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Channel With Test for Valid but Anomalous Status

IP.com Disclosure Number: IPCOM000065403D
Original Publication Date: 1985-Dec-01
Included in the Prior Art Database: 2005-Feb-19

Publishing Venue

IBM

Related People

Authors:
Cormier, RL Lydon, MJ Lynch, KR [+details]

Abstract

In some channel error conditions, it is possible for a data channel to receive a valid but anomalous device status byte. As an example, a status byte of all zeros signifies a normal operation during initial selection, but in other situations a status byte of all zeros would appear only as a result of a control unit error. As another example, a status byte having channel end without device end signifies a normal operation during command chaining but can be recognized as an error when presented at other times. Conventionally, some of these errors are detected and handled by the general error-handling components of the system. To detect these errors, device status bytes when presented are interpreted by the channel in the context of the state of the device and the operation. The status handler can be implemented in various ways.