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Method for isolated probing for multidrop SCSI bus

IP.com Disclosure Number: IPCOM000011839D
Publication Date: 2003-Mar-19
Document File: 5 page(s) / 105K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for the isolated probing for a multidrop SCSI bus. Benefits include improved reliability, improved test fixture design flexibility, and an improved test environment.

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Method for isolated probing for multidrop SCSI bus

Disclosed is a method for the isolated probing for a multidrop SCSI bus. Benefits include improved reliability, improved test fixture design flexibility, and an improved test environment.

Background

      Traditionally a probing solution called interposer is used as a probing solution for multidrop SCSI bus probing. Stubs are introduced by the interposer during multidrop SCSI bus probing. They lead to signal integrity issues on the SCSI bus during functional test. Conventionally, two ways exist to reduce the use of stubs. An interposer card that has a very short trace length can be implemented. Alternatively, SCSI drives can be directly plugged into the connector without an interposer.

      The trace length used on the conventional interposer is already at its minimum. The length cannot be reduced due to physical limitation, such as a connector’s placement and interposer mounting location. If the SCSI drives are plugged directly into the SCSI enclosure board, the drive’s connector wears out and results in higher maintenance costs for the test drives. The test fixture’s design flexibility is limited because the SCSI drive must be directly connected to the board under test, cramming the drives into a very limited space inside the test fixture. Additionally, the signal integrity of the bus has been significantly affected as the speed of the signals propagating through the bus continues to increase.

General description

              The disclosed method is isolated probing for a multidrop SCSI bus. Integrating signal isolation circuitry inside the interposer card is used for multidrop SCSI bus probing during functional test. The circuitry (chip) expands the SCSI bus length over the maximum limit designated in the specification.

      The disclosed chip samples the signal from the first SCSI bus segment and regenerates it on another SCSI bus segment, extending the total length of the bus. The first and second segments of the SCSI bus each remain within the specification’s designated limits.

      The disclosed method integrates this functionality into the probing solution of the multidrop SCSI bus. The interposer samples the signal from the enclosure board connector and regenerates it on another SCSI bus segment between the interposer and the drives.

              The key elements of the disclosed method include:

•             Interposer probing solution with integrated signal isolation circuitry that isolates the SCSI bus segment on the interposer from the main SCSI bus on the enclosure board

•             Reduction of the stub that is introduced into the SCSI bus by the interposer

Advantages

              The disclosed method provides advantages, including:

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