JPS6412144B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission method in an information transmission system having a detour.

In this type of information transmission system, even a partial abnormality on the transmission path makes the entire transmission system unusable, and the reliability of the system is low. In order to improve the reliability of a transmission system, conventionally, transmission paths were duplicated, transmission control devices were installed on each transmission path, and data was transmitted between terminal devices via these transmission control devices. ing. When the entire transmission system is normal, both transmission paths are used independently to perform transmission between terminal devices. A method has also been proposed in which when an abnormality occurs in a part of the transmission system, the abnormal part of the transmission path is bypassed.

In this case, one closed transmission path (hereinafter referred to as a closed route) is formed by multiple terminal devices and transmission paths.
is formed.

If a message is sent through such a closed route, the message will be repeatedly transferred between terminal devices and may never disappear.

An object of the present invention is to provide a transmission method that can prevent messages from being transmitted permanently within a closed route.

In order to achieve such an object, in the present invention, a transmission control device switches and transmits a message from one transmission path to another transmission path, and circulates the message through a closed route formed by the other transmission path. When transmitting a message to the other transmission path, the transmission control device counts up the number of circulations of this message in a closed route, and when the number of circulations of this message exceeds a predetermined value, The feature is that the sending of this message is stopped.

The present invention will be explained below based on Examples.

The loop transmission system shown in FIG. 1 has a large loop 1 that transmits messages in a counterclockwise direction and a large loop 2 that transmits messages in a clockwise direction. 1
2 and 13 are connected, and the large loop 2 is connected to transmission control devices 21, 22, and 23 that form pairs with these devices 11, 12, and 13, respectively. Each pair of devices 11 and 21, 12 and 22, and 13 and 23 are connected to each other by detour transmission paths 100, 200, and 300 that can transmit messages in both directions, and are connected to sending and receiving terminals 31, 32, and 33. , lines 311 to 3 capable of transmitting data in both directions, respectively.
13, 321-323. The message includes data from each transmitting/receiving terminal or a command for communication control. device 11,
When 12, 13, 21, 22, 23 and large loops 1 and 2 are normal, large loop 1 transmission system consisting of these devices 11 to 13 and large loop 1 or large loop 2 consisting of devices 21 to 23 and large loop 2 The transmission system communicates messages without mutual interference. devices 11-13, 21-23,
If there is a failure in either large loop 1 or 2, devices 11 to 13 and 21 to 2 will be
3. One closed-loop composite transmission system is formed using the detour transmission lines 100, 200, 300 and the large loops 1 and 2, and mutual communication is performed using this transmission system. For example, if there is an abnormality in the large loop 1 transmission system and the large loop 2 transmission system is normal, the transmitting and receiving terminals 11 to 13 will communicate using the large loop 2 transmission system, and transmission lines 100-300, devices 11-13, 21-
Communication is performed via a composite transmission system formed by appropriately combining 23.

For this reason, the transmission control devices 11, 12, 13 or 21, 22, 23 have the function of transmitting messages on the corresponding large loop 1 or 2 and receiving messages on the large loop 1 or 2 during normal operation. If there is an abnormality in the transmission system of large loop 1 or 2, detour route 10 is
0, 200, and 300, and also has the function of receiving messages on this detour route.

FIG. 2 shows the internal circuit blocks of the transmission control device 11. Other transmission control devices also have exactly the same structure. The device 11 has a large loop 1
Interface 51 for exchanging messages with
, an interface 61 that exchanges messages with the detour transmission path 100 and exchanges messages with the line 311, and these interfaces 51, 61.
first and second reception buffers 71 and 73 for storing messages received via the
, a transmission buffer 81 for storing messages to be transmitted via these interfaces 51 and 61, and a processing device 41 and a timer 90 for controlling the transmission and reception of these messages.
-92 and registers 93-95.
Of the transmission control device 11, the interface 51,
The parts other than 61 are realized by a microcomputer.

FIG. 3 is a detailed block diagram of the interface 51, and FIG. 4 shows a portion of the interface 61 connected to the detour transmission line 100. The configuration of the portion of the interface 61 connected to the line 311 is not shown because it is exactly the same as that in FIG. 4. In Figure 4, the reference symbols shown in Figure 3 with a prime (') added are:
It is exactly the same as the one in Figure 3. The circuit of FIG. 4 includes the gates 61 to 64 and the register 6 of FIG.
The circuit differs from the circuit shown in FIG. 3 only in that it does not have the circuit 5, and detailed explanation thereof will be omitted. The portion of the interface 61 connected to the line 311 is connected to the third
Reference numbers for corresponding parts of figures will be appended with a double prime ('') when necessary.

