JP2002368772A - Data transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data transmission system in which frame data of a LAN are inexpensively configured without using a converter and which can easily be handled. SOLUTION: A TDM transmitter 2A for transmitting data according to the TDM system converts asynchronous communication data from LANs 3A, 3B into a plurality of time slot divisions of synchronous communication data and transmits the converted data to a transmission line 1A. A TDM transmitter 2B receiving the synchronous communication data converts the synchronous communication data into asynchronous communication data and transmits the data to a terminal 4C via a LAN 3C. Thus, the system can simply realize data conversion without need for a particular converter to reduce the cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time division multiplexing (TDM) transmission device for connecting a plurality of LANs,
The present invention relates to a data transmission system for transmitting data between N nodes.

[0002]

2. Description of the Related Art TD used for digital communication transmission
M (time-division multiplexing) transmission is performed by dividing and transmitting individual communication lines at fixed time intervals (time slots).
This is a synchronous communication system for performing communication of a plurality of channels on one transmission path, and is a synchronous digital system (SDH).
l Hierarchy; synchronous digital hierarchy). For synchronous transmission, it is necessary to synchronize time slots assigned to individual communication lines.

On the other hand, in a LAN (Local Area Network) which is a communication system for connecting terminals distributed in a relatively small area such as the same room or the same site, data is transmitted to a transmission line in units called frames. Is done. In a LAN, a frame is transmitted at an arbitrary timing (asynchronous) by each terminal, so that synchronization control is not required. However, it is necessary to control the transmission order between a plurality of terminals.

As described above, the method of sharing a transmission path differs between TDM transmission and LAN. In TDM, the transmission rate is fixed depending on the assigned time slot, whereas the data on the LAN is several kbps to 100 Mbps.
s, and the transmission speed is also different. Therefore, it is not possible to directly connect the LAN to the TDM transmission device and directly transmit the LAN data by the TDM method. For this reason,
In a conventional data transmission system, a conversion device is provided between a transmission device that performs data transmission by the TDM method and a LAN, and the conversion device converts the format of LAN frame data and the time slot data of the TDM method (synchronous communication method) by the conversion device. Along with converting the format, it was necessary to convert the data transmission speed.

In the TDM system, as described above, time-divided time slots are assigned to individual lines,
Communication is performed by transmitting and receiving data carried in time slots. One-to-one or one-to-one communication lines sharing the same time slot are made to correspond to one-to-one or one-to-N communication lines. Can communicate only with each other. This is because if a plurality of communication lines share the same time slot without making the communication lines sharing the same time slot one-to-one or one-to-N, the plurality of communication lines simultaneously transmit data to the same time slot. This is because it starts and data duplication occurs.

As a prior art related to the present application, Japanese Patent Application Laid-Open No. Hei 8-46590 is listed.

[0007]

Since the conventional data transmission system is configured as described above, there are the following problems. (1) First, while converting the data format,
A conversion device for converting the data transmission speed is defined as a transmission device and an L.
Since it is provided between the network and the AN, there are problems such as an increase in the price of the data transmission system, and an increase in handling of the data transmission system. (2) Next, in the TDM system (synchronous communication system), communication lines sharing the same time slot must be made to correspond one-to-one or one-to-N in order to prevent duplication of data carried in the time slot. In addition, there is a problem that it is not possible to perform communication between a plurality of communication lines by sharing the same time slot among the plurality of communication lines. (3) Further, in the TDM system (synchronous communication system), the transmission speed is fixed depending on the assigned time slot, and there is a problem that asynchronous data with variable speed cannot be transmitted as it is. Here, the conversion from the frame data (asynchronous data) to the demultiplexed data (synchronous data) is performed by dividing the frame data into the data amount of the time slot as shown in FIG. It is possible to handle even frame data (asynchronous data).

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a data transmission system which can be constructed at a low cost and can be easily handled by using no LAN frame data conversion device. The purpose is to gain.

Another object of the present invention is to provide a data transmission system in which a plurality of communication lines can share the same time slot with each other to perform communication between the plurality of communication lines.

[0010]

(1) A data transmission system according to claim 1 of the present invention comprises a transmission line for multiplexing and transmitting synchronous communication data, and a time division multiplexing system connected to both ends of the transmission line. A time-division multiplex transmission device for transmitting the synchronous communication data, and a LAN connected to each of the time-division multiplex transmission devices for connecting terminals and transmitting the asynchronous communication data. In a data transmission system for performing data transmission between the LAN and the device via the transmission path, the time division multiplex transmission device includes a LAN interface unit and a multiplexing / demultiplexing unit.
An AN interface unit converts the asynchronous communication data from the LAN into synchronous communication data which is time-divided into a plurality of time slots, multiplexes the data in the multiplexing / demultiplexing unit, transmits the multiplexed data to the transmission path, and When the multiplexing / demultiplexing unit receives multiplexed synchronous communication data from another time division multiplex transmission device, it converts the received data into time division synchronous communication data of a plurality of time slots, and converts the converted data to the LAN interface. The section converts the data into asynchronous communication data and transmits the data to a predetermined LAN.

(2) A data transmission system according to a second aspect of the present invention includes: a transmission line formed in a ring shape for multiplexing transmission of synchronous communication data; and a transmission line connected to the ring transmission line.
A plurality of time-division multiplex transmission apparatuses for transmitting the synchronous communication data in a time-division multiplex system, and LANs connected to the respective time-division multiplex transmission apparatuses while connecting terminals to transmit asynchronous communication data. In a data transmission system for transmitting data between the time-division multiplex transmission device and an arbitrary LAN via the transmission path, the time-division multiplex transmission device includes a LAN interface unit and a multiplexing / demultiplexing unit. The LAN interface unit converts the asynchronous communication data from the LAN into synchronous communication data time-divided into a plurality of time slots, multiplexes the data in the multiplexing / demultiplexing unit, and transmits the multiplexed data to the transmission line. When the multiplexing / multiplexing / demultiplexing unit receives multiplexed synchronous communication data from another time division multiplex transmission device, the multiplexing / demultiplexing unit demultiplexes the received data into a plurality of time slots. When the converted time-division synchronous communication data is addressed to the own interface unit, the LAN interface unit converts the data into asynchronous communication data and transmits the data to a predetermined LAN, and transmits the data to another interface unit. Is transmitted as relay data via the multiplexing / demultiplexing unit.

(3) A data transmission system according to a third aspect of the present invention, in the data transmission system according to the second aspect, wherein the asynchronous communication data has a configuration including a header and frame data storing the data itself, and a LAN interface unit. Is transmitted together with the frame data as a header including the ID number information of the own LAN interface unit. When the synchronous communication data is received, if the ID number of the header is the ID number of the own LAN interface unit, the received The synchronous communication data is transmitted from its own interface unit and is determined to have circulated through the transmission path, and the frame data is discarded.

