JP3279486B2 - Data link method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data link method based on a token ring system used in a computer network, and more particularly to a data link method used in a programmable controller, an FA controller, etc., for constructing a data link system based on a token ring system. is there.

[0002]

2. Description of the Related Art FIG. 6 shows a general programmable controller (hereinafter, referred to as a PC) having a data link function.
1 shows a hardware configuration and a data link system thereof. Each of the PC1 to PC4 stations exists as a node (terminal station) and is connected in a ring shape by a transmission cable (transmission path) 30.

Each PC (PC1 to PC4) has a data communication control unit 10 for controlling a data link, and a sequence control unit (PC main unit) 20 for controlling execution of a sequence program and input / output unit. ing.

[0004] The data communication control unit 10 includes a C for communication control.
PU11 and link data (transmission cable 30)
A line control unit (I / F) 12 for sending and receiving data from and a ROM 13 for storing software such as a communication control system program, and a RAM 14 for storing link data received from the line, link data to be transmitted to the line, and the like. , And a two-port RAM 15 for interfacing with the sequence control unit 20.

[0005] The sequence control unit 20 includes a CPU 21 for sequence control, a ROM 22 for storing software such as a system program for sequence control, a RAM 23 for temporarily storing the operation results of the sequence program and other information. It has an input / output interface 24 for exchanging input / output ON / OFF information with an output unit (not shown), and a user memory 25 for storing a sequence program.
6 and the internal bus 16 of the data communication control unit 10 are connected by a two-port RAM 15 so that data can be transferred bidirectionally.

The operation of the transmission gate of the PC constituting the data link system according to the token ring system and performing the token ring will be described with reference to FIG.

In a data link system based on the token ring system, a transmission gate in a transmitting station state, in other words, a transmission gate of a node having a transmission right is called a transmission mode, and a transmission gate in a receiving station state is called a repeat mode. I say. In FIG. 7, the PC 1 station is a transmitting station, and the PC 2 stations to P
Station C4 is the receiving station.

A station in the transmission mode has a right to transmit a token, and a station in the transmission mode receives a token only when the token transmitted to the next station returns to its own station after circulating the circuit safely. That is, the token transmission right has been successfully transferred to the next station. This allows
The token transmitting station lets the next station transmit the token by extinguishing the token received by the transmission gate in the transmission mode.

A transmission gate in the repeat mode receives the token. The token passes through the receiving station without disappearing and moves to the next station. When the transmitting station sends a token to the next station, the token passes through each receiving station and returns to the transmitting station again. Upon receiving the transmitted token, the transmitting station confirms that the transmitted token has passed the data link line safely, changes the transmission gate from the transmission mode to the repeat mode, and shifts the transmission right to the next station.

The transmitting station transmits the token with the station number of the station to be the next transmitting station in the token, and the receiving station transmits the token to its own station if the station number included in the token matches the own station number. After the token is received, the transmission gate is shifted from the repeat mode to the transmission mode after receiving the token, becomes the transmitting station, and if not coincident, continues the receiving station.

By repeating the above operation,
The data link by the token ring system is operating.

Next, as shown in FIG. 8, in a data link system composed of two PCs,
The processing operation when the station C1 transmits the token will be described with reference to the flowcharts of FIGS.

FIG. 9 shows a processing flow of the PC 1 station after transmitting the token. The PC1 station that has transmitted the token waits for the transmitted token to go around the transmission path and return to the PC1 station again in order to confirm that the transmitted token has been transmitted normally (step S50). If no error occurs on the transmission line, the token goes around the transmission line of the data link system and is received again by the PC1 station.

When a token is received (step S50)
In reception), the PC1 station confirms that the token has been transmitted to the PC2 station normally, and sets the transmission gate to the repeat mode after receiving the token transmitted by itself (step S6).
0), transition from the transmitting station to the receiving station.

[0015] With no token received (step S
50 not received), as indicated by the crosses in FIG.
When an error occurs due to noise or the like on the transmission path from the second station to the first PC, the first PC cannot receive the token transmitted by the own station, and detects a reception error (step S70).
Yes).

The PC1 station that has detected the reception error determines that an error has occurred on the transmission line and the token could not be transmitted to the PC2 station normally, and immediately retry-transmits the token to transmit the token to the PC2 station normally. (Step S80).

FIG. 10 shows a processing flow when the PC 2 receives a token addressed to itself. PC that is the receiving station
Upon receiving the token addressed to the own station, the two stations receive the data addressed to the own station from the data on the transmission path, and start the receiving process according to the setting of the parameters owned by the own station (S100).

