JPH0519855B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a loop communication system in which a plurality of stations are connected in a loop and signals are transmitted in one direction on the loop.

Against the backdrop of demands for improving the efficiency of accident work, research and development of local area networks that can accommodate voice and non-voice communications in a unified manner is underway, and one of these is a loop-type communication system. be. As a conventional loop communication system that integrates voice communication and non-voice communication,
purpose local network using optical loop
highway” (Takasi MATSUDA et al.
Proceeding of National Telecommunicat−
ions Conference.1981) and “A reliable token-ring
“system for local−area communication”
(Werner Bux et al., Proceeding of National
There is a token system with priority rights as described in Telecommunications Conference, 1981). In the former time-division method, once a time slot is acquired, it can be secured until the end of the call, so it is suitable for continuous synchronous communication such as voice. However, since only one time slot can be allocated to one communication, there is a problem in that it is not possible to accommodate wideband communication, such as image communication, which requires a plurality of time slots. In the latter token method with priority, the length of the transmission block can be set freely, so it is relatively easy to increase the communication capacity between stations.
Additionally, tokens can be given priority to provide continuous synchronous communications such as voice communications.
That is, a node station that has acquired the reservation right, which means the right to send a transmission block of a reserved block length to the loop every cycle, can always carry out a certain amount of communication prior to low-priority communication. However, in order for a node station to acquire reservation rights, it must communicate with a central control station located on the loop. Therefore, the central control station is required to have extremely sophisticated functions such as a loop traffic monitoring function, a determination function for granting reservation rights, and a communication function with the node stations. Therefore, if a failure occurs in the reservation control function of these central control stations, the failure will spread throughout the communication system, creating a problem. Therefore, it is desirable to distribute communication control for call setup to each node station as much as possible to reduce the load on the central control station.

The purpose of the present invention is to uniformly accommodate continuous synchronous communication using a wide range of various bands, have each node station have functions for call setup, monitor the status of transmission traffic on the loop, etc. The objective of the present invention is to provide a highly reliable loop communication system that does not require a highly functional central control station.

The present invention provides a loop communication system in which a clock station and a plurality of node stations are connected by a loop and a signal is transmitted through the loop in one direction, wherein the clock station transmits a synchronization signal to the loop at regular intervals. When the transmitted synchronization signal is received after going around the loop, the synchronization signal is removed from the loop, and the node station that has acquired the reservation right detects an idle state on the loop after the synchronization signal passes. After the synchronization signal has passed, the node station that sends the transmission block to the loop, and when the transmission block has gone around the loop and received it, removes the transmission block from the loop and tries to acquire the reservation right. Acquisition of a reservation right having a length equal to or longer than the length of a transmission block periodically transmitted based on the reservation right when it is detected that the idle state on the loop has continued for a time longer than the signal propagation time of one round of the loop. The present invention is characterized in that a signal block is sent to the loop and the reservation right is acquired when all the reservation right acquisition signal blocks are received after going around the loop.

Further, in the present invention, when the node station attempting to acquire the reservation right detects that the idle state on the loop has continued for a longer time than the signal propagation time for one round of the loop after the passage of the synchronization signal, the node station If the remaining time until the start of the cycle is equal to or longer than the loop occupation time of the reservation right acquisition signal block, which has a length equal to or longer than the length of the transmission block periodically transmitted based on the reservation right, the reservation The present invention is characterized in that a right acquisition signal block is sent to the loop, and when all the blocks are received after passing through the loop, the reservation right is acquired.

Further, the present invention provides a loop communication system in which a clock station and a plurality of node stations are connected by a loop and a signal is transmitted on the loop in one direction, in which the clock station transmits a synchronization signal at regular intervals. When the synchronization signal sent to the loop is received after going around the loop, the synchronization signal is removed from the loop, and a specific station among the clock station and the node station is activated when the loop is in an idle state. It has a function to monitor and detect when the loop idle continues longer than the signal propagation time for one round of the loop, and when it is detected that the loop idle continuation state is longer than the signal propagation time for one round of the loop after passing the synchronization signal, reservation right communication is performed. Send a termination signal on the loop; remove the reservation right communication termination signal from the loop after one cycle of the loop; and transmit the reservation right communication termination signal when the node station that has acquired the reservation right detects an idle state on the loop after the synchronization signal has passed. A node station that sends a block to the loop, removes the transmitted block from the loop when it is received after going around the loop, and attempts to acquire the reservation right after passing the reservation right communication end signal. When an idle state is detected, a reservation right acquisition signal block having a length equal to or longer than the length of the transmission block sent synchronously based on the reservation right is sent to the loop, and the loop goes around the loop. The feature is that the reservation right is acquired when all the reservations are received.