(4) In the data transmission system according to a fourth aspect of the present invention, in the data transmission system according to the third aspect, the LAN interface unit transmits the header together with the frame data as a header including the lifetime of the frame data. As described above, when the synchronous communication data is received, if the frame data exceeds the lifetime, the frame data is discarded.

(5) The data transmission system according to claim 5 of the present invention is the data transmission system according to claim 4, wherein the LAN interface unit checks the ID number of its own LAN interface unit and checksum against the lifetime. When the synchronous communication data is received, the checksum of the received synchronous communication data does not match the test information calculated from the synchronous communication data. The frame data is discarded.

(6) A data transmission system according to a sixth aspect of the present invention is the data transmission system according to any one of the third to fifth aspects, wherein a test such as CRC is performed on the frame data or the header and the frame data. If the test information of the received synchronous communication data does not match the test information calculated from the received synchronous communication data, the frame is transmitted when the synchronous communication data is received. Discard the data.

(7) In a data transmission system according to a seventh aspect of the present invention, in the data transmission system according to any one of the third to sixth aspects, the LAN interface unit includes an ID number of the received synchronous communication data. Is provided with a function of receiving the frame data without discarding it even if it is the ID number of the own LAN interface unit, and the above function is operated at the time of maintenance so that the test can be performed.

(8) In a data transmission system according to claim 8 of the present invention, in the data transmission system according to any one of claims 3 to 7, the LAN interface unit internally transmits synchronous communication data to be transmitted. A function to receive data directly is provided, and the above function is operated during maintenance to enable testing.

(9) In a data transmission system according to a ninth aspect of the present invention, in the data transmission system according to any one of the third to eighth aspects, the LAN interface unit has an ID number of another LAN interface unit. A function of receiving synchronous communication data of at least one ID number is provided, and the above function is operated at the time of maintenance to enable a test.

(10) In a data transmission system according to a tenth aspect of the present invention, in the data transmission system according to any one of the third to ninth aspects, the LAN interface unit detects an error in the received synchronous communication data. A function of detecting and counting is provided.

(11) A data transmission system according to claim 11 of the present invention, in the data transmission system according to any one of claims 2 to 10, wherein the LAN interface unit relays synchronous communication data. A first congestion control function is provided to limit the transmission of asynchronous communication data from the LAN in accordance with the degree of congestion of the relay operation.

(12) A data transmission system according to a twelfth aspect of the present invention, in the data transmission system according to any one of the second to eleventh aspects, wherein the asynchronous communication data is a frame data storing a header and data itself. When relaying the synchronous communication data, the LAN interface unit transmits the synchronous communication data to be relayed by including the congestion information corresponding to the congestion degree of the relay operation in the header, and receives the synchronous communication data. The LAN interface unit has a second congestion control function for detecting the congestion state and restricting the transmission of asynchronous communication data from the LAN.

(13) A data transmission system according to a thirteenth aspect of the present invention, in the data transmission system according to any one of the second to twelfth aspects, wherein the asynchronous communication data includes a header and a frame storing the data itself. When the flag is given to the synchronous communication data to be transmitted, the LAN interface unit includes a scrambler for scrambling the synchronous communication data to be transmitted,
If there is one predetermined value or character to which a flag is to be added to the scrambled synchronous communication data, it is converted into a plurality of specific values or specific characters, an encoding function for adding a flag and transmitted, and receiving the synchronous communication data An interface unit having a decoding function for restoring a plurality of specific values and specific characters of the synchronous communication data excluding the flag to the predetermined one value and character, and a descrambler for descrambling the decoded data; When a plurality of specific values or specific characters are present in the synchronous communication data in large numbers, the appearance probability is reduced, and an increase in the amount of data on the transmission path is suppressed.

(14) A data transmission system according to a fourteenth aspect of the present invention is the data transmission system according to any one of the second to thirteenth aspects, wherein a first to a second transmission apparatus are provided in one time division multiplex transmission apparatus. When a plurality of LAN interface units up to n are provided, the transmitting end and the receiving end of the plurality of LAN interface units are sequentially cascaded to form a first LAN interface.
From the transmitting end of the LAN interface unit to the receiving end of the second LAN interface unit, from the transmitting end of the second LAN interface unit to the receiving end of the third LAN interface unit,... The receiving section of the first LAN interface section, which is connected so that a signal can pass from the receiving end of the interface section to the transmitting end of the n-th LAN interface section, and corresponds to one end of the cascade connection, is composed of the plurality of LAN interface sections. All of the synchronous communication data to be received or relayed is received via the multiplexing / demultiplexing unit, and the n-th L
The transmitting end of the AN interface unit transmits all the synchronous communication data to be transmitted or relayed from the plurality of LAN interface units via the multiplexing / demultiplexing unit, and the LAN and the terminal connected to the one time division multiplex transmission device. Can be increased.

(15) A data transmission system according to a fifteenth aspect of the present invention, in the data transmission system according to any one of the second to fourteenth aspects, is a mesh transmission path instead of a ring transmission path. , A logical link is formed between the time division multiplex transmission devices, and synchronous communication data is transmitted between the time division multiplex transmission devices.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a data transmission system according to a first embodiment of the present invention. In FIG. 1, reference numeral 1A denotes a transmission line for synchronous communication data connected by an optical fiber, and 2A and 2B denote a plurality of communication line data by TD.
This is a TDM transmission device for transmitting data in the M system, and the TDM transmission devices are connected to each other by a transmission line 1. 3A-3
C is a LAN connecting terminals 4A to 4C via a communication line to form a communication network. The access control method of the LANs 3A to 3C is CSMA / CD (Carrier Sense Multiple Acces).
s with Collision Detection), but other access control methods may be used. 4A to 4C are LAN terminals such as computers.

FIG. 2 shows a detailed configuration of the TDM transmission apparatus 2 (2 is representative of 2A and 2B). In FIG. An electrical / optical converter (E / O) 51 for converting synchronous communication data from the separation bus 7 from an electric signal to an optical signal;
An optical / electrical conversion unit (O / E) 52 for converting synchronous communication data from (corresponding to 1A in FIG. 1) from an optical signal to an electric signal. A multiplexing / multiplexing / demultiplexing unit 6 demultiplexes the synchronous communication data from the transmission line 1 and converts it into demultiplexed data (data obtained by separating a plurality of time slots of the synchronous communication data). Is transmitted to the demultiplexing bus 7, and conversely, the demultiplexed data from the demultiplexing bus 7 is multiplexed and converted into synchronous communication data, and the synchronous communication data is transmitted to the transmission line 1. Reference numeral 7 denotes a demultiplexing bus for transmitting demultiplexed data, and reference numeral 8 denotes a LAN interface unit connected to the terminals 4A and 4B via the LANs 3A and 3B and having a function of converting asynchronous communication data and synchronous communication data.

