Browse Prior Art Database

Hardware Generated Signature Analysis Trace Diagnosis

IP.com Disclosure Number: IPCOM000048127D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 3 page(s) / 57K

Publishing Venue

IBM

Related People

Zobniw, LM: AUTHOR

Abstract

Self stimulating Signature Analysis (SA) is tailored to test and to diagnose printed circuit boards (PCBs) which include functional elements such as microprocessors and microprocessor support devices. There is available literature that describes Signature Analysis (SA) and provides designer guidelines. Generally, the Signature Analyzer compresses a string of response values (logic 1, 0) into a signature, a distinct 16 bit number usually written in hexadecimal form. The traditional SA guidelines require that the feedback loops be opened, electrically or physically, during the SA analysis.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 3

Hardware Generated Signature Analysis Trace Diagnosis

Self stimulating Signature Analysis (SA) is tailored to test and to diagnose printed circuit boards (PCBs) which include functional elements such as microprocessors and microprocessor support devices. There is available literature that describes Signature Analysis (SA) and provides designer guidelines. Generally, the Signature Analyzer compresses a string of response values (logic 1, 0) into a signature, a distinct 16 bit number usually written in hexadecimal form. The traditional SA guidelines require that the feedback loops be opened, electrically or physically, during the SA analysis.

The preceding article describes an SA approach for production testing that does not require physical loop breaking. This PSA testing approach illustrates how to create and use the additional knowledge of when in the test sequence the net failed to isolate a fault along the failing loop, thereby relaxing or eliminating the SA requirement to break SA loops. The PSA required SA Trace data which provides the intermediate signatures (per net per test cycle). The SA Trace used to identify "when" in the test sequence a net failed.

This Hardware Generated Signature Analysis Trace (HGSAT) does not require SA Trace tables, but instead uses a tester "golden" (known to be good) card to create the SA Trace at real time during the diagnostic procedure.

The HGSAT tester consists of three subsystem: Control Unit, tester "golden" card portion 6, and the DUT (device under test) portion 7 with the "golden" card and DUT portions being held in a test fixture 8:

1. The Control Unit loads the needed test data (from disk), card is good and determines whether the DWT is good; if DUT fails, then the Control Unit executes the diagnositic routines; and finally it identifies the terminal net(s). The control unit can be a host computer or implemented microcode (consisting of a microprocessor, ROM (read-only memory), and RAM (random access memory)). The ROM contains the microcode routines to initiate the testing and to diagnose the DUT. The RAM is used to store the test data consisting of the PASS/FAIL signature per net and the net dependency data which identifies the input nets that control the dependent net. If the dependent net has a bad signature, but the dependent net's input nets are good, then the failing dependent net is called the terminal net. The control unit initiates the SA test as often as required to identify the terminal net or until the "range" (of test cycles) has been reduced to null set. A bisect technique is used to reduce the "range", whose limits are the highest test cycle at which the DUT tested good and the lowest test cycle at which the DUT failed.

2. The control unit loads into the Termination Test Cycle (TTC) register the test cycle at which the tester is to capture the signature for both the golden car...