JPH05191418A - Transmission control system - Google Patents

Abstract

(57) [Abstract] [Purpose] In a token passing bus or a transmission control method having a communication protocol similar to this, it is possible to reduce fluctuations in data transmission time of a slave station and to easily perform a synchronization control procedure of a master station. To do. [Structure] This transmission control method enables the slave master station to update the slave station when the master station determines from the address information of the network participants that all slave stations required to form the system are participating in the network. A command to cancel the solicitation of stations was issued, and subordinate stations did not execute solicitation of new stations by this command.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 transmission control method for simultaneously sampling signals.

[0002]

2. Description of the Related Art A local area network (hereinafter referred to as L
AN) is rapidly gaining popularity in recent years, and one of the notable trends among them is General Motors (G)
MAP (Manufacturing) advocated by M)
Automation Protocol Manufacturing Automati
There is increasing interest in industrial LANs called "on Protocol". Many devices such as robots and computers have been installed in factories and offices for factory automation (FA) and office automation (OA), but these devices can be interconnected easily and inexpensively. For that purpose, standardization of the MAP is in progress. It aims to be an industry standard rather than a LAN for one company, and many leading companies are participating. ISO
(International Standardization Organization) OSI (Open System Interconnection) standardization is underway by filling each layer of the hierarchical model,
The lower two layers (physical layer, data link layer) except for the logical link control sublayer are IEEE (US
Electronic Engineers Conference The Institute of Electrical and El
The ectronics Engineers Inc.) 802.4 Committee token passing bus will be used. Currently IEEE80
According to the 2.4 standard, a coaxial cable is used as a physical layer transmission medium, but application of an optical fiber cable is also under consideration. It is the same.

FIG. 5 is a block diagram showing a network in which the token passing bus is composed of an optical fiber. 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 an optical star coupler. Next, the operation will be described. A method in which each station arbitrarily sends data to the bus network (CSM
A / CD) is also available, but there is a drawback in 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 by a deterministic access scheme. That is, a transmission right called a token is sequentially transmitted among the stations that are subscribing to the token passing bus, and a plurality of stations are prevented from transmitting at the same time. Tokens are passed 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 pass the token, and this constitutes a logical ring (logical ring) in which the token circulates. However, if this logical ring is fixed, it will not be possible to join when a new station wants to join, and if any of the joining stations fails, the logical ring will break and communication will stop. Therefore, the token passing bus has the following ring maintenance function.

When the token temporarily disappears due to noise or the like, the previous token holding station reissues the token. If the successor station fails, it tokens the successor station of the failing station and removes the failing station from the logical ring. New stations are solicited at almost regular intervals and stations wishing to join the logical ring are allowed to join. On the other hand, there is an application field in which high-speed control of equipment is performed by using this token passing bus, and there is a system in which each station needs to repeatedly generate a specific signal at the same time. For example, in the case of a system that requires synchronization of sampling signals to simultaneously obtain instantaneous values of voltage, current, etc. at multiple points, a method of synchronizing signals using a token passing bus is to use a specific station as the main station. A method is conceivable in which a station (slave station) other than the master station synchronizes with the master station by using a data frame periodically transmitted by the master station. That is, the master station 1 ₁ generates the master synchronization signal S ₁ in the cycle T, and the data frame D ₁ of the master station 1 ₁ is transmitted by the master synchronization signal S ₁
And the slave stations 1 ₂ to 1 _n transmit the data frame D.
It becomes possible to know the generation time of the main synchronization signal S ₁ by back-calculating from the arrival time of ₁ , and it becomes possible to perform signal synchronization of all stations participating in the network.

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. Further, since the main synchronization data frame D ₁ is transmitted at a constant cycle in synchronization with the main synchronization signal S ₁ , an empty data frame is transmitted prior to the transmission of the main synchronization data frame, and the transmission completion time of the main synchronization data frame is by changing the length of the null data frames according to the time difference between the main synchronization signals S _1, it is possible to main synchronization signal transmitted in the main synchronization data frame D ₁ in synchronization with the S _1. On the other hand, in the slave station, the station synchronization control signal in the local station is phase-controlled by the time difference between the reception completion time of the main synchronization data frame D ₁ and the station synchronization control signal, so that the station synchronization control follows the main synchronization signal S _1. Signal synchronization of signals is performed.

