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Module in Place Isolation Technique using Analog to Digital Converters

IP.com Disclosure Number: IPCOM000051341D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Zobniw, LM: AUTHOR

Abstract

The increased use of microprocessors from widely divergent sources, large arrays and other complex VLSI (very large-scale integration) modules on cards and the accelerated rate at which such products are introduced have led designers to select "divide and conquer" test strategies, such as Module-In-Place Testing (MIPT). MIPT uses the original "module" test patterns during the printed circuit board (PCB) test. MIPT also allows regions which consist of one or more modules or a portion of a module. This test method requires that the modules contain additional control (enable/inhibit) circuitry that will inhibit (place in high impedance state) or enable all "module/ region" output drivers. Pull-up/pull-down resistors enable the isolation control circuitry when the card is used functionally from the edge connectors.

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Module in Place Isolation Technique using Analog to Digital Converters

The increased use of microprocessors from widely divergent sources, large arrays and other complex VLSI (very large-scale integration) modules on cards and the accelerated rate at which such products are introduced have led designers to select "divide and conquer" test strategies, such as Module-In-Place Testing (MIPT). MIPT uses the original "module" test patterns during the printed circuit board (PCB) test. MIPT also allows regions which consist of one or more modules or a portion of a module. This test method requires that the modules contain additional control (enable/inhibit) circuitry that will inhibit (place in high impedance state) or enable all "module/ region" output drivers. Pull-up/pull-down resistors enable the isolation control circuitry when the card is used functionally from the edge connectors. During MIPT testing, the tester internal test points (ITPs) control (inhibit or enable) the isolation logic. The key advantage of MIPT is that this test strategy minimizes the test generation and fault simulation costs in creating card test data.

A disadvantage of MIPT is that it may require more ITPs than are available on the tester. This analog/digital isolation technique does not require as many ITPs to control the inhibit/enable circuitry, but it does require that the designer add an isolation module to the PCB. The analog-to-digital converter (A/D) converts analog (multi-value) signals to digital (binary) values. In other words, one analog physical net can control many physical nets that propagate binary signals. Therefore, one physical net can control (enable/inhibit) many logical modules.

Fig. 1 illustrates the concept. The isolation module consists of an analog input pin that is connected to the PCB edge-connector, digital output pins that are connected to a module (inhibit...