JPH01112838A - Network clock synchronization system - Google Patents

Abstract

PURPOSE:To make the hierarchy of clock distribution in a network, and to automatically maintain the synchronism of a network clock even against the dynamic variation of the network due to the increase or the trouble, etc., of a device by letting each node have a clock synchronization hierarchical status. CONSTITUTION:The initial state of the status is assumed to be infinity . At such a time, the smallest status among the statuses of an adjoining device obtained from a communication circuit 5 is selected, and a value, that is, the value plus '1' is set in the status of its own device. A synchronizing clock is obtained from a line with the smallest value. Besides, the status of its own device is transferred to respective adjoining nodes. The clock generated in its own device (clock synchronized with a device with a high-order status) is supplied to the line with the value larger than the status of its own device. When the status from the adjoining node changes, as well, the synchronism can be established by executing an above-mentioned operation. Besides, at the time of trouble, a clock synchronizing line can be switched automatically by turning the status of the troubled line into infinity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a network C2 constituted by synchronous data transmission devices, and more particularly to an automatic distribution system of synchronous clocks for synchronous data transmission devices.

[Conventional technology]

Conventionally, in this type of clock distribution system, clock synchronization within a network has been established by determining a distribution path in advance and setting the synchronous data transmission device C accordingly.

[Problem that the invention seeks to solve]

However, in the conventional network clock synchronization method described above, the clock distribution route is determined externally, so there is a problem when adding a new synchronous data transmission device or a failure in the clock system.

If a line failure, lead failure, etc. occurs (2.

I have to specify the clock distribution route again.

The disadvantage is that the entire network may become out of sync.

Furthermore, if the clock distribution path changes dynamically due to a failure or the like, network synchronization will not be established autonomously, so it will not work indefinitely.

The drawback is that synchronization across the network may not be established.

Therefore, the object of the present invention is to solve the above drawback C: in view of the above.

An object of the present invention is to provide a network clock synchronization method that can automatically perform network synchronization.

[Means for solving problems]

According to the present invention C; in a network clock synchronization system having a synchronous data transmission device.

By giving each node a clock synchronization hierarchy status, the network clock distribution path is set, and the network clock distribution path is switched before dynamic changes in the network to establish network synchronization. A network clock synchronization method featuring the following is obtained.

In other words, the network clock synchronization method of the present invention checks the oscillator for the device to become the clock master, the status for indicating the clock synchronization hierarchy, and the status of the clock synchronization hierarchy of the adjacent node. The device has a status communication circuit for transferring the status of the clock synchronization layer of the device itself, and a synchronization clock selection circuit.

〔Example〕

Next, one embodiment of the present invention will be explained with reference to the drawings. FIG. 1 shows the configuration of the device (node) 2.

Does device 2 extract the clock from line 3?

a clock extraction circuit 4 that supplies a clock to line 3;
A communication circuit 5 for receiving the clock synchronization hierarchy status of the adjacent node from the line 3 and transmitting the clock synchronization hierarchy status of the own device 2 to the adjacent node, and each line 3
It also stores the clock synchronization hierarchy status of own device 2.
According to the clock synchronization hierarchy status circuit 6 which creates the status of the device 2, and the status of the own device 2.

A clock switching circuit 7 that determines a synchronized clock and switches the clock to supply it to devices lower than the own device 2; and a clock switching circuit 7 that synchronizes with the clocks and clocks supplied from the clock switching circuit 7 and generates a clock to be supplied to the lower devices. It is composed of a clock generation circuit 8.

FIG. 2 shows the clock synchronization relationship of a network to which the single-line method is applied. Note that the thick line indicates the synchronization relationship: master/slave, and the number in parentheses indicates the clock synchronization hierarchy status of that device. That is, the adjacent node that receives the clock.

A synchronization clock is always supplied to a node that has a clock synchronization hierarchy status one lower than itself and one higher than its own device.

Next, the operation of this system will be briefly explained using FIG.

The initial state of the status is ω. At this time.

Select the smallest one among the statuses of the adjacent devices obtained from the communication circuit 5, and set the status C of the own device: 1 to that value.
The synchronization clock is obtained from the line with the minimum value (in the figure, the line with the value (1)). Also, the status of the own device is transferred to each adjacent node. A clock generated by the own device (
(synchronized clock) to devices with higher status. 2 also when the status from the adjacent node changes
By performing the above operations, you can synchronize with the upper level network clock. Also, in the event of a failure, by setting the status of the failure line to infinity,
The clock synchronization line can be switched automatically. Incidentally, FIG. 4 shows the status and clock distribution path before the failure (a) and after the failure (b).

〔Effect of the invention〕

As explained above (:1) The present invention captures the clock synchronization hierarchy status of adjacent nodes and synchronizes with the clock of the line with the minimum value among them.
It is possible to create a hierarchy of clock distribution within a network, so all devices within the network can be synchronized to one master clock. It also has the effect of automatically keeping the network clocks synchronized.

eternity hereafter

[Brief explanation of the drawing]

FIG. 1 is an internal configuration diagram of a device for realizing the method of the present invention.
Fig. 2 is an example of a network synchronization hierarchy diagram when the method of the present invention is applied, Fig. 3 is an example of execution of the method of the present invention (in-device processing), and Fig. 4 (a) l (t)) is FIG. 3 is a diagram of the synchronization hierarchy of network clocks when the method of the present invention is applied before and after a failure; 1... Master clock, 2... Device (node). 3... Line, 4... Clock extraction circuit, 5...
Communication circuit, 6... Clock synchronization hierarchy status circuit. 7... Clock switching circuit, 8... Clock generation circuit. Figure 1 Figure 2 ○ Device (tado) ■~■ Node No. 8 (1)~(3) Tarotsuku's D11 brain status Figure 3

Claims (1)

[Claims] 1. In a network clock synchronization system with a synchronous data transmission device, by giving each node a clock synchronization hierarchy status, the network clock distribution path can be set, and the network clock can be adjusted in response to dynamic changes in the network. A network clock synchronization method characterized by establishing network synchronization by switching the distribution path of the network.