[0006]

Normally, in order to maintain and expand the network, the participating stations of the network must send a solicitation frame at regular intervals to solicit new stations, but perform high-speed control of equipment. When applied to an application field, there are cases in which the stations required to configure the system can be limited, and operation can be performed on the condition that all the required stations have joined the network. For example, as an example applied to a power system protection system, there is a case where a synchronous main station is configured by a bus protection relay device and a synchronous slave station is configured by a terminal device installed in each feeder. In the case of this system, the busbar protection relay device and each terminal device are all in the state of participating in the network, and it is not possible that even one device is not participating in the network except during maintenance and inspection. .. However, in the conventional network, new stations are solicited even when all the stations necessary for configuring the system are participating in the network. Furthermore, in the conventional transmission control method, new stations are solicited for each station. Since they are performed independently, the transmission completion time of the main synchronization data frame varies greatly each time a new station solicitation is executed, as shown in (a) and (c) of FIG.
Therefore, 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 provide a transmission control method that reduces fluctuations in data transmission time of a slave station and facilitates a procedure of synchronization control of a master station. There is.

[0007]

In the transmission control method according to the present invention, the master station for synchronization judges from the address information of the network participating stations that all slave stations necessary for forming the system are participating in the network. In this case, the slave station issues a command to stop solicitation of new stations, and the slave stations do not execute solicitation of new stations by this command.

Therefore, according to this transmission control method, by the above means, it is determined whether or not the main station has a station configuration for forming a system from all the participating stations of the network, and a station configuration that does not require solicitation of a new station. When this happens, a command is issued to the subordinate station to stop soliciting new stations, so that the subordinate stations can stop soliciting new stations and prevent temporary loss of signal synchronization when soliciting new stations. It is possible to eliminate the fluctuation of the data transmission timing of

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a method of transmitting a main synchronization data frame of a main station according to the signal synchronization method of the present invention. A _{1 to} A _n respectively represent station addresses of the stations 1 ₁ to 1 _n in FIG. 5, and A ₁ > A
₂ > ... A _n holds. Token passing of Figure 5
In the bus, station 1 ₁ is the main station for signal synchronization, station 1 ₂ ~
1 _n is a slave station. FIG. 2 shows a method of transmitting a solicitation synchronization command from a master station according to an embodiment of the present invention. FIG. 3 shows an operation flow of the master station, which is a feature of the present invention, and FIG. 4 shows an operation flow of the slave station. a. Detailed description of operation of station serving as master station Each time the master station passes the token to the succeeding station, the master station performs the operation of the flow shown in FIG. That is, it has an invitation synchronization control counter CNT that decrements by 1 each time a token pass is executed,
In step 1, if the current value of the solicitation synchronization control counter CNT is not 0, 1 is subtracted, and if 0, the maximum set value CNT
Substitute _max . In step 2 of measuring the time difference t ₁ between the main synchronization signals S ₁ and the main synchronization transmission completion time of the data frame D _1. As Step 3 in the previous transmitted null data frame length of D _s other frame summation and silence the sum is not changed, by a length t _{s before} and the measured time difference t ₁ of the previous empty data frame , Calculate the length t _s of the empty data frame to be originally transmitted.
The formula for calculating the length of a normally empty data frame is, for example, t _{s current}
= T _{s before-} t ₁ , but other t _{s present} = t _{s before} -1 / 2
· T ₁ or t _{s current} = 2t _{s before} -t _{s before the previous} -t _{1 current} +
_Before t ₁ is considered, but it is not a feature of the present invention.
Let t _{s present} = f (t ₁ ).

Next, in step S1, the main station determines that all the stations (system stations) necessary for constructing the system participate in the network. If it is determined that all stations are subscribed, step S2 is performed, and if it is determined that the required station is not subscribed, step 4 is performed. In this case, it goes without saying that the stations necessary for forming the system may be set not only as constants in advance but also externally or by remote control. As the length t _{s' current} empty data frame to be transmitted this time in step S2, the length of the null data frames to send the original to use t _{s current.} Step S3
Then, the length t _s ′ of the empty data frame to be transmitted this time
Add an empty data frame D _s with the _current to the transmission queue. Further, in step S4, 0 is substituted into the solicitation synchronization control counter CNT, and the process is moved to step 11.

If it is determined in step S1 that the necessary station has not yet joined, in step 4 the value of the solicitation synchronization control counter CNT and the address A _n of the minimum address station among the participating stations of the network are set. It is determined whether or not the results of multiplication by the constant a times match. If they match, the operation in step 8 is performed, and if they do not match, the operation in step 5 is performed. In step 5, it is determined whether or not the result of multiplying the value of the solicitation synchronization control counter CNT by a predetermined constant a times the addresses A _{1 to} A _n-1 of stations other than the minimum address station participating in the network is a constant. It is determined whether or not they match, and if they do not match, the operation of step 7 is performed. In step 6, it is judged that none of the stations participating in the network is soliciting a new station, and the length t _s ′ of the empty data frame to be transmitted this time is the _current length t _{s of the} empty data frame to be originally transmitted. _{s Use current} . In step 7, the solicitation of new stations of the stations 1 ₁ to 1 _n-1 excluding the lowest address station in the network is predicted, and the empty data frame length t _s ′ _present to be transmitted this time is used as the empty data to be originally transmitted. The value obtained by subtracting the length t _{c of the} invitation frame and the length t _w of one response window from the length t _{s of the} frame is used. In step 8, the new station invitation of the smallest address station 1 _{n in} the network is predicted, and the empty data frame length t _s ′ _present to be transmitted this time is set as the empty data frame length t _{s present} to be originally transmitted. using the value obtained by subtracting the length t _c and 2 length 2 · t _w of the response window solicitation frame.

In step 9, the empty data frame D having the length t _s ′ of the empty data frame to be transmitted this time is _present.
Add _s to the send queue. In step 10, the solicitation synchronization control counter CNT is referred to. If the counter value is 0, the operation in step 11 is performed, and if not 0, the operation in step 12 is performed. In step 11, for example, a main synchronization data frame with an invitation synchronization command as shown in FIG. 2 is added to the transmission queue. In step 12, the main synchronization data frame without the solicitation synchronization command is added to the transmission queue. The method of collecting the network configuration information can be achieved by, for example, extracting the source address of the frame every time the data frame is received and arranging the addresses in the order of reception. Also, the maximum set value CNT _max
It is necessary to select a value larger than a predetermined constant a times the address A ₁ of the main station. When the master station operates as described above, if it is determined in step S1 that all of the stations necessary for configuring the system are participating in the network, the solicitation synchronization control counter is set to 0, and the steps are always performed. 11 will be executed. If there is a station that should join the network, execute step 4 and subsequent steps.
As a result, the subordinate side invites a new station.

B. Detailed description of operation of slave station The slave station executes the operation of the flow shown in FIG. 4 every time the token is passed to the succeeding station. That is, in step 1, it is judged whether or not there is an invitation synchronization command in the main synchronization data frame received from the main station, and if there is an invitation synchronization control counter CNT is substituted with 0 in step 2 and the operation of step 3 is executed. To do. If there is no solicitation synchronization command, the operation of step 3 is executed as it is. In step 3, the solicitation synchronization control counter CNT is referenced, and if it is not 0, 1 is subtracted, and if it is 0, the maximum set value CNT _max is substituted. If the result of multiplying the value of the solicitation synchronization control counter CNT by the predetermined constant a times the slave station addresses A _{1 to} A _n in step 4 is the same, the new station solicitation is executed in step 6 and they match. If not, solicitation is prohibited in step 5. When the slave station operates as described above, if the master station determines that all stations required to configure the system have joined the network, the master station continuously outputs the solicitation synchronization command, and the slave station side It is judged that there is a synchronization command, solicitation synchronization control counter CN
Substituting the maximum setting value CNT _max for T, CNT does not become the own station address, and as a result, solicitation is prohibited.

By the operations of the master station and the slave stations as described above,
The operation is as shown in FIG. That is, in the case of (a), the new synchronization station CNT is decremented by 1 for each token pass after the maximum setting value CNT _max is set in the solicitation synchronization control counter CNT. Data frame D to be sent this time without solicitation
as the length t _{s' current} of _s, using the length t _{s current} original empty data frame (t _{s current} = f (t _1)), primary synchronization transmission completion time of the data frame D ₁ main sync The signal S ₁ is synchronized. In the case of (b) is performed new station soliciting main station 1 _1, the main station 1 ₁ empty data frame D _s to be transmitted this time
Of the original empty data frame t _s as the _current length t _s ′ of the solicitation frame length t _c and one response window length t _c
Use result of subtracting _w a (t _{s' current} = t _{s current} -t _c -t _w), primary synchronization transmission completion time of the data frame D ₁ main sync signal S ₁ is synchronized. In the case of (c), slave station 1
₂ solicits a new station, and the transmission completion time of the main synchronization data frame D ₁ and the main synchronization signal S ₁ are synchronized as in the case (a). In the case of (d), minimum address station 1 _n will perform new station invitation, 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 value of the solicitation synchronization control counter CNT 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 main station 1 ₁ transmits this time. using the length t _{s current} of empty data frame to be transmitted originally as the length of t _{s' current} of should do an empty data frame.

Further, in the case of (f), the main station judges that the stations participating in the network are all the stations necessary for configuring the system, and the stations are participating in the network. for which station also does not perform new station invitation, the data frame to be transmitted this time the main station 1 ₁ length t
_s' to use an empty data frame t _{s current} to be transmitted originally as the _current. Therefore, the transmission completion time of the main synchronization data frame D ₁ and the main synchronization signal S ₁ are synchronized. The length t _c of the invitation frame is defined length in the IE ³ 802.4 standard, the length t _w of the response window is pre-set as system-specific value. Therefore, the length t _{c of the} solicitation frame and the length t _w of the response window must be held by the main station 1 ₁ as fixed values. Further, both the master station and the slave stations need operations other than those shown in FIGS. 3 and 4, but the description is omitted because they are not the characteristic parts of the present invention. In the above embodiment, the main station does not execute the new station solicitation by continuously outputting the solicitation synchronization command, but the main station sends the new station solicitation prohibition command in the main synchronization data frame and Will not solicit new stations in accordance with this new station solicitation prohibition directive. Alternatively, the value of the invitation synchronization control counter counting in the main station is transmitted in the main synchronization data frame, and this count value is transmitted as a constant value (for example, maximum value) when new station invitation is prohibited. Even if it does so, the same effect can be obtained.

[0015]

As described above, according to the present invention, when all the slave stations necessary for constructing the system have joined the network, the solicitation of the new station is stopped, so that the master synchronization data frame of the master station is canceled. The transmission completion time is kept constant in synchronization with the main synchronization signal, and the transmission timing on the slave station side is also kept constant in synchronization with the main synchronization signal. Therefore, stable signal synchronization can be obtained, and software for signal synchronization control can be facilitated.

[Brief description of drawings]

FIG. 1 is a diagram showing the operation of a token passing bus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a main synchronization data frame according to an embodiment of the present invention.

FIG. 3 is an operation flow diagram of a master station according to an embodiment of the present invention.

FIG. 4 is an operation flow diagram of a master station and a slave station according to an embodiment of the present invention.

FIG. 5 is a block diagram of a bus network using an optical star coupler.

FIG. 6 is a diagram showing an operation of a token passing bus when soliciting a new station by a conventional signal synchronization method is periodically executed.

[Explanation of symbols]

T _{1 to} T _n token frame D _{1 to} D _n data frame D _s empty data frame A _{1 to} A _n station address CNT solicitation synchronization control counter a default value (new station solicitation interval) t _c solicitation frame length t _w response window length t _{s Current} empty data frame length to be originally transmitted t _s ′ _Currently empty data frame length to be transmitted S ₁ Main synchronization signal t ₁ Time difference between main synchronization signal and transmission completion time of main synchronization data frame 1 ₁ to 1 _n Station 2 _{1 to} 2 _n Optical fiber cable 3 Optical star coupler

Claims (1)

[Claims] 1. A transmission control method using a network having an IEEE802.4 token passing bus or a communication protocol similar to the IEEE802.4 token passing bus, provided that all stations in the system configuration participate in the network. A transmission control method characterized by mainly soliciting new stations on the network.