# US 5,706,430 A · Method and system for sequentially broadcasting data according to pre-assigned time slots with and without the reception of a synchronization packet

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- Number: US 5,706,430 A
- Document ID: US5706430A
- Status: Granted
- Kind: A
- Application number: 08/355,682
- Filed: 1994-12-14
- Granted: 1998-01-06
- Earliest claimed: 1993-12-22
- Assignees: Hitachi, Ltd.
- Inventors: Emiko Yanagisawa; Minoru Koizumi; Tetsuhiko Hirata; Kenji Kataoka; Osamu Takada; Hirashi Wataya
- Web page: https://patentgrep.com/patent/US5706430A

## CPC

- H04L 12/417: with deterministic access, e.g. token passing
- Y10S 707/99952: Coherency, e.g. same view to multiple users
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A distributed memory computer system periodically performs memory copy among a plurality of computers by using general-purpose communication control devices and a transmission line of the CSMA/CD type. A master computer periodically generates a synchronizing packet, and transmits data for memory copy and normal data in a time slot immediately after the transmission of the synchronizing packet. Each computer other than the master computer transmits the data for memory copy and the normal data in its own time slot after the elapse of a predetermined time. The respective computers complete their transmissions within predetermined times. Since the time slots are assigned to the respective computers, the number of computers which may compete with each other on a transmission line can be restricted and each computer can be assured a periodic opportunity to transmit data.

## Claims

### Claim 1

A memory copy data transmission control method for use in a distributed memory computer system in which a plurality of computers, each having a processor and a memory, are connected to a transmission line via respective communication control devices, comprising the following steps:
each computer intermittently broadcasting memory copy data to all others of the computers so that memory data contents of all of the computers will coincide with one another by memory copy;
broadcasting a synchronizing packet at intervals from one of the computers serving as a master computer, wherein each computer other than the master computer has a pre-assigned time slot, identified by said each computer by using a timer thereof, beginning when a pre-assigned time has elapsed after receiving the synchronizing packet, in which to respectively perform said broadcasting in said pre-assigned time slot;
starting to repeat said step broadcasting memory copy data by a timer activation when no succeeding synchronizing packet arrives within a predetermined time after a preceding time slot; and
resetting the timer with a subsequently received synchronizing packet.

### Claim 2 (depends on 1)

A data transmission control method according to claim 1, wherein said step broadcasting a synchronizing packet is performed so that the synchronizing packet is broadcast at the rate of one synchronizing packet to a plurality of said broadcasting memory copy data for each computer.