When the reception data processing of the own station is completed, creation of transmission data for the next station is started (step S11).
0) When the creation of the transmission data is completed, the transmission gate is changed to the transmission mode (step S120), and the token is transmitted to the next station (step S130).

FIG. 11 shows the state of the transmission gate of each station when one PC performs retry transmission. FIG. 12 shows the timing of token transmission / reception of each station in this state. Under this condition, the transmission gate of each station is P
Station C1 is in transmission mode to perform retry transmission, and station PC2 of the receiving station is also in transmission mode because it has successfully received the token.

Referring to the timing chart of FIG. 12 showing the transmission / reception state of each station in this state, first, the token transmitted by the PC1 station has been normally received by the receiving station PC2 station, but the token is transmitted from the PC2 station to the PC1 station. PC1 station has not received the token because an error has occurred on the transmission path.

Therefore, at the timing of t1, the transmitting station P
In C1, a retry transmission is transmitted, and in the receiving station PC2,
Send the token to the next station. Thereby, on the transmission path,
Two stations whose transmission gates are in the transmission mode are generated. A station in the transmission mode performs a retry transmission on the assumption that the token has not been properly transmitted to the next station until the token transmitted by the own station is received again.

Therefore, if there are two transmission mode stations on the token ring transmission line, the token transmitted by the PC1 station is always taken into the PC2 station, and the token transmitted by the own station returns to the own station. do not come. Therefore, the token ring is interrupted.

FIG. 13 shows the PC1 station when an error occurs in the transmission path between the PC1 station and the PC2 station in the system configuration shown in FIG. 8 and the token transmitted by the PC1 station does not reach the PC2 station. 6 is a timing chart of token transmission and reception in the PC 2 station.

When the token transmitted by the PC1 station does not reach the PC2 station, a reception error is detected by both the PC1 station and the PC2 station. At this time, the PC1 station retry-transmits the token after detecting the reception error, and the PC2 station waits for the token retry transmission after detecting the reception error. Thereafter, a token retry is received from the PC 1 station, and the process is normally continued.

[0025]

In the data link method based on the conventional token ring method, as described above, after the token transmitting station transmits the token, an error occurs on the transmission path between the receiving station and the transmitting station. generated if, at the next transmission timing, because the colliding token becomes possible there are two stations of transmission mode to the transmission path of the token ring,
There was a problem that the token ring was interrupted and the data link was not restored until the device was reset.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in a data link method using a token ring system, it is possible to surely confirm transmission and reception of a token, and to configure a data link system. Prevents two or more transmission gates of each station such as a PC from being in the transmission mode at the same time. That is, two or more stations transmitting tokens at the same time, thereby interrupting the token ring due to a temporal collision of tokens. The purpose is to obtain a data link method that accurately prevents the problem.

[0027]

In order to achieve the above-mentioned object, a data link method according to the present invention, after transmitting a token in a token ring system, confirms that the token has been transmitted by being able to receive the token. When the token cannot be received due to a reception error or the like, in the data link method using the transmitting station that retransmits the token, the transmitting station performs the retry transmission of the token after waiting for a predetermined time after the occurrence of the reception error, and performs the retry transmission for the predetermined time. When the transmitting station receives the token transmitted by the token receiving station during the standby, the retry process of the transmitting station is stopped and the transmission gate is set to the repeat mode for only receiving the token.

In the data link method according to the present invention, when the transmitting station receives the token transmitted by the token receiving station during the waiting time for a fixed time, that is, during the waiting time for the retry transmission, the transmitting station stops the retry process and transmits the token. Since the gate is set to the repeat mode only for token reception, it is possible to prevent token collision between the transmitting station and the receiving station.

[0029] In the data link method according to the next invention, in the data link method described above, the waiting time for retry transmission is a predetermined margin for the time required for the token to make a round on the ring-shaped transmission path in the constructed data link system. Gives time.

In the data link method according to the present invention, the waiting time for retry transmission is set appropriately without excess or shortage.

[0031] In the data link method according to the next invention, in the above data link method, if it takes a predetermined time or more until the token receiving station completes the preparation for token transmission from the reception of the token from the transmitting station, , And waits for a retry transmission token from the transmitting station.

In the data link method according to the present invention, if it takes a predetermined time or more for the token receiving station to complete the preparation for token transmission from the reception of the token from the transmitting station, the token transmission is prohibited and the transmission station retries. Since a transmission token is waited for, the token retransmission of the transmitting station and the token transmission of the receiving station do not overlap in time.

In the data link method according to the next invention, in the above data link method, the predetermined time is shorter than (retry waiting time)-(token transmission time)-(margin time).

In the data link method according to the present invention, the threshold time during which the receiving station prohibits the token transmission due to the processing delay is set without excess or shortage.

[0035]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(Embodiment 1) The data link method according to the present invention is implemented in a token ring type data link system shown in FIG.

In the data link method according to the present invention, after the occurrence of a reception error, the transmitting station waits for the retry transmission for a certain period of time, and sets a transmission prohibition time zone in the token transmission.

Thus, if the transmitting station cannot receive the token due to a receiving error after the receiving station receives the token transmitted by the transmitting station, the transmitting station detects the receiving error and then transmits a token retry transmission. Wait for a certain time.

The station that has received the token normally starts the receiving process, and after the process is completed, sends the token within the waiting time.

The transmitting station that waits for a fixed time after the occurrence of a reception error in the token retry transmission receives the token, confirms that the receiving station has received the token normally, and repeats the transmission gate. Mode. This avoids a token collision between the transmitting station and the receiving station.

FIG. 1 shows an operation flow of one transmitting PC station when the data link method according to the present invention is applied to the data link system shown in FIG.

When the PC1 station transmits the token to the PC2 station, the PC1 station waits for the token after transmitting the token (step S10). If an error occurs in the transmission path between the PC2 stations and PC1 stations (× mark position), the PC1 stations that token not come back. However, PC2 station is P
Since the token has been normally received from station C1, PC1
After that, the token from the PC2 station is transmitted to the station.

At this time, if the PC1 station waits for not only the token transmitted by the own station but also the reception of the token from the next station, the token transmitted from the own station does not return and the PC1 station receives the token from the next station. Then, it is possible to know that the token has been successfully transmitted to the next station.

To this end, the PC1 station waits for the reception of the token transmitted by the own station and the token reception from the PC2 station (step S11). The PC1 station transmits the token within a specified time after transmitting the token. If a token is received (Step S10 reception) or a token from the PC 2 station is received (Step S11 affirmative), the token transmission of the own station is completed normally and the transmission gate is set to the repeat mode (Step S12).

In other words, the PC1 station, which has received the token from the PC2 station, confirms that the token has been transmitted to the PC2 station normally because the token has been transmitted from the PC2 station. Assuming that the token transmission has been completed normally, the PC1 station sets the transmission gate to the repeat mode.

On the other hand, after transmitting the token, the PC1 station must not receive either the token transmitted by itself or the token from the PC2 station within the specified time (step S1).
11 negative), timeout occurs (step S13 affirmative), and the token is retried (step S1).
4).

The specified time, that is, the retry waiting time, is set to a value larger than (token holding time) + (token transmission time). The token holding time is the time required for the PC to transmit the token to the next station after receiving the token, and the token transmission time is the time required for the token to be transmitted between the PCs. In short, the retry waiting time is established. In this data link system, a predetermined margin time is given to the time required for the token to make one round on the ring-shaped transmission path.

FIG. 2 is a flowchart of FIG. 1 in which the flow proceeds from step S10 to step S11 to step S12, that is, an error occurs on the transmission line between the PC2 station and the PC1 station (marked by "x" ), and a retry is performed. During standby time, PC1
It shows the operation timing of token transmission and reception of the transmitting station and the receiving station when the station receives a token from the PC2 station instead of the token transmitted by the own station.

In FIG. 2, t1 to t2 is a retry waiting time period (retry prohibition time period) until a timeout occurs in the token retry transmission after the reception error of the PC 1 station. In this example, the PC 2 station has completed the receiving process within the retry waiting time, and the PC 2 station has transmitted the token, so that the PC 1 station receives the token transmitted by the PC 2 station within the retry waiting time.

In this case, the token transmitted by the PC1 station has been normally transmitted to the PC2 station.
The station places the transmission gate in repeat mode.

At this time, since the transmission gate of the PC1 station is in the transmission mode of waiting for the token transmitted from the PC1 station or the token from the PC2 station, the token transmitted by the PC2 station disappears at the PC1 station.

However, since the PC1 station shifts to the repeat mode by receiving the token transmitted by the PC2 station, even if the PC2 station does not receive the token transmitted by the PC2 station thereafter, the PC2 station can be operated at the timing of t3. The retransmitted token returns to the PC2 station through the repeat mode transmission gate of the PC1 station. As a result, normal communication is continued.

That is, when an error occurs on the transmission path between the PC2 station and the PC1 station, the token to the PC2 station is transmitted normally, but the token transmitted to the PC1 station does not return to the normal state. Is normally performed without interruption.

FIG. 3 shows the operation timing of token transmission / reception between the transmitting station and the receiving station when the token receiving station also has a reception error.

In the first embodiment, the time until the PC receives the token, prepares the transmission data, and becomes ready to transmit the token to the next station, that is, the token holding time becomes equal to the timeout of the token retry transmission This time is shorter than the retry waiting time, that is, when the communication speed is relatively low, the reliability of the data link can be improved.

(Embodiment 2) When a receiving station receives a token transmitted by a transmitting station and the transmitting station cannot receive a token transmitted by the transmitting station due to a receiving error, the transmitting station detects a receiving error and then detects a receiving error. It waits for a token retry transmission for a certain period of time (retry waiting time).
The token receiving station starts the receiving process at the same time as receiving the token, but if the receiving process takes time and the receiving station cannot send the token within the retry waiting time, the receiving station sends the token regardless of this. Then, there is a possibility of collision with token retry transmission.

Thus, in the second embodiment, if the receiving station cannot complete the receiving process within a certain time, the receiving station sets the token transmission prohibition time and prohibits the token transmission for a certain time. .

Therefore, if the receiving process takes a long time,
The receiving station does not transmit the token because it enters the token transmission prohibition time zone, and even if the transmitting station performs token retry transmission after the retry waiting time of token retry transmission, the receiving station receives this, It is possible to avoid that the token retransmission of the transmitting station and the token transmission of the receiving station overlap in time.

Next, the operation in the second embodiment will be described in detail. In the second embodiment as well, the transmitting station operates in the same manner as in the first embodiment (the processing flow in FIG. 1), and a description thereof will be omitted.

FIG. 4 shows an operation flow of the two receiving PCs when the data link method according to the present invention is applied to the data link system shown in FIG.

When the PC2 station receives the token from the PC1 station, it sets a timer (step S20), and starts processing of received data (step S21) and processing of creating transmission data (step S22).

If it takes time from the reception of the token to the completion of the transmission data creation processing, and the preparation of the token transmission in the PC2 station is not completed within the retry waiting time of the PC1 station, the PC1 station transmits the token retry transmission.
A certain period of time for the PC2 station to prepare for token transmission to its own station (threshold time during which the receiving station prohibits token transmission due to processing delay)
If you send a token after it has crossed over, the token will collide.

Therefore, if the PC2 station receives the token and the preparation for transmitting the token to the next station is not completed within the token transmission prohibition threshold time, the PC2 station enters a time period during which the token transmission is prohibited. (Step S23 affirmative), it waits for the retry transmission of the token from the PC1 station without transmitting the token (step S24).

The PC2 station receiving the token retransmitted from the PC1 station (Yes at step S24),
An error occurs again on the transmission path between the station and the PC1 station,
When the token retransmitted by the PC1 station does not return to the PC1 station, if the PC2 station cannot transmit the token while the PC1 station waits for a certain period of time until the timeout of receiving the token transmitted by the own station, the PC1 station is re-transmitted. Token transmission must be prohibited in order to wait for the retry transmission from. A timer is set for this (step S25).

Here, the threshold time for prohibiting the transmission of the token is as follows.
The C2 station reliably receives the retry transmission, and if the prohibition time is set too long, the token of its own station cannot be transmitted forever, so the prohibition time zone (token transmission prohibition threshold time) is set to (retry waiting time). -(Token transmission time)-α <(prohibited time zone) <(retry waiting time)
+ (Token transmission time) + α. Here, α is a margin time.

FIG. 5 shows the operation timing of token transmission and reception between the transmitting station and the receiving station in this case.

If preparation for transmitting the token to the next station is completed before the PC2 station enters the token transmission prohibition time zone (No at Step S23), the PC2 station sets the transmission gate to the transmission mode (Step S26), The token is transmitted (Step S27).

By receiving the token from the PC2 station, the PC1 station knows that the token has been normally transmitted to the PC2 station. In this way, it is possible to prevent the retry transmission of the PC1 station and the token transmission of the PC2 station from overlapping in time, and the data link is normally performed without interruption.

The second embodiment is effective in the case where the token holding time of the PC also increases the retry waiting time due to the use of a relatively high-speed system.

[0070]

As can be understood from the above description, according to the data link method of the present invention, when the transmitting station receives the token transmitted by the token receiving station during the waiting time for the retry transmission, the transmitting station performs the retry. Since the processing is stopped and the transmission gate is set to the repeat mode only for token reception, token collision between the transmitting station and the receiving station can be prevented, and when an error occurs between the transmitting station and the transmitting station, the transmitting station is disabled. It is possible to avoid that the token ring is not normally performed due to the time overlap between the retry transmission and the token transmission of the receiving station, and it is possible to dramatically improve the reliability of the data link by the token ring method.

According to the data link method of the next invention, the waiting time for retry transmission is appropriately set without excess or shortage, so that the retry transmission of the transmitting station and the token transmission of the receiving station can be prevented from overlapping in time. Retry transmission necessary when the receiving station cannot transmit the token transmission is compromised.

According to the data link method of the present invention, when it takes a predetermined time or more for the token receiving station to complete the preparation for token transmission from the reception of the token from the transmitting station, the token transmission is prohibited and the transmission is prohibited. Waiting for the retry transmission token from the station, the token retransmission of the transmitting station and the token transmission of the receiving station do not overlap in time. Is performed normally, and the reliability of the data link by the token ring method can be remarkably improved.

According to the data link method of the next invention, the threshold time during which the receiving station prohibits the token transmission due to the processing delay is set without excess or shortage. Therefore, the receiving station reliably receives the retry transmission, and forever. Also, there is no problem that the token of the own station cannot be transmitted.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation after transmitting a token by a token transmitting station in a data link method according to the present invention.

FIG. 2 is a timing chart showing the operation timing of token transmission and reception of the transmitting station and the receiving station when the transmitting station receives a token from the receiving station within the retry waiting time in the data link method according to the present invention.

FIG. 3 is a timing chart showing the operation timing of token transmission and reception between a transmitting station and a receiving station when a token receiving station also has a reception error.

FIG. 4 is a flowchart showing an operation after a token is received by a token receiving station in the data link method according to the present invention.

FIG. 5 is a timing chart showing the operation timing of token transmission and reception between the transmitting station and the receiving station when the token transmission of the receiving station exceeds the token transmission prohibition threshold time in the data link method according to the present invention.

FIG. 6 is a block diagram showing a hardware configuration of a general programmable controller having a data link function and a data link system thereof.

FIG. 7 is a block diagram showing transmission gates in a transmitting station and a receiving station of the data link system based on the token ring system.

FIG. 8 is a block diagram showing a configuration example of a data link system based on the token ring system.

FIG. 9 is a flowchart showing an operation of a transmitting station in a conventional token ring system.

FIG. 10 is a flowchart showing the operation of the receiving station in the conventional token ring system.

FIG. 11 is a block diagram showing a gate state of each station at the time of retry transmission in the conventional token ring system.

FIG. 12 is a timing chart showing a state of token transmission and reception when an error occurs in a transmission path from a receiving station to a transmitting station in a conventional token ring system.

FIG. 13 is a timing chart showing a state of token transmission / reception when an error occurs in a transmission path from a transmitting station to a receiving station in a conventional token ring system.

[Explanation of symbols]

10 data communication control unit, 11 CPU, 12 line control unit, 13 ROM, 14 RAM, 152 2-port R
AM, 16 internal bus, 20 sequence controller, 21
CPU, 22 ROM, 23 RAM, 24 input / output interface, 25 user memory, 26 internal bus, 30 transmission cable

Claims (4)

(57) [Claims] 1. After transmitting a token in the token ring system, confirming the token transmission by receiving the token, and after transmitting the token, if the token cannot be received due to a reception error or the like, a transmitting station that retransmits the token. In the data link method using, the retry transmission of the token in the transmitting station is performed after waiting for a certain time after the occurrence of a reception error, and the transmitting station receives the token transmitted by the token receiving station during the waiting for the predetermined time, A data link method, wherein a retry process of a transmitting station is stopped and a transmission gate is set to a repeat mode for only receiving a token. 2. The waiting time for retry transmission is obtained by adding a predetermined margin time to a time required for a token to make a round on a ring-shaped transmission path in a constructed data link system. 2. The data link method according to 1. 3. When the token receiving station takes a predetermined time or more from the reception of the token by the transmitting station to the completion of the preparation for the token transmission, the token transmission is prohibited and the token of the retry transmission is waited from the transmitting station. The data link method according to claim 1, wherein: 4. The predetermined time is (retry waiting time)
4. The data link method according to claim 3, wherein the time is shorter than-(token transmission time)-(margin time).