In the LAN interface section 8, 81
Is the frame data of the terminals 4A and 4B and the demultiplexing bus 7.
A layer 2 (data link layer) switch circuit for mutually relaying frame data on the side, a transmission buffer 82 for temporarily storing frame data sent from the layer 2 switch circuit 81, and a demultiplexer 83 for frame data from the transmission buffer A transmission control unit for multiplexing data on the bus 7, a reception control unit 84 for demultiplexing data from the demultiplexing bus 7, and a reception buffer 85 for temporarily storing data from the reception control unit 84.

FIG. 3 shows a detailed configuration of the transmission control unit 83. 831 is, for example, 7Eh in the flag.
7Eh and 7Dh (code of each one byte) included in the data transmitted from the transmission buffer 82 into 7Eh · 7Dh (code of 2 bytes). , 832 are flag adding units for adding a flag 7Eh (1 byte code) to the encoded data.

FIG. 4 shows a detailed configuration of the reception control section 84. Reference numeral 841 denotes a frame data extraction unit that extracts a frame data portion from data received from the demultiplexing bus 7, and reference numeral 842 denotes a 7E / 7D decoding unit that decodes the extracted frame data.

FIG. 5 shows a format of data transmitted to the demultiplexing bus 7. FIG. 6 is a diagram showing the correspondence between time slots on the transmission line 1 and frame data on the LAN 3.

Next, the operation will be described. (1) The asynchronous communication data (frame data) transmitted from the terminal 4 to the LAN 3 is received by the LAN interface unit 8 of the TDM transmission device 2. (2) When the layer 2 switch circuit 81 of the LAN interface unit 8 receives the frame data from the LAN 3,
The transmission destination address of the frame data is confirmed, and if the relay destination is on the demultiplexing bus 7 side, the frame data is sent to the transmission buffer 82, and the frame data is stored in the transmission buffer 82. (3) When the transmission control unit 83 detects that the frame data is stored in the transmission buffer 82, the transmission control unit 83 divides the frame data from the transmission buffer at the timing and the data amount requested by the multiplexing / demultiplexing unit 6, and extracts the frame data. The frame data is sent to the separation bus 7.

(4) The format of the data transmitted to the demultiplexing bus 7 at this time is as shown in FIG. 5, and the frame in the figure is the data extracted from the transmission buffer 82 by the 7E / 7D encoding unit 831. 7Eh (1 byte code) is converted to 7Dh · 5Eh (2 byte code)
(1 byte code) converted to 7Dh / 5Dh (2 byte code).
At 2, 7Eh (1 byte code) is added as a flag before and after the frame. This flag is data that fills the space between frame data in the time slot, and at least one
Insert bytes. As a result, there is no data having a value of 7Eh other than the flag in the data on the time slot.

(5) Here, conversion from frame data (asynchronous data) to demultiplexed data (synchronous data) is performed as follows.
As shown in FIG. 6, this is performed by dividing the frame data into the data amount of the time slot, so that it is possible to cope with frame data (asynchronous data) with variable speed. (6) The multiplexing / multiplexing / demultiplexing unit 6 multiplexes the data output to the multiplexing / demultiplexing bus 7 according to a normal TDM process to obtain synchronization data, and converts the synchronization data from an electric signal to an optical signal by the E / O 51. Then, the data is transmitted to the transmission path 1.

(7) On the other hand, the TDM transmission apparatus 2
Receive synchronization data from. The multiplexing / demultiplexing unit 6 demultiplexes the synchronous data converted from the optical signal to the electric signal by the O / E 52 from the transmission line 1 and converts the received synchronous data into demultiplexed data. To the demultiplexing bus 7. (8) The demultiplexed data is transmitted to the LAN interface unit 8
First, a frame data extracting section 841 extracts a frame data portion by separating a data area sandwiched between 7Eh from the demultiplexed data by a frame data extracting section 841, and further extracts a frame data portion. At 842, 7Dh · 5
The value of Eh is converted to 7Eh and the value of 7Dh / 5Dh is converted to 7Dh, thereby decoding the original frame data and storing it in the reception buffer 85.

(9) At this time, the reception buffer 85 sequentially stores the frame data divided by the time slot of the multiplexing / demultiplexing unit 6. (10) Then, the reception control unit 84 sets the reception buffer 85
When it detects that one frame of data has been stored in the frame data, the frame data (asynchronous data) for one frame is transmitted to the layer 2 switch circuit 81. (11) Upon receiving the frame data, the layer 2 switch circuit 81 checks the destination address of the frame data and sends the frame data to the LAN 3 connected to the destination terminal 4.

As described above, according to the first embodiment, in the data transmission system in which the TDM transmission device 2 supports the TDM transmission device 1: 1 via the transmission line 1A,
Provided with a data conversion function (a function of converting synchronous data and asynchronous data and a function of converting data transmission speed) in the LAN interface unit 8 of the first embodiment, there is no need to provide a conversion device, and the interface units of the TDM transmission devices 2A and 2B are provided. 8, the LAN 3 can be directly connected, and as a result, a data transmission system that can be configured at low cost and that can be easily handled can be obtained.

Embodiment 2 FIG. 7 is a configuration diagram of a data transmission system according to Embodiment 2 of the present invention.
1 is a transmission line of synchronous communication data connected by an optical fiber,
Reference numerals 2A to 2D denote TDM transmission devices, which are ring-connected by a transmission line 1. 3A-3G
And LAN terminals 4A to 4G such as computers.

FIG. 8 is a diagram showing a detailed configuration of the TDM transmission apparatus 2. In FIG. 8, reference numeral 86 denotes a relay buffer for relaying frame data received by the reception control unit 84 to the transmission control unit 83. Other configurations are the same as those in FIG. 2, and overlapping descriptions will be omitted.

FIG. 9 shows that the transmission control unit 83 of FIG.
The transmission / relay selection unit 833 for selecting data from the transmission buffer 82 and data from the relay buffer 86 is provided. FIG. 10 shows the reception control unit 84 of FIG.
And a 7E / 7D decoding unit 842 for sending data to the reception buffer 85 and the relay buffer 86.

FIG. 11 shows a transmission / relay selection unit 833.
3 is a flowchart showing the operation of the first embodiment.

Next, the operation will be described. (1) In a data transmission system in which a plurality of TDM transmission devices are connected on a ring as shown in FIG. 7, a plurality of communication lines share the same time slot to perform communication between the plurality of communication lines. In this case, it is necessary to prevent duplication (overwriting) of data carried in the same time slot. In the second embodiment, duplication of data is prevented by performing relay / transmission selection control. (2) The reception control unit 84 sends the frame data decoded by the 7E / 7D decoding unit 842 to the reception buffer 85 and the relay buffer 86. (3) The transmission control unit 83 selects, in the transmission / relay selection unit 833, a buffer from which the frame data is extracted according to the frame data storage status of each of the transmission buffer 82 and the relay buffer 86, and a multiplexing / demultiplexing unit. The frame data is divided and extracted from the selected buffer at the timing and the data amount requested by 6, and the frame data is transmitted to the demultiplexing bus 7.

