JPH0218623B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data transmission control device used in a data transmission system in which a plurality of data transmission control devices are connected by a transmission path, and particularly relates to a data transmission control device that handles data with an identification code attached. Regarding.

In a data transmission system that exchanges data between multiple stations, each station is connected by a data transmission path, and a data transmission control device is provided for each station or each main station.
It controls the data flowing through the transmission path. Although there are various forms of transmission paths, here, a loop-shaped transmission path will be mainly explained as an example.

In a transmission system using a conventional loop transmission path, a transmission control device is used to determine the timing of data transmission and reception in each of a plurality of transmission control devices connected to the loop transmission path, and to take measures against partial failures of the loop transmission system. One of the transmission control devices is used as a master transmission control device, and the other transmission control device is used as a slave transmission control device, and the former grasps the transmission status of the entire loop, thereby determining the above-mentioned transmission and reception timing and taking measures against failures of the loop transmission system. I was gone. Therefore, there is a problem that the master transmission control device becomes a large-sized device, and if the master transmission control device breaks down, transmission becomes completely impossible.

In order to improve this problem, it was proposed that
This is a double loop transmission system shown in Fig. 1 (Japanese Patent Application Laid-Open No. 56-40344).

In Fig. 1, 1A, 2A, 3A, 4A are transmission control devices, 5A is a loop transmission line connecting these transmission control devices, and 1B, 2B, 3
B, 4B are transmission control devices, 5B is a loop transmission line connecting these transmission control devices, 6, 7,
8 and 9 are transmission control devices 1A, 1B, and 2A, respectively.
This is a detour transmission line connecting 2B and 2B, 3A and 3B, and 4A and 4B. The transmission directions of the loop transmission lines 5A and 5B are opposite to each other as shown by the arrows. In addition, each transmission control device 1A to 4A, 1B to 4
All of B have the same configuration, and each has a transmitting and receiving function.

Furthermore, 10, 11, 12, and 13 are host computers of each station that actually perform data processing using the data transmission system as described above;
A and 14B are the host computer 10 and the transmission control device 1
Similarly, the terminal transmission line connecting A and 1B is 15A and 1
5B is 11, 2A, 2B, 16A, 16B is 1
2, 3A, 3B, 17A, 17B are 13 and 4
These are terminal transmission lines connecting A and 4B respectively.

In this transmission system, when all the transmission control devices are normal, data transmission is performed through one loop transmission path, for example 5A, and the transmission control devices 1A to 4A connected thereto. When one of the transmission control devices fails, a detour is formed using the other loop transmission path 5B to remove the failed device, and data transmission can be performed (described later). In addition, in this transmission system, all transmission control devices are in an equal relationship,
When a transmission control device attempts to transmit data, it sends the data onto the loop transmission path without checking the status of the transmission control device on the receiving side, and the transmission control device on the receiving side uses the identification code attached to the data. , the station determines whether the data is necessary for its own station, and if it is necessary, it is imported.

The transmission format of data with an identification code is, for example, as shown in FIG. That is, 18
19 is a start flag area indicating the start of data, and 19 is a function code area indicating the content of the data to be transmitted. The function code area is 1 byte, and 256 types of codes are allowed. 20 is a source address field indicating the source of the data, which is also 1.
byte, and can identify 256 transmission control devices. 21 is a control information area for data transmission;
This is also 1 byte. This consists of a serial number to prevent double reception of data and a counter for detour control when a detour occurs in data transmission (described later). 22 is an area for data to be actually transmitted, and has a variable length of up to 256 bytes.
23 is a 2-byte FCS code area for error detection during transmission. 24 is an end flag area indicating the end of data. The data surrounded by the start flag 18 to the end flag 24 constitutes one transmission unit.

Since the data to be transmitted is sent out onto the loop transmission path in the above format, each transmission control device uses its function code 19 to
It is possible to determine whether or not 2 is necessary for one's own station, and to import only what is necessary. Also,
When each transmission control device determines that the source address 20 of the data belongs to its own station, it assumes that the data has gone around the loop transmission path and returned, and erases the data. .

