JP2978623B2 - Network synchronization system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network synchronization system which is used in, for example, a digital microwave communication system and has a plurality of devices which individually operate in response to a clock signal on a network.

[0002]

2. Description of the Related Art Generally, a network synchronization system includes a plurality of devices,
For example, it includes a transmission / reception device, a computer, and the like (hereinafter, simply referred to as a device). These devices connected as a network supply a clock to establish synchronization. Conventionally, in a network synchronization system of this type, a clock supply device provided for each device supplies a reference clock signal to each device individually to establish synchronization of each device, and the network synchronization system as a whole. Synchronization has been established. At this time, it is common practice to use a reference clock signal as a redundant system in order to avoid a failure in the clock supply system.

FIG. 2 is a block diagram showing a conventional network synchronization system. Here, two clock supply devices 3, 9 are respectively connected to two devices 100, 200.
Operate in subordinate synchronization. Also, clock supply devices 3, 9
Supplies the reference clock signals S1 and S2 and the reference clock signals S3 and S4 to two devices 100 and 200, respectively, forming a 1 + 1 redundant system.

In the first device 100, the reference clock signal S1 and the reference clock signal S2 supplied from the clock supply device 3 are transmitted to the clock receiving circuit 1 in the device 100.
0 and the clock receiving circuit 11 separately receive the signals. The clock switching control circuit 6 outputs the reference clock signal S
The clock receiving circuits 10 and 11 are controlled so as to monitor the states of S1 and S2 and to select the other reference clock signal when one of the reference clock signals is disconnected. The clock receiving circuits 10 and 11 internally generate a clock signal synchronized with any of the reference clock signals selected by the clock switching control circuit 6 and distribute the clock signal to each unit in the device 100.

On the other hand, the second device 200 is also the first device 1
It operates similarly to 00. That is, the reference clock signal S3 and the reference clock signal S supplied from the clock supply device 9
4 are separately received by the clock receiving circuit 12 and the clock receiving circuit 13 in the device 200. The clock switching control circuit 14 monitors the states of the reference clock signals S3 and S4, and controls the clock receiving circuits 12 and 13 so as to select the other reference clock signal when one of the reference clock signals is disconnected or the like. Control. Clock receiving circuit 1
2, 13 internally generate a clock signal synchronized with one of the reference clock signals selected by the clock switching control circuit 14, and distribute the clock signal to each unit in the device 200. In the above-described configuration, when the clock supply device 3 and the clock supply device 9 are in a synchronized state, the two devices independently perform a synchronous operation with respect to the reference clock signal.

[0006]

As described above, the conventional network synchronization system requires a clock supply device for each device, and therefore has the disadvantage of increasing the configuration scale of the entire system. In addition, it is necessary to provide a clock switching control circuit in each device, and the configuration scale of the device alone increases. In short, the conventional network synchronization system has a problem that the configuration of the entire system is complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a technical problem of the present invention is to provide a network synchronization system capable of simply configuring a system and stably performing slave synchronization with a reference clock signal. To provide.

[0008]

According to the present invention, in a network synchronization system having a first device and a second device which individually operate in response to a clock signal on a network, A single clock supply device for generating a second reference clock signal forming a redundant system together with the first reference clock signal, the first device comprising:
And a switching control unit that specifies which of the reference clock signal and the second reference clock signal to select, and is connected to the switching control unit to monitor the first reference clock signal and the second reference clock signal. While selecting one of the first reference clock signal and the second reference clock signal designated by the switching control unit and sending the selected signal as a first internal clock signal to the inside of the device; A first synchronous clock signal and a second synchronous clock signal are generated based on one reference clock signal and the second reference clock signal, and the first synchronous clock signal and the second synchronous clock signal are generated. Clock distributing means for outputting to the second device together with a control signal indicating which of these should be selected, the second device comprising a first synchronous clock signal and a second synchronous clock signal. It said receiving a signal and a control signal 1
And a second synchronization clock signal and a second synchronization clock signal, the network synchronization system including an internal clock signal generating means for generating a second internal clock signal to be transmitted to the inside of the apparatus according to the selected one.