The operation of the transmission / relay selection unit 833 at this time will be described with reference to the flowchart of FIG. (1) The transmission / relay selection unit 833 transitions from all states and starts control in response to all reset requests including power-on. (2) First, the process waits until frame data is stored in one of the transmission buffer 82 and the relay buffer 86 (step 8331). While waiting, the flag 7Eh is continuously transmitted to the demultiplexing bus 7. (3) When frame data storage is detected in step 8331, and when frame data is stored only in relay buffer 86, the frame data stored in relay buffer 86 is transmitted (step 8332 → step 8333). → Step 8335). (4) When frame data is stored only in the transmission buffer 82, the frame data stored in the transmission buffer 82 is transmitted (step 8332 → step 8333 → step 8336).

(5) When frame data is stored in both the relay buffer 86 and the transmission buffer 82, if the frame data in the transmission buffer 82 has been transmitted previously, the frame data in the relay buffer 86 is transmitted. (Step 8332 → Step 8334 → Step 83
35). (6) Conversely, if the frame data of the relay buffer 86 was previously transmitted, the frame data of the transmission buffer 82 is transmitted (step 8332 → step 8334 → step 8336). (7) In step 8335 or step 8336,
When transmission of one frame of frame data is completed, the process returns to step 8331 and waits until frame data is stored. (8) As described above, if the frame data is stored in one of the buffers, the frame data is transmitted, and if the data is stored in both the frames, the transmission is performed alternately.

As described above, according to the second embodiment, the provision of the relay buffer 86 and the transmission / relay selection section 833 allows the plurality of LAN interface sections 8 sharing the same time slot to be connected to other LAN interface sections. 8 can be transmitted at a safe timing without breaking the transmission data of the LAN interface unit 8 (relay data of the own LAN interface unit 8).
They can communicate with each other. As a result, a communication system between LANs can be flexibly constructed.

Embodiment 3 In the second embodiment, since the transmission data of another station is successively relayed by each station, there is a possibility that all of the shared time slots on the transmission path 1 are occupied by old transmission data. Therefore, Embodiment 3
Then, as shown in FIG. 12, the transmission control unit 83 of FIG.
834 having a function of adding a header to the frame data is provided. As shown in FIG. 13, the reception control unit 84 of FIG. 10 is provided with a header determination unit 843. FIG.
Shows the format of the data transmitted to the demultiplexing bus 7 at this time.

Next, the operation will be described. (1) When transmitting the frame data stored in the transmission buffer 82 in the transmission control unit 83, the header addition unit 834 adds a header to the head of the frame data. (2) The format of the data at this time is as shown in FIG. 14, and the ID number of the own LAN interface unit 8 is placed as the content of the header. At this time, an ID number is uniquely assigned to each of the TDM transmission devices 2A to 2G (or the LAN interface unit 8) connected to the transmission line 1. (3) The frame data to which the header is added is transmitted by the transmission control unit 8
3 is sent to the demultiplexing bus 7.

(4) On the other hand, the frame data is extracted by the frame data extraction section 841 of the reception control section 84, and the 7E / 7D decoding section 8
The header and frame decoded at 42 are sent to the header determination unit 843, and the frame data whose ID number of the own LAN interface unit 8 matches the ID number of the header is sent to the own LA.
Regarding the frame as transmitted by the N interface unit, the frame is not transmitted to the reception buffer and the relay buffer (the frame data is discarded). (5) If they do not match, the header and the frame data are transmitted to the relay buffer 86 and the reception buffer 8
5, only the frame data from which the header has been removed is transmitted.

As described above, according to the third embodiment, by providing the header adding section 834 and the header determining section 843, the frame data transmitted to the transmission path 1 The frame data is removed from the transmission line 1 by preventing the frame data from being relayed when the device 2 is relayed, makes a round of the ring, and returns to the TDM transmission device 2 of the transmission source again.
It is possible to prevent all of the above shared time slots from being occupied by old transmitted data. Thereby, communication between LANs can be efficiently performed in a limited band.

Embodiment 4 In the third embodiment, when a failure, degeneration, removal, or the like of a certain LAN interface unit 8 occurs, the frame data and header transmitted by the LAN interface unit 8 to the transmission line 1 are not removed, and There is a risk that it will continue to remain. Therefore,
In the fourth embodiment, as shown in FIG. 15, the lifetime of the frame data (Time To Live; T) is included in the header.
TL).

Next, the operation will be described. (1) When transmitting the frame data stored in the transmission buffer 82 in the transmission control unit 83, the header addition unit 834 determines the content of the header added to the beginning of the frame data as the content of the frame on the transmission path 1 The lifetime of the data (TTL) is listed. (2) The header including the TTL is transmitted to the relay buffer 86 by the header determination section 843 of the LAN interface section 8.
TTL is decremented by one each time the data is transmitted. (3) When the header determination unit 843 detects that the value of TTL is 0, it considers that the lifetime of the frame on the transmission path 1 has ended, and transmits the frame to the reception buffer and the relay buffer. No (discard frame data).

(4) In a network in which TDM transmission devices are connected in a ring shape, it becomes unnecessary at the time of one round of a frame. Therefore, the TTL value is usually set to the LAN interface unit 8 connected to the transmission line 1. Set the maximum number of. In the case of a network in which the TDM transmission devices are connected in a mesh type or linearly, the same effect can be obtained by making the TTL value changeable.

As described above, according to the fourth embodiment, L
It is possible to prevent the frame data from remaining on the transmission line 1 without being removed from the transmission line 1 due to an abnormality of the AN interface unit 8 or the like. Improvement and communication quality can be achieved.

Embodiment 5 In the fourth embodiment, when the value of the flag transmitted on the transmission line 1 changes due to abnormality, disturbance, or the like of the transmission line 1 and the TDM transmission device 2,
There is a possibility that the frame data extraction unit 841 erroneously takes in the frame data. Therefore, in the fifth embodiment, as shown in FIG.
The exclusive OR of the value of TL is added as a checksum.

Next, the operation will be described. (1) When transmitting the frame data stored in the transmission buffer 82, the header addition unit 834 uses the ID number and the T
Add the TL checksum. Since the checksum uses an exclusive OR in this embodiment, for example, the ID number and the TTL are as follows, each having 1 byte. ID number 10101
111TTL 10000000 checksum
00101111

(2) On the other hand, the header judgment unit 843 compares the checksum calculated from the ID number and TTL of the received header with the checksum of the received header, and if they do not match, it is invalid data. Is not transmitted to the reception buffer and the relay buffer (the frame data is discarded). (3) When the checksums match, the checksum is calculated again from the received ID number and the TTL obtained by subtracting the TTL described in the fourth embodiment, added to the header, and transmitted to the relay buffer 86. (4) Only frame data is transmitted to the reception buffer as in the third and fourth embodiments. In the present embodiment, the checksum is calculated by performing an exclusive OR of the ID number and the TTL, but another code error test method may be used.

