Browse Prior Art Database

Avoiding Nonfunctional Faults During Microchip Self Test

IP.com Disclosure Number: IPCOM000108425D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Clark, SD: AUTHOR [+3]

Abstract

A simple yet effective way to prevent nonfunctional logic paths through growable register arrays (GRAs) from being tested during microchip self-test functions is disclosed. It is assumed that the reader is familiar with microchip self-test and data writethrough in GRAs.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Avoiding Nonfunctional Faults During Microchip Self Test

      A simple yet effective way to prevent nonfunctional logic paths
through growable register arrays (GRAs) from being tested during
microchip self-test functions is disclosed. It is assumed that the
reader is familiar with microchip self-test and data writethrough in
GRAs.

      When built-in self-test randomizes the read and write address
registers to the same address, a write-through condition occurs.  The
approach in preventing write-through from ever occurring was to
always assure that both read and write addresses are never equal when
the chip is in self-test (see Fig. 1 for details of the logic
implementation).  The least significant bit of the read address is
compared to the least significant bit of the write address.  The
comparison circuit is simply an XOR and inverter.  If the two are the
same and the chip is in self-test (designated by the IN_SELF_TEST
signal being high), the least significant bit of the write address is
inverted so it is opposite of the least significant bit of the read
address.

      The write address line was chosen because it was not as timing
critical as the read address line.  Only one line of each address
register is required.  This will not have any impact on the self-test
coverage.  The large number of patterns that are generated by
self-test assures that complete coverage of the paths to and from the
GRAs are obtained.

      Disclosed anonymously.