Browse Prior Art Database

Channel for Data Processing System

IP.com Disclosure Number: IPCOM000050345D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Cormier, RL: AUTHOR [+2]

Abstract

Various systems exist for controlling the transfer of messages between a channel of a processor and an I/O device. For example, in the IBM System/370 a message from a controller to a channel is in fact initiated by the channel: the channel first commands the device controller to transmit a status byte to the channel, and it subsequently commands the controller to transmit its message. As another example, in a system called SDLC (Synchronous Data Link Control), one station can transmit a Receive Ready signal to a second station and thereafter the second station can transmit its message without further control.

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Channel for Data Processing System

Various systems exist for controlling the transfer of messages between a channel of a processor and an I/O device. For example, in the IBM System/370 a message from a controller to a channel is in fact initiated by the channel: the channel first commands the device controller to transmit a status byte to the channel, and it subsequently commands the controller to transmit its message. As another example, in a system called SDLC (Synchronous Data Link Control), one station can transmit a Receive Ready signal to a second station and thereafter the second station can transmit its message without further control.

This I/O system provides two signals, Ready to Receive and Ready to Send, that can be used with either of the systems described in the preceding paragraph. A control byte has two bit positions that are set to 10 or 11 to designate one of these signals. A controller that would otherwise use the Receive Ready signal with its attached devices can similarly use the Ready to Receive signal in communication with a channel. A controller for devices that require commands for transmitting a message can similarly communicate with the channel by using the Ready to Send signal.

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