JPH01132244A - Frame communication system - Google Patents

Abstract

PURPOSE:To avoid influencing other frames and tokens by an abnormality such as the destruction, etc., of one frame by setting the time set value of a frame round supervising timer provided in each communication device at a time in which a frame rounds a transmitting path and returns or below. CONSTITUTION:At the time of transmitting a transmitting source address field 54 of the frame, a round time measuring timer 29 is activated, when a comparator 27 detects the round of the frame, the round time measuring timer 29 is stopped, thus, the measurement of the round time is executed, and by an ALU 31, a fixed value is subtracted and it is set in a set value register 33 as a frame disappearance detection time. When the frame disappears during a transfer, that the value of a round supervising timer 32 coincides with a frame disappearance detection time is detected by a comparator 34, the transmission of a fill is stopped and a reproducing relay state is attained. Thus, by a trouble such as the disappearance, etc., of one frame, the other frames and the tokens are not influenced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a loop communication system using a token for obtaining a transmission right, and particularly to a frame communication system in which a token is transmitted immediately after transmitting a 17th frame.

[Conventional technology]

In recent years, local area networks (LANs) have become popular in factories, offices, etc., and the IBEB802 committee is also considering standardizing LAN communication methods. I recommend it.

As one of the communication methods for this type of LAN, a communication method using tokens for obtaining transmission rights is known.

Generally, in a communication system that requires a token, a communication device that requests frame transmission acquires tokens circulating on a transmission path T, transmits a frame Z containing data χ to be transmitted from the device itself, and then sends idle data χ called fill.
After transmitting the frame, it is confirmed that the transmitted frame has returned after going around the transmission path, or the disappearance of the frame is detected by a frame cycle monitoring timer provided in the communication device, and then used for other communication devices. Send the token to be
Operates to enter regeneration relay state. Therefore, the time setting value of the frame cycle monitoring timer in this communication method is set to a value less than or equal to the sum of the propagation delay time of the transmission path and the delay time of each of the plurality of communication devices connected to the transmission path. Therefore, when the number of communication devices connected to the transmission path is less than the maximum number, the frame-to-frame travel time is considerably larger than the actual frame-to-frame travel time. In this communication method, tokens are not sent onto the transmission path until one frame completes one cycle or during the set time of the monitoring timer, resulting in poor utilization of the transmission path.

In the communication system using this token, as a conventional technique that can improve the efficiency of using the transmission path, for example, "Enhancement to the Token Ring Protocol: Early Token IJ 17-ZN, C., Stroll, November, 17.1986 Ai Ei Ei 802, 5/86/22 (“Enh
ance to th'l"oken-H+
ing Protocol: EarjyToken
Kelease ” N, C, 8trole, N
ov.

17.1986 IEEE 802,5/86/2
2) etc. are known.

In this prior art, a communication device that requests frame transmission acquires a token that circulates on a transmission path, then transmits a frame χ carrying data to be transmitted from the own device, immediately after transmitting this frame, transmits a request for a token, In addition, it is possible to continue transmitting idle data, confirming that the transmitted frame has gone around the transmission path and returning, or detecting frame disappearance by using a frame cycle monitoring timer installed in the communication device. Then, the transmission of the fill is stopped and a reproducing/relaying state is entered.

In such a communication method, if the time setting value χ of the frame cycle monitoring timer is set to less than the sum of the propagation delay time of the transmission path and the delay time of the communication device, as in the case of the communication method using tokens described above, the transmission will be delayed. A problem arises in that all frames and tokens on the road disappear.

The communication system according to this prior art will be explained below with reference to the drawings.

FIG. 2 is a block diagram showing an example of the configuration of the loop communication system J, and FIG. 3 is a timing diagram illustrating frame transmission and reception operations according to the prior art. @2 In the figure, 1 is a terminal device, and 2 is communication devices A to D.

3 is a transmission line, and 4 is a bus.

