JPH01227547A - Data communication system - Google Patents

Abstract

PURPOSE:To prevent the lowering of a data transmission efficiency due to transmission control information at the time of dividing a frame by sending collectively data having a long updating period sent from one and the same station. CONSTITUTION:A synchronizing data frame is transmitted from a main station to a slave station at every fixed transmission frequency, a counter is set at a value common to all stations on a network according to a counter setting command flag at each slave station, the counter is made to advance for each token pass, the the data frame is sent only when the value of the counter is made equal to the address value of its own station. In such a way, for the station to send even the data having the long updating period, control is executed so as to sent the data only in a cycle balanced to the updating period, and the data having the long updating period are transmitted collectively. Thus, the transmission efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to a data communication system that utilizes token passing paths to efficiently transmit data with different update cycles.

[Conventional technology]

Local area network (hereinafter referred to as LAN)
has rapidly become popular in recent years, and one noteworthy trend is MAP (Manufacturing Automation Protocol) proposed by General Motors (GM) in the United States.
An industrial L called ATM on Protocol)
One example of this is the growing interest in AN. FA (Factory Automation)
ation), OA (office automation 0
A large number of devices such as robots and computers have been introduced into crab farms and offices for the purpose of ``office automation'', and the standardization of the MAP is being promoted with the aim of interconnecting these devices easily and inexpensively. .

It aims to become an industry standard rather than a single company's LAN, and many leading companies are participating. ISO (International Organization for Standardization) O8I (Oven System Interconnection)
Standardization is progressing by filling in each layer of the hierarchical model, and the lower two layers (physical layer, data link layer) except for the theoretical link control sublayer are IE.
EE (U.S. Electrical and Electronic Technology Ordinance 11TheInst
Itute of Electrical and E
electronics Engineera Inc.
) 802.4 Committee (D-'):/-hash:/g pass is used. Currently IEEE 802.4
Although the standard specifies that coaxial cables be used as the physical layer transmission medium, the application of optical fiber cables is also being considered. be.

Figure @2 is a configuration diagram showing a network in which this token passing path is constructed using optical fiber cables. In the figure, 1. ~1n is the station that constitutes neck 1 work,
21 to 2n are optical fiber cables, and 3 is an optical star coupler.

Next, the operation will be explained. In the path type network, each station arbitrarily transmits data <C3MA/CD)
However, as the amount of transmitted data increases and the load increases, the transmission efficiency decreases rapidly. The token passing path, on the other hand, avoids this drawback through its deterministic access scheme. That is, a transmission right called a token is passed in order among the stations participating in the token passing path, thereby preventing a plurality of stations 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 remembers the station to which it should pass the token (successor station). ) is configured.However, if this logical ring is fixed, new stations will not be able to join if they wish to join, and if one of the joining stations fails, the logical ring will be broken and communication will stop. Therefore, the token
The passing path has the following ring maintenance functions.

(13) If the token is temporarily lost due to noise or the like, the previous token holding station will reissue the token.

(2) When a successor station fails, a token is passed to the successor station of the failed station and the failed station is removed from the logical ring.

(3) Solicitation of master stations is carried out at approximately regular intervals, and stations desiring to join the logical ring are permitted to join.

On the other hand, there are six application fields that use this token passing path to transmit measurement information and high-speed control of equipment, but if you actually try to use the token passing path to perform the above applications, for example, The breaker control command is 1 to 2.
Although it is necessary to transmit data within mJ1, it becomes necessary to transmit data with different update cycles over the same path, such as transmitting measurement information such as current and voltage at time intervals of 20 m5 to 50 m5.

In the token-to-pass mode, the content of the data to be transmitted is determined by the user, but generally data with different update cycles are mixed. First, we introduce a general transmission method that does not take into account the update cycle of transmitted data.
This will be explained using the diagram and the fourth factor.

Figure 3 shows such a conventional IEE
E) This is a general description of the status of data transmission on a path using the 802.4 committee's token-passing path method. D( is a data frame that station i1 sends in the j-th cycle, and Tj is a token frame that station 1s sends toward station j.

The term ξ here indicates a period during which a token passes through each station once and each station sends out a data frame. Further, the address value of station 11 is 1. Figure 4 shows the structure of the data frame, which is based on the IEEE
As stipulated by the 802.4 Committee.

Below is the data in this data frame Wh
Preamble (PR), starting delimiter (SD), frame control (FC), decision address (DA), source address (SA), frame check sequence (FC8), and ending delimiter (ED) other than For convenience, this part is called transmission control information.

Here, as a series of examples, consider a case +i in which the amount of data to be transmitted generated at each station and the update period of that data are as follows.

○Station 17 to station l (k+1): Data amount...ni
Octets (im(k+1)~#) Update cycle...Every cycle Station 0 lk~Station 11: Data amount...mj octets (j1~k) Update cycle...M cycles Here, the relationship between k and M is as follows.

k<M In such a case, a method can be considered in which all stations from station 1 to station 11 transmit data equally every time they obtain the transmission right every cycle. That is, the following transmission method can be considered.

After the data of ni octets (ism(k+1) to g) to be transmitted is generated, station 1t to station 1 (k+) is stored at - time t, and when it obtains the right to transmit in each cycle, it transmits this data. Send out.

Station 0 1kN, 11 has mj octets Cj■ to be transmitted.
After data 1 to k) is generated, store it at - time,
Each time the transmission right is obtained in each cycle, the packet is divided into M times of mj/M auctions and sent.

[Problem to be solved by the invention]

Since the conventional data communication method using the token passing path method is configured as described above, in the frame of the token passing path, the transmission control information is constant regardless of the amount of data, as shown in Part 4. Therefore, if the number of stations with a small amount of data to be transmitted increases, there is a problem that the transmission efficiency will decrease.In this case, in order to improve the transmission efficiency, the data of stations 1 to 11, whose update period is M cycles, is sent every time. Instead of sending data every cycle, it is also possible to send all data at once every M cycles, but in that case, the token rotation time will be long (so the next cycle There is a problem in that there is a possibility that some stations will be unable to send data because the token hold time has expired.

The present invention was made to solve the above-mentioned problems, and therefore, it is an object of the present invention to provide a data communication system that can efficiently and sequentially transmit data with different update cycles.

[Means to solve the problem]

In the data communication system according to the present invention, one of the stations on the network is the master station and the other stations are the slave stations, and a synchronous data frame with a counter set command flag is sent to a certain number of stations in order to perform counter synchronization control of all the stations. Each slave station sends a message from the master station to the slave station for each transmission count, and each slave station sets the counter to a value common to all stations on the network according to its counter set command flag.The counter is incremented every time the token passes, and this counter The data frame is sent only when the value of the address becomes equal to the address value of the local station.

[Effect]

In the data communication system of the present invention, a station that transmits data with a long update cycle does not transmit data every time it obtains the right to transmit, but controls the station to transmit data only in cycles that match the update cycle. , the number of transmitted data frames is reduced overall, and data with a long update cycle is transmitted in batches, thereby improving transmission efficiency.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a general explanatory diagram of the data transmission situation on the path in the data communication system according to the present invention.
, Dl is the data frame that station 11 sends in the j-th cycle, and Tj is the token frame that station 1 sends to station J. A similar notation method is used.

Next, the operation will be explained. The amount of data to be transmitted generated by each station and the update period of that data are the same as described in the prior art, and each station operates as described below.

Station 1 is the master station, has a counter set command flag in its data frame, and issues a counter set command to other stations once every *M cycles, every cycle of nIl octets. Send updated data. Station 1 <1-t) to station 1(k+1) are ni (im(k+1) to (#-1)) every cycle.
It sends out data that is updated every octet cycle. Stations 1 to 11 generate mi (j=-1) octets of data that are updated every M cycles.

Station 1 to station 11 sets its own counter to (M-13) based on the counter set command flag of the master station IR. If the counter value and the address of the own station are equal, mj(j
■kN1) Sends octet data, decrements its own counter value by "l", and passes the token. If the counter value of the own station is different from the address value of the own station, no data is sent, the counter value of the own station is decremented by "l", and the token is passed. If the counter value of the local station is "0", the value (M-1) is reset instead of subtraction.

FIG. 1 will be explained cycle by cycle.

1st cycle> The master station 17 issues a counter set command to other stations at D]. Station 1 ~ Station 11 receives D) and sets the counter to CM.
-1). Station 1 (j-1) ~ Station 1 (k+t
) is sequential data ni (im(#-13~(k+1)
) and pass the token. Next station 1
To do so, it receives the token and compares it with its own counter value. Since the counter value of the own station is (M-1) and does not match the address value of the own station, the data 7 is not sent, the token is passed, and the counter is subtracted. Below station 1 (k-0 ~ station 11
operates in accordance with station 1k, and none of the stations transmits data.

2nd cycle> Master station 1O does not issue a counter set command using Dl.

Station 1 (J-*) to station 1 (k+t) transmit data according to the first cycle. The operations of the station 11 will be explained in the following section, 3rd cycle to (M-1)th cycle.

3rd ~ (M-1) cycle> Stations 11 to 1 (k10 is the same as the second cycle.

Station 1 ~ station 11 compares the address value of its own station and the counter, and only when they match, mj (j11 ~
k) To transmit octets of data, only the following stations transmit data in each cycle:

@(M-k) cycle: station 1 th (+1) cycle bilayer 1 (k+s) 1st cycle: station 1 (M-1) th (M-2) cycle bilayer 1! (M-1)th cycle two-layer 11 <11M cycles> Stations 1 and 1 (k+t) are the same as the second cycle.

No data is sent to station 1 to station 1 because the counter value is "0". After the token pass, the counter is not subtracted and is set to the value (M-1). After the (M+1)th cycle, the above-mentioned 1st to Mth cycles are repeated. - However, since the counter set command of master station 1□ is sent once every *M cycles, which is a multiple of M cycles, the counter of each station is forced to set (() once every k*M cycles).
M-1).・In the above embodiment, the timing for subtracting the counter is defined as after the own station's token pass, but this timing may also be set as reception of a simultaneous communication frame sent by the master station, and the same effect as in the above embodiment can be obtained. is obtained.

〔Effect of the invention〕

As described above, according to the present invention, data with a long update cycle transmitted from the same station is transmitted at once without dividing the frame, and the station that transmits at once is 1 cycle. Since the structure is configured such that the station to transmit data in the relevant cycle is also determined in advance, it is possible to prevent a decrease in data transmission efficiency due to transmission control information when dividing frames, and furthermore, it is possible to prevent data transmission efficiency from decreasing due to transmission control information when dividing frames. This also has the effect of simplifying the process.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a data transmission situation showing a data communication method according to an embodiment of B's invention, Fig. 2 is a configuration diagram of an example of a path type network to which this invention is applied, and the third factor is the conventional I
An explanatory diagram of a data transmission situation showing a data communication method using a token passing path of the EEE802.4 committee,
FIG. 4 is a configuration diagram of the conventional data frame shown in FIG. 3. 11+11..., 1n is the station, 2. ~2n is an optical fiber cable, and 3 is an optical star coupler. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a data communication method in which a path-shaped network is formed by a plurality of stations and tokens are sequentially transferred, one of the plurality of stations is a master station and the others are slave stations, and the master station is responsible for all the slave stations. The system transmits a simultaneous broadcast type synchronous data frame for performing counter synchronous control, and includes a counter set command flag in the synchronous data frame, and sets the counter set command flag every fixed number of transmissions. At the same time, the slave station sets its own counter to a value common to all stations on the network according to the counter set command flag in the received synchronization data frame, and sets this counter value as a token. A data communication system characterized by incrementing the counter each time a pass is made and transmitting a data frame only when the value of the counter is equal to the address value of the local station.