JPH01317044A - Time information transmission system - Google Patents

Abstract

PURPOSE:To prevent time matching between control stations of a remote monitor control station in the occurrence of a transmission fault and the generation of an error of time management by inhibiting the retransmission of time information when an information discrimination means discriminates it that the sent information is the time information. CONSTITUTION:In the data transmission by the HDLC system, the information discrimination means discriminating whether or not the transmission information is the time information is provided to the sender side so as to make the data retransmission function effective or ineffective in response to the result of discrimination. That is, when the information discrimination means discriminates it that the transmission information is the time information, the retransmission of the time information is inhibited. Thus, even if any transmission fault takes place, the error of the time matching or time management between control stations of the remote monitor control station is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention is directed to high-level data link control procedures (Ilig).
h Level Data Link Control
The present invention relates to a data transmission method for transmitting data according to the HDLC method (hereinafter abbreviated as HDLC method), and particularly to a time information transmission method for transmitting time information using the HDLC method.

B1 Summary of the Invention This invention provides a time information transmission system that transmits time information using an HDLC system that is equipped with a function to retransmit information when a transmission failure occurs, in which an information determination means determines that the transmitted information is time information. By prohibiting the retransmission of the time information, it is possible to prevent errors in time synchronization and time management between remote monitoring and control stations in the event of a transmission failure.

C1 Prior Art In recent years, in remote monitoring and control, there has been a demand for expanding the range of monitoring and control and combining it with computers to speed up troubleshooting and improve operational efficiency. In order to meet the above-mentioned demands, HDLC has recently been adopted as a data transmission method that allows easy expansion of the amount and types of information and also facilitates computer processing. This HDLC method has the following advantages.

(You can check whether the other party's computer is ready to receive data, whether the other party's computer is capable of receiving data, etc.)

(2) When a busy situation occurs, the other station can keep transmitting until it ends.

(3) Data can be automatically retransmitted when a transmission failure occurs, and data loss can be prevented.

(4) Continuous transmission in which multiple pieces of data are sent together, full-duplex transmission in which they communicate with each other simultaneously, etc. are possible, and the transmission time can be shortened.

The Consultative Committee on International Telegraph and Telephone (CCITT) divides the responsibility for transmission systems into levels as shown in Figure 3. Level I has the role of recognizing data, and to explain it using the transmission format (frame structure) of the HD LC method shown in Figure 4, it is F (8 bits) to clarify the beginning and end of the frame. This corresponds to A (address section consisting of 8 bits) for indicating the station that should receive the command and the station that sent the response.

In level 2, the receiver has the role of controlling operations such as commands to the other station and responses to the commands as responses, and corresponds to C (control unit composed of 8 bits). In addition, high levels above level 3,
The receiver has various types of information, and falls under ■ (information section with no restrictions on bit configuration).

Currently, the above level in HDLC method! , LSIs have been created that perform all the work that should be done at level 2, and computers only need to perform work at level 3 or higher. Therefore, the burden on the computer is significantly reduced. Furthermore, the transmission efficiency of the HDLC method is also extremely good compared to other methods. In other words, the transmission efficiency is determined by the number of raw data bits/the number of transmitted bits, and in the case of the CDT (cyclic digital transmission) method, it is as follows, in the case of the basic method, it is, and in the case of the HDLC method, it is as follows.

Next, the state of data transmission using the HDLC method will be explained with reference to FIG. FIG. 5 shows a case where a transmission failure occurs as shown in G during communication between stations A and B. For example, “I・3・4” of “rA-B code” in the figure is information (I)
The transmission order number is 3 and the reception order number is 4 in the frame with
, and the number in the "Sent data available" column indicates the number of remaining data sets. Also, if a transmission failure occurs at time tl as shown in G, the data of "■・3・4" becomes B.
I can't reach the station. Since station A does not know that the failure has occurred, the next time t is 1, the transmission order number is increased by 1 to ``■・4''.
・Send the data of 4.

Then, on the B station side, the previous time it received the data with the transmission order number "2", and this time it receives the data with the transmission order number "■・4・4", so the transmission order number jumps from 2 to 4. It is recognized that a failure has occurred.

Therefore, a retransmission request is issued at time t, and the retransmission request is sent at time t.

In the frame without ■, the reject signal “REJ・
3" is emitted. "rREJ.3" means that the frame with transmission order number 3 is expected to be transmitted next, since up to transmission order number 2 has been received. Then, at time t6, the retransmission request is recognized by station A, the retransmission conditions are established, and data of frames with transmission order numbers 3 to 5 are retransmitted from time t to time t8.

