validity is optimal. Drive-signal vectors can be stored in the queue, which can be a dual-ported RAM, during a test-setup mode, and readout to driven-signal nodes in test-drive mode. Compression can be implemented by not incrementing the queue write pointer when a signal matches its immediate predecessor.