The shape of the message is shown in Figure 5. message 5
000 is an area 501 for a flag F indicating that it is the start part of a message, an area 502 for a reception address RA that specifies the transmission control device to receive the message,
An area 503 for sending address SA that displays the transmission control device that sends the message, an area 504 for data or command DC to be transmitted, an area 505 for error detection data FCS of the message, and an area 505 for indicating the end of the message. Area 5 of flag F shown
06, an area 507 for a detour code BC indicating the detour status, and an area 508 for indicating the number of detours BN.
The data area 504 includes a command flag CF area 509 for indicating whether a command is included instead of data.

The addresses of the transmission control devices 11 to 13 and 21 to 23 consist of the corresponding loop number part and the intra-loop number part, and the addresses of a pair of transmission control devices connected to the same transmitting/receiving terminal are based on the loop number. It is predetermined that only the parts are different. The loop number portions are "0" and "1" for loops 1 and 2, respectively.

As a result, as shown in Figure 6, the receiving address
The area 502 of RA is the portion 50 of loop number RA ₁
2' and a portion 502 _' ' of the loop number RA 2.Similarly, the area 503 of the sending address SA is:
Part 503' of loop number SA ₁ and internal loop number
It consists of part 503'' of SA _2.The detour code BC and the detour number BN are the large loop 1 and the large loop formed by the method described below when there is an abnormality in the loop 1 transmission system or the loop 2 transmission system. They are used to form a composite transmission system consisting of the large loop 2 and a plurality of detour transmission lines, and to prevent messages from circulating forever through the composite transmission system.

When each transmission control device transmits a message as a transmission source, the detour code BC and detour number BN of the message are both set to 0.

In addition, when each transmission control device receives a message, the detour code BC in the message,
It is configured to execute different operation modes as described below based on the number of detours BN, address information RA and SA, and its own address.

(1) When the in-loop number RA ₂ in the receiving address RA is equal to the in-loop number from itself, and BC = 0, and CF = 0, the message is sent to the transmitting/receiving terminal connected to itself, and ,
Forward the message. When CF=1,
Perform the action specified by the command in the message.

(2) When the loop number SA ₁ and intra-loop number SA ₂ in the sending address SA are equal to the own loop number and intra-loop number, respectively, the message is canceled regardless of whether BC is 0 or 1.

(3) The loop number SA ₂ in the sending address SA is equal to the own loop number, but the loop number SA ₁
is not equal to its own loop number, and BC=
When CF=0, the message is
It is sent to the transmission control device paired with itself via the detour transmission path. When CF=1, the operation specified by the command in the message is performed.

(4) When the in-loop number SA ₂ in the sending address SA is equal to the own in-loop number and BC=1, the message is forwarded after modifying BC to 0.

(5) In cases other than (1) to (4) above, the received message is simply forwarded as is.

(6) CF received from the first or second loop = 0
When forwarding a message, if the small loop to which it belongs is abnormal, the detour code BC of the received message is modified from 0 to 1 or from 1 to 0, and the detour number BN of the received message is added by 1. The message is then forwarded to the corresponding detour transmission path. However, in case (3), when CF=0, the message is transferred to the corresponding detour transmission path even if this small loop is normal.

(7) When forwarding a message received from the bypass transmission path, forward it to the first or second large loop.

(8) In the case of (5), if the number of detours BN of the received message exceeds a predetermined number, for example 2, the message is canceled.

Below, using FIGS. 2 to 5, the transmitting/receiving terminal 3
Devices 11 to 33 when transferring data from 1 to 33
The operation of No. 13 will be explained.

In the device 11, if there is no abnormality in the transmission system of the large loop 1, "0" is set in the registers 93 to 95 as described later. At this time, the device 11 transmits data from the terminal 31 to another terminal, for example, the terminal 33, in the following manner.

First, the data DC to be transmitted is received by the processing device 41 from the terminal 31 via the interface 61 along with the data transmission address SA, and is converted into a message in the form shown in FIG. 5 under the control of the processing device 41. The data is converted and stored in the transmission buffer 81. The diversion code BC and diversion number BN of the newly generated message are 0. When large loop 1 is normal, this detour code BC and detour number BN are:
Remains 0 during message transmission. Command flag CF is 0.

In the transmission buffer 81, this message is stored together with data indicating the number of times the message has been transmitted from the device 11. As in the present case, for a message that is formed based on data DC input from the terminal 31 and has not yet been transmitted, the number of times of transmission is "0".

