JPH08136675A - Time correction method of communication terminal - Google Patents

Abstract

PURPOSE: To accurately match the time of a clock circuit of each terminal device in units of ms in a system consisting of a central device including a clock circuit and a plurality of devices which are connected to the central device by a serial communication line and include the clock circuit each. CONSTITUTION: A central device and a plurality of terminal devices including a clock circuit each are connected by a serial communication line. The central device transmits transmission clock data which are configured by a certain number of bits successively at a certain time interval to each terminal device and each terminal device obtains the difference between the reception time data which is obtained by adding a certain communication required time determined for each terminal to the transmission time data received by the central device and the time of a built-in clock circuit as a compensation value and then stores the difference (S1, S2). When compensation value data within a certain range are obtained for a determined number of times (n) (S3, S4, and S5), the clock circuit of the terminal device is corrected based on n compensation values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a central device such as an airport facility or a traffic system and a plurality of terminal devices. The present invention relates to a method for adjusting the time of a communication terminal.

[0002]

2. Description of the Related Art There is a system in which a plurality of terminal devices synchronously perform a fixed operation to achieve a desired purpose as a whole. For example, there is a case where a central device collectively controls the operation of a number of traffic lights arranged along a road in a traffic system so that a traffic flow is smoothed through a serial communication line. For this application, the operation timing is not required to be excessively strict, but in some cases, extremely strict synchronization is required.

An example of an application that requires extremely accurate time adjustment is an approach road indicator light control device as an airport facility, for example. This device turns on a plurality (for example, 20 points) of approach road indicator lights arranged on the ground along a landing approach road that is often determined to draw a curve toward the airport in the traveling direction. It is designed to guide aircraft landing at an airport to a proper course in advance, and individual approach lights are installed at a considerable distance from a position far from the airport. Then, a lighting instruction to the approach road indicator light is issued from the central device of the airport through a communication line, and each approach road indicator light performs a flasher operation for turning on the indicator light for a short time (for example, 25 ms) based on a built-in clock circuit. The landing approach road is clearly indicated to the pilot by sequentially lighting a series of indicator lights in the traveling direction. Since human vision is sensitive, the difference (deviation) in lighting start time of each indicator light is about 2.5 ms in order to make the light spot move along the approach path without a sense of discomfort. Since control is required, it is necessary to accurately synchronize (correct) the clock circuit. In such a case, there is a method in which the central device directly controls each terminal device, but since it is via a communication line, there is a possibility that delays and errors will occur due to the communication procedure and the lighting timing is likely to be incorrect and highly reliable control Is difficult

Therefore, the clocks of the clock circuits individually provided in the respective terminal devices are set in advance, and the operation start time is transmitted from the central device to each traffic signal (terminal device) via a communication line. It can be configured to start operation based on the time, and higher reliability is obtained (time synchronization method). In such a system, the central device and the terminal device each have a clock circuit and recognize the current time. In order for each terminal device to operate in perfect synchronization, it is necessary that the times of the clock circuits be the same. As a method of synchronizing the terminal devices in such a system, conventionally, a method of synchronizing with a commercial power supply frequency for timekeeping, a method of incorporating a circuit for receiving a radio and correcting the time according to a time signal sound, and the like have been used.

However, in the method of counting the frequency of the commercial power source, the time is incorrect when there is a power failure. It is possible to provide a power failure compensation circuit, but a slight deviation occurs and cannot be used depending on the application.
Above all, it cannot be applied to terminal devices that operate on battery power. In addition, it is difficult to precisely adjust the time in units of (ms) because the radio time signal sound is used to detect the time signal sound level.

For this reason, a configuration is also used in which the clock circuit of each device updates the time based on an individual clock signal from a crystal oscillator or the like. In this case, if the respective devices continue to operate without being synchronized with each other at all, there is a possibility that the time of each device may deviate due to the variation of the respective clock signals. The clock accuracy these days is quite accurate,
A lead or a lag of about 10 ms per day cannot be avoided, and if accumulated, there is a non-negligible effect.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and enables the recognition time of a plurality of terminal devices having a clock circuit by an independent clock to be adjusted with high accuracy in units of (ms). The purpose is to propose a method for adjusting the time of a communication terminal.

[0008]

SUMMARY OF THE INVENTION The first invention of the present application includes a central device including a clock circuit, and a plurality of terminal devices connected to the central device by serial communication lines and individually including a clock circuit. A method for adjusting the time of a communication terminal for making the time of the clock circuits of all terminal devices of the system consisting of, wherein the central device transmits transmission time data to each terminal device, The difference between the reception time data obtained by adding the fixed communication required time determined for each terminal to the received transmission time data and the time of the built-in clock circuit is calculated and stored (S1, S2), based on the correction value group. The clock circuit of the terminal device is corrected (S6).

