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Browse Prior Art Database

Universal Mechanism for Model-Independent I/O-Device Operations

IP.com Disclosure Number: IPCOM000101991D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 42K

Publishing Venue

IBM

Related People

Hefferon, EP: AUTHOR

Abstract

Disclosed is a mechanism that allows programs to invoke an identical operation on different I/O devices using different I/O command codes while maintaining I/O-device independence.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 75% of the total text.

Universal Mechanism for Model-Independent I/O-Device Operations

       Disclosed is a mechanism that allows programs to invoke
an identical operation on different I/O devices using different I/O
command codes while maintaining I/O-device independence.

      Currently, the sense-ID command is implemented on all IBM I/O
devices using the same I/O command code.  By extending the data that
is returned for the sense-ID command from a maximum of 7 bytes to a
maximum of 256 bytes, it is possible for every I/O device to provide,
in a common way, a list of the I/O command codes that it uses for
operations that are common across all I/O devices.

      By obtaining a list of I/O command codes from every I/O device
in the configuration, the program is able to invoke a particular
operation on every I/O device that provides that operation by using
the I/O command code associated with that operation for each I/O
device.

      The extended sense-ID data consists of a series of 4-byte
fields called command-information words (CIWs).  Each
command-information word describes a command that can cause the I/O
device to perform a specific operation.
      A command-information word has the following format:
      Entry Type (ET):  Bits 0 and 1 of byte 0 are zero and
      one, respectively.
      R:  Bits 2-3 of byte 0 are reserved.

      Command Type (CT):  Bits 4-7 of byte zero contain a code that
specifies the I/O-device-independent operation t...