At the time determined by itself, the processing device 41
A search is made to see if there is a message to be sent in the first and second receiving buffers 71, 73 and sending buffer 81. In this case, when it is detected that there is a message to be transmitted in the transmission buffer 81, the processing device 4
1 sets "1" in the register 65 in the interface 51 via the line 65A to indicate that the transmission is in progress, and the interface 51
The first eight bits of the message to be sent are input to the register 59 in the memory via line 59A, and the counter 60 is reset via line 60A.

The 8-bit data in register 59 is responsive to the clock from clock generator (CLK) 58.
Output serially. AND gate 62 is in an open state because the output of register 65 is "1".
Therefore, the output of the register 59 is sent to the transmitter 53 via the AND gate 62 and the OR gate 64.
and output to large loop 1. At this time,
There is no other input to OR gate 64. This is because the AND gate 63 is in a closed state due to the output "0" of the inverter 61. The counter 60
This is a 3-bit counter that counts the output of CLK58, and when it counts 8 bits of clocks, it outputs an overflow signal on line 60B. In response to this overflow signal, processing unit 41 sends the next eight bits of the message to be sent in transmission buffer 81 to register 59. By repeating these operations, a message of a predetermined length can be sent to the large loop 1. In this way, when the transmission of the message to be transmitted in the transmission buffer 81 is completed, the transmission count data of the message is set to "1" and the register 65 is set to "0". The processing device 41 also sets a timer 90. The set time of the timer 90 is set to a value somewhat larger than the time required for a message to make one round on the large loop 1.

When the message sent from this device 11 reaches the receiver 52 of the device 12, the synchronization signal detector 5
4 detects the bit sequence of this received message and outputs a synchronization signal synchronized with each bit of this bit sequence. Data received by the receiver 52 is stored in an 8-bit register 56 in synchronization with this synchronization signal. The counter 55 is
It is a 3-bit counter, and when it counts eight synchronizing signals, it outputs an overflow signal on line 55A. Processor 41 within device 12 responds to this overflow signal by capturing the eight bits in register 56 via line 56A and storing them in first receive buffer 71. Thereafter, the same process is repeated to store the messages inputted from the large loop 1 into the first receiving buffer 71 in units of 8 bits.

If the device 12 is not transmitting a message when receiving this message, "0" is stored in the register 65. Therefore, since the AND gate 63 is in the open state, each bit of the received message is stored in the first receiving buffer and is directly passed through the AND gate 6.
3, is sent to the transmitter 53 via the OR gate 64, and transferred onto the large loop 1 again.

When the processing device 41 receives the reception address RA, transmission address SA, detour code BC, and detour number BN, it determines which of the above-mentioned operation modes (1) to (8) should be performed based on these data. to decide. If both large loops 1 and 2 are normal, this can only occur in operation modes (1), (2), and (5). That is, if the processing device 41 determines that operation mode (1) or (5) should be adopted, it continues to receive messages. Since this received message has already been transferred onto the large loop 1, the processing device 41 does not need to transfer this message to the large loop 1 again. In order to indicate that this transfer is not necessary, the content "0" of the register 65 is fetched from the line 65B and stored in the first reception buffer as data accompanying the received message. On the other hand, if the processing device 41 determines that operation mode (2) should be adopted, the processing device 41 selects the line 65A.
, the register 65 is immediately set to "0", the transfer of the remaining part of the message from the receiver 52 to the transmitter 53 is stopped, and this remaining part is stored in the first receiving buffer 71. do.
When the processor 41 learns by decoding the flag area 506 (FIG. 5) in the message that the entire message has been received, it sets the register 65 to "0" again and cancels the message. Show what you should do.

If device 12 is sending a message,
The register 65 is set to "1". Therefore, the message received by the receiver 52 is not sent to the transmitter 53, but is stored in the first reception buffer 71, and it is determined which operating mode should be used in the same manner as in the case where no transmission is in progress. Ru.

If, as in the current example, the sending address SA of this received message is not your own,
When operating mode (5) is adopted, this message must be forwarded to loop 1 again. To indicate this necessity, the content of register 65 is “1”.
is stored in the first receiving buffer 71.