As mentioned above, in the HDLC system, the local station and the other station communicate while mutually confirming the transmission order number, so when a transmission failure occurs, data can be automatically retransmitted.
Data loss can be prevented.

Problems to be solved by the D0 invention As an example of expanding the types of information in remote monitoring and control,
There is an application in which the time is unified among all controlled stations, data from each controlled station is tagged with time, and events that occur are analyzed.

For this reason, time information is transmitted from the centralized control center (general control) to each controlled station (child station) via the control center (master station) to perform time adjustment, time management, etc. When managing the time of information generated at a controlled station, transmission failure occurs before and after time information is transmitted.

If a transmission error occurs, the time information is automatically retransmitted as explained in FIG. 5, so the time difference between the initial transmission and the retransmission becomes a time error. This error disrupts the time relationship between occurring events, making it impossible to analyze the phenomenon.

Below, frame transmission states will be described for four cases when a transmission failure occurs. In FIGS. 6(a) to (d), the frame marked with "Jiyo" inside is a frame containing a time advance signal, and the frame marked with "JIJI" inside is a frame containing a time execution signal. The frame with numbers inside is a frame that contains other general data, and the numbers are symbols to distinguish time relationships. It is also a frame that includes a beam direct signal written as rREJJ inside. The interval from the time notice signal to the time execution signal is set in advance to a constant time T1. This time information (time notice signal and time execution signal) is transmitted at a predetermined cycle. FIG. 6(a) shows a case where a transmission failure occurs at the time point x2, that is, the frame transmitted next to the time execution signal (frame containing data +t). In this case, the upstream side cannot receive +1 data, but receives +2 data, and since the transmission sequence number of that data has jumped, it can recognize that there is a transmission failure, and issues a reject REJ. Make a retransmission request. Then, on the downstream side, although not shown, the +1 and +2 data are retransmitted.

Therefore, in the case of FIG. 6(a), there is no effect on the time information transmitted before the +1 data.

FIG. 6(b) shows a case where a transmission failure occurs at time x3, that is, a frame containing a time execution signal. In this case, the upstream side cannot receive the time execution signal, but receives +1 data, and since the transmission sequence number of that data is skipped, it can recognize that there is a transmission failure and issue a reject REJ. Make a retransmission request. Then, on the downstream side, from the next transmission frame (+2) in the same time zone as the rejected REJ, the time execution signal, +l and +2
Resend the data. Since the data is automatically retransmitted in this way, the time from the completion of transmission of the time advance signal to the completion of transmission of the time execution signal is T, which is significantly longer than the set time T. For this reason, time adjustment cannot be performed using the first time execution signal (time point x3), and time adjustment is performed using the retransmitted time execution signal, resulting in a large time error (E).

FIG. 6(c) shows a case where a transmission failure occurs at the time point x5, that is, the frame containing the time advance signal.

In this case, the upstream side cannot receive the time advance signal but does receive the time execution signal, and since the transmission order number is skipped, it can recognize that there is a transmission failure, and reject R.
EJ is issued to request retransmission. Then, the downstream side retransmits the time advance signal 0 time execution signal and +1 data from the transmission frame (+) in the same time zone as the rejected REJ (in addition, the time advance signal and time execution signal at the time of retransmission are simply (The time difference T3 is completely different from the set time T1.) Since the data is automatically retransmitted in this way, the time must be adjusted when the time execution signal is sent for the first time. Therefore, the time is adjusted using the retransmitted time execution signal, resulting in a large time error (E).

FIG. 6(d) shows a case where a transmission failure occurs at a time point of x6, that is, a frame transmitted immediately before the time notice signal (a frame containing data of -1). In this case, the upstream side cannot receive the -1 data, but receives the time advance signal, and since the transmission sequence number is skipped, it can recognize that there is a transmission failure, and reject REJ.
to issue a retransmission request. Then, the downstream side retransmits the data of the time advance signal and time execution signal 110 times after the time execution signal. In this case, since the transmission order number of the first time notice signal is skipped, the signal is not recognized as a normal time notice signal, and therefore, time adjustment is not performed using the first time execution signal. Since the data is automatically retransmitted in this way, the time cannot be adjusted when the first time execution signal is sent, and the time is adjusted using the retransmitted time execution signal, resulting in a large time error (
E) occurs.

