JPH0666793B2 - Signal synchronization method - Google Patents

Description

The present invention relates to a data transmission system, and in particular, data at a plurality of points separated from each other by using a token passing bus (for example, instantaneous values of voltage, current, etc.). The present invention relates to a signal synchronization method for sampling simultaneously.

[Conventional technology]

Local area networks (hereinafter referred to as LANs) have been rapidly spreading in recent years, and one of the notable trends in them is the MAP proposed by General Motors, Inc. in the United States.
There is a growing interest in industrial LANs called (Manufacturing Automation Protocol). F
A (Factory Automation, Factory Automati
on), OA (Office Automation Office Aut
A large number of devices such as robots and computers have been introduced into factories and offices for the purpose of automation, but the standardization of the MAP is being promoted for the purpose of easily and inexpensively connecting these devices. It aims to be an industry standard rather than a LAN for one company, and many leading companies are participating. International Organization for Standardization (ISO) OSI (Open System Interconnection Open Syste
(m Interconection) Standardization is underway by filling each layer of the hierarchical model, and the lower two layers (physical layer, data link layer) except for the logical link control sublayer are
American Institute of Electrical and Electronic Engineers (The Institute of Elect
rical and Electronics Engineers Tnc. hereafter referred to as IEEE) 802.4 Committee token passing bus is used. At present, the IEEE802.4 standard uses a coaxial cable as a transmission medium of a physical layer, but application of an optical fiber cable is also under consideration. As a medium, an optical fiber cable or a data link layer communication method is used. Exactly the same.

FIG. 5 is a block diagram showing a network in which this token passing bus is composed of optical fibers. In the figure, 1 ₁ to 1 _n are stations forming a network, 2 ₁ to 2 _n are optical fiber cables, and 3 is the optical fibers 2 ₁ to 2 _n, which connect the stations 1 ₁ to 1 _n to each other. It is an optical star coupler.

Next, the operation will be described. Although there is a system (CSMA / CD) in which each station arbitrarily transmits data in the bus type network, it has a drawback that the transmission efficiency rapidly decreases when the amount of transmission data increases and the load increases. The token passing bus, on the other hand, avoids this drawback with a deterministic access scheme. That is, the transmission right called a token is sequentially transmitted between the stations subscribing to the token passing bus, and a plurality of stations are prevented from transmitting at the same time. Tokens are passed in order from the station with the largest address to the station with the smallest address, and each station stores the station (successor station) to which the station should give the token. Called a ring) is configured.

However, if this logical ring is fixed, it cannot be joined when a new station wants to join, and if one of the joining stations fails, the logical ring is broken and communication stops. Therefore, the token passing bus has the following ring maintenance function.

(1) When the token temporarily disappears due to noise, the previous token holding station reissues the token.

(2) If the subsequent station fails, give the token to the subsequent station of the failed station and remove the failed station from the logical ring.

(3) New stations are solicited at almost constant intervals and stations that wish to join the logical ring are allowed to join.

On the other hand, there is an application field in which the token passing bus is used for high-speed control of equipment, and there is a system in which each station needs to repeatedly generate a specific signal at the same time. For example, consider a system that requires synchronization of sampling signals for obtaining instantaneous values of voltage, current, etc. at a plurality of points at the same time. In such a system, a method of performing signal synchronization using a token-passing bus, the particular station, for example station 1 ₁ master station relating to signal synchronization, the slave station concerning the signal synchronization other stations 1 ₂ to 1 _n and then, the main station 1 ₁ is using the data frame to be transmitted cyclically slave stations 1 ₂ to 1 _n is conceivable method to synchronize in accordance with the master station 1 _1.

Figure 6 is a time chart showing such a conventional signal synchronization method, the main station 1 ₁ has a main synchronization signals S ₁ causes generated in the period t _0, the main station in synchronization with the main synchronization signals S ₁ 1 ₁ transmits a data frame D _1, slave station 1 ₂ to 1 _n is intended to know the occurrence time of the data frame D ₁ of the arrival time by calculating back from the main synchronization signal S _1, which by all participating in the network Enables signal synchronization of stations. Here, the data frame D ₁ for synchronization transmitted by the main station 1 ₁ will be referred to as a main synchronization data frame. To send further main synchronization signal in synchronization with the S ₁ main sync data frame D ₁ at a predetermined period, the main station 1 ₁ sends an empty data frame D _s prior to the transmission of the main synchronization data frame D _1, and The length of the empty data frame D _s is changed according to the time difference between the transmission completion time of the main synchronization data frame D ₁ and the main synchronization signal S ₁ . As a result, the master station 1 ₁ can transmit the main synchronization data frame D ₁ synchronized with the main synchronization signal S ₁ . On the other hand, in the slave station, by phase-controlling the station synchronization control signal in the own station by the time difference between the reception completion time of the main synchronization data frame D ₁ and the station synchronization control signal, the slave synchronization signal follows the main synchronization signal S _1. Signal synchronization is performed.