The device 12 that received the message transmits the message to loop 1 again at the transmission time determined by itself, under the condition that the bit indicating whether transmission is necessary or unnecessary accompanying this message is "1", and then transmits this message to the loop 1 at the transmission time determined by itself. 1 from the receiving buffer 71. if,
When this bit is "0", this message is erased without being sent. When the message sent out on this loop 1 reaches the interface 51 of the device 13, it is stored in the first receiving buffer 71 in the terminal 13, in the same way as described above with respect to the device 12, and the message is received by the address
RA, sending address SA, detour code BC, number of detours
Based on the BN, the processing device 41 determines which operation mode should be adopted. As in the current example,
Loop number RA ₂ in receiving address RA is device 1
3, when BC=0, operation mode (1) is executed. That is, the processing device 41
The data DC in the message in the first reception buffer 71 is sent to the terminal 3 at the transmission time determined by the terminal.
3 via the interface 61. Furthermore, the message in the first receiving buffer 71 is sent to the large loop 1 via the interface 51. In this way, data is transmitted from the terminal 11 to the terminal 33, and a message sent from the device 13 to the large loop 1 is transmitted through the large loop 1 and reaches the device 11. The device 11 receives this message via the interface 51 and sends it to the first
The data is stored in the receiving buffer 71 of. The device 11 detects that the sending address SA in the message in the receiving buffer 71 designates itself, and since BC=0, the first
The message in the receive buffer 81 and the original message in the transmit buffer 81 are erased and are not forwarded to the large loop 1. The processing device 41 is a timer 9
Reset to 0.

The above is equipment 1 when the large loop 1 transmission system is normal.
These are operations 1 to 13. The operations of the devices 21 to 23 when the large loop 2 transmission system is normal are exactly the same. When transferring a certain data DC, either the loop 1 transmission system or the loop 2 transmission system transfers that data.
Selected by the terminal sending the DC. In this way, the terminals 31 to 33 mutually exchange data via both loop transmission systems 1 and 2.

Device 1 that sent the message for some reason
If the message does not return to 1, timer 90 times up. The processing device 41 responds to the time-up signal of the timer 90 by increasing the transmission buffer 81.
The previously sent message stored in is sent again to loop 1. Each time this message is retransmitted, the number of transmission data in the transmission buffer 81 that accompanies this message is counted up. This retransmission is performed unless the message sent by the device 11 is received by the device 11 within a predetermined one-round time.
It is repeated a predetermined number of times.

Even if the device 11 repeatedly transmits the same message a predetermined number of times, this message completes the large loop 1 by 1.
When the processing device 41 learns that the data has not been returned to the device 11 because the transmission count data in the transmission buffer 81 exceeds a predetermined value, the processing device 41 determines that there is a loop abnormality and starts forming a detour. Start processing for This process will be explained using FIG. 7.
In FIG. 7, the same reference numerals as in FIG. 1 indicate the same things. In FIG. 7, transmission control devices 14, 15, 16 and 2 are added to the system of FIG.
4, 25, 26 and detour transmission lines 400, 50
0,600 is added. The configuration of these added devices is the same as the device 11 in FIG. In addition, in FIG. 7, transmission control devices 11 and 21, 12 and 22, 13 and 23, 14 and 24, 1
The transmitting and receiving terminals connected to 5 and 25 and 16 and 26, respectively, are not shown for simplicity.

In the device 11 that detected an abnormality in the loop transmission system,
After setting "1" in the register 93 indicating that the processing device 41 has received a small loop check request, the command flag CF=1 and the small loop check command placed in the transmission data area 504 are sent.
A first message containing a reception address RA specifying an adjacent transmission control device 12 on the large loop 1 and a transmission address SA consisting of the address of the device 11 itself is transmitted onto the large loop 1. At the same time, a second message containing the reception address RA specifying the device 21, the check command placed in the transmission data area 504, and the transmission address SA having its own address is sent onto the detour transmission line 100. Furthermore, a timer 91 is set. timer 9
1 set time is the device 11, 12, 22, 21
The time required for a message to make one round on the small loop 201 including The detour number BN and detour code BC in the message containing this small loop check command are 0. The transmission control device that receives the message containing this small loop check command will use the detour code BC and the detour number BN.
will not be changed.

