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Fast Connect Input/Output Control Block Word

IP.com Disclosure Number: IPCOM000038465D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Bourke, DG: AUTHOR [+4]

Abstract

This article describes a technique for use in the input/output (I/O) subsystem of a data processing system that provides a reserved word in an I/O for exclusive use of the program that drives the I/O device. The figure illustrates a representative set of essential I/O com mand 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.

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Fast Connect Input/Output Control Block Word

This article describes a technique for use in the input/output (I/O) subsystem of a data processing system that provides a reserved word in an I/O for exclusive use of the program that drives the I/O device. The figure illustrates a representative set of essential I/O com mand 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. On receipt of the command 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 itself contains a more specific definition of the operation to be performed, such as device specific parameters, definitions of main storage areas for data and status reports, and so forth. It has a fixed length of 8 words. One word at a known relative location within the IOCB, word 0, is reserved for use of the processor programs only. This word may be read by the dev...