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A Communications Controller Command Set

IP.com Disclosure Number: IPCOM000076031D
Original Publication Date: 1971-Dec-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Rommelfanger, AC: AUTHOR

Abstract

This article presents a set of commands for a communications controller (CC) to accomplish these objectives: 1) To make it possible for the Host Central Processing Unit (CPU) to communicate with a terminal, without the need to know if the terminal is on a switched or a nonswitched line. 2) To make it possible to simultaneously support interactive exchanges and message switching in the same network. 3) To be able to accomplish both of the above objectives when the CC is connected to multiple channels not necessarily attached to the same CPU and without allocating individual terminals or lines to each channel on a static basis.

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A Communications Controller Command Set

This article presents a set of commands for a communications controller (CC) to accomplish these objectives: 1) To make it possible for the Host Central Processing

Unit (CPU) to communicate with a terminal, without the

need to know if the terminal is on a switched or a

nonswitched line.

2) To make it possible to simultaneously support interactive

exchanges and message switching in the same network.

3) To be able to accomplish both of the above objectives

when the CC is connected to multiple channels not

necessarily attached to the same CPU and without

allocating individual terminals or lines to each channel

on a static basis.

The Command set presented is structured without line-type dependencies. That is, the commands always result in the same logical function, even though the physical operations are unique to a particular line or terminal type.

The command set used is: Symbol Name Meaning Session Establishing Commands

I Invite Allows the terminal to start

a session by sending data to

the host CPU.

C Contact Starts a session by making it

possible for the host CPU to

send data to the terminal.

Session Terminating Commands

D Disconnect Terminates the current session

and breaks the current

physical.

Data Transfer Commands

W Write Transfers a block of data from

the host CPU to the terminal.

R Read Transfers a unit of data from

the terminal to the host CPU.

Data Transfer Control Commands

X Reset Stops the current operation

and empties the queues.

Session Definition.

A session is a sequence of command and data interchanges between the CPU and a terminal.

A session can be started in either of two ways: Contact The CPU can start a session, when it has data to send to a terminal, by issuing a Contact command. In

this case, the session is started when the CC

successfully executes the Contact command.

Invite The CPU can allow a terminal to start a session by

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issuing an Invite command. For polled terminals,

the CC will periodically attempt to establish a

session by polling the terminal. For other terminals,

it will monitor the line for the start of data

transfer. The session is started when the terminal

responds positively to polling or starts data

transmission.

A session is always concluded with a Disconnect command. The CC plays a role in the session by insuring that no data is transferred to the terminal, other than that within a session.

With one exception, session initiating commands must always be sent to the CC in the following sequence: Contact or Invite, Data Transfer commands, Disconnect.

The exception to this sequence is the Invite command followed by a Contact command. If the Invite command has not established a session wh...