In the device 12 specified by this first message, this first message is stored in the first receiving buffer 71, and the processing device 41 uses the detour code.
It detects that BC=0 and that the in-loop number RA ₂ in the received address RA is equal to its own in-loop number, and performs operation mode (1). That is, this first
commands and sending addresses in messages of
Decipher SA. As a result of decoding, this command is
This is a small loop check command, and the sending address
Upon learning that the SA is not its own, device 12
The processing device 41 in the
Device 2 that pairs with itself without transferring to
A message consisting of the receiving address RA specifying 2, the sent command, and the sending address SA is sent onto the detour transmission line 200. When device 22 detects that a signal is input to interface 61 on line 200, processing device 41 takes the message on line 200 into second receiving buffer 73 in response to this detection result.
the receiving address in this captured message
It detects that the loop number RA ₂ in RA is equal to its own loop number and BC = 0, and the command in this message is a small loop check command, and the sending address SA is its own. It detects that this is not the case, changes the reception address RA of this message to an address specifying the device 21, and sends the message onto the large loop 2. When this message passes through the large loop 2 and reaches the device 21, the device 21 stores the message in the first receiving buffer 71 via the interface 51. Processing device 4 in device 21
1 means that the in-loop number RA ₂ in the receiving address RA in this message is equal to its own, and BC
= 0, that the command in this message is a small loop check command, and that the sending address SA is not its own, and sends this message to the detour line 100 via the interface 61. . When the device 11 detects that a message has been input via this line 100, it takes this message into the first reception buffer 71, and the in-loop number RA ₂ in the reception address RA in this message is its own. , it detects that BC = 0, decodes the command and sending address SA in the sent message, and since the sending address SA is its own, it does not forward this message further, It is known that the small loop 201 connecting the devices 11, 12, 22, and 11 is normal. Thereafter, the timer 91 is reset, and the register 94
is set to “1” to indicate that it is a small-looped woodpecker. Inside register 95 is large loop 1
In order to indicate that the bit can be used, the bit is left as “0”.

On the other hand, when the device 21 receives the second message sent on the line 100 from the device 11, the processing device 41 stores the second message in the second reception buffer 73, and then When detecting that the in-loop number RA ₂ in the reception address RA in this message is equal to its own and BC=0, it decodes the command and transmission address SA in this message. As a result of deciphering,
This code requests a check of a small loop, and the device 1 paired with the device 21 is on a different loop 1 from the loop 2 to which the device 21 is connected.
1, that is, in the sending address SA, the loop number SA ₂ is the same as the own loop number, and the loop number
Knowing that SA ₁ is different from its own loop number,
The processing device 41 sets "1" in the register 93 to indicate that it has received the small loop check, and then sends the sending address SA indicating itself, the receiving address RA indicating the device 26, and the small loop check command. A message containing the following is sent onto loop 2. Furthermore, a timer 91 is set. The set time of this timer is
The time is set to be somewhat longer than the time it takes for the message to make one round on the small loop 106 connecting the nodes 11 and 11. Device 2
6, 16, 11, the devices 12, 22,
When the same process as described for 21 is performed and the small loop 106 is normal, the device 21 receives a message containing a small loop check command that uses the addresses of this device as the receiving and sending addresses on the detour transmission line 100. input from the device 22
decodes this message and leaves the register 95 at "0" to indicate that the small loop 106 is normal and there is no need to use the detour 100, and also indicates that the small loop check has been completed. Therefore, the register 94 is set to "1" and the timer 91 is reset.

In this way, the small loop check of the small loops 201 and 106 is completed.

Regarding the check processing of the small loop 106, among the devices 26, 16, and 11 involved in message transfer, the device 2 that issued the small loop check command
When device 21 on the same loop as device 1 receives a message containing a small loop check command therein, it sets register 93 to ``1'' to indicate this.

Regarding the check processing of the small loop 201, among the devices 12, 22, and 21 involved in message transfer, the device 12 that is on the same loop as the device 11 that issued the message containing the small loop check command.
sets "1" in register 93 therein.

As a result of the above processing, "1" is set in the registers 93 of the devices 12 and 26, but "1" is not set in the registers 94. In this way, a device whose register 93 is set to "1" and whose register 94 is not set to "1" transmits a message containing the small loop check command, with itself as the transmission source.

For example, device 26 does exactly what device 21 did, and devices 26, 25, 15, 16
After checking the small loop 605 connecting the
is set to "1", and the register 95 remains at "0".

Device 12 also checks the small loops connecting devices 12, 13, 23, 22 in exactly the same way as devices 21 and 26. In this case, if the device 13 is out of order, the message containing the small loop check command issued from the device 12 will not be returned to the device 12 when the timer 91 times out. At this time, the device 12 repeatedly transmits the message for the above-mentioned small loop check a predetermined number of times, and if it still cannot detect that this loop is capable of transmission, sets "1" in the register 94, This indicates that the small loop check has been completed, and also indicates "1" in the register 95, indicating that this small loop is abnormal and that the detour transmission path 200 should be used. At this time, the register 65 is also set to 1, and further transfer of the received message to the large loop 1 is prohibited.

