Browse Prior Art Database

Real Time Feature on Standard I/O Channels

IP.com Disclosure Number: IPCOM000079455D
Original Publication Date: 1973-Jul-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 65K

Publishing Venue

IBM

Related People

Mitchell, MJ: AUTHOR

Abstract

A method is provided for converting a standard I/O (input/output) channel to a real-time channel, that can be used by an Operating System to selectively prioritize and to selectively accept interruptions from many devices. With this channel extension, programming can attain a high measure of "responsiveness" in communicating with an externally attached device.

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Real Time Feature on Standard I/O Channels

A method is provided for converting a standard I/O (input/output) channel to a real-time channel, that can be used by an Operating System to selectively prioritize and to selectively accept interruptions from many devices. With this channel extension, programming can attain a high measure of "responsiveness" in communicating with an externally attached device.

By way of example, the method will be described in conjunction with standard S/370 (IBM System 370) channels. The feature requires the addition of an interruption register in which each position is assigned a level number 0, 1, 2, ... n, where the smallest level number represents the highest priority. A program controlled mask register is provided where each position controls the corresponding position in the interruption register. The External Interruption Class is extended to include the new interruption register. Channel program execution over the standard I/O interface remains unchanged. Channel changes are made in the instruction interpretation at the instruction beginning and in the device status handling or instruction ending. The feature would function as follows: 1) At instruction time for a device, the program (user) specifies

the interruption level which that device will use for any

subsequent interruptions. The level number is recorded in the

Unit Control Word (UCW) for that device. 2) The channel program execution proceeds exactly according to S360/370 I/O Architecture. 3) When the ending status condition is noted on the interface,

the status is accepted and stored in the UCW for that...