JPH0380797A - Time synchronizing system - Google Patents

Abstract

PURPOSE:To always maintain time synchronism with high accuracy by taking the time synchronism by transmitting state change information from a slave station to a master station after attaching notice time, comparing it with its own clock at the master station, and performing time correction only when an error exceeding a constant level exists. CONSTITUTION:When the state change information occurs at the slave station 2, a state change information transmission circuit 11 is started up, and a start-up signal is transmitted to a notice time information transmission circuit 8. At the notice time information transmission circuit 8, the present time (notice time) being displayed on a clock 7 is attached on the state change information, and it is transmitted to the master station. At the master station, notice time information is extracted from reception information, and a difference between a time displayed with a clock 3 and the time shown by received notice time information is detected at an error circuit 4, and a time t set in advance is compared with a detected error at a comparator 5, and a time information transmission circuit 6 transmits the present time displayed on the clock 3 to the slave station 2 as a time correction signal only when the error exceeds the time t. At the slave station, when a reception circuit 9 receives the time correction signal, a time correction circuit 10 is started up, then, the clock 7 is corrected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a monitoring system having a monitoring station and a plurality of monitored stations, and particularly relates to a time synchronization method performed between a monitored station and a monitoring station. .

[Conventional technology]

Conventionally, time synchronization in this type of system is, for example, 0
At a predetermined time such as 0:00:00:00:00 minutes, each monitored station (hereafter: "slave station") receives a broadcast notification from the monitoring station (hereinafter: "master station") and changes its own clock. This was done in the form of a correction.

[Problem to be solved by the invention]

Since the conventional time synchronization method described above uses regular notifications, there is a possibility that the notification may not reach the slave station due to a failure in the transmission line, or the slave station clock may be reset due to restarting the slave station device (returning the power supply). If this happens, there is a drawback that the accuracy of time synchronization between the master station and the slave stations decreases significantly until the next scheduled time.

[Means to solve the problem]

In the time synchronization method of the present invention, in a monitoring system including a monitoring station and a plurality of monitored stations, when notifying the monitoring station of information on a change in the state of a monitored item that has occurred in the monitored station, A notification time of the occurrence time information of the state change is transmitted to the monitoring station together with the occurrence time information, and the monitoring station compares the notification time with the time of its own clock, and the difference is determined by a preset value. When the value is larger than the value, the time of the own clock is transmitted to the monitored station, and the time of the monitored station is corrected.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention.

In FIG. 1, ■ is a master station, 2 is a slave station, 3 is a clock owned by the master station, 4 is an error detection circuit between the reporting time transmitted from the slave station and the time of the clock owned by the master station, 5 is a comparator for error and Δt, 6 is a time information transmission circuit of the master station, 7 is a clock of a slave station, 8 is a reporting time information transmission circuit of a slave station, 9 is a time information reception circuit, 10 is a time correction circuit, 11 is a state change information transmitting circuit.

When state change information to be reported to the master station 1 is generated in the slave station 2, the state change information transmitting circuit 11 is activated and an activation signal is transmitted to the reporting time information transmitting circuit 8. The reporting time information transmission port i\88 adds the current time (reporting time) displayed on the clock 7 to the state change information and transmits it to the master station.

The master station that receives the time information from the slave station extracts the reporting time information from the received information and transmits it to the time error detection circuit 4. The error circuit 4 detects the difference between the time displayed by the clock 3 and the time indicated by the received notification time information, and notifies the comparator 5 of this information. Then, the comparator 5 compares the preset time Δt with the detected error,
Only when the error is greater than Δ, a time correction request signal is sent to the time information transmitting circuit 6. Upon receiving the time correction request signal, the time information transmitting circuit 6 transmits the current time displayed on the clock 3 to the slave station 2 as a time correction signal. In the slave station, when the receiving circuit 9 receives the time correction signal, the time correction circuit 10 is activated and corrects the clock 7.

In this way, the slave station adds the notification time to the status change information and transmits it to the master station, and the master station compares this with its own clock and only performs time correction and synchronizes the time if there is an error above a certain level. As a result, high accuracy of time synchronization can always be maintained without reducing the information transmission efficiency of time synchronization information transmission.

〔Effect of the invention〕

As explained above, in the present invention, the slave station adds the notification time to the state change information and transmits it to the master station, and the master station compares this with its own clock and corrects the time only if there is an error of more than a certain level. By performing time synchronization, high accuracy of time synchronization can always be maintained without reducing the information transmission efficiency of time synchronization information transmission.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention. 1...Monitoring station (master station), 2...Monitored station (slave station),
3... Master station clock, 4... Error detection circuit between reporting time and current time, 5... Comparator between error and set value Δt, 6
...Time information transmitting circuit, 7...Slave station clock, 8...
- Report time information transmission circuit, 9... Time information reception circuit, O... Time correction circuit, 1... State change information transmission circuit.

Claims (1)

[Claims] In a monitoring system that includes a monitoring station and multiple monitored stations,
When notifying the monitoring station of information on a state change of a monitored item that has occurred in the monitored station, transmitting a notification time of the state change occurrence time information to the monitoring station together with the state change occurrence time information; The monitoring station compares the reporting time with the time on its own clock, and when the difference is greater than a preset value, transmits the time on its own clock to the monitored station. A time synchronization method characterized by correcting the time of the monitored station.