JPS6170832A - Frequency synchronizing system between communication networks - Google Patents

Abstract

PURPOSE:To apply frequency synchronism between communication networks without using a special line by detecting a frequency included in data or a clock flowing to a line connected to the 2nd communication network to change the frequency of a master node. CONSTITUTION:Data terminal devices 11, 12 of the 1st communication network and data terminal devices 13, 14 of the 2nd communication network are coupled via lines 20, 21. A slave node 31 extracts a clock from a frame signal inputted from a feeder 40 and compares the frequency of the extracted clock and the frequency of a clock line of the line 20. Then the result of comparison is transmitted to a master node 30 inserted to a frame. The master node 30 changes the frequency of a frequency variable oscillator 50 according to received frequency information to synchronize the frequency of the 1st communication network with that of the 2nd communication network.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital communication system, and in particular, to synchronize the operating frequency of a first communication network with the frequency of a second communication network, The present invention relates to an inter-communication network frequency synchronization system that enables interlocking of a network and a second communication network.

[Conventional technology]

At least one master node (highway supervisory word W)
A data highway system in which a plurality of slave nodes (communication devices) are connected to a circular data transmission path has been used for some time.

This data network system is normally used as a closed communication network, but forms of interconnection with other communication networks are also being adopted. In that case, if another communication network is positioned as an upper communication network, it is necessary to match the frequency of the data highway system to the frequency of the other communication network.

Therefore, as one method, a method has been adopted in which a line for frequency synchronization is specially connected to the master node in order to detect the frequencies of other communication networks.

[Problem that the invention seeks to solve]

According to the above method, if the other communication network is, for example, a communication carrier, a line usage fee will be charged.

Furthermore, if the above-mentioned special line leading to the master node is disconnected, frequency synchronization may become impossible.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention uses a node as a master node, which has a function of generating and transmitting frames and a function of relaying and transmitting frames that have made one cycle in accordance with the frame phase that it is transmitting. A clock is extracted from a signal constituting a frame sent from a master node, and a node that operates in synchronization with the frequency (fm) of the master node is defined as a slave node, and the master node and slave nodes are connected in a ring via a trunk line. In a communication system configured such that a first communication network to be coupled is linked with a second communication network via a line accommodated in the slave node, the slave node of the first communication network The frequency (fm) of the second communication network included in the data or clock flowing through the line connected to the second communication network is detected, and the frequency (fm) and the frequency (fm) of the master node are detected.
) is not synchronized, it notifies the master node of late/early instruction information using part of the frame,
The master node is characterized in that it is configured to synchronize the frequency of the first communication network with the frequency of the second communication network by changing the frequency of the master node based on the information.

[For production]

In the present invention, since the frequency (fm) of the second communication network (another communication network) is extracted from the line for performing inter-network coupling, if even one of the lines survives, that is, , when frequency synchronization is required to link the first communication network (data highway system) and the second communication network, the frequency (fm) of the second communication network is always synchronized in some slave node. Can be detected.

All slave nodes follow the master node's frequency (fm)
The frequency fz extracted from the line coupled to the second communication network is synchronized in all related slave nodes. Therefore, it is possible to make the frequency of the first communication network follow the frequency of the second communication network by utilizing the fact that the late/early instruction information detected and sent by all related slave nodes is the same. can.

〔Example〕

Each communication network that forms a digital line has an oscillator that determines the communication speed. When interconnecting two different communication networks, for example, when interconnecting the data highway system as a local area communication network as the first network and the digital network of the Telegraph and Telephone Public Corporation as the national network as the second network, the individual networks If the communication speeds of the two do not match completely, transmission errors due to bit slips will occur. The same thing can also be said when two data highway systems are linked. In the present invention, the first communication network is configured to be capable of frequency synchronization with the second communication network, and a means for completely matching the communication speeds is provided.

