Browse Prior Art Database

Dual-Signature Checking for Built-In Self-Test

IP.com Disclosure Number: IPCOM000099966D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Garofalo, FJ, Jr: AUTHOR [+2]

Abstract

The use of multiple signatures that allow Built-In Self-Test to run with different, but co-existing levels of the same hardware without requiring complete field update of new modules is described.

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This is the abbreviated version, containing approximately 64% of the total text.

Dual-Signature Checking for Built-In Self-Test

       The use of multiple signatures that allow Built-In
Self-Test to run with different, but co-existing levels of the same
hardware without requiring complete field update of new modules is
described.

      When a logic module is tested with BIST (Built-In Self-Test), a
signature is generated.  this generated signature is compared to the
signature for the "known good" module.  Each different type module
has a unique signature giving very high error detection.

      This unique "good" signature for each module is stored in
memory and then used for the compare when the test is run.  The
problem arises when a logic change is made to the module.  Any logic
change, no matter how small, will result in a different "good"
signature needed for the compare. When the changed logic module is
installed in the machine, the stored signature must be updated to
match the new module.  This means that earlier modules of the same
type will also have to be changed, because the new stored signature
will now not match the earlier level module already in the machine.

      Many times logic changes are such that the old level still
works, but the new level is an improvement.  There is no functional
reason why the different levels of module cannot work in the machine
at the same time.  When a module has to be replaced because of a
failure, the new level is used, but other modules of that type need
not be replaced.

     ...