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Diagnostic Testing of Half-Duplex I/O Devices

IP.com Disclosure Number: IPCOM000062680D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Heuer, DA: AUTHOR [+2]

Abstract

This article describes an asynchronous, serial diagnostic arrangement especially suitable for testing half-duplex input/output devices coupled to a processor through an adapter interface. Peripheral devices to a computer system are usually coupled to the main processor via an adapter between the device drive interface and the system bus. Adapters have differing levels of intelligence; some adapters offer little more than read and write capability whereas others provide features such as buffering (to help separate the drive transfer rate from the system transfer rate), error retry, error correction, and multi-drive commands such as copy. Most adapters now include a microprocessor for interpreting high level system commands and controlling adapter operation.

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Diagnostic Testing of Half-Duplex I/O Devices

This article describes an asynchronous, serial diagnostic arrangement especially suitable for testing half-duplex input/output devices coupled to a processor through an adapter interface. Peripheral devices to a computer system are usually coupled to the main processor via an adapter between the device drive interface and the system bus. Adapters have differing levels of intelligence; some adapters offer little more than read and write capability whereas others provide features such as buffering (to help separate the drive transfer rate from the system transfer rate), error retry, error correction, and multi-drive commands such as copy. Most adapters now include a microprocessor for interpreting high level system commands and controlling adapter operation. Some adapters, like communications adapters, wrap the adapter output to the adapter input at the non-system interface to verify adapter operation. Hard disk and diskette adapters are half duplex devices, capable of sending data in only one direction at a time. Therefore, a wrap-around technique cannot be used in a half-duplex adapter. Because the adapter isolates the system from the drive interface, fault determination is difficult when problems develop. To determine whether the drive or the adapter is at fault, a method for verifying adapter operation is needed. The solution described in this article is to provide an additional asynchronous connection to the drive interface. This interface can be switched into the adapter in place of the drive interface. To test re...