JPS6154737A - Data transmission system - Google Patents

Abstract

PURPOSE:To improve data transmission efficiency and conformity by sending a privilege frame forcibly at the time of a disconnection from a network system and acquiring the right of communication, and reporting the disconnection from the network system to other transmitters. CONSTITUTION:A microprocessing unit (MPU)1 instructs a collision detecting circuit 6 to transmit a frame while ignoring the occurrence of a collision so as to report the disconnection from the network and commands a token control circuit 5 to transmit the frame regardless of whether the right of communication depending upon a token is obtained or not, and then a transmission control circuit 2 is actuated. Consequently, data are transmitted without the right of communication even if a collision occurs. Then, the transmission control circuit 2 sends out the frame stored in a buffer 3 onto a communication medium 8 through a token control circuit 5, collision detecting circuit 6, and transceiver 7. Then, the sent frame is transmitted continuously until the collision detecting circuit 6 detects no collision, and then the state of no collision is reported by the collision detecting circuit 6 to the MPU1, which sends the end of transmission to the transmission control circuit 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a data transmission method in a data transmission network system using a token method, and more particularly to a data transmission method that allows quick withdrawal from the network system.

[Prior Art] Conventionally, in a token bus access control system in which acquisition of communication rights is controlled using tokens, which are communication rights delegation commands having destination addresses, each transmission device (hereinafter referred to as a node) connected to each other through a communication medium has a unique address, and constitutes a logical ring.

In such a network system, when a logical ring is disconnected due to a power outage of a connected (network entry) node, it is necessary to reconfigure the logical ring of the network. A method is used in which a mask-like node constantly monitors the transmission status of the network and reconfigures the logical ring.

For this reason, mask-like nodes require complex processing, such as countermeasures against the disappearance of tokens by inactivating nodes when the power is turned off, and a reconfiguration phase to search for nodes that make up the network.

The drawback is that the effective transmission efficiency on the communication medium is not necessarily good.

[Purpose] The present invention aims to eliminate the drawbacks of the prior art described above, and acquires communication rights by forcibly transmitting a privileged frame when leaving the network system, and allows other transmission devices to access the network from the network system. The purpose of this invention is to propose a data transmission method that improves data transmission efficiency and responsiveness by notifying the departure of a network system, and allows for easy reconfiguration of a network system.

[Example] An embodiment of the present invention will be described below based on one drawing.

FIG. 1 is a block configuration diagram of a transmission device (node) equipped with a data transmission method in a bus-like network system according to an embodiment of the present invention.

In the figure, 1 is a microprocessing unit (hereinafter referred to as MPU) that performs overall control, 2 is a transmission control circuit, 3 is a buffer for temporarily storing transmitted and received data, 4 is a reception control circuit, 5 is a token control circuit, 6 7 is a collision detection circuit, 7 is a transceiver with a communication medium, and 8 is a communication medium.

FIG. 2 is a conceptual diagram of a frame flowing on the communication medium 8, and the token control unit 10 is information necessary for communication medium access control, indicating the DAAlI3 receiving node address, and SA! 12 is the information section 1 indicating the sending/doing address.
3 includes information used in a layer higher than the token control layer as communication medium control (hereinafter referred to as MAC), user-issued data, and the like.

The control for leaving the data transmission system of this embodiment will be explained below with reference to the flowcharts of FIGS. 3 and 4.

FIG.

In step Sl, the MPUI informs the collision detection circuit 6 to ignore the occurrence of a collision and transmit a frame in order to notify the withdrawal from the network, and the token control circuit 5
After issuing a command to transmit a frame regardless of the presence or absence of the communication right based on the token, the transmission control circuit 2 is activated. This makes it possible to transmit data even if there is no communication right or even if a collision occurs. and send fl, IJ
The control circuit 2 transfers the frames stored in the buffer 3 to the token control circuit 5, collision detection circuit 6. It is transmitted via transceiver 7 onto communication medium 8 .

