JP2679506B2 - Clock switching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a clock switching system of a transmission device having a synchronous network ring structure. In particular, the present invention relates to a clock switching system for a transmission device having a synchronous network ring configuration in which all transmission devices are operated in synchronization with one clock signal.

[0002]

2. Description of the Related Art Conventionally, in a clock switching system, a slave device extracts a clock signal from data on a transmission line transmitted from a master device and uses it as a clock signal for the device, and then transmits the data to the next device. Was being transmitted.

Therefore, in the event of a transmission line failure, the clock signal on the transmission line cannot be extracted, and the clock signal of the master device is supplied to the clock signal of the device subsequent to the device in which the failure is detected. The clock signal of the device subsequent to the device in which was detected was manually switched so as to be extracted from the data in the opposite direction.

[0004]

However, in such a conventional clock switching system, since the switching of the clock signal must be manually controlled when the transmission line fails,
There is a problem that a manual operation is required for the switching and a clock signal synchronized with the master clock signal cannot be obtained until the switching is completed.

The present invention solves the above problems,
An object of the present invention is to provide a clock switching system which can automatically and rapidly recover a synchronous clock signal without requiring humans to switch the clock signal in the case of a transmission path failure.

[0006]

According to the present invention, there are provided a master transmission device for transmitting data in synchronization with a master clock signal and two transmission lines for transmitting data to the master transmission device in opposite directions. In the clock switching system, which is connected via a plurality of slave transmission devices that transmit data to the two transmission lines in synchronization with a clock signal extracted from received data in a predetermined direction, the master transmission device is , A means for adding the identifier of the transmission device to data and transmitting the data, and when an identifier other than the transmission device is detected in the received data from the predetermined direction, the specified identifier is data for the direction opposite to the predetermined direction. The slave transmission device includes a plurality of slave transmission devices, each of which transmits itself to the slave device when a failure in the transmission path in the predetermined direction is detected. Means for switching the internal clock signal to add the identifier of its own device to the data and transmitting the data, and when the specified identifier is detected from the received data from the direction opposite to the predetermined direction, the received data from the direction opposite to the predetermined direction And a switching means including means for switching to the clock signal extracted from.

According to the present invention, the adding means detects an identifier added to the received data from the predetermined direction, and when the detected identifier is an identifier other than the master transmission device, the first control signal. A first identifier detecting means for outputting and transmitting the identifier of the master transmission device by adding it to the data, and transmitting the master signal in a direction opposite to the predetermined direction based on the first control signal. It is possible to include an identifier adding means for adding the above-mentioned specified identifier to the data instead of the device identifier and transmitting the data.

Further, according to the present invention, the switching means detects the failure of the transmission line and outputs a second control signal, and the above-mentioned stipulation is based on received data from a direction opposite to the predetermined direction. Identifier detecting means for outputting a third control signal when the identifier is detected, and its own device instead of the identifier of the master transmission device added to the received data from the predetermined direction based on the second control signal Second identifier inserting means for adding the identifier to the data and transmitting the data, and switching the clock signal extracted from the received data from the predetermined direction based on the second control signal to the internal clock signal of the own device, The clock signal extracted from the received data from the predetermined direction is switched to the clock signal extracted from the received data from the direction opposite to the predetermined direction based on the third control signal. Tsu may include a click switching means.

[0009]

The master transmission device adds the identifier of the master transmission device to the data by the adding means and transmits the data. When the identifier other than the master transmission device is detected in the received data from the predetermined direction, the master transmission device is in the opposite direction to the predetermined direction. For the direction, a specified identifier is added to the data and transmitted. When the switching means detects a failure of the transmission path in the predetermined direction, each of the plurality of slave transmission devices switches the internal clock signal of the own device, adds the identifier of the own device to the data, and transmits the data. When a prescribed identifier is detected from the received data from the device, the clock signal is switched to the clock signal extracted from the received data from the direction opposite to the predetermined direction.

As described above, it is possible to automatically and rapidly restore the synchronous clock signal without requiring manpower for switching the clock signal when the transmission line fails.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a clock switching system according to an embodiment of the present invention. FIG. 2 is a block diagram of a master transmission device of a clock switching system. FIG. 3 is a block diagram of a clock transmission type slave transmission device.

1 to 3, in the clock switching method, a master transmission device 0 that transmits data in synchronization with a master clock signal and two data transmissions to the master transmission device 0 in opposite directions. A plurality of slave transmission devices 1 to 5 which are connected via transmission lines and which transmit data to the two transmission lines in synchronization with a clock signal extracted from received data in a predetermined direction.