[Problems to be Solved by the Invention]

Since the conventional signal synchronization method is configured as above, when the participating stations of the network send solicitation frames at regular intervals to solicit new stations in order to maintain and expand the network, the conventional signal synchronization method is used. Since the new station solicitation is performed independently for each station in the synchronization method, the transmission completion time of the main synchronization data frame fluctuates greatly every time the new station solicitation is executed, as shown in (a) and (c) of FIG. 6, for example. However, there is a problem that the data transmission time of the slave station fluctuates, and signal synchronization may be temporarily lost depending on the method of adjusting the empty data frame of the master station.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a signal synchronization method that reduces fluctuations in data transmission time of a slave station and facilitates a synchronization control procedure of a master station. And

[Means for Solving the Problems] The signal synchronization system according to the present invention has a length based on the time difference between the transmission completion time of the main synchronization data frame and the main synchronization signal prior to the main synchronization data frame from the main station. A set empty data frame is transmitted, and the length of this empty data frame is corrected by the token circulation time and the timing of solicitation of new stations predicted based on the information on the constituent stations of the network. Upon detection of completion of reception of the synchronization data frame, the station synchronization signal of the own station is synchronized with the main synchronization signal.

[Action]

The main station relating to signal synchronization in the present invention sets the length based on the time difference between the main synchronization data frame transmission completion time and the main synchronization signal before transmitting the main synchronization data frame to be transmitted for synchronization. An empty data frame is transmitted, and at this time, the length of the empty data frame is corrected by using the token circulation time predicted based on the network constituent station information and the new station solicitation timing, and the signal synchronization is performed. The slave station concerned detects the completion of reception of the main synchronization data frame and synchronizes the station synchronization signal of its own station with the main synchronization signal to reduce fluctuations in the timing of data transmission between the stations.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
The figure is a time chart showing a signal synchronization system according to an embodiment of the present invention. In the figure, A _{1 to} A _n respectively indicate station addresses of the stations 1 ₁ to 1 _n in FIG. 5, and A ₁ > A ₂ > ...
... The relationship of A _n is established.

Here, as in the prior art, the main station a station 1 ₁ to signal synchronized in the token-passing bus of FIG. 5,
The station 1 ₂ to 1 _n and the slave station to signal synchronization. Also, the second
Figure is a diagram showing the construction of a primary synchronization data frame to explain a method of transmitting invitation synchronization command by the master station 1 _1, Figure 3 is the main station 1
Flow chart showing the _first operation, Fig. 4 is a flowchart showing the operation of the slave station 1 ₂ to 1 _n.

Next, the operation will be described. First, the operation of the station 1 ₁ which is the main station for signal synchronization will be described.

Main station 1 ₁ executes the operation of the flow chart shown in Figure 3 whenever the pass tokens to subsequent stations. That is, it has a counter for invitation synchronization control that decrements by 1 each time the token is circulated, checks the current counter count value CNT in step ST1, and if it is not 0, subtracts 1 from the count value CNT. However, when it is 0, the maximum set value CNT _max is substituted as this count value CNT. In step ST2 measuring a time difference t ₁ between the main synchronization signals S ₁ and the main synchronization transmission completion time of the data frame D _1. At step ST3, the sum of the lengths of the last transmitted null data frame D _s other frames, and assuming that silence sum is not changed, the time difference t ₁ measured before and length t _s of the previous empty data frame By using, the length t _s of the empty data frame to be originally transmitted is calculated. Usually, the formula for calculating the length of this empty data frame is, for example, t _s present = t _s previous −t ₁ ,
Other Or t _s current = 2t _s before -t _s but before the previous -t ₁ current + t ₁ before the like are considered, it is not a feature of the invention, t _s current = f
(T ₁ ).

Next, in step ST4, the count value CNT of the counter is
And the result obtained by multiplying the address n of the smallest address station 1 _n among the participating stations of the network by a predetermined constant a are coincident, and if they are coincident, the operation of step ST8 is performed, and if they are not coincident, the operation of step ST5 is performed. I do. Step S
At T5, the count value CNT of the counter and the addresses A _{1 to} A of the stations other than the minimum address station 1 _n among the participating stations of the network.
It is determined whether or not one of the results obtained by multiplying _n-1 by the predetermined constant a matches, and if any of them matches, step ST
7. If they do not match, the operation of step ST6 is performed.