As described above, according to the fifth embodiment, by using the checksum, the value of the flag transmitted on the transmission line 1 due to abnormality or disturbance of the transmission line 1 and the TDM transmission device 2 Is changed, it is possible to prevent the LAN interface unit 8 from erroneously taking in the frame data, and the communication quality can be further improved as compared with the fourth embodiment.

Embodiment 6 FIG. In the fifth embodiment, when the value of the frame data transmitted on the transmission line 1 changes due to abnormality, disturbance, or the like of the transmission line 1 and the TDM transmission device 2, an illegal frame is transmitted to the LAN interface unit 8. Data may be captured. Therefore, in the sixth embodiment, as shown in FIG. 17, instead of a checksum, a CRC (Cyclic Red) is added at the end of frame data.
undancy check).

Next, the operation will be described. (1) In the header adding unit of the transmission control unit 83, the CR including the range from the beginning of the header to the end of the frame data is included in the calculation range.
C is added to the end of the frame data. (2) On the other hand, in the header determination unit 843, the CRC calculated from the received header and the frame data and the received CR
Compared with the value of C, if they do not match, it is regarded as invalid data, and the frame data in the reception buffer and the relay buffer is discarded. (3) When the CRCs match, the value of the header changes due to TTL subtraction. Therefore, the CRC is recalculated, the value is exchanged with the last CRC of the frame data, and transmitted to the relay buffer 86. (4) Only frame data is transmitted to the reception buffer 85 as in the fifth embodiment.

In the present embodiment, X32 + X26 + X23 + X22 + X16 + X12 +
X11 + X10 + X8 + X7 + X5 + X4 + X2 + X +
Although 1 is used, another test method may be used.

As described above, according to the sixth embodiment, C
By using the RC, when the value of the frame data transmitted on the transmission line 1 changes due to abnormality or disturbance of the transmission line 1 and the TDM transmission device 2, the illegal frame data is transmitted by the LAN interface unit 8. Can be prevented from being captured, and the communication quality can be further improved as compared with the fifth embodiment.

Embodiment 7 FIG. In the second to sixth embodiments, when a large amount of frame data is transmitted from each terminal 4, the vacant band of the time slot on the transmission line 1 decreases, that is, the relay buffer 86 of the LAN interface unit 8 A large amount of frame data is transmitted, and while the transmission / relay selection unit 834 selects the transmission buffer 82 or the relay buffer 86 and transmits the frame data to the demultiplexing bus 7, the other relay buffer 8
6 or the transmission buffer 82 may overflow (congestion). Therefore, in the seventh embodiment, as shown in FIG. 18, the transmission / relay selection unit 833 shown in FIG.
37 is provided.

Next, the operation will be described. (1) In a state where a large amount of frame data is transmitted on the transmission path 1 and a large amount of transmission request is received from the terminal 4 connected to a certain LAN interface unit 8, the frame is stored in the relay buffer 86 of the LAN interface unit 8. Data is accumulated more and more. (2) At this time, if the used capacity of the relay buffer 86 exceeds a predetermined threshold, the congestion detection 8337 determines that the relay buffer 86 is in a congested state, and regardless of whether the transmission buffer 82 stores frame data. Then, the frame data in the relay buffer 86 is transmitted to the demultiplexing bus 7 with priority (step 8337 → step 8335). (3) Also, when the used capacity of the transmission buffer 82 exceeds a predetermined threshold value, flow control (back pressure) is performed on the layer 2 switch circuit 81, and the transmission from the layer 2 switch circuit 81 to the transmission buffer 86 is performed. Suppress transmission of frame data.

As described above, according to the seventh embodiment, the relay buffer 86 and the transmission buffer 82 are provided with congestion control of the relay buffer 86 and the transmission buffer 82.
To prevent the frame data from being lost, and further improve the communication quality as compared with the eighth embodiment.
Further, since it is unnecessary to retransmit data from the terminal 4 due to the data loss, the use efficiency of the transmission band can be improved.

Embodiment 8 FIG. In the seventh embodiment, the congestion control is performed in a certain LAN interface unit 8 and the terminal 4 connected to another LAN interface unit 8
If the frame data continues to be transmitted to the transmission path 1, the data in the relay buffer 86 is continuously transmitted in the LAN interface unit 8, so that the frame data stored in the transmission buffer 82 is transmitted no matter how long. There is a possibility that transmission to the road 1 cannot be performed. Therefore, in the eighth embodiment, a congestion notification is provided in the header as shown in FIG.

Next, the operation will be described. (1) In the LAN interface unit 8, the relay buffer 8
When the usage amount of the packet No. 6 exceeds the predetermined value and enters the congestion state, the header determination unit 843 of the reception control unit 84 sets a value indicating the congestion state in the header congestion notification shown in FIG. To send to. The setting of the congestion notification may be performed by the transmission control unit 83 that extracts the frame data from the relay buffer. (3) Thus, at the time of congestion, the header and the frame data carrying the congestion information are transmitted from the relay buffer 86 to the transmission line 1.
Sent to (4) On the other hand, the information of the congestion notification of the header received from the demultiplexing bus 7 is read by the header judgment unit 843, and when the congestion is notified, the transmission / relay selection unit 83
For the third congestion detection 8337, a congestion notification is made for a predetermined time. (5) Accordingly, the transmission / relay selection unit 833 gives priority to the relay buffer 86 and suppresses transmission of data from the transmission buffer 82 to the transmission path 1.

With this operation, a congestion state occurs in a certain LAN interface 8, and when the congestion state is set in the congestion notification of the header and transmitted to the transmission line 1, the TDM transmission device 2 connected to the transmission line 1 The header (congestion notification) is successively relayed to the LAN interface unit 8, and the transmission of data from the transmission buffer 82 is suppressed one after another in the LAN interface unit 8 that has received the congestion notification. As a result, transmission of new frame data to the transmission path 1 is suppressed for a predetermined period, and the frame data transmitted to the transmission path 1 is discarded by the LAN interface 8 of the transmission source. Free bandwidth will increase. As a result, the used capacity of the relay buffer 86 falls below a predetermined threshold, and it becomes possible to transmit frame data to the transmission line 1 from the transmission buffer 82 of the LAN interface 8 that has notified the congestion.

As described above, according to the eighth embodiment, by adding the congestion notification to the header, congestion control is performed in a certain LAN interface unit 8 and another TDM is performed.
Even when the terminal 4 connected to the transmission apparatus tries to continue transmission, the congestion is notified to the entire ring, the inflow to the transmission line 1 is suppressed over the entire ring, and the band used by the transmission line 1 is reduced. Thus, frame data can be transmitted to the transmission line 1 from the transmission buffer 82 of the LAN interface unit 8 in which the congestion control has occurred. As a result, communication bias can be prevented.