The transmission control device has two modes depending on whether or not it is transmitting data from its own station. First, when data is not being transmitted from its own station, the data coming in from the loop transmission path is sent out one after another onto the loop transmission path without being stored. This is called through communication mode. On the other hand, when data is being transmitted from the own station, the data coming in from the loop transmission path is temporarily stored in the own transmission control device, and when the transmission from the own station is completed, the data is transferred to the loop transmission path. send to. This is called store-and-forward communication mode. In either case, if the data is necessary for the own station, it is imported. By employing these two modes, data transmission efficiency is increased.

Next, the specific operation of the double loop transmission system shown in FIG. 1 will be explained.

Now, if data is transmitted from the transmission control device 1A, this data goes around the loop transmission path 5A and returns to the transmission control device 1A. During this time, the other transmission control devices 2A, 3A, and 4A determine whether the data is necessary based on the function code attached to the data, and if determined to be necessary, take it in. At that time, for example, the second and third transmission control devices 2A,
Assuming that 3A is not transmitting data from its own station, they operate in through communication mode, and if the fourth transmission control device is transmitting data from its own station, it is a store and forward mode. Operates in communication mode.
The data returned to the transmission control device 1A, which is the source, is erased there because its source address is that of its own station.

Further, assume that when data is transmitted from the transmission control device 1A, the third transmission control device 3A is out of order. Then, since the transmitted data is not returned, the transmission control device 1A, which is the transmission source, knows that a failure has occurred somewhere. Therefore, the transmission control device 1A issues a check signal to locate the faulty location, and forms a detour that avoids the faulty location using only one loop transmission line 5B. That is, when the third transmission control device 3A is out of order, the data transmitted from the transmission control device 1A enters the bypass transmission path 7 from the second transmission control device 2A, and is transmitted from the transmission control device 2B to the third transmission control device 2A. The second loop transmission path 5B is detoured in the opposite direction to reach the transmission control device 4B, from there it passes through the detour transmission path 9, enters the transmission control device 4A, and again passes through the first loop transmission path 5A to reach the transmission source. Return to the transmission control device 1A. By taking such a route, it is possible to ensure the data transmission function except for only the failure location.

By the way, in a data transmission system that handles data with such identification codes, each transmission control device uses the identification code to determine whether the data is necessary or not and when data comes in from the transmission path. Since the data transmission speed is determined by the identification code determination processing time in this transmission control device, the data transmission speed is determined by the identification code determination processing time in the transmission control device. A transmission control device generally includes a control computer for data transmission control, and conventionally, the identification code is determined within this control computer, so that the determination process takes time. Therefore, when a conventional transmission control device is used, it takes time for data to go around the loop transmission line, and there is a problem that the transmission speed cannot be increased.

In addition, in conventional transmission control devices, when erasing data that has gone through one cycle, when a decision is made to erase the data based on the source address attached to the data,
Since the previous start flag and function code have already been sent onto the transmission path, an undesirable situation may occur in which data with a corrupted transmission format flows on the loop transmission path.

Similar problems, especially the problem of slow transmission speed, are not limited to the double loop transmission system as described above, but also in single loop transmission systems, or in end-shaped transmission systems as shown in Figure 3. Alternatively, even in a transmission system in which the transmission control devices do not all have the same configuration, and some have a transmitting/receiving function and others only have a receiving function, it is possible to import data from the transmission path and determine its identification code. This is a common problem in transmission systems having a type of transmission control device that transmits data from In addition, in FIG. 3, 25~
28 is a transmission control device, 29 is an end-shaped transmission line, 3
0 to 33 are host computers.

SUMMARY OF THE INVENTION An object of the present invention is to provide a data transmission control device capable of eliminating the above-mentioned problems of the prior art, quickly determining an identification code attached to data, and improving the transmission speed of a data transmission system. be.

In order to achieve this objective, the present invention provides data transmission control that determines whether or not data sent through a transmission path is necessary for its own station based on its identification code, and captures only the necessary data. In addition to the control computer for data transmission control, the apparatus is provided with a determining means for determining whether or not the data is necessary for the own station based on the identification code, and only the data that the determining means determines as necessary is transmitted to the station. It is characterized in that it is imported into a control computer and processed.

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG.

In FIG. 4, 1A is the transmission control device of this embodiment, 5A is a loop transmission line, 14A is a terminal transmission line,
10 is a host computer. That is, the transmission control device 1A is shown here as being equivalent to one transmission control device 1A in FIG. below,
The configuration of the transmission control device 1A will be explained in detail.

34 is a shift register for temporarily registering data coming in from the loop transmission path 5A, and is 4 bytes long. 35 is a code register that stores function codes of data necessary for its own station, and up to 256 function codes can be registered.
36 compares the contents in the shift register 34 with the function code registered in the code register 35, and also determines whether or not the contents in the shift register 34 include the source address of its own station. This is a determination circuit that determines whether or not data should be received, or whether data should be erased. These shift register 34, code register 35, and determination circuit 36 constitute determination means 37.
The determining means 37 is provided outside the control computer 38 for data transmission control, and operates without being controlled by the control computer 38.

39 is a data transmission/reception circuit; here,
The data sent serially on the loop transmission line 5A is converted into parallel 8-bit data, and a check is performed to detect errors during transmission, such as an FCS check, etc.
Perform CRC check. Also, the data transmission format is created here. Reference numeral 40 denotes an oscillation circuit for generating a clock signal, which regenerates a transmission clock synchronized with received data when data is input from the loop transmission line 5A. This transmission clock is used as a reception and transmission clock in the through communication mode, and is used only as a reception clock in the store-and-forward communication mode. A clock that is not synchronized with the receiving clock is used as the transmitting clock.

41 is a receiving data transfer device, and 42 is a receiving data buffer. The reception data transfer device 41 transfers the data to the reception data buffer 42 without being controlled by the control computer 38 when the determination circuit 36 determines that the data coming from the loop transmission path 5A needs to be received. 4
3 is a transmission data buffer for temporarily storing transmission data, and 44 is a transmission data transfer device for transferring the transmission data in the transmission data buffer 43 to the loop transmission path 5A via the transmission/reception circuit 39.

The control computer 38 controls the code register 3
5, registering and erasing function codes in the data buffer 42, reading received data from the receiving data buffer 42, writing transmitting data to the transmitting data buffer 43, setting the timing for starting the transmitting data transfer device 44, etc.

The operation of this transmission control device 1A is as follows.

First, the operation during data transmission will be explained.
When attempting to transmit data from its own station, the control computer 38 stores the transmission data and its data length in the transmission buffer 43. Next, the control computer 38 determines whether or not data is currently being transmitted in the through communication mode.
In the through communication mode, the transmission data transfer device 44 is activated in the store-and-forward communication mode after the transmission of the data is completed, or immediately when the data is not being transmitted. When the transmission data transfer device 44 is activated by the control computer 38, it is then activated by the control computer 38.
The transmission data is automatically read out from the transmission data buffer 43 and sent to the loop transmission line 5A via the transmission/reception circuit 39 without being controlled by. The operation of the transmission data transfer device 44 continues until all the data in the transmission data buffer 43 has been transmitted.

Next, the operation at the time of data reception will be explained with reference to the flowchart of FIG. The determination circuit 36 constantly monitors the contents of the shift register 34, and when a data start flag is registered in the first byte of the four bytes of the shift register 34, the determination circuit 36 reads the contents of the second byte according to the transmission format shown in FIG. is determined to be a function code, the third byte to be the source address, and the fourth byte to be transmission control information. The determination circuit 36 then compares the second byte of the shift register 34 with each function code in the code register 35 to see if there is a match (fifth byte).
Figure step 101). If there is no match, the data is unnecessary, so the determination circuit 36 is idle until the start flag appears again in the first byte of the shift register 34 (step 113). If there is a match, the determination circuit 36 further checks whether the third byte of the shift register 34 matches the transmission source address of the station (step
102). If they do not match, the data was sent from another station and is necessary for reception, so first determine whether or not your own station is currently transmitting data (step 1).
103), if transmitting is in progress, the mode is set to store-and-forward communication mode (step 104), and if not transmitting, the mode is set to through communication mode (step 105), and the receiving data transfer device 41 is immediately activated (step 106). As a result, the received data is stored in the received data buffer 42. After starting the reception data transfer device 41, the determination circuit 36 is kept idle until the start flag is again entered in the first byte of the shift register 34 (step 113). Further, the receiving data transfer device 41 operates until the transmitting/receiving circuit 39 receives the data end flag and notifies the data end (step 114). During this data reception, the control computer 38 does not participate in the reception operation.

On the other hand, in step 102, if the third byte of the shift register 34 matches the source address of the own station, the data is transmitted from the own station, so the fourth byte of the shift register 34 Depending on the content, it is determined whether the data has been around or is being detoured (step 107). If the data has gone through one cycle, the determination circuit 36 issues a command to the transmitter/receiver circuit 39 to set the reception mode to the store-and-forward communication mode and to ignore the received data. As a result, the reception data transfer device 41 is not activated,
The received data will be erased (step
108). Then, the judgments in steps 101, 102, and 107 are as follows.
Since the start flag, function code, source address, and transmission control information of the received data are erased while they are still in the shift register 34, data can be erased from the start flag, and data with corrupted transmission formats can be erased as before. is no longer sent onto the loop transmission line 5A. After this step 113
(Already mentioned).

On the other hand, if it is determined in step 107 that the data is being detoured, first determine whether or not the own station is currently transmitting data (step 107).
109), if the data is being transmitted, it is set to store and forward communication mode (step 110), and if it is not being transmitted, it is set to through communication mode (step 111), and the reception data transfer device 41 is immediately activated (step 112). The determination circuit 36 becomes idle (step 113), and the receiving data transfer device 41 operates until a stop command is received from the transmitting/receiving circuit 39 (step 114).

According to the embodiment described above, since the various identification codes attached to the transmitted data are determined by the determination means provided separately from the control computer, the processing time for determining the identification code is controlled. It takes much less time than doing it on a standard computer.
Therefore, if a data transmission system is configured using such a transmission control device, there is an advantage that the data transmission speed can be significantly improved. In addition, since the shift register has a capacity of 4 bytes that can store everything from the start flag to transmission control information, data deletion can be determined before the start flag is sent to the loop transmission path. When erasing data, data with corrupted transmission formats is never sent to the loop transmission path.

In the above embodiment, a transmission control device having a transmitting and receiving function has been described, but the present invention can also be applied to a transmission control device having only a receiving function.

In addition, in the above embodiment, the function code, the source address, and the transmission control information were used as the identification code, but one or more of these or other identification codes are required as the identification code. Can be used according to your needs.

Further, in the above embodiment, an example was explained in which the transmission control device was used in a loop transmission system, but the transmission control device of the present invention can also be used in a transmission system other than the loop transmission system, for example, as shown in FIG. can.

As explained above, the transmission control device of the present invention is provided with an identification code determination means outside the control computer, and uses it to determine the identification code attached to the transmission data. Data can be quickly forwarded without being restricted by processing speed. Therefore, by using the transmission control device of the present invention, the transmission speed of the data transmission system can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an example of a double loop transmission system, Fig. 2 is an explanatory diagram showing an example of a transmission format of data with an identification code attached, and Fig. 3 is an example of an end-shaped transmission system. Schematic configuration diagram,
FIG. 4 is a block diagram showing one embodiment of the transmission control device of the present invention, and FIG. 5 is a flowchart for explaining the operation of the device shown in FIG. 1A to 4A, 1B to 4B...transmission control device, 5
A, 5B...Loop transmission line, 10-13...Host computer, 34...Shift register (capture unit),
35... Code register (storage section), 36... Judgment circuit, 37... Judgment means, 38... Control computer, 39... Transmission/reception circuit, 41... Reception data transfer device, 42... Reception data buffer,
43... Transmission data buffer, 44... Transmission data transfer device.

Claims (1)

[Scope of Claims] 1. A device connected to a dual-system transmission line capable of forming a detour, and equipped with a control computer for controlling data transmission, and identifying the data sent through the transmission line using an identification code. A data transmission control device that determines whether data is necessary for its own station and imports only the necessary data, includes at least a data start flag, a function code, and a source address among the data received from the transmission path. When a data start flag is registered in the storage means, it is determined based on the function code whether or not the received data is necessary at the own station, and this determination determines whether the received data is necessary. determining means for determining whether or not the source address is the own address when it is determined that the source address is the own address; and means for importing the received data into the control computer when the determination result by the determining means is that it is another address. A data transmission control device comprising: 2. The storage means further includes an area for storing transmission control information indicating whether the received data has gone around or is being detoured among the received data, and the source address determination means can determine whether the received data is the own address. 2. The data transmission according to claim 1, wherein the received data is taken into the control computer when the transmission control information indicates that the data is being detoured. Control device.