In step ST6, none of the stations in the network of participating stations is determined that the new station invitation is not performed, an empty data frame D _s length t _s' of null data frames to send the original as a current to be transmitted this time Use length t _s current. In step ST7, station 1 excluding the lowest address station in the network
₁ to 1 new station invitation _n-1 to predict, as the length t _s' current of the current transmission null data frame D _s to be solicitation than the length t _s current empty data frames to send the original frame C _{1 to} C
_The value obtained by subtracting the length t _c of _{n−1 and} the length t _w of one response window is used. In step ST8, the solicitation of a new station of the smallest address station 1 _{n in} the network is predicted, and the length t _s ′ of the empty data frame D _s to be transmitted this time is set as the current length t _{s of the} empty data frame to be originally transmitted. _s the length t _c of the solicitation frame C _n from the present and 2 the length of the response window 2
· T _w a using a value obtained by subtracting.

When these steps ST6 to ST8 are completed, the operation is moved to step ST9. In step ST9, the empty data frame D _s having the length t _s ′ of the empty data frame to be transmitted this time obtained in this way is added to the transmission queue. In step ST10, the counter is referred to, and if the count value CNT is 0, step ST11,
If not 0, the operation of step ST12 is performed. In step ST11, for example, the main synchronization data frame D ₁ with the solicitation synchronization command SS as shown in FIG. 2 is added to the transmission queue. In step ST12, the main synchronization data frame D ₁ without the solicitation synchronization command SS is added to the transmission queue.

A method of collecting the network constituent station information can be obtained, for example, by extracting the source address of the frame each time a data frame is received and arranging it in the reception order internal memory. Further, it is necessary to select the maximum set value CNT _{max which} is larger than the predetermined constant a times the address A ₁ of the station 1 ₁ which is the main station. Further, the main station 1 ₁ is not only the operation of the flow chart shown in FIG. 3, also the operation of the flow chart shown in Figure 4 perform. In that case, the operations of steps ST21 and ST22 are omitted. The operation shown in the flowchart of FIG. 4 will be described in the operation of the following slave station.

Next, the operation of the stations 1 ₂ to 1 _{n that} are slave stations related to signal synchronization will be described.

Each of the slave stations 1 ₂ to 1 _n executes the operation of the flowchart shown in FIG. 4 every time the token is passed to the succeeding station. That is, in step ST21, determines whether or not there is invitation synchronization instruction SS to the main synchronization in the data frame D ₁ received from the master station 1 _1, the count value of the counter for invitation synchronous control at step ST22, if CNT 0 is substituted for and the operation of step ST23 is executed. If there is no solicitation synchronization command SS, the operation of step ST23 is executed as it is.

In step ST23, the counter is referred to and its count value C
If NT is not 0, 1 is subtracted from the count value CNT, and if it is 0, the maximum set value CNT _max is substituted for the count value CNT. In step ST24, the count value CNT of the counter
And the result of multiplying the addresses A _{1 to} A _n of the own station by the predetermined constant a are in agreement, the new station solicitation is executed in step ST26, and if they are not in agreement, solicitation prohibition is executed in step ST25. .

The operation of the master station 1 ₁ and the slave stations 1 ₂ to 1 _n as described above is illustrated in the time chart of FIG. Ie the first
In the case of (a), the maximum set value CNT _max is set to the count value CNT of the counter, and then 1 is set for each lap of the token.
In the process of subtracting the count value CNT one by one,
The new station solicitation is not performed, and the original empty data frame length t _s present (t _s present = f (t ₁ )) is used as the length t _s ′ present of the empty data frame D _s to be transmitted this time. Thus, the main synchronization signal S ₁ synchronizes the transmission completion time of the main synchronization data frame D ₁ .

Case in the new station solicitation of the main station 1 ₁ Lee) is performed, the main station 1 ₁ length t _s current of the original empty data frame as the length of t _s' current of empty data frame D _s to be transmitted this time from using the solicitation frame C ₁ length t _c and 1 response window of the result of subtracting length t _w (t _s' current = t _s current -t _c -t _w), the main synchronization data frame D ₁ The transmission completion time is synchronized with the main synchronization signal S ₁ . In the case of c), the slave station 1 ₂ performs new station invitation, transmission completion time and the main synchronization signal S ₁ of the same as the case of i) primary synchronization data frame D ₁ are synchronized. In the case of d), the new station invitation minimum address station 1 _n, as the length t _s' current empty data frame D _s to be transmitted this time the master station 1 _1, t _s current -t _c -2 · using the t _w, also primary synchronization transmission completion time of the data frame D _1, the main synchronization signal S ₁ is synchronized.

