JPH0666792B2 - Data communication method - Google Patents

Description

The present invention relates to a data communication system for efficiently transmitting data having different update cycles by utilizing a token passing bus.

[Conventional technology]

Local area network (LAN) is spreading rapidly in recent years, and one of the notable trends is the MAP proposed by General Motors (GM) of the United States.
There is growing interest in industrial LANs called the Manufacturing Automation Protocol (Manufacturing Automation Protocol). FA (Factory Automation),
OA (Office Automation)
There are many equipments such as robots, computers for factories,
Although introduced in the office, standardization of the MAP is in progress for the purpose of connecting these devices easily and inexpensively. It aims to be an industry standard rather than a one-company LAN, and many leading companies are participating.
ISO (International Organization for Standardization) OSI (Open Systems Interconnection)
Standardization is progressing in such a way that each layer of the hierarchical model is filled, and the part of the lower two layers (physical layer, data link layer) excluding the theoretical link control sublayer is IEEE (US electrical,
Electronic Engineers Conference, The Institute of Electrical and El
ectromics Engineers Tnc) 802.4 Committee token passing bus is used. At present, the IEEE802.4 standard uses a coaxial cable as a physical layer transmission medium, but application of an optical fiber cable is also under consideration, and even if an optical fiber cable is used as a medium, a communication method of a data link layer is completely eliminated. It is the same.

FIG. 2 is a block diagram showing a network in which the token passing bus is composed of an optical fiber cable. In the figure, 1 ₁ to 1 _n are stations constituting a network, 2 _1
2n is an optical fiber cable, and 3 is an optical star cutler.

Next, the operation will be described. Although there is a system (CSMA / CD) in which each station arbitrarily sends data in the bus network, there is a drawback that the transmission efficiency decreases rapidly 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, a transmission right called a token is transmitted in an item number among 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 remembers the station to which it should give the token (subsequent station), which allows the token to go around in a logical ring (logical ring). Is configured. 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.

(1) When the token temporarily disappears due to noise or the like, the 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 for transmitting measurement information and high-speed control of equipment by using this token passing bus, but when actually using the token passing bus for the above application, for example, The control command of the breaker and the breaker is 1-2 m
It needs to be transmitted within s, but measurement information such as current and voltage needs to be transmitted on the same bus at different update intervals, such as at 20ms to 50ms intervals.

In the token passing bus method, the content of the data to be transmitted is determined by the user, but generally, data having different update cycles are mixed. First, the general transmission method that does not consider the update cycle of the data to be transmitted
This will be described with reference to FIG. 4 and FIG.

FIG. 3 shows such a conventional IEE.
E), which generally represents the status of data transmission on the bus in the token passing bus system of the 802.4 Committee. (D ⁱ _{l · j)} is the j-th data frame transmitted by the station 1 _l in the i-th cycle, and the station 1 _l sends out a K _l data frame when the token is received. ▲ T ⁱ _j ▼
Is a token frame transmitted from the station 1 _i to the station 1 _j . In addition, here, the cycle indicates a period in which the token passes over each station once and each station transmits a data frame. Further, the address value of station 1 _i is i. FIG. 4 shows the structure of the data frame, which is IEEE802.
4 As prescribed by the committee.

The preamble (PR) other than the data part in this data frame, the starting delimiter (SD), the frame control (FC), and the decision address (D
A), lease address (SA), frame check sequence (FCS) and ending delimiter (ED) are called transmission information for convenience. Here, as an application example, consider the case where the amount of data to be transmitted generated at each station and the update cycle of the data are as follows.

○ Station 1 _l to Station 1 _{(k + 1)} : Data volume ... ni Octets (i = (k +
1) to l) Update cycle… Every cycle ○ Station 1 _k to Station 1 ₁ : Data amount… mj (= mhj + mlj) Octets (j = 1 to k) Update cycle …… mhj… Every cycle mlj… M cycle Here, The relationship between k and M is as follows.

k <M In such a case, a method is conceivable in which all stations from station 1 ₁ to station 1 _l obtain the transmission right every cycle, and the same data update cycle is collected in the same frame and transmitted uniformly. . That is, the following transmission methods are possible.

○ Station 1 _l to station 1 _{(k + 1)} have ni octets (i =
After the data of (k + 1) to l) are generated, one data frame having this data as a data portion is transmitted when the transmission right is obtained in each cycle.

○ stations 1 _k ~ station 1 ₁ sends out the second data frame each time to obtain a transmission right. At this time, mhj (j
= 1 to k) octets of data are transmitted in the first data frame, and the mlj (j = 1 to k) octets of data generated every M cycles are temporarily stored, and mlj / M octets are stored M times each. The data is divided and transmitted, but the data of this mlj / M octet is transmitted in the second data frame.

[Problems to be Solved by the Invention]

Since the conventional data communication method using the token passing bus is configured as described above, the frame of the token passing bus is transmitted because the transmission control information is constant regardless of the data amount as shown in FIG. There is a problem in that the transmission efficiency decreases when the number of stations with a small amount of data is increased.
And split-cycle in which the station 1 _k ~ station 1 ₁ MLJ the (j = 1 to k) octet of data MLJ / M octet, rather than splitting sends data at every cycle, all per M cycles It is possible to send data all at once, but in that case, since the token rotation time becomes long, there is a possibility that some stations cannot send data because the token hold time expires in the next cycle. There was a problem that the sex appeared.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a data communication system capable of efficiently sequentially transmitting data having different update cycles.

[Means for Solving the Problems]

The data communication system according to the present invention uses one of the stations on the network as a master station and the other as a slave station to maintain a constant synchronization data frame with a counter set command flag for counter synchronization control of all stations. Is transmitted from the master station to the slave stations at each transmission number of times, and each slave station sets the counter to a value common to all stations on the network according to the counter set command flag, and advances the counter every token pass. Then, 2 data frames are sent out only when the value of this counter becomes equal to the address value of the own station, and 1 when it is different.
A data frame is transmitted.

[Action]

In the data communication method according to the present invention, a station that also sends data with a long update cycle does not send data with a long update cycle each time it obtains a transmission right, but instead of sending data only with a cycle that matches the update cycle. The transmission efficiency is improved by controlling transmission of long data, comprehensively reducing the number of data frames to be transmitted, and collectively transmitting data having a long update cycle.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
The figure is an explanatory view generally showing the transmission status of data on the bus in the data communication system according to the present invention. In the figure, ▲ D ⁱ _{l · j} ▼ is the j-th data frame transmitted by the station 1 _l in the i-th cycle. , {Circumflex over (T ⁱ _j) } is a token frame transmitted from the station 1 _i to the station 1 _j , and has the same notation method as in the case of the conventional token passing bus system shown in FIG.

Next, the operation will be described.

The amount of data to be transmitted at each station and the update period of the data are the same as those described in the prior art, and each station operates as follows.

Station 1 _l is a new station, has a counter set command flag in its data frame, and sends a counter set command to other stations once every K * M cycles, and every cycle.
The data updated in every cycle of nl octets is transmitted in the first data frame. Station 1 _(l-1) to Station 1 _{(k + 1)}
Sends the data updated in each cycle of ni (i = (k + 1) to (l-1)) octets in each cycle in the first data frame. Stations 1 _k ~ station 1 _1, MLJ updated every mhj (j = 1~k) octet of data and M cycles are updated every cycle (j = k~1) data octet is generated. Stations 1 _k ~ station 1 ₁ is based on the counter excisional command flag of the parent station 1 _l, to excisional common value (M-1) the counter of the own station to all stations on the net work. Station 1 _k to Station ₁₁
Is a token receiver destined for the local station, and transmits mhj (j = 1 to k) octets of data in the first data frame. If the local station counter value and the local station address are equal, mlj (j = k). ~ 1)
Send the octet data in the second data frame,
The counter value of its own station is decremented by "1" and the token is passed. If the counter value of the own station and the address value of the own station are different, the mhj octet is transmitted in the first frame, the counter value of the own station is decremented by "1", and the token passes. If the counter value of your own station is “0”, use (M-1) instead of subtraction.
Value is reset.

FIG. 1 will be described for each cycle.

<First cycle> The master station 1 _l issues a counter set command to the other stations by using ▲ D ¹ _{l ・ 1} ▼. Stations 1 _k ~ station 1 ₁ is excisional the counter receives the _{^{▼ ▲ D 1 l · 1 (}} M-1). Station 1 _(l-1) to station 1 _{(k + 1)} sequentially send data of ni (i = (l to 1) to (k + 1)) octets,
Pass the token. Next, the station 1 _k receives the token, transmits the data of mhk octets in the first data frame, and then compares it with the counter value of its own station. Since the counter value of the own station is (M-1) and does not match the address value of the own station, the second data frame is not transmitted, the token is passed, and the counter is decremented. The following station 1 _(k-1) ~ station 1 _1, according to the station 1 _k, work, which station also sends only the first data frame.

<Second cycle> The master station 1 _l does not issue a counter set command at ▲ D ² _{l ・ 1} ▼. Station 1 _(l-1) to station 1 _{(k + 1)} send data according to the first cycle. Station 1 the operation of the _k ~ station 1 _1, in the next section <Third
Cycle to the (M-1) th cycle>.

<Third to M-1 cycles> Stations 1 _l to 1 _{(k + 1)} are the same as the second cycle.

Stations 1 _k ~ station 1 _1, only when the matching while comparing the delivery matches the address value and the counter of the station at the token after receiving mhj (j = 1~k) first data frame data octet Since the data of mlj (j = 1 to k) octets is transmitted in the second data frame, the following stations transmit the second data frame every cycle.

Cycle (Mk): Station 1 _k Cycle (M-k + 1): Station 1 _{(k + 1)} : i-th cycle: Station 1 _(Mi) : Cycle (M-2): Station 1 ₂ (( M-1) Cycle: Station 1 ₁ <Mth cycle> Stations 1 _l to 1 _{(k + 1)} are the same as the second cycle.

Stations 1 _k ~ station 1 _1, the counter value is sent only the first data frame for "0". After the token pass, the counter is not decremented and the value is set to (M-1). After the (M + 1) th cycle, the above 1st to Mth cycles are repeated.

However, since the counter set command of the master station 1 _l is sent once every K * M cycles, which is a multiple of M cycles, the counter at each station is forced to (M
-1) is set in the above embodiment, the subtraction timing of the counter is defined to be after the token pass of the own station.
It may be a simultaneous broadcast frame sent by the master station,
The same effect as in the above embodiment can be obtained.

〔The invention's effect〕

As described above, according to the present invention, with respect to data having a long update period, which is transmitted from the same station, the data is transmitted in a batch without dividing the frame, and the station transmitting in the second data frame at a time is 1 Since it is one station in a cycle, and the station that sends data in the cycle is determined in advance, it is possible to prevent a decrease in the data transmission efficiency due to the transmission control information when the frame is divided, and further to send and receive data. The accompanying data processing method has the effect of being simplified.

[Brief description of drawings]

FIG. 1 is an explanatory view of a data transmission state showing a data communication system according to an embodiment of the present invention, FIG. 2 is a block diagram of an example of a bus type network to which the present invention is applied, and FIG. 3 is a conventional IEEE.
802.4 is an explanatory view of a data transmission state showing a data communication system using the token passing bus of the 802.4 committee, and FIG. 4 is a configuration diagram of the conventional data frame shown in FIG. 1 ₁ , 1 ₂ ..., 1 _n is a station, 2 ₁ to 2 _n are optical fiber cables, 3 is an optical star cutler. In the drawings, the same reference numerals indicate the same or corresponding parts.

Front page continuation (72) Inventor Tadao Matsumoto 1-3-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Within Tokyo Electric Power Co., Inc. (72) Innovator Shintomi Ohashi 1-3-1 Uchisaiwai-cho, Chiyoda-ku, Tokyo Tokyo Electric Power Company Incorporated (72) Inventor Katsuki Sano 1-1-1, Kokubuncho, Hitachi City, Ibaraki Hitachi Co., Ltd. Kokubun Factory, Hitachi Ltd. (72) Inventor Tatsuya Kano, No. 1, Toshiba Town, Fuchu City, Tokyo Toshiba Fuchu Factory, Ltd. (72) Inventor Yasuhiko Terao 1-2-2 Wadazaki-cho, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Electric Corporation Control Works (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 data communication system in which a bus-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 other is a slave station, and the master station sends out a broadcast synchronous data frame for performing counter synchronous control of all the slave stations, and in the synchronous data frame Is provided with a counter set command flag, the counter set command flag is set and transmitted at a fixed number of transmissions, and the slave station automatically follows the counter set command flag in the received synchronous data frame. Set the station counter to a value common to all stations on the network, run this counter every time a token pass is made, and set 1 if the value of the counter is different from the address value of the own station. A data communication method characterized in that two data frames are transmitted when the data frame is equal to the address value of the own station.