A feature of the present invention is that the master transmission device 0 adds means for transmitting the identifier of the master transmission device 0 to the data and transmits the received data from a predetermined direction to the master transmission device 0. When an identifier other than the above is detected, the slave transmission devices 1 to 5 are each provided with an addition means for adding a prescribed identifier to the data in a direction opposite to the predetermined direction and transmitting the data. When an internal clock signal of the own device is detected, a means for adding the identifier of the own device to the data and transmitting it, and when a specified identifier is detected from the received data from the direction opposite to the predetermined direction, the direction opposite to the predetermined direction There is provided switching means including means for switching to the clock signal extracted from the received data from.

Further, the adding means of the master transmission device detects the identifier added to the received data from the predetermined direction, and when the detected identifier is an identifier other than the master transmission device 0 , the first control signal is sent. The identifier detecting means 11 as the first identifier detecting means to output, and the master transmission device 0
Is added to the data and transmitted, and in the direction opposite to the predetermined direction based on the first control signal, a prescribed identifier is added to the data instead of the identifier of the master transmission device 0 and transmitted. The identifier adding means 12 is included.

Further, the switching means of the slave transmission devices 1 to 5 defines the failure detection means 21 for detecting a failure of the transmission path and outputting the second control signal, and the received data from the direction opposite to the predetermined direction. Identifier detecting means 22 as a second identifier detecting means for outputting a third control signal when the identifier of the above is detected, and a master transmission device added to received data from a predetermined direction based on the second control signal. An identifier inserting means 24 for adding the identifier of the own device to the data and transmitting the data instead of the identifier of 0 , and the internal clock signal of the own device for the clock signal extracted from the received data from the predetermined direction based on the second control signal. The clock signal extracted from the received data from the direction opposite to the predetermined direction based on the third control signal. And a clock switching means 23 to switch to.

The operation of the clock switching device having such a configuration will be described. FIG. 4 is a flow chart showing the operation of the identifier detection means of the clock switching master transmission device of the present invention. FIG. 5 is a flow chart showing the operation of the failure detection means of the clock transmission type slave transmission device of the present invention. FIG. 6 is a flowchart showing the operation of the identifier detecting means of the clock switching type slave transmission device of the present invention. FIG. 7 is a diagram showing the operation of the slave transmission device that has detected a transmission path fault of the clock switching system of the present invention and the slave transmission device adjacent thereto. In FIG. 7, FIG. 7A shows a state when a transmission line failure occurs, and FIG. 7B shows the operation of the slave transmission device 2 that has detected the transmission line failure and the slave transmission device 3 adjacent to it. Show. FIG. 8 is a diagram showing operations of the master transmission device and the slave transmission device at the time of clock switching of the clock switching system of the present invention. 8A shows the operation of the slave transfer devices 4 and 5 which transmits the identifier 02 of the slave transmission device 2 to the master transmission device 0, and FIG.
(B) shows an operation in which the master transmission device 0 transmits the specified identifier FF and then the slave transmission device 5 transmits the identifier FF. FIG. 9 is a diagram showing a state at the end of the clock signal switching of the clock switching system of the present invention.

2 and 3, in the master transmission device 0 , the identifier adding means 12 adds the own device identifier 00 to the data and transmits the data. When the identifier detecting means 11 detects an identifier other than the own device in the received data, the identifier detecting means 11 controls the identifier adding means 12 to add the prescribed identifier FF to the transmitted data in the direction of the received data and to transmit it.

In FIGS. 3, 5 and 6, in the slave transmission devices 1 to 5, the fault detecting means 21 for detecting a fault in the main signal is instructed to the clock switching means 23 when the fault is detected. It issues a command to transmit data clockwise and counterclockwise using the station's internal clock. At the same time, it issues a command to the identifier inserting means 24 to add the own station identifier and transmit the data.

The identifier detecting means 22 other than the transmission device 0 for transmitting the master clock signal detects the identifier inserted by the upstream station, and when this identifier is other than FF, the clock signal of the clockwise received data is turned clockwise. And clock switching means 23 for use in counterclockwise data transmission.
Command. When the identifier is FF, the clock switching means 23 is instructed to use the clock signal of the counterclockwise received data for clockwise and counterclockwise data transmission. When detecting an identifier other than 00, the identifier detecting means 22 of the transmission device that transmits the master clock inserts the FF identifier in the direction in which the identifier other than 00 is detected and transmits the data. Then, a command is issued to the identifier inserting means 24.

The switching procedure of the present invention will be described with reference to FIGS. 1 and 4 to 8.

In FIG. 1, all transmission devices operate in synchronization with the clock signal of the master transmission device 0 in the normal state, and the master transmission device 0 has its identifier 00 (1).
Hexadecimal number) is transmitted as data on the transmission path. In this state, the other transmission devices 1 to 5 also receive the received identifier 00 (16
The base number) is transmitted as data on the transmission path.

FIG. 7A shows the occurrence of a transmission line failure between the transmission device 1 and the transmission device 2.