In the case of (e), when the count value CNT of the counter becomes smaller than the predetermined constant a times the address A _n of the minimum station 1 ₁ , the new station is not solicited and the empty space to be transmitted by the main station 1 ₁ this time. using the length t _s current empty data frame to be transmitted originally as the length t _s' current data frame D _s. Therefore,
The main synchronization signal S ₁ is synchronized with the transmission completion time of the main synchronization data frame D ₁ .

The length t _c of the solicitation frames C _{1 to} C _n is IEEE802.4.
The length in the standards are defined, the length t _w of the response window is pre Ji because set as system-specific value. Thus the length t _w of length t _c and response window of C ₁ -C _n of the invitation frame needs to be held by the main station 1 ₁ as a fixed value. Further, although operations other than those shown in FIGS. 3 and 4 are required for the master station 1 ₁ and the slave stations 1 ₂ to 1 _n, they are not a feature of the present invention, and therefore description thereof will be omitted.

In the above embodiment, as a synchronization method for soliciting new stations, a solicitation synchronization command is periodically sent from the master station and a counter for solicitation synchronization control is provided for each station so that all participating stations in the network perform signal synchronization. The new station is solicited at regular intervals in synchronization with the master station, but the master station transmits the count value of the counter each time, and the slave station refers to the received counter value each time. The control for soliciting a new station may be performed based on the determination of the above, and the same effect as that of the above-described embodiment is obtained.

〔The invention's effect〕

As described above, according to the present invention, the length of the empty data frame transmitted from the main station prior to the main synchronization data frame is predicted based on the information about the constituent stations of the network, and the token circulation time and new station invitation Since it is configured to correct the transmission end time of the master synchronization data frame of the master station in synchronization with the master signal, the slave station transmission timing is also synchronized with the master synchronization signal. Since it is maintained at a constant timing, stable signal synchronization can be obtained, and the synchronization control procedure can be facilitated, and restrictions on software on the system operation side can be reduced.

[Brief description of drawings]

FIG. 1 is a time chart showing a signal synchronization method according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a main synchronization data frame transmitted in this embodiment, and FIG. 3 is a main relating to signal synchronization of this embodiment. FIG. 4 is a flow chart showing the operation of the station, FIG. 4 is a flow chart showing the operation of the slave station concerning the signal synchronization of this embodiment, FIG. 5 is a block diagram of the bus network to which the present invention is applied, and FIG. 6 is the conventional signal synchronization. It is a time chart which shows a system. 1 ₁ master station, 1 ₂ to 1 _n are slave stations, 2 ₁ to 2 _n denotes an optical fiber cable, 3 an optical star Kapusera, T ₁ through T _n is a token frame, D ₁ is the main synchronization data frame, S ₁ The main synchronization signal, t ₁ is the time difference between the transmission completion time of the main synchronization data frame and the main synchronization signal, D _s is an empty data frame, and SS is an invitation synchronization command. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mamoru Suzuki 1-3-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Within Tokyo Electric Power Co., Inc. (72) Yuji Hoshino 1st, Toshiba-cho, Fuchu-shi, Tokyo Toshiba Fuchu, Ltd. Inside the factory (72) Inventor Sachito Sejima 1-1-1, Kokubuncho, Hitachi City, Ibaraki Hitachi Co., Ltd. Inside Kokubun Factory (72) Inventor Toshio Anzai 1-2-1, Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo (56) Reference JP-A-63-263938 (JP, A) JP-A-63-263939 (JP, A) JP-A-63-318842 (JP, A)

Claims (1)

[Claims] 1. A token passing bus in which a plurality of stations form a logical ring, a token is circulated in the logical ring, and only stations holding the token are allowed to transmit data. , Or in a network having a communication protocol similar thereto, in a signal synchronization method for synchronizing the transmission timing of data transmitted by each station, one of the plurality of stations is a master station for signal synchronization,
The other is a slave station for signal synchronization, and the master station determines the length based on the time difference between the transmission completion time of the master synchronization data frame and the master synchronization signal before transmitting the master synchronization data frame to be transmitted for synchronization. While transmitting the determined empty data frame, at the time of transmitting the empty data frame, predict the token circulation time and new station solicitation timing based on the network constituent station information, and based on them, the empty data frame A signal synchronization system characterized in that the slave station synchronizes the station synchronization signal of its own station with the main synchronization signal by correcting the length and detecting completion of reception of the main synchronization data frame.