FIG. 2 (The loop communication system shown in FIG.
are connected and configured.

Now, in the communication system shown in FIG. 2, a frame transmission request is generated in each communication device A to D, and communication device A first
The operation of the system shown in FIG. 2 will be explained with reference to FIG. 3, assuming that the user has acquired a token.

Communication device A acquires a token, transmits frame Fa'4, and immediately thereafter transmits the token.

Communication device B connected downstream of transmission path 3 acquires the token transmitted by communication device A, and obtains the frame Fb'?
il-transmit, then tokenbi-transmit.

Such an operation will be performed in the same way by communication devices C and D, so when frame Fa transmitted by communication device A returns to communication device A after going around the transmission path 3,
On the transmission path 3, a plurality of consecutive frames F a % F d are followed by tokens. In this way, this communication system can use the transmission path 3 extremely efficiently.

Communication device A continues transmitting fills until frame Fa returns. If frame Pa disappears due to noise or the like and cannot be detected, communication device A detects the disappearance of frame Pa using a frame cycle monitoring timer and enters a regenerative relay state. . However, if the time setting value of this frame cycle monitoring timer is larger than the frame cycle time as described above, the frame Fb following frame Fa will be destroyed by the communication device operator. In the communication system shown in FIG. 2, the same thing as described above occurs in communication devices B, C, and D, and all seven frames and tokens on the transmission path end up disappearing.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional technology, the time setting value of the frame cycle monitoring timer that monitors frames cycle by cycle is longer than the actual frame-by-frame time, so all frames and tokens on the transmission path disappear, resulting in one communication. There is a problem that it becomes impossible.

Normally, in a communication system as shown in FIG. 2, the number of communication devices connected to the transmission path reaches from several tens to several hundreds, and the influence thereof is extremely large.

The purpose of the present invention is to solve the problems of the prior art described above,
To provide a frame communication system χ in which an abnormality such as destruction of one frame does not affect other frames or tokens.

[Means for solving problems]

According to the present invention, the purpose is to determine whether the frame is on a transmission path or not, based on the time setting value Y of a frame cycle monitoring timer provided in each communication device. This is achieved by setting the time to be shorter than the time it takes to return once.

[For production]

The time setting value of the frame cycle monitoring timer is set to be less than or equal to the sum of the delay times of all communication devices connected to the transmission path and the propagation delay time of the transmission path. This allows even if a certain frame disappears during transmission.

The communication device that transmitted this erased frame no longer destroys other frames or tokens.

〔Example〕

Hereinafter, one embodiment of the frame communication method according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an example of the configuration of a communication device used in an embodiment of the present invention, FIG. 4 is a timing diagram illustrating frame transmission and reception operations in an embodiment of the present invention, and FIG. 5 is a)
*tbs st frame and token format χ FIG. 6 is an operation timing chart of the one-round time measurement timer. In Figure 1&C, 10 is a receiver, 11.14.23 is a shift register, and 12 is a reception FI.
FO circuit, 13 is receiving panzer memory, 15.22! A selection circuit, 16 a driver, 17 a transmission packer memory, 18 a transmission FIFO circuit, 19 a fill generation circuit,
20 is a delimiter generation circuit, 21 is a token generation circuit, 2
4 is a token detection circuit, 25 is a delimiter detection circuit, 26
is an address extraction circuit, 2La4sz comparator, 28 is a local station address setting register, 21"! One round waiting time measurement timer 30 is a fixed value setting register, 31 is an ALU, 32 is one round monitoring timer, 33 is a set value register, 35 is This is a transmission control section.

A communication system using the communication method according to the present invention has a 5&C configuration as shown in FIG. 2, as in the case of the prior art, and the communication device 2 is configured as shown in FIG.

Made by Tsushin shown in Figure 1! When a transmission request occurs, 1k-2 waits for a token to be received in the transmission buffer memory 17 (with the transmission data sound set).

In this state, when a token arrives from the upstream side of transmission path 3,
Receiver 10. When detected by the token detection circuit 24 via the foot register 11, the transmission control circuit 35
This activates it and starts the transmission operation. The transmission control circuit 35 takes out the transmission data stored in the transmission buffer memory 17 through the transmission FIFO circuit 18,
The delimiters from the delimiter generation circuit 20 are combined, the selection circuit 22 arranges the frame format, and the shift register 23 . Selection circuit 15. Transmission line 3 via driver 16
Immediately after, the token generation circuit 2
The token generated in step 1 and the fill generated by the fill generation circuit 19 are transmitted.

The format of this frame and token is shown in Figure 5 1ad.
, lb).

As shown in FIG. 5 1al, the frame 5 includes a start delimiter 51 and an end delimiter 57 indicating the frame delimiter χ, an access control field 52, a destination address field 53 indicating the address of the destination communication device, and an address of the source communication device. It consists of a source address field 54, an information field 55, and a frame check sequence field 56. Also, token 6 is the fifth
As shown in FIG. 1b), it has a start delimiter 51 and an end delimiter 57Y similar to frame 5, and further includes a control field 52Y indicating that it is a token.

When the communication device 2 detects that the frame transmitted as described above has gone around the transmission path and returned, or when it detects the disappearance of the 71 norm χ, it stops the fill transmission χ and transmits the frame from the upstream transmission path via the reflector 10Y. A regenerative relay state is entered in which the received signal t is transmitted to the downstream transmission path via the shift register 14, selection circuit 15, and driver 16. Next, the operation in this case will be explained.

After transmitting a frame for data transmission from the communication device 2 described above, the communication device 2 transmits a frame from the upstream transmission path 3 to the receiver 1.
0, the source address field 54 of the received frame received through the shift register 11 is extracted by the address extracting circuit 26, and the address in the local address setting register 28 set in advance by the terminal device 1 and the extracted address are A comparator 27 compares the received source address with the received source address, and when a match is found, one round of the frame is detected. Also, since the first communication device 2 activates the one-cycle monitoring timer 31' when transmitting the end delimiter 57 of the frame 5 as described above, the value of this one-cycle monitoring timer 32 and the frame extinction detection time are set. When the values in the set value register 33 match, erasure of the frame is detected.

There is a method of calculating and initializing the frame erasure detection time in advance from the number of communication devices in the system and the transmission path length, but this method does not work when the number of communication devices changes.
The setting time will be longer than the actual frame cycle time.
Other frames and tokens following the destroyed frame may be destroyed.

Therefore, in the embodiment of the present invention, the time for one round of frames is measured, and the frame extinction detection time χ is set in the set value register 33. That is, to measure the frame cycle time, when the frame transmission operation button is pressed and the frame transmission source address field 54 is transmitted, the sequential measurement timer 29'Y is activated, and the comparator 27 detects the frame cycle. This is done by stopping the - slow time measurement timer 29 when this occurs.

The starting and stopping operations of the slow time measuring timer 29 will be explained with reference to the timing diagram shown in FIG.

The transmission control unit 35 starts transmitting a frame as described above in response to the token detection signal from the token detection circuit 24, and when transmitting the source address field 54 of the frame, - to the delay time measurement timer 29. Give a start-up command. As a result, the surgical time measurement timer 29 starts measuring the elapsed time. The frame transmitted above is received after going around the transmission path χ, and the comparator 27 detects that the address extracted by the address extraction circuit 26 matches the address set in advance in the local address setting register 28. Then, this detection signal causes the slow time measurement timer 29 to stop its time measurement operation. This was measured. The ALU 31 subtracts a certain value set in advance in a constant value setting register from the frame cycle time.

The result is set in the setting value register 33 as the frame erasure detection time. The constant value set in advance in the constant value setting register 30 is determined by the frame erasure detection time set in the setting value register 33 after the frame yx is transmitted and then the period from the information field 55 of the frame to the end delimiter 570 goes around and returns. It is desirable to set the time so that the

The frame transmitting/receiving operation when the frame erasure detection time calculated in this way is set in the setting value register 33 will be explained with reference to FIG.

In a communication system as shown in FIG. 2 to which the present invention is applied, it is assumed that each communication device A-DK frame transmission request is generated and the communication device A obtains a token first.

In order to acquire this token, communication device A sends a data request frame Fay! from its own device. /transmits that frame Fa.

Then send the token and fill. Then, when the communication device Fa sends the end delimiter 57 of the sent frame Fa, the communication device Fa activates the one-cycle monitoring timer 32. The other communication devices BD operate in exactly the same manner as the communication device described above, acquire tokens from terminal devices connected upstream of the transmission path 3, and transmit frames. Communication device A
Thereafter, the device monitors the frame Pa transmitted from its own device as it goes around and returns, but if the frame Fa disappears during transmission, the value of the one-round monitoring timer 32 changes to the setting value register 33.
According to the coincidence output of the comparator 34, which detects when the frame erasure detection time coincides with the frame erasure detection time set in , frame erasure is detected, the transmission of the fill is stopped, and a reproducing relay state is entered. As mentioned above, the frame erasure detection time set in the setting value register 33 is set to be smaller than the actual 7-frame cycle time, so the frame erasure detection time set in the setting value register 33 is set to be smaller than the actual 7-frame cycle time. frame Fb.

Fc, Fd, and the token are reproduced and relayed by communication device A without being destroyed.

〔Effect of the invention〕

As explained above, according to the present invention, in a loop communication system, a failure such as disappearance of one frame will not affect other frames or tokens, so that the reliability of the system can be improved. At the same time, the throughput of the system can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of a communication device used in an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the configuration of a loop communication system, and FIG. 3 explains frame transmission and reception operations according to the prior art. 4 is a timing diagram explaining the frame transmission/reception operation in an embodiment of the present invention; FIG. 5 is a diagram explaining the format of frames and tokens; FIG. 6 is the operation of the one-cycle time measurement timer. FIG. 1...Terminal device, 2...Communication device, 3
...Transmission line, 4...Bus, 5...
...Frame, 6...Token, 10...
...Receiver, 11, 14.23...Shift register, 12...Reception FIFO circuit, 13...
...Receive buffer memory, 15.22...
Selection circuit, 16... Driver, 17...
・Transmission buffer memory, 18...Transmission FLFO
Circuit, 19...Fill generation circuit, 20...
... Delimiter generation circuit, 21 ... Token generation circuit, 24 ... Token detection circuit, 25 ...
... Delimiter detection circuit, 26 ... Address extraction circuit, 27.34 ... Comparator, 28 ...
... Own station address setting register, 29 ... - slow time measurement timer, 30 .... constant value setting register, 31 ..... ALU, 32 ..... round Monitoring timer, 33... Setting value register, 35...
...Transmission control section. 12!1! 3 2nd j deficiency
QFigure 5 (Q) (b)

Claims (1)

[Claims] 1. Loop communication in which a plurality of communication devices are connected to a loop-shaped transmission path, and only the communication device that has acquired a token, which is the right to transmit a frame, transmits a frame, and the token is transmitted immediately after transmitting the frame. In the system, the communication device is equipped with a frame cycle monitoring timer that monitors whether the frame transmitted by the communication device makes one cycle on the transmission path, and the set value of the timer is set to a frame cycle time or less. frame communication method. 2. The set value of the frame cycle monitoring timer is set to be less than or equal to the sum of the propagation delay time of the loop-shaped transmission path and the delay time of a communication device connected to the transmission path. The frame communication method described in Section 1. 3. The communication device is equipped with a means for measuring the time required for a frame transmitted by the communication device to travel around the transmission path, and sets a set value of the frame round monitoring timer to be equal to or less than the measured time. A frame communication method according to claim 1.