FIG. 1 shows a conceptual diagram of a communication system according to an embodiment of the present invention, in which data terminals 11 and 13, 12 and 14 are accommodated in a first network and a second network, respectively, and are connected via a line 20 and 21. The figure shows how the networks are connected. In the figure, 30 is the master node, 31/32/33 are slave nodes, 4
0 indicates a main line connecting the nodes, and 50 indicates a variable frequency oscillator (VCO) included in the master node 30. 5
1 shows the direction in which frames flow and the concept of frequency propagation within the slave nodes 31 to 33 shown in FIG. 270 denotes an oscillator in the second network, line 2
The second network mask clock is shown to determine the multiplication rate (frequency) of 0.25 and 21.26.

FIG. 2 shows the master node 30. A detailed example of the slave node 31 is shown. Slave nodes 32 and 33 may have the same configuration as node 31. Line 20 is a line that connects to the second network, and has a synchronous modem interface as shown in CCITT Recommendation V, 24.

A circuit 21 not shown in FIG. 2 also has a similar interface. The line 20 includes a reception data line 203, a transmission data line 202. It includes a clock line 201. The master node 30 has a frame sending circuit 301. Frame receiving circuit 303 that receives frames input from trunk line 40
．． A clock extraction circuit 304 that extracts the bit clock of the frame input from the main line 40. Frame receiving circuit 3
In order to relay the frame received in 03, the frame buffer 302 is configured to match the frame sending phase of the frame sending circuit 301. 303 extracts the late/early instruction information E, L in the frame shown in FIG. 3 and notifies it to the frequency variable oscillator 50. The variable frequency oscillator 50 uses this information to set E=1. If L=0, increase the oscillation frequency, if E=O, L=1, lower the oscillation frequency, E=O, L=
If it is 0, each oscillates at the free running frequency.

On the other hand, in the slave node 31, a circuit 313 extracts a clock from a frame signal input from the main line 40, a circuit 312 reproduces a frame using the extracted clock 317, and so on. Circuit 3111 that inserts data into a frame or branches data from a frame 3111 Frame sending circuit 3101 that sends a frame to be sent to the next node Line 20
A circuit 314 . generates E and L by comparing the frequency of the clock line 201 of the clock line 201 and the clock extracted by the clock extraction circuit 313 . It includes a circuit 315 for converting the data format between the data on data lines 202, 203 and the data in time slots To-Tn shown in FIG. clock line 2
01 and the frequency of the extraction clock 317 are transmitted to the data insertion/branching circuit 311 via a signal line 316, and the E and L bits of the frame shown in FIG.
The frame reception circuit 3 in the master node 30 is connected to the frame reception circuit 3 through the master node 30.

〔Effect of the invention〕

Since the node 32 can notify the node 30 whether the numbers match, frequency synchronization is ensured until both lines 20 and 21 are disconnected (inter-network communication is impossible).

Lines 20 and 21 are lines for the purpose of communication,
Unlike the conventional system, there is no need to connect a special line from the second network, and line charges can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a communication system according to an embodiment of the present invention, FIG. 2 is a diagram showing a detailed example of a master node and slave nodes, and FIG. 3 is a diagram showing a frame structure of the embodiment. In FIG. 1, 11 to 14 are data terminals, 30 is a master node, and 31 to 33 are slave nodes. 40 is a main line connecting nodes, 50 is a variable frequency oscillator, and 270 is a second network oscillator (master clock).
It is. r′ °−−1

Claims (1)

[Claims] A node that has a function of generating and transmitting frames and a function of relaying and transmitting frames that have gone through a cycle in accordance with the frame phase that it is transmitting is defined as a master node, and the data is transmitted from the master node. The clock is extracted from the signals that make up the frame, and the frequency of the master node (
A first communication network in which the master node and the slave nodes are connected in a ring via a trunk line is connected to a second communication network via a line accommodated in the slave node. In a communication system configured to operate in conjunction with a communication network, a slave node of the first communication network receives data of the second communication network included in data or a clock flowing through a line connected to the second communication network. Detect the frequency (f_2) and select the frequency (f_2)
If the frequency (f_m) of the master node and the master node are not synchronized, the master node is notified of slow/early instruction information using a part of the frame, and the master node uses the information to notify the master node of the master node. A frequency synchronization method between communication networks, characterized in that the frequency of the first communication network is synchronized with the frequency of the second communication network by changing the frequency of the communication network.