The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 04, 2001
Filed:
Mar. 26, 1999
Dilip K. Bhavsar, Shrewsbury, MA (US);
Compaq Computer Corporation, Houston, TX (US);
Abstract
A method and apparatus for built in self test, BIST, of content addressable memory, CAM, and associated random access memory, RAM, is described. The method and apparatus may most beneficially be used for difficult to test situations such as embedded CAM or other memory types. There are no external memory read operations to determine the contents of a memory location, so little additional circuitry or overhead, such as separate read ports, is required on the embedded memory for implementation of the BIST. Only a number generator, a shift register and an OR gate with inputs from each of the CAM word match lines are added to the circuit in which the memory is embedded. The test uses a set of unique data patterns, each one spaced from the others by two bit locations, a walking inversion test, and a complement and reverse pattern test to determine what type of error and the error location. With such a system the testing of embedded CAM or other memory types such as RAM and FIFO is simplified, and the test fault coverage is improved.