Further, according to the present invention, there is provided a network synchronization system comprising a third device together with the first device and the second device in the network synchronization system, wherein the internal clock signal generating means further comprises a first device. Generating a first monitoring signal representing a monitoring result of the synchronous clock signal and the second synchronous clock signal, and transmitting the first supervisory signal to a third device based on the first synchronous clock signal and the second synchronous clock signal. Generating a first output clock signal and a second output clock signal, and generating and outputting the first output clock signal and the second output clock signal together with a control signal indicating which of them is to be selected. Wherein the third device generates a third internal clock signal to be transmitted into the device according to a selected one of the first output clock signal and the second output clock signal. And another internal clock signal generating means for outputting a second monitoring signal indicating a monitoring result of the first output clock signal and the second output clock signal to a second device. The first device uses the logical sum of the first monitor signal and the second monitor signal as the monitor signal,
And a network synchronization system for outputting to the device of (1).

[0010]

The network synchronization system according to the present invention is provided with a clock switching control circuit only in a specific device, and this specific device receives a reference clock signal supplied from one clock supply device by forming a redundant system. The system is configured so that the device can be subordinately synchronized.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a basic configuration of a network synchronization system according to one embodiment of the present invention. Here, the synchronization operation in the two devices 1 and 2 will be described. However, the present invention is not limited to this, and is also applicable to a case where there are N (where N is 3 or more) devices. It is possible.

This network synchronization system comprises a first device 1,
A second device 2 that operates in synchronization therewith, and a clock supply for transmitting the first reference clock signal S1 and the second reference clock signal S2 to the first device 1 in a 1 + 1 redundant system And an apparatus 3.

The first device 1 includes two reference clock signals S1 and S2 supplied from a clock supply device 3.
2 and a clock switching control circuit 6 for designating which of the reference clock signals S1 and S2 to select and controlling the switching. .

The clock distribution device 4 of the first device 1
Reference numeral 5 is connected to a clock switching control circuit 6, monitors the reference clock signals S1 and S2, and outputs a reference clock signal selected and designated from the reference clock signals S1 and S2 by the clock switching control circuit 6 to the device. 1 as the internal clock signal, while the reference clock signal S1,
First synchronous clock signal S11 generated based on S2
And a clock distributing means for outputting the second synchronous clock signal S12 to the second device 2 together with a first control signal S31 and a second control signal S32 indicating which of them is to be selected.

In order to perform the above-described operation, the clock distribution means includes reference signal receiving means for receiving the reference clock signals S1 and S2, monitoring means for monitoring the states of the reference clock signals S1 and S2, and monitoring results. Selecting means for selecting one of the normal reference clock signals S1 and S2 from the reference clock signals S1 and S2 based on the reference clock signals S1 and S2;
A distributing means for generating S12 internally and distributing it inside the apparatus, and a synchronizing signal transmitting means for transmitting the synchronous clock signals S11 and S12 to the clock distributing apparatus 7 and the clock distributing apparatus 8 of the second apparatus 2, respectively. Contains.

Further, the clock distribution devices 4 and 5 are provided with monitoring signal receiving means for receiving monitoring signals S31 and S32 generated from the second device 2 with respect to the synchronous clock signals S11 and S12, respectively, and their own reference clock signals. S1, S
2 and the monitoring signals S31, S12 related to the synchronous clock signals S11, S12 received from the second device 2.
And control signal transmitting means for transmitting control signals S21 and S22 for selecting one normal synchronous clock signal S11 or S12 from the synchronous clock signals S11 and S12 to the second device 2 based on C. Have. Since each means in each of the above clock distribution devices 4 and 5 can be easily configured by using a known microprocessor or the like, it will not be described in detail here. The clock distribution device 4,
5 are connected to each other so that data can be exchanged.

On the other hand, the second device 2 includes clock distribution devices 7 and 8 connected to the clock distribution devices 4 and 5 of the first device 1, respectively. The clock distribution devices 7 and 8 of the second device 2 generate synchronous clock signals S11 and S12.
And an internal clock signal generating means for generating a second internal clock signal to be transmitted to the inside of the device in accordance with a selected one of the synchronous clock signals S11 and S12 upon receiving the control signals S21 and S22. ing.

