Browse Prior Art Database

Loop Polling Method

IP.com Disclosure Number: IPCOM000082673D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Donnan, RA: AUTHOR

Abstract

Described is an improvement in the operation of loop polling described in U.S. Patent 3,752,932 which is particularly useful in lightly loaded loops driven by programmed control units, which may be dedicated to performing other functions along with operating the loop.

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Loop Polling Method

Described is an improvement in the operation of loop polling described in U.S. Patent 3,752,932 which is particularly useful in lightly loaded loops driven by programmed control units, which may be dedicated to performing other functions along with operating the loop.

According to the above patent, a loop polling operation is preceded by the issuance of a command to all of the terminals on the loop, which enables the terminals to respond to seven contiguous 1 bits. Any of the terminals after being reset by the command detecting seven continuous 1 bits may seize the loop on one occasion and transmit a message. After all the terminals have transmitted a message, the central control station reissues the command and transmits a continuous stream of 1 bits and receives data from the terminals on the loop. This process is repetitive and continues.

In a lightly loaded situation, the control unit would issue the command and receive an uninterrupted stream of 1 bits, if none of the terminals on the loop has data to transmit. This would require the issuance of the command again. In the lightly loaded situation, the control unit could spend a considerable amount of its processing capability issuing the command, monitoring the line and reissuing the command.

The necessity for reissuing the command for enabling the terminals may be eliminated by issuing a second command, Enable Interrupt (ENI) following the issuance of a first command and no data from the...