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Browse Prior Art Database

Cylindrical Scan Path Test Method

IP.com Disclosure Number: IPCOM000118020D
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 119K

Publishing Venue

IBM

Related People

Okazawa, J: AUTHOR

Abstract

Disclosed is a circuit for "Cylindrical Scan Path Test Method". This circuit makes high fault coverage of Large Scaled Integration (LSI) tests using a scan path test method with fewer controllable input or observable output pins than the current method. This method can be applied not only to the LSI chip test but also to the macro test which is a portion of the LSI chip.

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Cylindrical Scan Path Test Method

      Disclosed is a circuit for "Cylindrical Scan Path Test
Method".  This circuit makes high fault coverage of Large Scaled
Integration (LSI) tests using a scan path test method with fewer
controllable input or observable output pins than the current
method.  This method can be applied not only to the LSI chip test but
also to the macro test which is a portion of the LSI chip.

      Fig. 1 shows the concept of the current scan path test
method, and Fig. 2 shows the concept of the cylindrical scan path
test method.  In Fig. 2, the output signals from the internal
circuit-D are connected with the input signals to the internal
circuit-A through the test circuit.  This test circuit should select
the source of the input signals to the internal circuit-A from the
Input/Output (I/O) and the output signals from the internal circuit-D
and have one signal pin, named TMD_, which selects the test mode or
the normal function mode.  Fig. 3 shows examples of the simple test
circuit cell.  The test circuit consists of these circuit cells.

      Using the current test method, it needs many controllable pins
to test the circuit-A; it also needs many observable output pins to
test the circuit-D.  On the other hand, using this method, by
controlling scan  path-A and scan path-B, it is possible to test both
circuit-A and circuit-D.

      Using this method, only to control scan-in signal pins and only
to observe scan-out signal pins,...