The internal clock signal generating means is used in the clock distribution devices 7 and 8 to synchronize the synchronous clock signals S11 and S12 supplied from the first device 1 with the control signals S21 and S21.
S22 and the synchronous clock signal S11,
A clock synchronized with the same selected from S12 is internally generated and distributed to each unit in the second device 2.

Further, the clock distribution device 7 in the second device 2 monitors the state of the synchronous clock signal S11, and the clock distribution device 8 monitors the state of the synchronous clock signal S12, for example, detection of a disconnection state indicating the monitoring result. Are sent to the clock distribution devices 4 and 5 of the first device 1 as monitoring signals S31 and S32 as first monitoring signals, respectively. Note that the clock distribution devices 7 and 8 are also connected to each other so that data can be exchanged.

In such a network synchronization system, the second device 2 can be subordinately synchronized with the first device 1. That is, the first device 1 receives a reference clock signal forming a redundant system supplied from one clock supply device 6, and outputs the synchronous clock signal S11,
Based on the synchronous clock signal selected from S12, the second
Device 2 is subordinately synchronized.

More specifically, the clock switching control circuit 6 connected in parallel to the first device 1 includes the clock supply device 3.
The clock distribution devices 4 and 5 are controlled to select the other reference clock signal when one of the reference clock signals is disconnected or the like based on the result of monitoring the state of the reference clock signals S1 and S2 supplied from the other. . In response to this, the clock distribution devices 4 and 5 internally generate the synchronous clock signal S11 or the synchronous clock signal S12 synchronized with one of the reference clock signals S1 and S2 selected by the clock switching control circuit 6, and And distribute to each part. Thereby, a normal internal clock signal can be obtained in the first device 1.

Further, based on the reference clock signals S1 and S2, the clock distribution device 4
The clock distribution device 5 generates a synchronous clock signal S12, and the clock distribution device 7 of the second device 2,
8 respectively. At this time, the synchronous clock signal S
11 and S12 also form a redundant system.

Further, the clock distribution devices 4 and 5 of the first device 1 receive the monitoring signals S31 and S32 for the synchronous clock signal S11 and the synchronous clock signal S12 from the clock distribution devices 7 and 8 of the second device 2, respectively. Respectively, the clock distribution devices 4 and 5 receive the state monitoring results of the reference clock signals S1 and S2 and the monitoring signal S3
1 and S32, control signals S21 and S22 are sent to the clock distribution devices 7 and 8, respectively, in order to instruct the second device 2 to select one of the synchronous clock signals S11 and S12.

Thus, in the second device 2, the clock distribution devices 7 and 8 use the synchronous clock signals S11 and S1.
After selecting one of the two, an internal clock signal is generated inside the device according to the selected synchronous clock signal, so that the second device 2 is subordinately synchronized with the first device 1.

Further, also in the case where a third device (not shown) is provided together with the first device 1 and the second device 2, the second device is similarly provided with respect to the first device 1. The second and third devices can be slave synchronized. in this case,
In the network synchronization system, the second device 2 synchronizes the first device with the third device by using a first output clock signal and a second output clock signal, and the first output clock signal and the second output clock signal. A control signal instructing which of the signals to select may be transmitted, and a third internal clock signal may be generated in the third device based on the output clock signal and the control signal.

That is, the third device, like the second device 2, has two clock distribution devices, and these clock distribution means monitor the first output clock signal and the second output clock signal. It is only necessary to have another internal clock signal generating means for outputting the second monitoring signal indicating the result to the second device 2. In this case, the clock distribution devices 7 and 8 of the second device 2 are provided with a logical sum means, and the first monitor signal transmitted from the second device 2 to the first device 1 by the logical sum means and the third monitor signal. A new monitor signal may be generated from the logical sum of the second monitor signal and the second monitor signal input from the first device and sent to the clock distribution means of the clock distribution devices 1 and 2 of the first device 1. .