Furthermore, the transmission control device 2 that has received the message containing the small loop check command from the device 26
5 also performs a small loop check on its own.

In the example of FIG. 7, the device 25 sets "1" in the register 95 and also sets "1" in the register 65 to indicate that the detour transmission path 500 should be used because the device 24 is out of order. Set.

In this way, each transmission control device determines whether or not to use the detour transmission path by looking at the register 95. For example, in FIG.
2 and 25 each know that they should use the detour transmission path.

In the above operation, the transmission control device that received the small loop check request and issued the small loop check command as the source,
At the time of this transmission, a timer 92 is set. The set time of this timer is set to be somewhat longer than the time required for the small loop check command to complete one cycle of normal loop 1 or 2, respectively. When each transmission control device receives a message containing a small loop check command from an adjacent transmission control device on the same loop before this timer expires, it sends a message containing the small loop check command with itself as the source. Do not send messages. In this way, if loop 1 returns to normal after temporarily becoming abnormal, this small loop check process is prevented from being repeated permanently.

In this way, using the message including the small loop check command, the check as to whether or not the detour transmission path should be used is completed. In this way, when the check of the small loop is completed, the device 1
The operation of the system when transmitting a message containing normal data (CF=0) from device 1 to device 15 is as follows. When this message reaches the device 12, the processing device 41 in the device 12 takes the message into the first receiving buffer 71, and based on the address RA, SA, detour number BN, and detour code BC of this message, this message is further forwarded. determine whether it should be done or not. In the present example, the processing device 41 in the device 12 determines that this message should be further forwarded, and inverts the value of the detour code BC in this message from 0 to 1.
Furthermore, after counting up the value of the detour number BN by 1 from 0 to 1, this message is transferred to the detour transmission line 200.

On the other hand, in the device 22, the message input from the detour transmission line 200 is sent to the second receiving buffer 7.
3, and when it is determined that this message should be further forwarded, as in the current example, the message is forwarded to large loop 2. The contents of this second receive buffer are then erased. Device 2
In 1, when this message is received, the in-loop number SA ₂ in the sending address SA in this message matches its own, and when BC=1 is known,
Perform operation mode (4). In other words, BC from 1 to 0
, and then transfers the received message to large loop 2. This message is then forwarded to device 25 via device 26. In the device 25, the in-loop number RA ₂ in the reception address RA of this message is equal to its own, and the BC
Knowing that = 0, CF = 0, the operating mode
Do (1). That is, after transmitting the message to the corresponding transmitting/receiving terminal (not shown), the message is transferred to the detour transmission path 500.
At this time, change the detour code BC from 0 to 1, and change the detour number
Increase BN from 1 to 2. The device 15 determines the mode of operation to be performed for this message. In this case, the receiving address of this message
Among the RAs, the in-loop number RA ₂ matches its own, but since BC=1, it simply sends this message to the large loop 1. This message is then sent to device 11. The device 11 selects the loop number from the sending address RA of this message.
Since both RA ₁ and loop number RA ₂ match its own, it determines that transmission of this message is complete and cancels this message (operation mode (2)). As a result, the message output from the device 11 is transferred to the large loop 2 via the large loop 1, the detour transmission line 200, and the device 22, and
5, the detour transmission line 500 and the device 15 are connected again.
via the large loop 1 and returned to the device 11. In this way, loop 1, shown by thick line 4 in the figure,
2 and detour transmission paths 200 and 500 form one closed composite transmission system.

Further, the transmission control devices 12 and 25, which operate to set "1" in the register 95 and thereafter use the corresponding detour transmission paths 200 and 500 for message transmission, periodically perform a large loop. A message containing the check command is sent to the corresponding large loops 1 and 2, and a timer 90 is set. Receiving address in this message
Both RA and sending address SA are self-addresses. The other transmission control devices on the large loop 1 that have received the message containing this large loop check command from the device 12 will read this message regardless of whether "1" is set in the register 95 therein. It is retransmitted to the corresponding large loop 1. Therefore, when all of the transmission control devices on this large loop 1 are normal, this message returns to the transmission control device 12 that sent it.

The transmission control device 12 sets "0" in the registers 93 to 95, and thereafter uses the detour transmission path 200.
is not used for message transmission, and the message is transmitted to the corresponding large loop 1.