A second aspect of the present invention is a whole terminal device of a system comprising a central device including a clock circuit, and a plurality of terminal devices connected to the central device through a serial communication line and individually including a clock circuit. The time adjustment method of the communication terminal for making the time of the clock circuit coincide with each other, wherein the central device transmits the transmission time data composed of a certain number of bits in order at a certain time interval to each terminal device, In the device,
The difference between the reception time data obtained by adding the fixed communication required time determined for each terminal to the transmission time data received from the central device and the time of the internal clock circuit is calculated and stored as a correction value (S1,
S2), the number of times correction value data within a certain range is determined (n
(S3, S4, S5), the clock circuit of the terminal device is corrected based on the n correction values (S6). After the correction, all the stored data are discarded (S7).

[0010]

In both of the inventions of the present application, each terminal device receives the transmission time data indirectly meaning the transmission start time of the central device, that is, the time recognized by the clock circuit, and adopts the adopted communication procedure and installation of the terminal. The reception time data is obtained by adding a certain communication required time for each terminal device determined by the position and the individual difference of the communication network, and the value to be corrected is determined based on the plurality of reception time data. Particularly, in the second invention, the transmission time data transmitted from the central device is set to have a fixed number of bits, and is transmitted at fixed time intervals. Therefore, the normal data transmission time becomes the same, the accuracy is improved, and the next transmission time data can be predicted on the terminal device side, and the processing is simplified. On the receiving side, the difference (correction value) between the reception time data and the time of the built-in clock circuit is calculated for each reception and stored, and when a correction value within a certain range is obtained a plurality of times, the time is corrected based on these values. Averaging is performed and accurate correction can be performed.

[0011]

FIG. 4 is a simplified block diagram of an apparatus according to the time adjustment method for a communication terminal of the present invention, in which a central unit (M) including a clock circuit and each of them include a clock circuit. Multiple terminal devices (T1, T2, ..., Tn) and each terminal device (T1,
T2,…, Tn) Serial communication line connecting each to the central unit (M)
It is composed of (L1, L2, ..., Ln). The central device (M) sends the time held by the clock circuit of its own device to each terminal device (T1, T2, ..., Tn) in addition to sending the necessary command. Each terminal device (T1, T2, ..., Tn) performs a commanded process under the control of the central device (M), as well as a process determined based on the instruction time of its own clock circuit (for example, as described above). In the case of the approach road indicator light control device, the approach road indicator light, which is a terminal device, performs a lighting operation for a short time.)
The validity of the time information of (M) is judged, and the time of the clock circuit of the own device is corrected if necessary.

An embodiment of the method of the present invention will be described below with reference to the flow chart shown in FIG. 2 and 3 are explanatory diagrams that schematically show how transmission and reception are performed. In the embodiment, the central device including the clock circuit sequentially transmits the time data of its own clock circuit as the transmission time data to each terminal device connected by the serial communication line.
The transmission time data is generated so as to be composed of a fixed number of bits by performing necessary correction on the read value from the clock circuit.
The transmission time data thus prepared is transmitted at regular time intervals. The above process steps are not shown in FIG.

FIGS. 2 and 3 show an example of transmission / reception between a certain terminal device and a central device, and the central device transmits transmission time data meaning the present time to this terminal device every 10 minutes. Note that similar transmission is sequentially performed to other terminal devices during the illustrated transmission operation. On the terminal device side, data is received by adding a certain communication required time (α in FIG. 2) that is normally determined for each terminal to each transmission time. However, depending on the communication state, an error may occur and the same data may be repeatedly transmitted, which may increase the communication time required (β in FIG. 2). In extreme cases, communication may end incompletely.

When each terminal device receives the transmission time data from the central device in parallel with the originally defined main processing
In (S1), the reception time data is calculated by adding a certain communication required time (α in FIG. 2) determined for each terminal to this transmission time data, and this reception time data and the clock circuit built in the terminal device are calculated. Calculate the difference from the current time and store it as a correction value
(S2).