Embodiment 9 In the above first to eighth embodiments, when a large number of values of 7Eh or 7Dh exist in the frame data from the transmission buffer 82 or the relay buffer 86, the 7E / 7D encoding unit 83 of the transmission control unit 83
1, the amount of data transmitted to the demultiplexing bus 7 may increase, and the use efficiency of the transmission path 1 may decrease. For example, considering an example in which frame data is composed of only 7Eh or 7Dh (each 1-byte code), the data amount is doubled (2-byte code) by 7E / 7D encoding, and the transmission efficiency is reduced by half. Will do.

Therefore, in the ninth embodiment, as shown in FIG. 20, the transmission control unit 83 shown in FIG.
Is provided. Further, as shown in FIG. 21, the reception control unit 84 of FIG. 13 includes a descrambler 844.

Next, the operation will be described. (1) In the transmission control unit 83, the transmission / relay selection unit 83
The data transmitted from No. 3 is randomized by the scrambler 835, and each code in the data is randomly replaced with another code. At this time, the 7E code and the 7D code are also replaced with another one code, and transmitted to the 7E / 7D coding unit 831. (2) Since the appearance probability of a certain data value becomes constant in the randomized data, even when a large number of 7Eh and 7Dh exist in the frame data, the scrambler 83
5, the appearance probability of the data value of 7Eh or 7Dh in the data passed to the 7E / 7D encoding unit 831 can be kept constant. (3) On the other hand, the descrambler 844 of the reception control unit 84 restores the data (scrambled data) passed from the 7E / 7D decoding unit 842 to the original frame data.

As described above, according to the ninth embodiment, since the scrambler 835 and the descrambler 844 are provided, even when a large number of values of 7Eh or 7Dh exist in the frame data, the encoding of 7E · 7D can be performed. Can prevent an increase in data amount, and can improve the use efficiency of the transmission path as compared with the eighth embodiment.

Embodiment 10 FIG. When the number of LANs 3 connected to the TDM transmission device 2 increases, it is necessary to mount a plurality of LAN interfaces 8 in the same TDM transmission device 2. In the tenth embodiment, as shown in FIG. 22, two LAN interface units 8a and 8b are mounted in the same TDM transmission device 2, and a cascade connection is established between the LAN interface units. 87a, 87b
Is a cascade output unit, and 88a and 88b are cascade input units. FIG. 23 shows the transmission control unit 83 of FIG. 20 including an output destination switching unit 836, and FIG.
The first reception control unit 84 includes an input destination switching unit 845. Here, the cascade function is one T
A plurality of LAN interface units 8 in the DM transmission device 2 can share the same time slot (that is,
(Contained in the same logical ring).

Next, the operation will be described. (1) In the LAN interface unit 8b of FIG. 22, the input destination switching unit 845 of the reception control unit 84b selects the data transmitted from the demultiplexing bus 7 and transmits the data to the reception buffer 85b and the relay buffer 86b. The output destination switching unit 836 of 83b sends data from the relay buffer 86b and the transmission buffer 82b to the cascade output unit 87b. (2) Further, the cascade output unit 87b sends the LA of the connection destination.
The data transmitted to the cascade input section 88a of the N interface section 8a is transmitted to the input destination switching section 8 of the reception control section 84a.
45, the receiving buffer 85a and the relay buffer 86
b.

(3) Then, the output destination switching unit 836 of the transmission control unit 83a shown in FIG. 3 sends the data from the relay buffer 86a and the transmission buffer 82a to the demultiplexing bus 7. As described above, the selection of the input destination switching unit 845 shown in FIG. 24 in the reception control unit 83b of the LAN interface unit 8b is fixed to the demultiplexing bus 7, and the output destination switching unit 836 shown in FIG. 23 in the transmission control unit 83b. Of the cascade output unit 87
b. (4) On the other hand, the selection of the input destination switching unit 845 shown in FIG. 24 in the reception control unit 84a of the LAN interface unit 8a is fixed to the cascade input unit 88a, and the output destination switching unit shown in FIG. 23 in the transmission control unit 83a. Reference numeral 836 designates that the transmission data from the LAN interface unit 8b is all relayed to the LAN interface unit 8a by setting the demultiplexing bus 7 fixed, and the transmission / reception frame data of the terminals 4A to 4D is shared by the same time slot. You.

As described above, according to the tenth embodiment,
A plurality of LAN interface units 8 in the same TDM transmission device 2 can be cascaded, and the same time slot can be shared. Thus, even when the number of terminals 4 to be connected to a certain TDM transmission device 2 is larger than the allowable number of connections of one LAN interface unit 8, it is not necessary to increase the number of TDM transmission devices 2 and cost can be reduced.

Embodiment 11 FIG. FIG. 25 shows a data transmission system according to an embodiment of the present invention.
Reference numerals 1a to 1f denote transmission paths for synchronous communication data connected by optical fibers, and 2A to 2D denote TDM transmission devices.
The M transmission devices are connected in a mesh by transmission lines 1a to 1f. 3A to 3G are LANs, 4A to 4G are LAN terminals such as computers, and 8A to 8D are LAN interface units. FIG. 26 is a diagram showing a connection relationship of the TDM transmission device 8A. TD for signals on transmission lines 1f and 1a
The M transmission apparatus 8A performs the same operation as that described in the second embodiment, and transmits the signal from the transmission path 1d to the transmission path 1e to the transmission path 1b.
To 1c are relayed by the multiplexing / demultiplexing unit 8, respectively.

Next, the operation will be described. In a data transmission system in which a plurality of TDM transmission devices 2 are connected in a mesh by the transmission line 1 as shown in FIG. 25, logical paths to the LAN interface units 8A to 8D are indicated by dotted lines in FIG. By making in 2D, L
The AN interface units 8A to 8D are connected in a ring shape.

As described above, according to the eleventh embodiment,
In a data transmission system of a mesh configuration, by logically connecting the LAN interface units 8 with each other by a ring,
Embodiments 2 to 10 can be applied to a data transmission system having a mesh configuration as it is, and the application range of a communication system between LANs can be further expanded.

Embodiment 12 FIG. FIG. 27 shows the reception control unit 8.
4 is provided with an ID number determination prohibition unit 846.

Next, the operation will be described. (1) When the ID number determination prohibition unit 846 receives the ID number determination prohibition instruction, the ID number determination prohibition unit 846 sends the reception control unit 8
4 prohibits the header determination unit 843 from performing ID number determination processing. (2) Therefore, the ID number determination prohibition unit 846 causes the own L
The frame data transmitted to the transmission line 1 by the AN interface unit 8 is transmitted to the reception control unit 8 of the own LAN interface unit 8.
4, the frame data can be transmitted to the reception buffer 85 without being discarded. (3) Regarding the relay buffer 86, regardless of the presence or absence of the ID number determination prohibition instruction, the I
Discard the frame that matches the D number. During normal operation,
The ID number determination prohibition instruction is OFF.