On the other hand, if any of the transmission control devices on loop 1 is still out of order, the timer 90 times out before the message containing the large loop check command is returned to the transmission control device 12 that sent the message. do. When the timer 90 times up, the transmission control device 1
2 determines that the corresponding large loop 1 is abnormal and leaves the registers 93 to 95 as they are. At this time, the transmission control device 12 periodically sends a message containing a small loop check command to the device 13 to check the small loop consisting of the devices 12, 13, 23, and 22. When the device 12 detects that these small loops are normal, it sets "0" in the register 95 and thereafter uses the detour transmission line 20.
0 is not used for sending messages, and large loop 1 is used for sending messages.

The operation of the transmission controller on large loop 2 upon receiving the message containing the large loop check command sent from device 25 and the subsequent operation of device 25 is the same as that associated with device 12.

In the manner described above, a transmission line check is performed after the composite transmission system is formed.

In FIG. 7, this check indicates that device 1
When the failure recovery of 3 and 24 is detected, each transmission control device 11 to 16 and 21 to 26 performs the operation when the transmission line is normal as described in connection with FIG. Further, if failure recovery of the devices 13 and 24 is not detected by this check, each transmission control device performs the operation at the time of a transmission line abnormality as explained in connection with FIG. However, with this check, device 2
If only 4 failures are recovered, the operation of each transmission control device will be as follows. Now, as an example,
It is assumed that only the device 24 has been recovered from the failure, and the system operation in this case will be explained based on FIG.

Immediately after the device 24 recovers from a failure, "0" is stored in the register 95 therein. Therefore, when the device 24 receives a message that is not addressed to it, it operates to send the message to the large loop 2.

Consider a case where a message (CF=0) containing normal data is transmitted from the device 11 to a transmitting/receiving terminal (not shown) connected to the device 15.
This message is transmitted from device 11 to devices 12, 22,
The operations of these devices up to 21, 26, and 25 are the same as in FIG. The device 25 is
After sending the received message to the corresponding sending/receiving terminal, the message is further forwarded. At this time, this message is different from the case shown in FIG. 7 in that the message is transferred to the large loop 2 instead of the detour transmission line 500. Register 95 in device 25
Since the content of is 0, the device 25 does not use the detour transmission path 500. Therefore, when forwarding this message, the detour code BC and the detour number BN are:
Neither is changed and remains at 0 and 1, respectively. When device 24 receives this message, it forwards this message to large loop 2. This message will be sent to device 2 in the same way from now on.
3 and 22 to reach the device 21. Device 21
is the sending address SA of the received message,
Under the conditions that the loop number RA ₂ is equal to its own address, the loop numbers are different, and BC = 0,
This message is sent to the detour transmission line 100 (operation mode (3)), and the detour code BC is changed from 0 to 1 and the detour number BN is changed from 1 to 2. When the device 11 receives this message and learns that the sending address matches its own, it cancels the message.

In this way, a composite transmission system indicated by solid line 4 in FIG. 8 is formed.

In addition, in the transmission system shown in FIG. 8, the operation of the transmission system shown in FIG. 8 when all the transmission control devices are initially in a normal state but when the device 13 breaks down is almost the same as in the case described above. . That is, in FIG. 8, when device 11 detects an abnormality in large loop 1, a small loop check is performed as described with respect to FIG. As a result, the device 24:
When an abnormality is detected in the small loop consisting of the devices 24, 23, 13, and 14, "1" is set in the register 95 therein, and when a message containing normal data is received from the large loop 2, the message is The data is transferred to the detour transmission line 400. As a result, devices 11, 12, 22, 21, 26, 2
A composite transmission system is formed that connects 5, 24, 14, 15, 16, and 11 in this order. After that, the device 24 that stored "1" in the register 95 sends a large loop check command to the large loop 2, and when it learns that the large loop 2 is normal, it sets "0" in the register 95, and from then on, The detour transmission path 400 is not used. Therefore, the operations of each device at this time are the same as those described above with respect to FIG.

When transmitting a message from, for example, device 11 to a transmitting/receiving terminal connected to device 13 using the composite transmission system shown by the solid line in FIG. , it should be noted that this message can be transmitted to the sending and receiving terminals.

It is possible to form the composite transmission system 4 of FIG. 7 without using the detour code BC. but,
The composite transmission system 4' of FIG. 8 can be formed by using the detour code BC. Therefore, by using the detour code, various failure conditions can be dealt with.