In FIG. 7B, the transmission device 2 which has detected the failure of the transmission line switches to the internal clock signal and transmits the identifier 02 (hexadecimal number) of the transmission device 2 as the data of the transmission line. The transmission device 3 receives the identifier 02 (hexadecimal number) of the transmission device transmitted by the transmission device 2 and further transmits the identifier 02 clockwise and counterclockwise.

Similarly, in FIG. 8, the transmission devices 4 and 5 are
This shows that the identifier 02 (hexadecimal number) is transmitted clockwise and counterclockwise.

In FIG. 8B, since the master transmission device 0 receives the identifier 02 (hexadecimal number) other than the identifier 00 (hexadecimal number) transmitted by the self transmission device, the identifier FF (16
The transmission device 5 transmits the (adic number) in the counterclockwise direction, and the transmission device 5 receiving this transmits the reception clock signal from the counterclockwise direction to the clockwise and counterclockwise transmission clock signals.

Similarly, in FIG. 9, the transmission clock signals of the transmission devices 4 and 3 are sequentially switched, and finally the transmission clock of the transmission device 2 is a counterclockwise reception clock from the clock signal of the own transmission device. The signal is switched, and the switching of the clock signal is completed.

[0027]

As described above, the present invention has an excellent effect that the synchronous clock signal can be restored automatically and at high speed without requiring humans for switching the clock signal in the case of a transmission line failure.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of a clock switching system according to an embodiment of the present invention.

FIG. 2 is a block configuration diagram of a clock switching master transmission device of the present invention.

FIG. 3 is a block configuration diagram of a clock switching type slave transmission device of the present invention. flowchart.

FIG. 4 is a flowchart showing the operation of the identifier detection means of the clock transmission master transmission device of the present invention.

FIG. 5 is a flowchart showing the operation of the failure detection means of the clock transmission type slave transmission device of the present invention.

FIG. 6 is a flowchart showing the operation of the identifier detection means of the clock transmission type slave transmission device of the present invention.

FIG. 7 is a diagram showing the operation of a slave transmission device that has detected a transmission path fault of the clock switching system of the present invention and a slave transmission device adjacent thereto.

FIG. 8 is a diagram showing an operation of the master transmission device and the slave transmission device at the time of clock switching of the clock switching system of the present invention.

FIG. 9 is a diagram showing a state at the end of clock switching in the clock switching system of the present invention.

[Explanation of symbols]

 0 master transmission device 1-5 slave transmission device 11, 22 identifier detection means 12 identifier addition means 21 failure detection means 23 clock switching means 24 identifier insertion means 00 master transmission device identifier (hexadecimal number) 02 slave transmission device (2) Identifier (hexadecimal number) FF Specified identifier (hexadecimal number)

Claims (3)

(57) [Claims] 1. A master transmission device that transmits data in synchronization with a master clock signal, and a reception device in a predetermined direction that is connected to the master transmission device via two transmission lines that transmit data in opposite directions. In a clock switching system including a plurality of slave transmission devices that transmit data to the two transmission lines in synchronization with a clock signal extracted from the data, the master transmission device uses the identifier of the transmission device as a data And a means for transmitting the received data from the predetermined direction, and an additional means for adding a prescribed identifier to the data and transmitting the data in the direction opposite to the predetermined direction when the identifier other than the transmission device is detected. Each of the plurality of slave transmission devices is switched to its own internal clock signal when a failure in the transmission path in the predetermined direction is detected. A means for adding the identifier of its own device to the data and transmitting it, and a clock signal extracted from the received data from the direction opposite to the predetermined direction when the specified identifier is detected from the received data from the direction opposite to the predetermined direction. A clock switching system characterized by comprising switching means including means for switching to. 2. The adding means detects an identifier added to the received data from the predetermined direction, and outputs a first control signal when the detected identifier is an identifier other than the master transmission device. One identifier detection means and the master transmission device identifier is added to the data and transmitted,
An identifier adding means for adding the specified identifier to the data instead of the identifier of the master transmission device and transmitting the data in a direction opposite to the predetermined direction based on the first control signal. Clock switching method described. 3. The switching means detects a failure in the transmission path and outputs a second control signal, and detects the specified identifier from received data from a direction opposite to the predetermined direction. When a second identifier detecting means for outputting a third control signal at the time, and instead of the identifier of the master transmission device added to the received data from the predetermined direction based on the second control signal of its own device An identifier inserting means for adding an identifier to the data and transmitting it, and a clock signal extracted from the received data from the predetermined direction based on the second control signal is switched to the internal clock signal of the own device, and the third control signal And a clock switching means for switching the clock signal extracted from the received data from the predetermined direction to the clock signal extracted from the received data from the direction opposite to the predetermined direction. The clock switching system according to claim 1, further comprising: