JPS6348215B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an initialization method in a loop bus network system.

Generally, in a loop bus network system in which host computers 11 to 16 as shown in FIG. It is necessary to control bus contention in some way.

One of the typical contention control methods is a bus right pass method. In this method, when a node obtains the right to use the bus, it performs data transmission, and when this is completed, the right to use the bus is handed over to the next node. When there is no data to send, the right to use the bus is immediately passed to the next node. In this method, when the system starts operating, it is necessary to give the right to use the bus to only one node by some means (initialization).
The same problem often occurs when other contention control methods are employed.

One of the simplest methods for granting the right to use the bus to a node when the system starts operating is to fix the node to which the right to use the bus is initially given. However, when this method is adopted, if the initially fixed node is removed due to a change in the network configuration, when restarting operation, the first node to be given the right to use the bus is set again, and The disadvantage is that the software must be changed accordingly.

An object of the present invention is to provide a simple initialization method for a loop bus network system that does not require troublesome software changes.

The present invention is characterized in that in a loop bus network system in which a plurality of nodes are connected by a unidirectional loop bus, and each node has a connecting device connected to the loop bus, each connecting device has a connecting device for each node. A unique number is assigned to each node, and prior to the start of operation of the network system, each coupling device transmits its own unique number to the coupling device of the forward node, and also transmits the number from the coupling device of the rear node. Each coupling device receives a number and sends it to the coupling device of the forward node only if the received number is larger (or smaller) than the number previously sent to the coupling device of the preceding node. Only the maximum (or minimum) of the numbers sent goes around the loop bus, and when the maximum number is received by the coupling device of the node that sent it, a signal is sent to the loop to notify that it has been received. By sending the signal to the bus, other nodes are set as slaves, and when the signal goes around the loop bus, the node that sent it is set as the master and the loop bus network system is initialized. .

This will be explained below with reference to the drawings.

In this invention, a unique number NCPNO is first assigned to each node or their coupling device. Then, prior to the start of operation of the network system, each coupling device sends the number NCPNO assigned to each device to the unidirectional loop bus. The network system is initialized by recognizing the coupling device that sent the largest (or smallest) of these sent NCPNOs.

Next, a method for recognizing the coupling device that has sent out the maximum (or minimum) NCPNO mentioned above will be explained with reference to the flow diagram in FIG.

First, each coupling device has its own
Send the NCPNO to the coupling device of each forward node. Thereafter, it receives the NCPNO sent from the coupling device of each backward node. This received
The NCPNO is compared with the NCPNO previously sent from the coupling device to the coupling device of the forward node.
If the received NCPNO is larger than the transmitted NCPNO, the received NCPNO is sent as is to the coupling device of the forward node, and the received data is waited for again. Conversely, if the sending NCPNO is larger than the receiving NCPNO, the receiving NCPNO is ignored (or discarded).
and waits for the next received data.

As the coupling devices of each node perform the operations described above, the largest number of NCPNOs sent out from all the coupling devices goes around the loop bus. Note that in the above example, the maximum NCPNO is cycled once, but the minimum NCPNO may be cycled conversely. In this case, the receiving NCPNO mentioned above will send
Receive NCPNO only when less than NCPNO
is sent to the coupling device of the forward node. Otherwise, ignore the received NCPNO.

Determine the received data and determine if it is connected to another coupling device.
If it is an NCPNO, the above operation can be repeated (see route 20 in Figure 2), but
If the received data matches the coupling device's own NCPNO, it means that the NCPNO is the largest one that has passed around the loop bus. As a result, the coupling device learns that it is the first node (called a master; the remaining nodes are called slaves) that can use the loop bus first. Thereafter, that coupling device transmits a control signal STX to inform other coupling devices that it has acquired the right to use the bus first (see route 21 in FIG. 2).

By receiving the STX signal, the coupling devices of other nodes learn that the master node has been determined, and after transmitting the STX signal to the coupling device of the previous node, set themselves as slaves (see Figure 2). (see route 22).

After transmitting the STX signal, the coupling device waits for the signal to go around the loop bus and sets itself as the master. When the STX signal is received again, it is known that the initialization of the network system has been completed.

As described above, according to the present invention, a loop bus network can be initialized using a simple method.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining a loop bus type network system, and FIG. 2 is a flow diagram showing the operation of a coupling device according to the initialization method of the present invention. 11-16...Host computer, 21-2
6...Coupling device, 3...Loop bus.

Claims (1)

[Claims] 1. In a loop bus network system in which multiple nodes are connected by a unidirectional loop bus and each node has a coupling device connected to the loop bus, a unique number is assigned to each coupling device. Prior to the start of operation of the network system, each coupling device transmits its own unique number to the coupling device of the forward node, receives the number sent by the coupling device of the rear node, and receives this received number. is larger or smaller than its own unique number transmitted from its own node to the forward node, by transmitting this to the forward node's coupling device, the maximum or minimum of the numbers transmitted by each coupling device The coupling device that receives a number matching its own unique number from the rear node becomes the master node, and the coupling device sends a predetermined control signal onto the loop bus. A loop bus network system characterized in that the master node obtains the right to use the loop bus after the control signal goes around and returns to another coupling device as a slave. Initialization method.