Browse Prior Art Database

Input/Output Control Block Indirect Device Control Parameter Mechanism

IP.com Disclosure Number: IPCOM000038467D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Bourke, DG: AUTHOR [+3]

Abstract

This article describes a technique for use in the input/output (I/O) subsystem of a data processing system which eliminates device dependencies in an I/O control block. The drawing illustrates a representative set of essential I/O command parameters for starting an I/O operation. The sizes of fields chosen for the illustration are arbitrary. The parameters are: .The command byte; The I/O address, showing a field for specifying up to four main; I/O busses which may be attached to a processor, and a field for specifying the address of the target device. A storage address, pointing to an I/O control block (IOCB) in the; main storage of the processor. These parameters are passed to the specified device on the appropriate I/O bus, and are called the immediate command parameters (ICPs).

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Input/Output Control Block Indirect Device Control Parameter Mechanism

This article describes a technique for use in the input/output (I/O) subsystem of a data processing system which eliminates device dependencies in an I/O control block. The drawing illustrates a representative set of essential I/O command parameters for starting an I/O operation. The sizes of fields chosen for the illustration are arbitrary. The parameters are: .The command byte; The I/O address, showing a field for specifying up

to four main; I/O busses which may be attached to a

processor, and a field for specifying the address of

the target device.

A storage address, pointing to an I/O control

block (IOCB) in the; main storage of the processor. These parameters are passed to the specified device on the appropriate I/O bus, and are called the immediate command parameters (ICPs). On receipt of the ICP by the device, the processor disconnects and the device proceeds in a manner asynchronous to the processor, fetching the IOCB and carrying out the operation. When the operation is complete, the device reconnects to the processor program by means of an end interrupt. The IOCB is located in main storage of the processor and specifies the asynchronous part of the I/O operation.

It contains more specific definitions of the operation to be performed, such as definitions of main storage areas for data and status reports, and so forth. It has a fixed length of 8 words and is read-only by the device. Th...