Hitachi, Ltd.

Hitachi Process Computer Engineering, Inc.

Hisao Ogawa

Hiroaki Fukumaru

Kenichi Kurosawa

Hiroshi Arita

Tetsuaki Nakamikawa

Takuji Hamada

Seiichi Yasumoto

Sadao Mizokawa

Yoshiaki Adachi

Junji Fukuzawa

Hideaki Masuko

Ken Onuki

Toshiyuki Murakami

Hisayuki Maruyama

Masato Satake

Toshihiko Uchiyama

Osamu Anbo

Tomoyuki Harada

Shinichi Hanada

Yoshihiro Miyazaki

Masayuki Tanji

Koji Masui

Syoji Yamaguchi

The system includes optical bus-bridging devices for observing the modes of said electric buses and the modes of said optical fibers while said electric buses have not been driven (OFF mode), so that the modes of the two electric buses connected through optical fibers are brought into agreement and that the buses can be simultaneously driven by a plurality of nodes. While one or both of said electric buses have been driven (ON mode) by the nodes connected thereto, an optical output has been continuously produced from the buses that are being driven to said optical fibers, and while light has been inputted from said optical fibers, the modes of said buses are not observed, but an electric output is produced to the electric bus of the side to which light is inputted to drive the bus. The optical bus-bridging device changes the mode of the electric bus when the optical fiber does not change within a predetermined period of time after the optical bus-bridging device has outputted a signal to the optical fiber.

Optical communication method, optical linking device and optical communication system

Occurrence of significant difference of transmission rate between communication zones can be prevented to maintain the transmission rate of overall network uniform. The radio network system includes a plurality of radio communication control units are connected with each other via radio main line, and each radio communication control unit has a communication function with at least one radio communication terminal arranged within own communication area. Each of the radio communication control units includes means for broadcasting a transmission rate restriction demand to all of other radio communication control units and all of radio communication terminals when data amount stored in a transmission and reception buffer exceeds a predetermined threshold value, and means for lowering a transmission rate when a transmission rate restriction demand is received from any other radio communication control unit within a predetermined period and for increasing the transmission rate when no transmission rate restriction demand is received from any other radio communication control unit.

Radio network system

A data transmission method and system of a token passing type capable of periodically transmitting cyclic data produced in a station to other stations while enabling a packet data communication with high efficiency and without disturbing the periodicity of the cyclic communication. A token circulation time is set to be shorter than a cycle time for production of the cyclic data where no packet data to be transmitted. Also each station will pass an acquired token immediately to the next station if the station has no data to be transmitted. Thus, at least one station can have a token at least two times during the cycle time to transmit the cyclic data and the packet data. Upper limits may be set to capacities of the cyclic data and the packet data which are capable of being transmitted each time the token is acquired.

Data transmission method and system thereof

A data transmission method and system of a token passing type capable of periodically transmitting cyclic data produced in a station to other stations while enabling a packet data communication with high efficiency and without disturbing the periodicity of the cyclic communication. A token circulation time is set to be shorter than a cycle time for production of the cyclic data where no packet data is to be transmitted. Also each station will pass an acquired token immediately to the next station if the station has no data to be transmitted. Thus, at least one station can receives a token at least two times during the cycle time to transmit the cyclic data and the packet data. Upper limits may be set to capacities of the cyclic data and the packet data which are capable of being transmitted each time the token is acquired.

Transmission method and system thereof

A method and apparatus for controlling a dual bus system, capable of realizing high speed and continuous operation even if one of the buses of the dual bus system fails. The method and apparatus has a dual bus system, a plurality of electronic circuits connected to both buses of the dual bus system, and bus controller for providing a bus use allowance signal to one of the plurality of electronic circuits, the one electronic circuit being selected in accordance with bus occupation request signals issued from the plurality of electronic circuits requesting data transfer. If the bus occupation request signals for both buses of the dual bus system originates from the one selected electronic circuit and the outputs of the arbiters coincide, the bus use allowance signal is provided to the one selected electronic circuit for the allowance of occupying both buses of the dual bus system. A completion of data transfer at the dual bus system is determined when data transfer is completed at both buses. Continuous operation can be ensured immediately upon occurrence of a failure, and high speed operation of a computer system is possible.

Method and apparatus for controlling dual bus system

Growing community of inventors

Hitachi, Japan

Hisao Ogawa