As described above, according to the twelfth embodiment,
By providing the ID number determination prohibition unit 846, the terminal 4
The frame data transmitted by itself can go around the ring of the transmission path 1 and be received by the own terminal 4 again. As a result, by comparing the transmission data and the reception data,
It is possible to check the normal operation of the components (LAN 3, TDM transmission device 2, transmission line 1, etc.) of the path through which the data has flowed, thereby improving maintainability of the data transmission system.

Embodiment 13 FIG. In FIG. 28, the LAN interface unit 8 is provided with a return path 89 from the transmission control unit 83 to the reception control unit 84.

Next, the operation will be described. (1) The frame data transmitted from the transmission control unit 83 to the return path 88 is returned to the reception control unit 84, and when there is a return instruction, the input destination switching unit 845 receives the return data. (2) At this time, an ID number determination prohibition instruction is issued to prohibit the ID number determination of the header determination unit 843, and the folded data is transmitted to the reception buffer 85 without being discarded. (3) On the other hand, the return data is discarded to the relay buffer 86 and is not transmitted. During normal operation, the return instruction is O
FF.

As described above, according to the thirteenth embodiment,
With the function of returning from the transmission control unit 83 to the reception control unit 84, the frame data transmitted by the terminal 3 itself is returned in the LAN interface unit 8 and can be received by the terminal 3 itself. Thus, by comparing the transmission data with the reception data, it is possible to confirm the normal operation of the LAN 3 and the LAN interface unit 8, which are the components of the path through which the data has flowed.
The maintainability of the N interface unit 8 can be improved.

Embodiment 14 FIG. FIG. 29 shows the reception control unit 8.
4 is provided with a reception permission ID number setting unit 847.

Next, the operation will be described. (1) When the data transmitted from the demultiplexing bus 7 to the reception control unit 84 is instructed in the header determination unit 743 by the reception permission ID number setting unit 847, the specified ID is transmitted.
Only frames having a number are sent to the reception buffer, and other frames are discarded. (2) At this time, similarly to the third embodiment, frame data having an ID number other than the ID number of the own LAN interface unit 8 is transmitted to the relay buffer 86. (3) During normal operation, the instruction from the reception permission ID number setting unit 847 is OFF.

As described above, according to the fourteenth embodiment,
By providing the reception permission ID number setting unit 847, the reception permission ID number setting unit 847 can be provided from a specific LAN interface 8 or its LA.
When only one terminal is connected to the N interface 8, the own terminal 3 can receive only data transmitted from a specific terminal 3. This makes it possible to monitor data transmitted from a specific LAN interface 8 (or a specific terminal 3) flowing through the transmission path 1 from any of the TDM transmission apparatuses 2. The maintainability of the transmission system can be improved.

Embodiment 15 FIG. FIG. 30 shows the reception control unit 8.
4 is provided with an error counter section 848.

Next, the operation will be described. The data transmitted from the demultiplexing bus 7 to the reception control unit 84 is subjected to a TTL determination process and a checksum determination process in a header determination unit 843. At this time, the error counter 848 counts the number of detected errors (TTL = 0, checksum error) in each determination process.

As described above, according to the fifteenth embodiment,
The provision of the error counter makes it possible to know the number of errors that have occurred in the TTL determination and the checksum determination, so that the maintainability of the data transmission system can be further improved as compared with the fourteenth embodiment.

In the first to fifteenth embodiments, the transmission line transmits an optical signal. However, an electric signal may be used, or another signal may be used. Instead of using a cable, radio waves or light from wireless communication may be used. In the present invention, all of these communication media are regarded as transmission paths.

[0092]

As described above, according to the present invention, the conversion from asynchronous communication data to synchronous communication data (multiplexed / demultiplexed data) is divided into a plurality of time slot data amounts. To obtain a data transmission system in which the transmission of the transmission method can be applied to asynchronous communication data, the LAN asynchronous communication data can be configured at a low cost without using another device such as a conversion device, and the system can be easily handled. Can be.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a data transmission system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a TDM transmission apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a diagram showing a configuration of a transmission control unit according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a reception control unit according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a data format on a demultiplexing bus according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a correspondence relationship between a time slot on a transmission path and frame data on a LAN according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a data transmission system according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a TDM transmission device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a transmission control unit according to Embodiment 2 of the present invention.

FIG. 10 is a diagram illustrating a configuration of a reception control unit according to a second embodiment of the present invention.

FIG. 11 is a flowchart illustrating an operation of a transmission / relay selection unit according to the second embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a transmission control unit according to a third embodiment of the present invention.

FIG. 13 is a diagram showing a configuration of a reception control unit according to a third embodiment of the present invention.

FIG. 14 is a diagram showing a data format on a demultiplexing bus according to a third embodiment of the present invention.

FIG. 15 is a diagram showing a data format on a demultiplexing bus according to a fourth embodiment of the present invention.

FIG. 16 is a diagram showing a data format on a demultiplexing bus according to a fifth embodiment of the present invention.

FIG. 17 is a diagram showing a data format on a demultiplexing bus according to a sixth embodiment of the present invention.

FIG. 18 is a flowchart illustrating an operation of a transmission / relay selection unit according to the seventh embodiment of the present invention.

FIG. 19 is a diagram showing a data format on a demultiplexing bus according to an eighth embodiment of the present invention.

FIG. 20 is a diagram showing a configuration of a transmission control unit according to Embodiment 9 of the present invention.

FIG. 21 is a diagram showing a configuration of a reception control unit according to Embodiment 9 of the present invention.

FIG. 22 is a diagram illustrating a configuration of a TDM transmission apparatus according to a tenth embodiment of the present invention.

FIG. 23 is a diagram showing a configuration of a transmission control unit according to Embodiment 10 of the present invention.

FIG. 24 is a diagram showing a configuration of a reception control unit according to Embodiment 10 of the present invention.

FIG. 25 is a diagram showing a configuration of a data transmission system according to an eleventh embodiment of the present invention.

FIG. 26 is a diagram showing a configuration of a TDM transmission apparatus according to Embodiment 11 of the present invention.

FIG. 27 is a diagram illustrating a configuration of a reception control unit according to a twelfth embodiment of the present invention.

FIG. 28 is a diagram showing a configuration of a TDM transmission apparatus according to Embodiment 13 of the present invention.

FIG. 29 is a diagram showing a configuration of a reception control unit according to Embodiment 14 of the present invention.

