JPH0691547B2 - Frame synchronization method for loop communication network - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a frame synchronization system in a loop communication network in which a plurality of communication nodes are connected by a synchronous loop.

[Conventional technology]

The loop type communication network has a structure 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 loop is used as the loop 50, frames having 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 ₁ and F _{2 in} which a specific pattern for frame synchronization is inserted in the frame, and a plurality of time slots TS1 and TS2, which are used by each communication node to mutually transmit and receive data, ..., TSi, ..., TSn are provided.

There are various methods of using the time slot of each communication node. For example, according to the so-called throttling method, an empty time slot is searched for based on the idle / busy display provided in each time slot. Destination address,
Data is transmitted to the time slot together with the source address and the like. On the other hand, each communication node monitors the destination address of each in-use time slot on the loop, takes in the data addressed to itself to the node, and the communication between the nodes is realized.

In the above loop type communication network, the frame synchronization patterns F ₁ and F _{2 in} the frame format shown in FIG. 3 are used.
The insertion of a particular communication node, for example a communication node
51 had gone to a specialty. In a synchronous loop communication network, it is also necessary to have a function to adjust the delay around the loop to a constant value. Normally, this function and the insertion of the frame synchronization pattern are combined into one communication node (master node, operation management node, etc.). Say) is playing. Therefore, the other communication node (called a general node) establishes a loop frame synchronization based on the frame synchronization pattern inserted by the master node, and based on the result, displays the availability / busy display of each time slot. The transmission / reception operation to the loop is executed based on the control signal of.

FIG. 4 shows a schematic configuration of a conventional general node. In FIG. 4, the signal on the loop 50 coming from another node is frame-synchronized 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 in the elastic memory 11, and the received data is matched with the frame phase in the node. Further, the transmission / reception control circuit 13 determines from the received data that each time slot and an empty / busy display in it
The control signal such as the destination address is extracted, and the time slot destined for the own node controls the switch 12 to control the reception buffer memory.
In the empty time slot, the switch 55 is controlled based on the transmission request from the transmission buffer memory 15 and the transmission data stored in the transmission buffer memory 15 is sent to the loop in the empty time slot. When there is no transmission data and during a busy time slot addressed to another node, the switch 55 is tilted upward in the drawing to allow the node to pass through as it is. The frame synchronization bits F ₁ and F ₂ also pass through the node as they are.

[Problems to be solved by the invention]

The conventional method described above has the following problems.
That is, in the configuration of the general node shown in FIG.
When the frame synchronization is lost due to a transmission error on the loop or the like, the frame synchronization circuit 10 starts the heighting for pulling in the synchronization. That is, the frame phase when the received data is written in the elastic memory 11 is dynamically shifted. Therefore, elastic memory
The delay amount in 11 changes dynamically, the input of the elastic memory 11 is not transparently output, and as a result, the frame structure shown in FIG. 3 is destroyed. As a result, the frame synchronization is lost even in the communication node located next to the node, and thereafter, the frame synchronization is continuously transmitted to the node immediately before the master node. Naturally, during this time,
After the first communication node that has lost synchronization, the nodes immediately before the master node are in a communication disabled state.

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

An object of the present invention is to overcome such drawbacks of the conventional methods.

[Means for solving problems]

According to the present invention, 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 having a constant time period is provided on the loop, each communication node temporarily stores received data from the loop. An elastic memory and a sync pattern generation circuit for generating a frame sync pattern according to the frame phase of each communication node are provided, and the frame sync pattern is always inserted in the frame sync bit position on the loop according to the frame phase in the communication node. However, the contents of the elastic memory are read out according to the frame phase, or the data to be transmitted from each of the communication nodes is inserted.

[Action]

In the present invention, each communication node generates a frame synchronization pattern within itself and inserts it at the frame synchronization bit position in the transmission frame, regardless of whether frame synchronization is lost in the received data. Therefore, when viewed from the next node, the position and content of the frame synchronization bit do not change even if the preceding node causes frame synchronization loss, and the frame synchronization loss does not spread.

Therefore, although the data on the loop is blocked at the node where the frame synchronization is lost, the minimum amount of transmission and reception of the alarm signal and the like to the node located downstream is possible by the remaining loop section.

In addition, since the loss of frame synchronization does not spread to other nodes and is limited to only that node, the frame synchronization recovery time is also 1
Only the nodes will be compressed.

〔Example〕

 The present invention will be described below based on examples.

FIG. 1 is a diagram showing a configuration example of a general node in the embodiment of the present invention. In FIG. 1, the frame synchronization circuit 10,
The operation of the elastic memory 11 is similar to that of the conventional example. The transmission / reception control circuit 13 also operates almost similarly to the conventional example, except that at the frame synchronization bit position, the switch 16 is controlled to unconditionally insert the synchronization pattern generated by the synchronization pattern generation circuit 17. The synchronization pattern generation circuit 17 generates a synchronization pattern according to the frame phase in the node and supplies it to the switch 16. The frame phase in this node is constant, so to the next node,
Regardless of the frame synchronization state in the frame synchronization circuit 10, a signal in which a frame synchronization bit is inserted is always transmitted at a fixed position, and unless there is a transmission error, frame synchronization will not be lost.

〔The invention's effect〕

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

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a communication node in an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a configuration of a loop type communication network, and FIG. 3 is an explanatory diagram showing a frame configuration on a loop. FIG. 4 is an explanatory diagram showing a schematic configuration of a conventional communication node. 10 …… Frame synchronization circuit 11 …… Elastic memory 12,16,55 …… Switch 13 …… Transmission / reception control circuit 14 …… Reception buffer memory 15 …… Transmission buffer memory 17 …… Synchronization pattern generation circuit 50 …… Loop 51,52,53,54 …… Communication node

Claims (1)

[Claims] 1. In a frame synchronization system in a loop type communication network in which a plurality of communication nodes are connected by a loop and a frame of a constant time period is provided on the loop, each communication node temporarily stores received data from the loop. Elastic memory and a synchronization pattern generation circuit that generates a frame synchronization pattern according to the frame phase for each communication node, and always maintains the frame synchronization pattern at the frame synchronization bit position on the loop according to the frame phase in the communication node. A frame synchronization system for a loop type communication network, characterized in that the content of the elastic memory is read out or the data to be transmitted from each communication node is inserted according to the frame phase.