The frame sent out in the subsequent step S2 is sent to the collision detection circuit 6.
The transmission continues until no collisions occur, and when no collisions occur, the collision detection circuit 6 notifies MPU 1 that no collision has been detected, and MPU 1 ends the transmission to the transmission control circuit 2. is notified, and the process proceeds to step S3.

In step S3, the MPUI creates a withdrawal declaration frame in the buffer 3, activates the transmission control circuit 2, transmits it to the communication medium 8 via the token control circuit 5, collision detection circuit 6, and transceiver 7, and sends it to the communication medium 8 from the network system. The withdrawal process is completed.

FIG. 4 C-1: A flowchart showing processing at the time of transmission in a transmission device that has been delegated communication rights by a token and has acquired one communication right among the transmission devices that constitute the network system other than the transmission device that has left the network system. In particular, the case where a collision occurs in a transmitted frame by a leaving transmission device is described in detail.

First, in step 521, a frame is transmitted, and in step S22, the MPU 1 is informed via the collision detection circuit 6 whether or not a collision has occurred in the transmitted frame, and if no collision is detected, the process ends normally. If a collision is detected in step S21, the process proceeds to step 523, where the MPUI instructs the transmission control circuit 2 to stop transmission, and sets the own transmission device to frame reception mode.

As shown in the flowchart of FIG. 3, the transmission device leaving the network system transmits a leaving frame after a collision occurs, so this leaving frame is received in step S23. When the reception control circuit 4 has finished storing the frame received from the communication medium 8 via the transceiver 7 into the buffer 3, it notifies the MPU l of the completion of reception, and since the received frame is a detached frame, the MPUI first Update the node table that makes up the system and re-form the logical loop. Then, the node table updated in step S25 is notified to other transmission devices connected to the network system, and the node tables of all transmission devices are updated. Therefore, from now on, neither data nor tokens will be transmitted to the detached transmission device.

As explained above, the system can be easily rebuilt by simply using the token bus access control method to acquire communication rights, and adding unconditional frame sending and collision detection means on the communication medium as means for controlling withdrawal from the network. It is possible to provide an efficient data transmission method that can perform and control operations without compromising access time guarantees for establishing communication rights.

[Effects] As explained above, according to the present invention, withdrawal from a network system can be immediately and unconditionally notified to other devices, the network system can be easily reconstructed, and It is possible to provide a data transmission method that does not reduce communication efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the transmission control unit of a transmission device according to an embodiment of the present invention, FIG. 2 is a conceptual configuration diagram of an information frame used in this embodiment, and FIG. Control Flowchart FIG. 4 is an n-blade 1870-chart of network reconstruction in the transmission device having communication rights in this embodiment. In the figure, l...MPU, 2... transmission control circuit,
3... Buffer, 4... Reception control circuit, 5... Token control circuit, 6... Collision detection circuit, 7... Transceiver, 8... Communication medium. Figure 2 Figure 13 Figure 4

Claims (4)

[Claims] (1) In a data transmission method of a data transmission network system that is composed of a communication medium and a plurality of transmission devices connected to the communication medium, and in which communication rights are delegated using a token that is a communication right delegation command, the transmission device is The transmission device includes a collision detection means for detecting the occurrence of a data collision on a communication medium, and the transmission device transmits a privileged frame onto the communication medium when leaving the data transmission network, and detects a data collision on the communication medium. 1. A data transmission method, characterized in that the data transmission system generates a message, acquires communication rights, and notifies other transmission devices connected to the data transmission network of the withdrawal from the data transmission network. (2) The data transmission system according to claim 1, wherein the communication medium is in the form of a bus. (3) The data transmission system according to claim 1 or 2, wherein separation from the data transmission network is notified by sending a network separation frame. (4) The transmission device that has acquired communication rights when the collision detection means detects the collision receives the network withdrawal frame, reconstructs the data transmission network system, and sends reconstruction information to other transmission devices. A data transmission method according to claim 3.