Further, in the present invention, the node station that attempts to acquire the reservation right monitors a loop after the reservation right communication end signal passes, and the remaining time until the start of the cycle when an idle state is detected is used to acquire the reservation right. If the length of the reservation right acquisition signal block is equal to or longer than the loop occupation time of the reservation right acquisition signal block having the same length or longer than the length of the transmission block periodically transmitted based on the The feature is that the reservation right is acquired when all the messages are received after going through the loop.

Next, the present invention will be explained in detail with reference to the drawings.

A first embodiment of the invention is shown in FIG. The loop communication system shown in FIG. 1 includes a clock station 1 and a plurality of node stations 3, 4, 5,
6, 7, and 8, and each station is connected by a loop 2. FIG. 2a is a diagram showing an example of the basic configuration of the information transmission block sent by each node station, which includes a meaningless preamble signal PR start flag SP, destination address DA, sender address SA, information, and end. Consists of flag EF. Regarding the communication based on the reservation right and the procedure for acquiring the reservation right in this embodiment, the node stations 3 and 3 in FIG.
An example will be explained using the timing diagram of FIG. 3, taking as an example a case where node stations 5 and 8 have already acquired the reservation right and node station 6 wants to newly acquire the reservation right.

The clock station 1 sends a synchronizing signal F onto the loop 2 with a period T ₀ and removes it from the loop 2 after the synchronizing signal F has gone around the loop 2. After passing the synchronization signal F, the node station ₃ sends out a transmission block B3 onto the loop 2, and the node station 5 sends out a transmission block _B5 onto the loop 2 after the synchronization signal F and the subsequent transmission block _B3 have passed therethrough. The node station that has acquired the reservation right in this way immediately sends its own transmission block onto loop 2 if there is no transmission block after the passage of the synchronization signal F, and continues to transmit the transmission block after the passage of the synchronization signal F. If passed, wait for all sending blocks to pass and loop the own sending block 2
Send to. Therefore, the node station that has acquired the reservation right can send a transmission block onto loop 2 before the node station that does not have the reservation right, so that periodic communication, such as voice communication and image communication, is guaranteed.

Here, a periodic signal F and subsequent transmission blocks B ₃ and B ₅ are input to the input terminal 61 of the node station 6, as shown in FIG. 3a-1.
The node station 6 receives the signal input from the input terminal 61 after a certain intra-node delay time as shown in FIG.
-2, it is output to loop 2 via the output terminal 62, and the time is monitored until a new transmission block is input after passing the synchronization signal F and the transmission block, and the transmission delay time in loop 2 (each (including the total delay time within the station)
If a transmission block is not input to the input terminal 61 within a time period _T1 longer than Td, it is recognized that the communication based on the reservation right has ended, and a reservation right acquisition block is sent out. In this example, node station 8
has already acquired the reservation right, so Figure 3 a-
As shown in FIG. 1, after the passage of the transmission block _B5 , there is no signal for a while, but before the time _T1 has elapsed, the transmission block _B8 of the node station 8 is input to the input terminal 61. Therefore, time monitoring is stopped and restarted after passing transmission block _B3 .

