WIPO logo
Mobile | Deutsch | Español | Français | 日本語 | 한국어 | Português | Русский | 中文 | العربية |
PATENTSCOPE

Search International and National Patent Collections
World Intellectual Property Organization
Search
 
Browse
 
Translate
 
Options
 
News
 
Login
 
Help
 
Machine translation
1. (WO1980001426) BUS COLLISION A VOIDANCE SYSTEM FOR DISTRIBUTED NETWORK DATA PROCESSING COMMUNICATIONS SYSTEMS
Latest bibliographic data on file with the International Bureau   

Pub. No.:    WO/1980/001426    International Application No.:    PCT/US1979/001133
Publication Date: 10.07.1980 International Filing Date: 27.12.1979
IPC:
G06F 13/376 (2006.01)
Applicants:
Inventors:
Priority Data:
973684 27.12.1978 US
Title (EN) BUS COLLISION A VOIDANCE SYSTEM FOR DISTRIBUTED NETWORK DATA PROCESSING COMMUNICATIONS SYSTEMS
(FR) SYSTEME BUS DE PREVENTION DES COLLISIONS DANS UN SYSTEME DE COMMUNICATION DE TRAITEMENT DE DONNEES DISTRIBUEES PAR RESEAU
Abstract: front page image
(EN)A transmission collision avoidance scheme for a distributed network data processing communication system including a half-duplex communication board coupled to the system bus (3). In addition to a serial data bus (120) and a clock bus (121), the system bus is configured to include a busy status line (122) that is monitored by each device connected in the system. When a device desires to send a message, it initially proceeds to busy out the busy status line, by causing a busy flag (97) to be placed on the line. It also checks the busy status line (83) in order to ascertain whether a busy nag was already set namely, whether another device has already requested service. If the bus is busy, the device cannot transmit until the bus becomes free and the requesting device resets the bus busy flag for a retry interval. Assuming that the bus is free, the transmitting device (22) proceeds to transmit. When the device for whom the message is intended receives the message, it sends an acknowledgement message back to the transmitting device, signifying a successful transmission. Because of circuit operation and propagation delays, there exists the possibility of more than one device setting a busy nag and checking the status of the bus without being aware that another device is simultaneously requesting use of the bus. In this event, a transmission collision will occur, so that the intended receivers see no sensible transmission and, consequently, return no acknowledgement messages to the collision-participating transmitters. When a transmitter fails to receive an acknowledgement message, it assumes that a collision has occured, and proceeds to repeat the above procedure for transmitting its message pursuant to a prescribed priority scheme, the higher priority device being assured of transmitting its message without a collision on the bus with a message from the lower priority device.
(FR)Systeme de prevention de collisions de transmissions pour un systeme a reseau de distribution pour le traitement de donnees comprenant un tableau de communication semi-duplex couple a un systeme bus (3). En plus d"un bus de donnees en serie (120) et d"un bus horloge (121), le systeme bus comprend une ligne d"etat d"occupation (122) qui est controlee par chaque dispositif connecte au systeme. Lorsqu"un dispositif desire transmettre un message, il procede initialement a la liberation de la ligne d"etat d"occupation, en placant un indicateur d"occupation (97) sur la ligne. Il verifie egalement la ligne d"etat d"occupation (83) afin de se rendre compte si un indicateur d"occupation a deja ete pose notamment, si un autre dispositif a deja reclame le service. Si le bus est occupe, le dispositif ne peut pas transmettre jusqu"a ce que le bus devienne libre et le dispositif demandeur replace l"indicateur d"occupation du bus pour un nouvel interval d"essai. En supposant que le bus est libre, le dispositif transmetteur (22) se met a transmettre. Lorsque le dispositif, pour lequel le message est destine, recoit le message, il renvoie un message d"accuse de reception au dispositif transmetteur, en signe de transmission reussie. A cause des temporisations dues au fonctionnement et a la propagation dans les circuits, il se peut que plus d"un dispositif mette en place un indicateur d"occupation et verifie l"etat du bus sans savoir qu"un autre dispositif demande simultanement l"utilisation du bus. Dans ce cas, une collision de transmission se produira, et les recepteurs, ne recevant pas une transmission comprehensible ne renverront pas de messages d"accuse de reception aux transmetteurs ayant participe a la collision. Lorsqu"un transmetteur n"arrive pas a recevoir en retour un message d"accuse de reception, il suppose qu"une collision s"est produite et procede a la repetition de la procedure ci-dessus pour transmettre a nouveau le message en suivant un schema de priorite prescrit, le dispositif a haute priorite etant assure de la transmission de son message sans collision sur le bus avec un message provenant d"un dispositif a priorite d"un degre inferieur.
Designated States:
Publication Language: English (EN)
Filing Language: English (EN)