In addition, the present invention can be similarly applied to a network synchronization system provided with three or more devices. For a device for inputting / outputting a monitoring signal, a logical sum unit is provided as described above to perform a logical sum operation. A new monitoring signal is generated, and the second device and the subsequent devices can be brought into the dependent synchronization state with respect to the first device 1. In short, the clock distribution devices 4 and 5 of the first device 1 act as reference clock distribution devices for the internal clock signal generation means of other devices, that is, the clock distribution devices 7 and 8 and the like.

In each of the network synchronization systems, the 1 + 1 redundant reference clock signal supplied from one clock supply device is received by the first device 1 and the first device 1 is used as a center to other devices. Therefore, dependent synchronization can be established, so that the configuration can be simplified. Here, the first
Although the description has been given of the case where the 1 + 1 redundant system is formed in the device 1 and other devices, the present invention is similarly applicable to a case where three or more redundant systems are provided.

[0030]

As described above, according to the network synchronization system of the present invention, only the first device is provided with the clock switching control circuit, and the first device is supplied from one clock supply device. Since the system is configured so as to receive the reference clock signal forming the redundant system and enable the subordinate synchronization of the clock signal to another device, there is an advantage that the configuration can be simplified. In particular, since devices other than the first device receive the control signal for selecting any of the input synchronization clock signals, there is no need to provide a clock switching control circuit, and further, the input device includes an OR circuit. Since a monitoring signal is newly generated from the logical sum of the output monitoring signals and the slave synchronization is instructed based on the selection element of the reference clock signal, a clock supply device is not required. As a result, in the entire network synchronization system, the clock switching control circuit and the clock supply device are significantly reduced, and only the first device needs to be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a network synchronization system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a basic configuration of a conventional network synchronization system.

[Explanation of symbols]

 1,100 First device 2,200 Second device 3,9 Clock supply device 4,5,7,8 Clock distribution device 6,14 Clock switching control circuit 10,11,12,13 Clock receiving circuit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Yoshio Mori, Inventor 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Koshiro Akinaga 1-16-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan (56) References JP-A-3-102933 (JP, A) JP-B-55-33221 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04L 7 / 00

Claims (2)

(57) [Claims] 1. A network synchronization system comprising a first device and a second device that individually operate on a network in response to a clock signal, wherein the clock signal includes a first reference clock signal and a redundant signal. A single clock supply for generating a second reference clock signal forming a system, wherein the first device selects one of the first reference clock signal and the second reference clock signal A switching control unit that specifies whether to perform the switching, and a first control unit that is connected to the switching control unit, monitors the first reference clock signal and the second reference clock signal, and monitors the first reference clock signal that is specified by the switching control unit. Any one of the reference clock signal and the second reference clock signal is selected and sent to the device as a first internal clock signal, while the first reference clock signal and the second Based on the reference clock signal of
And a second synchronizing clock signal and a first synchronizing clock signal and a second synchronizing clock signal together with a control signal indicating which one of them to select. Clock distributing means for outputting, the second device receives the first synchronous clock signal, the second synchronous clock signal and the control signal, and receives the first synchronous clock signal and the second synchronous clock signal. 2. A network synchronization system comprising: an internal clock signal generating means for generating a second internal clock signal to be sent to the inside of the device in accordance with a selected one of the two synchronous clock signals. 2. The network synchronization system according to claim 1, further comprising a third device together with said first device and said second device, wherein said internal clock signal generating means further comprises: While generating a first monitoring signal representing a monitoring result of the first synchronization clock signal and the second synchronization clock signal, the third monitoring signal is generated based on the first synchronization clock signal and the second synchronization clock signal. A control signal for generating a first output clock signal and a second output clock signal to be sent to the device, and indicating which of the first output clock signal and the second output clock signal should be selected. And the third device outputs the first output clock signal and the second output clock signal.
And generating a third internal clock signal to be sent out inside the device in accordance with a selected one of the output clock signals, and displaying a monitoring result of the first output clock signal and the second output clock signal. And another internal clock signal generating means for outputting the second monitor signal to the second device, wherein the second device determines a logical sum of the first monitor signal and the second monitor signal by a monitor signal. Output to the first device as a network synchronization system.