Browse Prior Art Database

Half Duplex Synchronous Line Control

IP.com Disclosure Number: IPCOM000074565D
Original Publication Date: 1971-May-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Pung, BD: AUTHOR

Abstract

This half-duplex line control allows the attachment of displays 10, through display control units 12, to a full duplex high-speed backbone circuit 14 of the SABRE Airlines Reservation System. The half-duplex line control is made compatible with the full-duplex backbone circuit by isolating the backbone circuit with a remote concentrator 16 capable of operating a number of branch circuits 18 with a number of display control units (DCU) 12 attached to each branch circuit. The remote concentrator looks like a display terminal interchange (DTI) 20 to the backbone circuit.

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Half Duplex Synchronous Line Control

This half-duplex line control allows the attachment of displays 10, through display control units 12, to a full duplex high-speed backbone circuit 14 of the SABRE Airlines Reservation System. The half-duplex line control is made compatible with the full-duplex backbone circuit by isolating the backbone circuit with a remote concentrator 16 capable of operating a number of branch circuits 18 with a number of display control units (DCU) 12 attached to each branch circuit. The remote concentrator looks like a display terminal interchange (DTI) 20 to the backbone circuit.

The operator at the display readies a message for input by depressing an enter key. When the branch circuit to which the DCU is attached is direct polled by the remote concentrator 16, the DCU responds with a positive reply. The remote concentrator receives the positive reply, stops polling that branch circuit and stores the DCU device address in an address queue at the remote concentrator. There is sn address queue for each branch circuit. Polling continues on the remaining branch circuits until a positive reply is received on each of them.

When the remote concentrator is polled on the backbone circuit, all messages in the address queues for the branch circuits are requested by the remote concentrator in order. The transfer rate on the backbone and the branch circuits are the same, since no message buffering is provided by the remote concentrator.

Two data byte registers are provided for the transmit and receive data paths to compensate for bit synchronizati...