FIG. 30 is a diagram showing a configuration of a reception control unit according to Embodiment 15 of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1, 1A Transmission line 2, 2A-2D Time division multiplexing (TDM) transmission apparatus 3A-3G LAN 4A-4G terminal 5 Optical / electrical signal converter 6 Multiplexing / multiplexing / demultiplexing unit 7 Multiplexing / demultiplexing bus 8 LAN interface unit

Continued on front page F term (reference) 5K028 AA06 BB08 CC02 CC05 KK01 KK03 KK12 LL12 MM05 RR02 SS24 5K031 AA12 CA08 CB19 DA02 5K033 AA09 CA11 CB02 DA01 DA05 DA15 DB02 DB17 DB18

Claims (15)

[Claims] 1. A transmission line for multiplexing and transmitting synchronous communication data, a time division multiplex transmission device connected to both ends of the transmission line and transmitting the synchronous communication data in a time division multiplex system, and a terminal. While transmitting asynchronous communication data,
A data transmission system having a LAN connected to each of the time division multiplex transmission devices and performing data transmission between the LAN via the time division multiplex transmission device and the transmission path; A LAN interface unit and a multiplexing / multiplexing / demultiplexing unit, wherein the LAN interface unit converts the asynchronous communication data from the LAN into synchronous communication data time-divided into a plurality of time slots, and When the multiplexing / multiplexing / demultiplexing unit receives multiplexed synchronous communication data from another time division multiplex transmission device, the multiplexing / multiplexing / demultiplexing unit transmits the multiplexed synchronization data to a plurality of time slots. The data is converted into divided synchronous communication data, and the converted data is
A data transmission system, wherein the data is converted into asynchronous communication data by an interface unit and transmitted to a predetermined LAN. 2. A transmission line formed in a ring shape for multiplexing transmission of synchronous communication data, and connected to the ring transmission line,
A plurality of time-division multiplex transmission apparatuses for transmitting the synchronous communication data in a time-division multiplex system, and LANs connected to the respective time-division multiplex transmission apparatuses while connecting terminals to transmit asynchronous communication data. In a data transmission system for transmitting data between the time-division multiplex transmission device and an arbitrary LAN via the transmission path, the time-division multiplex transmission device includes a LAN interface unit and a multiplexing / demultiplexing unit. The LAN interface unit converts the asynchronous communication data from the LAN into synchronous communication data time-divided into a plurality of time slots, multiplexes the data in the multiplexing / demultiplexing unit, and transmits the multiplexed data to the transmission path. When the multiplexing / multiplexing / demultiplexing unit receives multiplexed synchronous communication data from another time division multiplex transmission device, the multiplexing / multiplexing / demultiplexing unit demultiplexes the received data into a plurality of time slots. When the converted time-division synchronous communication data is addressed to the own interface unit, the LAN interface unit converts the data into asynchronous communication data and transmits the data to a predetermined LAN, and transmits the data to another interface unit. , A data transmission system characterized in that the data is transmitted as relay data via the multiplexing / demultiplexing unit. 3. The data transmission system according to claim 2, wherein the asynchronous communication data includes a header and frame data storing the data itself, and the LAN interface unit includes a header including ID number information of the own LAN interface unit. When the synchronous communication data is received and the ID number of the header is the ID number of the own LAN interface unit, the received synchronous communication data is transmitted from the own interface unit and circulates through the transmission path. A data transmission system characterized in that the frame data is discarded by judging that the frame data has been transmitted. 4. The data transmission system according to claim 3, wherein the LAN interface unit transmits the frame data together with the frame data as a header including a lifetime of the frame data. A data transmission system characterized by discarding the frame data when the lifetime has expired. 5. The data transmission system according to claim 4, wherein the LAN interface unit transmits the ID number of the own LAN interface unit and a lifetime including a verification information such as a checksum to the LAN interface unit together with the frame data. Receiving the synchronous communication data, if the checksum of the received synchronous communication data does not match the test information calculated from the synchronous communication data, discards the frame data. . 6. The data transmission system according to claim 3, wherein test information based on a test method such as CRC is added to the frame data or the header and the frame data and transmitted. A data transmission system characterized in that upon receiving synchronous communication data, if the test information of the received synchronous communication data does not match the test information calculated from the received synchronous communication data, the frame data is discarded. 7. The data transmission system according to claim 3, wherein the LAN interface unit transmits the frame data even if the ID number of the received synchronous communication data is the ID number of the own LAN interface unit. A data transmission system characterized by providing a function of enabling reception without discarding the data, and enabling the function to be operated and tested during maintenance. 8. The data transmission system according to claim 3, wherein the LAN interface unit has a function of directly receiving synchronous communication data to be transmitted internally, and operates the function during maintenance. A data transmission system characterized by being testable. 9. The data transmission system according to claim 3, wherein the LAN interface unit receives synchronous communication data of at least one of the ID numbers of the other LAN interface units. A data transmission system provided with a function, wherein the function can be operated and tested during maintenance. 10. The data transmission system according to claim 3, wherein the LAN interface unit has a function of detecting and counting errors in the received synchronous communication data. Transmission system. 11. The data transmission system according to claim 2, wherein, when relaying the synchronous communication data, the LAN interface unit transmits the asynchronous communication data from the LAN in accordance with the degree of congestion of the relay operation. A data transmission system comprising a first congestion control function for restricting transmission of data. 12. The data transmission system according to claim 2, wherein the asynchronous communication data has a header and frame data storing a data itself, and the LAN interface unit transmits the synchronous communication data. In the case of relaying, the synchronous communication data to be relayed includes congestion information corresponding to the degree of congestion of the relay operation included in the header and is transmitted. A second congestion control function for limiting transmission of asynchronous communication data from the data transmission system. 13. The data transmission system according to claim 2, wherein the asynchronous communication data has a header and a frame storing the data itself, and a flag is included in the synchronous communication data to be transmitted. In the case where the LAN interface unit is provided with a predetermined value or a character to which a flag is to be added to the scrambled synchronous communication data, a plurality of specific values are provided. And an encoding function to convert to a specific character, add a flag, and send it.
A decoding function for receiving the synchronous communication data and restoring a plurality of specific values or specific characters of the synchronous communication data excluding the flag to the predetermined one value or character; and a descrambler for descrambling the decoded data. When a plurality of specific values and specific characters are present in the synchronous communication data in a large number, the appearance probability is reduced, and an increase in the amount of data on the transmission path is suppressed. Data transmission system. 14. The data transmission system according to claim 2, wherein a plurality of first to n-th LAN interfaces are provided in one time-division multiplex transmission apparatus. The transmitting end and the receiving end of the plurality of LAN interface units are sequentially cascaded, and from the transmitting end of the first LAN interface unit to the receiving end of the second LAN interface unit, from the transmitting end of the second LAN interface unit. To the receiving end of the third LAN interface unit,..., And one of the cascade-connected ones so that signals can be connected from the receiving end of the (n-1) th LAN interface unit to the transmitting end of the n-th LAN interface unit The receiving section of the first LAN interface section at the end multiplexes synchronous communication data received or relayed by the plurality of LAN interface sections. N-th LA at the other end of the cascade connection
The transmitting end of the N interface unit transmits all the synchronous communication data transmitted or relayed from the plurality of LAN interface units via the multiplexing / demultiplexing unit, and
A data transmission system, wherein the number of LANs and terminals connected to one time division multiplex transmission device can be increased. 15. The data transmission system according to claim 2, wherein a mesh transmission line is used instead of the ring transmission line, and a logical link is formed between the time division multiplex transmission devices. A data transmission system for transmitting synchronous communication data between the time division multiplex transmission apparatuses.