JPS62290234A - Frame synchronizing system for loop-type communication network - Google Patents

Abstract

PURPOSE:To prevent out-of-frame synchronization from occurring continuously and to shorten a time required for pull-in by always inserting the prescribed frame synchronizing pattern in a frame synchronizing bit in a loop at each communication node. CONSTITUTION:An exchange control circuit 13 at each node controls a switch 16 in the frame synchronizing bit position to insert the synchronizing pattern that a synchronizing pattern generator circuit 17 generates unconditionally. The circuit 17 generates the synchronizing pattern according to a frame phase at the node, and supplies it to the switch 16. Since the frame phase at the node is constant, the signal with the frame synchronizing bit in a fixed position without fail is transmitted regardless of the frame synchronization state in a frame synchronizing circuit 10, and out-of-frame synchronization never occurs unless otherwise the erroneous transmission happenes.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a frame synchronization method in a loop communication network that connects a plurality of communication nodes in a synchronous loop.

[Conventional technology]

The loop type communication network has a configuration in which a plurality of communication nodes 51, 52, 53, and 54 are connected by a loop 50, as shown in FIG. At this time, if a synchronous type loop is used as the loop 50, frames with a constant time period are provided on the loop. An example of the frame format is shown in FIG. In this format, frame synchronization bits F, TS2, .・
....

TSi, ..., TSn are provided.

There are various methods for using the time slots of each communication node, but for example, according to the so-called throttling method, an empty time slot is searched based on the empty/busy indication provided for each time slot. , the destination address,
Send the data along with the source address etc. to the relevant time slot.

On the other hand, each communication node monitors the destination address of each busy time slot on the loop, takes in data addressed to its own node, and communication between the nodes is realized.

In the loop communication network as described above, the frame synchronization pattern F in the frame format shown in FIG.
Conventionally, insertion of F2 has been carried out exclusively by a specific communication node, for example, the communication node 51.

In a synchronous loop communication network, a function to adjust the loop-period delay to a constant value is also required, and this function and frame synchronization pattern insertion are usually performed by one communication node (
master node, operation management node, etc.). Therefore, other communication nodes (referred to as general nodes) perform loop frame synchronization based on the frame synchronization pattern inserted by the master node, and based on the results, display empty/busy information for each time slot, etc. The transmission/reception operation to the loop is executed based on the control signal.

FIG. 4 shows a schematic configuration of a conventional general node.

In FIG. 4, the signal on the loop 50 arriving from the conversion node is subjected to frame synchronization by the frame synchronization circuit 10 based on the frame synchronization pattern inserted by the master node. Based on the result, the received data is written into the elastic memory 11, and the received data is adjusted to the frame phase within the node. In addition, the transmission/reception control circuit 1
3 extracts control signals such as each time slot, an empty/busy indication therein, and a destination address from the received data, and controls the switch 12 to import the time slot addressed to the own node into the reception panzer memory 14; In an empty time slot, the switch 55 is controlled based on a transmission request from the transmission panzer memory 15 to send out the transmission data stored in the transmission buffer memory IJ15 onto the loop. If there is no data to be transmitted or a busy time slot is addressed to another node, the switch 55 is turned upward in the figure to allow the time slot to pass through the node. The frame synchronization bits F, , F2 are also passed through the node as they are.

[Problem that the invention seeks to solve]

The conventional method described above has the following problems.

That is, in the configuration of the general node shown in FIG.
When frame synchronization is lost due to a transmission error on the loop, etc., the frame synchronization circuit 10 starts heightting for synchronization pull-in.

That is, the frame phase when writing received data to the elastic memory 11 is dynamically shifted. Therefore, the amount of delay in the elastic memory 11 changes dynamically, and the delay amount in the elastic memory 11 changes dynamically.
1 is not output transparently, and as a result, the frame structure shown in FIG. 3 is destroyed. As a result, the frame synchronization is also lost in the communication node located next to the node in question, and thereafter the frame synchronization is propagated to the node immediately before the master node. Naturally, during this time, communication becomes impossible from the communication node that first lost synchronization to the node immediately before the master node.

In addition, each node that detects an out-of-synchronization enters a synchronization pull-in operation, so a stable state cannot be reached unless the node enters the synchronization state in order starting from the most upstream node, and the synchronization pull-in time causes the out-of-synchronization. It will grow in proportion to the number of nodes.

It is an object of the present invention to overcome these drawbacks of the conventional methods.

[Means for solving problems]

The present invention provides a frame synchronization method in a loop type communication network in which a plurality of communication nodes are connected in a loop and a frame with a fixed time period is provided on the loop, in which each communication node is set at a synchronization bit position of a frame on the loop. , is characterized by always inserting a predetermined frame synchronization pattern.

[Effect]

In the present invention, each communication node generates a frame synchronization pattern within itself and inserts it into the frame synchronization bit position in the transmitted frame, regardless of whether or not frame synchronization occurs in received data. Therefore, when viewed from the next node, even if the previous node experiences frame synchronization, the position and contents of the frame synchronization bit do not change, and the frame synchronization does not spread.

Therefore, although data on the loop is interrupted at the node where frame synchronization has occurred, it is possible to send and receive at least an alarm signal and the like to downstream nodes using the remaining loop sections.

In addition, frame synchronization recovery time is also 1 because frame synchronization does not spread to other nodes and is limited to that node.
It will be compressed to only one node.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a diagram showing an example of the configuration of a general node in an embodiment of the present invention. In FIG. 1, a frame synchronization circuit 10
, the operation of the elastic memory 11 is the same as in the conventional example. The transmission/reception control circuit 13 also operates almost the same as in the conventional example, except that the switch 16 is controlled to unconditionally insert the synchronization pattern generated by the synchronization pattern generation circuit 17 at the frame synchronization bit position. The synchronization pattern generation circuit 17 generates a synchronization pattern according to the frame phase within the node and supplies it to the switch 16.

Since the frame phase within this node is constant, a signal with a frame synchronization bit inserted at a constant position is always transmitted to the next node regardless of the frame synchronization state in the frame synchronization circuit 10. , frame synchronization will not occur unless there is a transmission error.

〔Effect of the invention〕

As described above, according to the present invention, even if loop synchronization occurs in a synchronous loop communication network, the effect is limited to only that node, ensuring minimum communication and frame Synchronization recovery time can be minimized. Therefore, the present invention is extremely useful for improving the reliability of loop communication networks.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the schematic configuration of a communication node in an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the configuration of a loop communication network, and FIG. 3 is an explanatory diagram showing the frame configuration on the loop. , FIG. 4 is an explanatory diagram showing a schematic configuration of a conventional communication node. 10...Frame synchronization circuit 11...Elastic memory 12.16.5
5...Switch 13...Transmission/reception control circuit 14...Reception buffer memory 15...Transmission buffer memory 17...Synchronization pattern generation circuit 50...Loop

Claims (1)

[Claims] (1) In a frame synchronization method in a loop type communication network in which a plurality of communication nodes are connected in a loop and a frame with a fixed time period is provided on the loop, each communication node has a synchronization bit position of a frame on the loop. A frame synchronization method for a loop communication network characterized by always inserting a predetermined frame synchronization pattern.