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HARDWARE SHORT CIRCUIT FINDER THROUGH SOFTWARE

IP.com Disclosure Number: IPCOM000008649D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jul-01
Document File: 3 page(s) / 130K

Publishing Venue

Motorola

Related People

T. Murugappan: AUTHOR

Abstract

Conventional methods of finding short circuits while developing and testing hardware is typically done by injecting current to locate the shol-1 circuits. However. such conventional methods are expensive. A more cost effective and efticient way of finding short circuits is by using software. A software method is herein proposed to find short circuits in digital hardware such as controller hardware based on 68HCl I which typically has a microprocessor and various memories. In this method, a logic sequence is used to find such short circuits which can occur between Vcc, Address lines, Data lines or Ground. This method can run from an emulator or a test system 2. SOLUTION This method finds short circuits by writing specific patterns and reading the data back from the memory of a target board in which testing is required. By comparing written and read data, the method can find between which lines the short circuit is located. Details ofthis method is discussed below.

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HARDWARE SHORT CIRCUIT FINDER THROUGH SOFTWARE

by T. Murugappan

1. BACKGROUND OF THE PROBLEM

  Conventional methods of finding short circuits while developing and testing hardware is typically done by injecting current to locate the shol-1 circuits. However. such conventional methods are expensive. A more cost effective and efticient way of finding short circuits is by using software. A software method is herein proposed to find short circuits in digital hardware such as controller hardware based on 68HCl I which typically has a microprocessor and various memories. In this method, a logic sequence is used to find such short circuits which can occur between Vcc, Address lines, Data lines or Ground. This method can run from an emulator or a test system

2. SOLUTION

  This method finds short circuits by writing specific patterns and reading the data back from the memory of a target board in which testing is required. By comparing written and read data, the method can find between which lines the short circuit is located. Details ofthis method is discussed below.

3. SYSTEM SETUP

  Figure I illustrates a Short Circuit Finder (SCF) system. The ROM or EPROM in this system stores the code for the method of finding short circuits. When internal memory is accessed external buses arc put in high impedance automatically.

Short Circuit Finder System

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Fig. 1 Short Circluit Finder System Setup

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MOTOROLA Technicul Drvelopments

3.2 SHORT BETWEEN DATA LINES AND GROUND

  Write 'FF' in any location in the target memory and read it back. If the read value is not 'FF', then there is a short between a data line and ground. If the read value is 'FE' (111 I I I IO), then the short is between DO and ground.

3.3 SHORT BETWEEN DATA LINES AND VCC

  Write '00' in any location and read it back. If the read value is not 'OO', then there is a short between a data line and Vcc. If the read value is, say, '08 (0000 IOOO)', the short is between D3 and vcc.

3.4 SHORT BETWEEN DATA LINES

  Write '01' in any location and read it back. If the read value is, for example '2 I (0010 OOOI)', then there is a short between DO and D5. Write values '02', '04', '08' etc., and read them back to uncover shorts between other data lines.

3.5 SHORT BETWEEN ADDRESS LINES AND VCCfGROUND

  Write a value say '55' (or any other value) at location $00 and some other value at $02. Read the values at locations $00, $01, $02 & $03. If the values are the same at locations $00 and $01 and similarly if the values are the same at $02 and $03, then...