Unisys Corporation

Jeff A Engel

Larry L Byers

Gerald J Maciona

Donald W Mackenthun

Ferris T Price, Deceased

Joseph G Kriscunas

Aaron C Peterson

Dale K Seppa

Philip J Fye

An apparatus for efficiently testing a plurality of memory devices at the board level. The logic for the present invention is minimal and can be placed on a controller chip within the board design. In addition, the interconnect lines between the controller chip and each of the plurality of memory devices can also be tested. Finally, the present invention requires minimal setup time and performs a functional test of the memories in a very short period of time.

Built-in-self-test scheme for testing multiple memory elements

A method for comprehensively testing embedded RAM devices and a means for detecting if any of the cells within the embedded RAM devices have a slow write recovery time. The preferred mode of the present invention utilizes built-in self-test (BIST) techniques for testing the embedded RAM's within a VLSI device. In accordance with the present invention, a modified 5N march test sequence is performed on the embedded RAM devices. The modified 5N March test sequence is a simple algorithm implemented in programmable hardware that has the capability of ensuring that the embedded RAM devices are functional and that they meet the recovery time requirements. The preferred mode of the present invention uses this algorithm to determine if the embedded RAMs are operating properly before the VLSI devices are used in card assembly. However, this method can also be used after card assembly to monitor the embedded RAM's integrity.

VLSI embedded RAM test

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Chisago City, MN, United States of America

Jeff A Engel