It is determined whether there is a correction value already stored (S
3) If there is no stored correction value, return to the processing step (S1). If there is already a stored correction value, the difference between the obtained correction value and the first stored correction value is calculated to determine whether this difference is within a certain range (S4). If it is not within the fixed range, all stored correction values are discarded (memory clear: S7) and the process returns to the process step (S1). On the other hand, if it is within a certain range, it is determined whether the number of stored correction value data is n (for example, 5),
If it is n, the time of the built-in clock circuit is corrected based on the stored n correction values (S6).

For example, the time stored in the clock circuit is corrected by using the first stored correction value (difference). Alternatively, it is possible to make a correction based on the latest correction value. Further, the most frequently occurring value of each correction value may be used, or the average value may be used.
Whichever value is adopted, the difference between them is very small. After correction processing, discard all stored correction values (Memory clear: S
7) and returns to the processing step (S1).

In the above-described embodiment, the correction is performed when the substantially same correction value is obtained n times and continuously. In practice, the condition of continuity may be excluded, and sufficient accuracy can be obtained even if correction is performed every time n substantially identical correction values are obtained. Further, the transmission of the time data of the central device may not be evenly spaced depending on the application, and the required accuracy is often obtained even if the data lengths are not uniform.

As described in the above embodiments, in the time adjustment method for a communication terminal according to the second aspect of the present invention, the central device transmits to each terminal device transmission time data composed of a fixed number of bits in order at fixed time intervals. In each terminal device, the difference between the reception time data obtained by adding a certain communication required time determined for each terminal to the transmission time data received from the central device and the time of the built-in clock circuit is calculated and stored as a correction value. (S1, S2), when the correction value data within a certain range is obtained a predetermined number of times (n times) (S3, S4, S5), the clock circuit of the terminal device is corrected based on the n correction values. Yes (S6). In the method of the first invention, the central device transmits the transmission time data to each terminal device, and at each terminal device, the reception time obtained by adding the certain communication required time determined for each terminal to the transmission time data received from the central device. The difference between the data and the time of the built-in clock circuit is calculated and stored as a correction value (S1, S2), and the clock circuit of the terminal device is corrected based on the correction value group (S6), so there is a slight decrease in accuracy. However, the time of the communication terminal can be adjusted with sufficient accuracy for practical use.

The invention of the present application is, other than the system described in the embodiment, a central apparatus including a clock circuit and a plurality of terminals connected to the central apparatus by serial communication lines and individually including the clock circuits. The present invention can be widely applied to a system including a device and can accurately match the time of the clock circuit of each terminal device.

[0020]

As described above, the time adjustment method of the communication terminal of the present application is connected to the central side device including the clock circuit and the central device by the serial communication line by performing the steps already described. In a system composed of a plurality of terminal devices each individually including a clock circuit, the time of the clock circuit of each terminal device can be more accurately matched in units of ms than ever before.

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of the method of the present invention.

FIG. 2 is an explanatory diagram schematically showing a state of transmission and reception between a central device and a terminal device.

FIG. 3 is an explanatory diagram schematically showing a state of transmission and reception between a central device and a terminal device.

FIG. 4 is a simple block diagram of an apparatus according to the present invention.

[Explanation of symbols]

 (M) ... Central device (T1, T2, ..., Tn) ... Terminal device (L1, L2, ..., Ln) ... Serial communication line

Claims (2)

[Claims] 1. A central unit including a clock circuit,
A time adjustment method for a communication terminal for synchronizing the time of the clock circuits of all the terminal devices of a system consisting of a plurality of terminal devices each connected to the central device by a serial communication line and configured to individually include a clock circuit, In the central device, the transmission time data is transmitted to each terminal device, and in each terminal device, the reception time data and the built-in clock obtained by adding a certain communication required time determined for each terminal to the transmission time data received from the central device. A time correction method for a communication terminal, in which the difference from the circuit time is obtained and stored as a correction value (S1, S2), and the clock circuit of the terminal device is corrected based on the correction value group (S6). 2. A central unit including a clock circuit,
A time adjustment method for a communication terminal for synchronizing the time of the clock circuits of all the terminal devices of a system consisting of a plurality of terminal devices each connected to the central device by a serial communication line and configured to individually include a clock circuit, The central device transmits to each terminal device transmission time data composed of a certain number of bits in order at fixed time intervals, and at each terminal device, the transmission time data received from the central device is fixed for each terminal. The difference between the reception time data added with the communication required time and the time of the built-in clock circuit is calculated and stored as a correction value (S1, S2), and the correction value data within a certain range is obtained a predetermined number of times (n times). If (S3, S4, S5), the clock circuit of the terminal device is corrected based on the n correction values (S
6) How to adjust the time on the communication terminal.