Next, we will show how to use the number of detours BN in message transmission control. As shown in FIG.
Suppose that loops 4 and 21 fail and large loop 1 and 2 transmission systems become unable to transmit. When this is detected, for example, by devices 12 and 22, respectively, devices 11 and 22 issue a message containing a small loop check command and begin a small loop check. In response to the small loop check command from this device 11, the other transmission control devices 12 and 13 also perform a small loop check. The device 22 operates to transfer the message received from the large loop 2 to the detour transmission line 200 because the device 21 is out of order. Since the device 14 is out of order, the device 13 also sends messages received from the large loop 1 to the detour transmission path 300.
It works to transfer to. As a result, device 1
2, 13, 23, and 22 form one closed transmission path. For example, if device 11 sends a message containing normal data in this state, this message will be repeatedly transferred to devices 12, 13, 23, and 22 in this order, and there is a risk that this message will not disappear forever. be. However, in the present invention, when this message is transferred from device 13 to device 23 and from device 22 to device 1.
Number of detours in a message when forwarded to 2
Since the BN is counted up by 1, the devices 12, 13, 23, 22 that received this message
each detour number BN is a predetermined value, for example 3.
If this is the case, this message can be deleted. Therefore, messages can be prevented from being transmitted permanently within the small loop.

As described above, each transmission control device on the large loop 1 or 2 sends a message containing the small loop transmission availability check command if the transmission path of the large loop 1 or 2 is abnormal. Furthermore, when each transmission control device on large loops 1 and 2 receives a message containing a transmission permission check command, it forwards the message, sends a transmission permission check command from itself, and Checks whether transmission is possible for the small loop that is the starting point. Further, the transmission control device that has detected the abnormality and configured the detour route sends a large loop failure recovery check command, checks for failure recovery on the loop, and completes the configuration of the detour route. In this way, by having each transmission control device check whether or not transmission is possible in parts of large loops 1 and 2, even if a failure occurs in part of large loops 1 and 2, a detour can be established without using the master station. Can be formed and restored. Also, the detour code
By controlling the use of detours using BC,
It can effectively deal with failures on large loops 1 or 2,
Furthermore, by using the number of detours BN, transmission of unnecessary messages can be terminated.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a loop-shaped transmission system according to the present invention, FIG. 2 is a more detailed block diagram of a transmission control device used in the system of FIG. 1, and FIG.
4 is a more detailed block diagram of the interfaces 51 and 61, FIG. 5 is a diagram showing the format of a message to be transmitted, and FIGS. 6a and 6b are data formats of the receiving address area and sending address area, respectively. The diagrams showing the mat and FIGS. 7 to 9 are diagrams for explaining different types of detour forming processing in the case of a failure in the system of FIG. 1, respectively. 1, 2... Loop, 11-16, 21-26... Transmission control device, 31... Transmission/reception terminal, 41... Processing device, 51, 61... Interface, 71... First receiving buffer, 73... Second receiving buffer, 81...Transmission buffer, 90-92...Timer, 93...Register for indicating that the transmission availability check request has been accepted, 94...Register for indicating that the transmission availability check has been completed, 95...Indicating the transmission availability check result registers for, 100, 200, 30
0,400,500,600...Detour transmission line.

Claims (1)

[Claims] 1. A transmission path for transmitting messages, and a plurality of transmission control devices connected to the transmission path for controlling message transmission, the transmission control devices transmitting messages from one of the transmission paths. In an information transmission system configured to switch to the other transmission path for transmission and circulate the message in a closed route formed by the other transmission path and a transmission control device connected to the other transmission path, the transmission control device transmits the message. When transmitting the message to the other transmission path, the number of cycles of the message in the closed route is counted up, and if the number of cycles of the message does not exceed a predetermined value, the message is transmitted and the message is A transmission method characterized in that transmission of the message is stopped when the number of cycles exceeds a predetermined value. 2. The information transmission system includes first and second transmission paths for transmitting messages, a first transmission control device connected to the first transmission path and controlling message transmission, and the second transmission path. a second transmission control device that is connected to the first transmission control device and is provided as a pair with the first transmission control device and controls message transmission; and a second transmission control device that is connected to the first and second transmission control devices that form the pair. a detour transmission path, the transmission control device transmits a message to the detour transmission path, and the message is circulated through a closed route formed by the detour transmission path and the first and second transmission paths. The transmission control device counts up the number of detours when transmitting the message to the detour transmission path, and when the number of detours does not exceed a predetermined value, transmits the message to the detour transmission path. Claim 1, characterized in that when the number of circulation of the message exceeds a predetermined value, the transmission of the message to the detour transmission path is stopped. Transmission method described in section.