The present invention has been made in view of the above points, and its purpose is to:
An object of the present invention is to provide a time information transmission method that does not cause errors in time adjustment even if a transmission failure occurs when transmitting time information using an HDLC method.

Means and Effects for Solving Problem E1 'The present invention provides data transmission from a centralized control center to a controlled station via a control center in accordance with a high-level data link control procedure that has a function of retransmitting information when a transmission failure occurs. In a time information transmission method for transmitting time information to a sender, information determining means for determining whether or not transmitted information is time information is provided on the transmitting side, and the information determining means determines that the transmitted information is time information. When this occurs, retransmission of the time information is prohibited.

F. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present invention provides an information determining means for determining whether transmitted information is time information on the transmitting side in data transmission using the HDLC method, and enables or disables a data retransmission function according to the determination result. It is. FIG. 1 shows the processing flow of the information determining means of the present invention. First, in step S, it is determined whether the transmitted information is time information. As a result, if the transmission information is time information, transmission is performed without a retransmission function in step S, and if it is not time information, transmission with a retransmission function is performed in step S. In this case, after the information determination means makes a determination, it is determined whether the data is to be transmitted with or without the retransmission function depending on the high level of level 3 or higher described above. If there is no retransmission function, the sending side does not add a sending sequence number, and the receiving side does not recognize the sending sequence number either. Furthermore, even if a retransmission request is received, the transmitting side does not retransmit it. When the transmission data is received, Level 1.2 recognizes the data, requests retransmission for data with a retransmission function when a retransmission request is established, and for data without a retransmission function, the transmission sequence number is changed in the event of a failure. Since there is no retransmission, no retransmission request is made, and even if a retransmission condition is established due to a failure in the previous data with retransmission function, retransmission will not be performed.

Such a transmission method of the present invention is shown in FIGS. 6(a) to 6(d).
), the frame transmission state is 7th.
Figures (a) to (d) are shown. First, (a) in Figures 6 and 7
cases are not a hindrance.

Next, if the time execution signal transmitted from the downstream side is lost due to a transmission failure as shown in Figure 6(b), the transmission sequence number is not lost and is rejected on the upstream side as shown in Figure 7(b). No signal is emitted. Therefore, only the time advance signal is received, and time adjustment will not be performed at an incorrect time.

In this case, the time cannot be set, but if the precision of the clock is sufficiently improved, the time can be set using the time execution signal transmitted in the next cycle. Also, Figure 6 (c
In the case of ), similarly to the above, since no reject signal is issued on the upstream side, only the time execution signal is received as shown in FIG. 7(C), and time adjustment will not be performed at an incorrect time.

Furthermore, in the case of FIG. 6(d), the time advance signal and the time execution signal are not retransmitted as shown in FIG.
1. Only +2 data is retransmitted. This prevents time adjustment from being performed at an incorrect time, and moreover, time adjustment is performed correctly.

In addition, in order to transmit without the retransmission function, the address must be a global address frame consisting of all "L" bits as shown in Figure 2 so that commands common to multiple partner stations can be received, or the control section must be A non-numbered frame configured in a non-numbered format may also be used. Another method is to transmit in transparent mode, but this requires mode switching and is not practical. For time adjustment signals, it is more convenient to use the global address method, which allows signals to be sent to multiple partner stations at the same time.

G1 Effects of the Invention As described above, according to the present invention, time information is not retransmitted, so when data is transmitted using the HDLC method, even if a transmission failure occurs, each control of the remote monitoring and control center is maintained. This provides the excellent effect of eliminating errors in time adjustment and time management between locations.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing one embodiment of the present invention, and FIG.
The figure is an explanatory diagram showing the bit structure of the global address, and Figure 3 is an explanatory diagram showing the level of responsibility allocation in the transmission method.
Figure 4 is a frame configuration diagram showing the transmission format of the 1-I DLC method, and Figure 5 is the HDL when a transmission failure occurs.
Time chart showing the transmission form using C method, Fig. 6 (
a) to (d) are time charts for explaining each frame transmission state in the conventional example, and FIGS. 7(a) to (d) are time charts for explaining each frame transmission state when the present invention is applied. It is a chart.

Claims (1)

[Claims] (1) In a time information transmission method that transmits time information from a central control center to a controlled station via a control center in accordance with a high-level data link control procedure that is equipped with a function to retransmit information when a transmission failure occurs. The transmitting side is provided with information determining means for determining whether the transmitted information is time information, and when the information determining means determines that the transmitted information is time information, the retransmission of the time information is prohibited. A time information transmission method characterized by: