JPH0414532B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a loop transmission method in which a plurality of stations are connected to a loop transmission path and data communication is performed between the stations via the loop transmission path. In the conventional loop transmission method, each station transmits its own sent frames that reach the other station and returns by 8 times.
Data is erased bit by bit, and each station performs "0" insertion and "0" deletion operations, as will be described later, in order to maintain data transparency. In such a situation, for example, if we consider the case where "0" is inserted into the transmission frame,
The transmitted frame becomes longer by the number of bits of "0" due to the "0" insertion operation. Therefore, the remainder when the transmitted frame is divided by 8 becomes the frame erased residue. These causes various abnormalities. The sending station looks at the sending station address in the received frame and determines whether or not the frame has been sent by itself, and if it is the frame sent by itself, it erases the frame. If the sender station address is garbled into an absent station address, there will be no station to erase, resulting in a floating frame that continues to loop forever. These may further cause bit corruption and be taken in by other stations, or may cause various abnormalities. Therefore, the station that sent the outgoing frame does not continue data transmission until it confirms that the outgoing frame from the local station has arrived at the other station, that is, until the outgoing frame from the local station goes around the loop transmission path and returns. It has been considered to send a pattern that does not have any effect (hereinafter referred to as a time fill code), but such a method is also a special signal pattern known as a go-ahead (hereinafter referred to as GA). Alternatively, the transmission right is passed sequentially using a token, and once the frame transmission of the local station is completed, a loop is sent out that sends a special pattern immediately after the frame transmission without confirming that it has reached the other station. The following problems arose when applying this method to a transmission system. That is, the station that sent the frame continues to send out the time fill code until its own frame is returned. Here, if the own station's frame cannot be detected due to, for example, garbled bits,
The data of all stations can no longer complete the loop,
An abnormality regarding a particular station will affect the entire system. Here, all stations on the loop transmission path may transmit time-filter codes at the same time, but in this case, the reliability of data transmission decreases significantly as the number of stations increases, and the time-filter code is transmitted at each station. There is a problem in that the amount of hardware required to start and stop sending the code increases. An object of the present invention is to prevent interference such as frame erase debris and floating frames in loop transmission using a special pattern such as a GA pattern without reducing the reliability of data transmission or increasing the amount of hardware. The object of the present invention is to provide a loop transmission method that eliminates frames. In order to achieve such an object, in the present invention, one station on a loop transmission path transmits a second special pattern before transmitting the first special pattern, and this second special pattern is The communication frame is transmitted before each station other than the station transmits the communication frame, and after the one station transmits the first special pattern, the second special pattern goes around the loop transmission path and returns. The feature is that the system continues to send out signals with a pattern that does not affect data transmission until the data transmission is completed. Hereinafter, one embodiment of the present invention will be described. In FIG. 1, 1 is a loop transmission path, 2 is a main station, 3-1 to 3-n are general stations, and 4 is transmission information flowing on the loop. Generally, in a loop transmission system using a special pattern, information flowing on the loop transmission line 1 is as shown in FIG. When each station detects a special pattern, it erases the special pattern and transmits its own data. After sending out its own data, that is, the communication frame 41, the special pattern 42 is sent out.
Therefore, the loop time of the special pattern 42 increases in proportion to the amount of data sent from each station.
Note that the special pattern 42 is one on the loop transmission line 1.
There are only individuals. In the present invention, in a loop transmission method using a special pattern, the special pattern can be detected at all stations.
Pattern 42 such as GA pattern (hereinafter referred to as pattern G) and pattern 4 that can only be detected by the main station
3 (hereinafter referred to as pattern S). In the loop transmission system of the present invention, the transmission information flowing on the loop transmission line 1 is as shown in FIG. The main station 2 sends out pattern S before sending out pattern G. Pattern G is used for transmitting communication frames at each station, and the loop time for pattern G increases in proportion to the amount of communication frames transmitted at each station, but the loop time for pattern S is constant. FIG. 4 shows an example of the pattern configuration of patterns G and S. In normal transmission, data and flag patterns indicating the beginning and end of the data (“1” is 6
In order to distinguish between
It is configured so that six or more "1"s do not continue in the data. Therefore, pattern G is a flag pattern consisting of seven consecutive "0"s and "1"s. Pattern S is a flag pattern, flag pattern “0”
16 consecutive. These special patterns G, S
Only one of each exists on the loop. Note that the pattern G used is the same as the conventional GA pattern. This is used for transfer on the sending side as described above. The reason why the patterns S and G are special patterns, that is, patterns that do not appear in the communication data, is that in the HDLC procedure, six or more 1's do not continue in the communication data. That is,
The sending side forcibly inserts a “0” next when five “1”s continue in the general communication data, and the receiving side inserts a “1”.
If there are 5 "0"s in a row, then "0" is deleted. On the receiving side, “1” is 6
If it continues, it is regarded as the end of general communication data, a flag pattern indicating a frame break, etc. By performing the above operations, these special patterns will no longer occur. Further, here, the communication frame has the following configuration.

[Table] Furthermore, in the present invention, like the GA pattern,
The feature is that the space between the special pattern G transmitted at the end of the communication data frame and the special pattern S transmitted before the communication data frame is filled with a time fill code. In short, in the present invention, special patterns S and G are provided before and after the data section in order to distinguish between the data section and the data free section, and the identified data free section is coded as a time fill code (hereinafter referred to as E). It is distinctive in that it is filled with For example, a flag pattern can be used as the time fill code E that fills the empty data section on the loop. FIG. 5 shows an embodiment of the configuration of the main station 2 that implements the transmission system of the present invention. In Figure 5, S, G
After sending out the special patterns S and G, the sending device 21 causes the E sending device 22 to send out the time fill code E. When the S detection device 23 detects the special pattern S returning after going around the loop transmission path 1, it causes the erasing device 24 to erase the reception pattern S in the reception shift register 25, and also causes the E sending device 22 to send the time fill code E. stop sending. Note that the E sending device 22 continues to send out the time fill code E until the sending is stopped. When the G detection device 26 detects the pattern G,
By the erasing device 24 and the receiving shift register 25,
The received pattern G is erased, and the S, G sending device 21 is made to send out the special patterns S, G. Thereafter, the E sending device 22 is caused to send out the time fill code E. As mentioned above, the special pattern S is a pattern that can be detected only at the main station and is not delayed at each station, so it goes around the loop transmission path before the communication frame and returns, so the loop transmission Empty data sections other than the data sections on the road are filled with time fill code E. Note that the special pattern S does not necessarily have to be a pattern that can be detected only by the main station, and may be any pattern as long as it is sent prior to the communication frame. Further, in FIG. 5, a demodulator 27 and a modulator 28 demodulate and modulate data on the loop transmission path. FIG. 6 shows another embodiment of the main station 2 that implements the transmission method according to the present invention, in which the special pattern S
Here is an example considering the failure of In FIG. 6, the S, G sending device 21 and the E sending device 22 send out patterns S, G, and time fill code E, the S detecting device 23 and the G detecting device 26 detect the patterns S, G, and the erasing device 24. Erasing the reception patterns S and G by the reception shift register 25 is the same as in the example shown in FIG.
The pattern S is sent from the S, G sending device 21, and the S loop monitoring timer 29 is started. This timer 29 is reset when the pattern S is detected by the S detection device 23.
Note that this timer value is the loop time for pattern S, and is not affected by the amount of frames sent out at each station. If the pattern S disappears due to, for example, garbled bits, the S loop monitoring timer 29 times out, and at this point, the sending of the time fill code E from the sending device 22 is stopped. FIG. 7 shows an example of a specific configuration of the general station 3 that implements the transmission system according to the present invention. In FIG. 7, a communication control device 31 stores transmission information (communication frames) in a transmission information storage device 32. In FIG. The G detection device 33 is connected to the loop transmission line 1
When the special pattern G is detected, the erasing device 34
It instructs the receiver to erase the reception pattern G of the reception shift register 35, and also notifies the transmission control device 36. The transmission control device 36 instructs the transmission information storage device 32 to transmit the stored communication frames. After the transmission of the communication frame is completed, the transmission control device 36 transmits the pattern G to the G transmission device 37.
Instruct to send out. In this manner, the general station 3 transmits the communication frame and pattern G after receiving pattern G. It should be noted that the general station 3 destroys the time fill code E by the number of frames transmitted by the local station, and then transmits the pattern G. Time fill code E is sent out following pattern G. The special pattern S is a pattern that is detected only by the main station 2, which is a specific station. In the general station 3, this pattern S is handled in the same way as a flag pattern, data (frame) going from another station to another station, etc. The pattern S that has arrived at the general station is transmitted to the demodulator 3.
8, the receiving shift register 35, and the modulating device 39 before flowing downstream. Therefore,
The general station is not aware of the passage of pattern S. Note that the special pattern S described in the above embodiment
Instead, a communication frame intended for the main station 2 may be used, the frame may be sent from the main station 2, and after the special pattern G is sent, the time fill code E may be sent. Since there is no delay for this frame at each station, this frame will go around the loop and return after a certain period of time. When the main station detects this frame, it stops sending out the time fill code E, as in the case of the special pattern S described above. FIGS. 8 to 10 show details of some of the circuits shown in FIGS. 5 to 7. FIG. 8 shows an example of a specific configuration of the erasing device 24, in which the detection signal 50 from the S detection device 23,
Based on the detection signal 51 from the G detection device 26, the timing generation circuit 52 generates a timing signal 53, and the timing signal generates a pattern generation circuit 54.
is operated to generate an erase pattern 55, and the erase pattern is input to the reception shift register 25 with a signal corresponding to the timing signal. Further, the S, G sending device 21 and the G sending device 37 can also use circuits having the same configuration as shown in FIG. Furthermore, the pattern generation circuit 54 generates special patterns S,
It is designed to generate G or G. FIG. 9 shows an example of a specific configuration of the E sending device 22, and shows the signal 6 from the S, G sending device 21.
1, the E sending timing repetition generation control circuit 62 generates a predetermined signal 63, which activates the E sending timing generating circuit 64, generates a predetermined timing signal 65, and also sends a signal 66 to the control circuit 62. In response, the control circuit 62 sends the signal 63 again to the timing generation circuit 6.
Operate 4. Then, the control circuit 62 is reset by the detection signal 67 from the S detection device 23. A pattern generation circuit 68 is activated by a timing signal 65 from a timing generation circuit 64, and a special pattern E69 is generated and input to the reception shift register 25. In the case of the E sending device shown in FIG.
A signal from the S-loop cycle monitoring timer 29 is input. FIG. 10 shows an example of a specific configuration of the transmission control device 36, in which a detection signal 71 from the G detection device 33 and a data presence signal 72 from the transmission information storage device 32 are input to the data transmission control circuit 73. .
This data _sending control circuit 73 memorizes the previous state and determines the action to be taken based on the _AND result of the new input signal. When the logical product is "1", the result is sent to the storage device 32 as a data sending command signal 75. When the logical product is “0”, the G sending device 3
A signal 76 is sent to 7. The data transmission control circuit 73 also controls the storage device 3.
When the data sending completion signal 77 is input from 2, G
A signal 76 is sent to the sending device 37. FIG. 11 shows the state of data on the loop transmission path according to the embodiment of the present invention, and the free data section from special pattern G to special pattern S is
It is filled with a time fill code E, which is a predetermined special pattern. FIG. 12 is a diagram for explaining the effects of the transmission system according to the present invention, and shows the flow of data on the loop transmission path at each station. In the figure, SNP indicates the data flow at the main station 2, and NP-1, NP-2, and NP-n indicate the data flow at the general stations 3-1, 3-2, and 3-n. Furthermore, this figure shows a case where the general station 3-1 sends out communication frames A1 and A2, and the general station 3-2 sends out a communication frame B1. Now, when data is transmitted from the general station 3-2 to the general station 3-n, if bits become garbled in the source address in the communication frame A1, this frame A1 becomes a floating frame A1'. On general station 3-1,
I try to erase the communication frames A1 and A2 that I sent, but frame A1 is already floating frame A.
Since it is set to 1', it is not erased. Further, assume that frame erasure remains A2' are generated in the general station 3-2 when erasing its own communication frame A2. In the conventional loop transmission method using GA, the 12th
As shown in figure b, this kind of floating frame A1',
Since the frame erased remnant A2' is not erased at all and circulates around the loop transmission path semi-permanently, empty data sections are filled with these faulty data. On the other hand, in the loop transmission method according to the present invention, the first
As shown in Figure 2a, in the main station 2, after sending out the special patterns S and G, there is an empty data interval until pattern S returns, and the time fill code E is indicated by diagonal lines.
Therefore, the number of loops for frame erased remnant A2' is less than 1 (0.5 on average), and the number of loops for floating frame A1' is less than 2 (1 on average).
Therefore, the influence of these factors on data transmission can be eliminated. Furthermore, even if the data flowing on the loop is traced, the boundary between the data section and the free section becomes clear. Furthermore, in the present invention, since it is only necessary to send the time fill code at the main station, the reliability of data transmission is high, and the amount of hardware required to start and stop sending out the time fill code is small. . As described above, according to the present invention, frame erase remains, floating frames, etc. can be eliminated without deteriorating the reliability of data transmission or increasing the amount of hardware.

[Brief explanation of drawings]

The figures are all related to embodiments of the present invention, and Fig. 1 is a schematic diagram of a loop transmission device, Figs. 2 and 3 are diagrams showing an example of the structure of data flowing on a loop transmission path, and Fig. 4 is a schematic diagram of a loop transmission device. is a diagram showing a specific example of a special pattern, FIGS. 5 and 6 are diagrams each showing the configuration of an example of the main station, FIG. 7 is a diagram showing the configuration of an example of the general station, and FIGS. 8 to 10 The figure shows an example of a specific configuration of a part of FIGS. 5 to 7, FIG. 11 shows a data transmission situation on a loop transmission path, and FIG.
The figure is a diagram showing an example of the effect of the present invention. 21...S,G sending device, 22...E sending device, 2
3...S detection device.

Claims (1)

[Claims] 1. One of a plurality of stations connected by a loop-shaped transmission path sends out a first special pattern to the transmission path, and each station having data to be transmitted transmits the first special pattern to the transmission path.
In a loop transmission method, the right to transmit data is acquired when a special pattern is received, and the right to transmit data is passed to the next station by releasing the first special pattern onto the transmission path after transmitting the transmission data. , the one station 2 sends out a second special pattern S:43 to the transmission path, which is relayed at another station 3-i, prior to the first special pattern G:42, and It operates to continuously send out the time fill pattern E after sending out the special pattern,
Each of the other stations 3-i transmits the transmission data 41 on the condition that it receives the first special pattern, and the one station 2 receives the second special pattern that has passed through the looped transmission path once. Each time, the reception/relay operation of the transmission data E following the second special pattern, the second special pattern S: 43, the first special pattern G: 42, and the time fill pattern E
A loop transmission method characterized in that transmission operations are performed sequentially. 2 The second special pattern S:43 is the same as the first special pattern S:43.
2. The loop transmission method according to claim 1, characterized in that the loop transmission method consists of a pattern that is not detected by stations other than the one station. 3 The second special pattern S:43 is the same as the first special pattern S:43.
2. The loop transmission method according to claim 1, characterized in that the loop transmission method consists of a data frame destined for one station 2.