This time, since the transmission block does not pass during time T ₁ , it is recognized that the communication based on the reservation right has ended,
As shown in Figure 3 a-2, the reservation right acquisition block S ₆
is sent to loop 2 via output terminal 62. The configuration of this reservation right acquisition block is shown in FIG. 2b. The reservation right acquisition block is obtained by replacing the information in the transmission block shown in FIG. 2a with a dummy signal DMY having no information. However, the length of the dummy signal DMY is the length of the information in the transmission block sent after acquiring the reservation right, for example, 64 x _T0 kilobits in the case of 64 Kb/S voice communication, and 15 x T0 kilobits in the case of 15 Mb/S image communication. T ₀ Same as or longer than mechanical bit. Therefore, the length of the reservation right acquisition block is longer than or equal to the length of the transmission block.
In addition, in the reservation right acquisition block, the destination address DA and the sender address SA are made the same.
As shown in Figure 3 a-1, the reservation right acquisition block S ₆
goes around loop 2, and after delay time Td input terminal 6
1 is input. Note that the synchronization signal F and the transmission blocks B ₃ , B ₅ , and B ₈ are transmitted to the clock station 1 and the node station 3 after going around the loop 2.
5 and 8, respectively, are removed from loop 2. If the reservation right acquisition block S ₆ is input to the input terminal 61 without being interfered with by reservation right acquisition blocks of other node stations while going around loop 2, the node station 6 periodically sends out the data. Since the occupation time of loop 2 for its own transmission block has been secured within the cycle _T0 , communication based on the reservation right is performed in the next cycle, as shown in FIG. 3 b-1 and b-2. In addition, Fig. 3b-
1 shows the signal at the input terminal 61, and FIG. 3b-2 shows the signal at the output terminal 62. Since the occupied time of the communication loop 2 based on the reservation right does not exceed the period T ₀ , periodic continuous communication is guaranteed.

Next, a case in which reservation rights cannot be acquired will be briefly explained. When the node station 6 desires large-capacity communication based on the reservation right, the length of the reservation right acquisition block becomes long, and the reservation right acquisition block _S6 is outputted to the output terminal 62 as shown in FIG. 3c-2. However, when the clock station 1 receives interference from the synchronizing signal F, the reservation right acquisition block becomes a block S ₆ ' and is input to the input terminal 61, as shown in FIG. 3C-1. In this case, the block S ₆ ' is the reservation right acquisition block S ₆ output from the output terminal 62.
Since this is different, node station 6 cannot acquire the reservation right. Furthermore, there are cases where the reservation right cannot be acquired due to interference with reservation right acquisition blocks sent by other node stations. When each node station detects that no signal continues for a period of time (T1+Td), it is permitted to transmit a reservation right acquisition block, and it becomes possible to transmit without checking the presence or absence of a loop 2 signal. Therefore, loop 2
There may be cases where a signal block is transmitted even while receiving a signal block from the source. For example, as shown in FIG. 3d-2, even if the station 6 sends out the reservation right acquisition block _S6 to the output terminal 62, if the station 7 also sends out the reservation right acquisition block S7, the reservation right acquisition block at station ₇ is sent out. _S6 receives interference and becomes a block _S6 ' as shown in FIG. 3d-1, which is input to the input terminal 61. Therefore, the node station 6 cannot acquire the reservation right. As described above, in this embodiment, a node station that desires to acquire a reservation right can acquire a reservation right as long as its reservation right acquisition block is not interfered with by other stations. Signals at the input terminal 61 and output terminal 62 of the node station 6 when the node station 6 is performing communication based on the reservation right and when the node station 3 ends the communication based on the reservation right, that is, when the reservation right is abandoned. Figure 3 e
-1 and e-2 respectively. In this case, the sending block _S6 is shifted forward by the length of the sending block _B3 .

FIG. 4 shows a block diagram of the clock station 1 used in this embodiment, and FIG. 5 shows a block diagram of each node station used in this embodiment. Fourth
The clock station 1 shown in the figure has an input terminal 11 and an output terminal 12, a synchronization flag detection circuit 14, a loop control circuit 15, a synchronization signal transmission buffer 18,
It is composed of a switch 17 and an idle signal supply circuit 16. Note that the input terminal 11 and output terminal 12 in this figure are the same as the input terminal 11 and output terminal 12 in FIG. In the synchronization flag detection circuit 14, the signal from the input terminal 11 is supplied as is to the idle signal supply circuit 16. The loop control circuit 15 connects the switch 17 to the terminal 172 with a period T ₀ .
is turned on, and the synchronization signal F in the synchronization signal transmission buffer is sent to the loop 2 via the output terminal 12. The structure of this synchronization signal F is shown in FIG. 2c. Synchronization signal F is preamble signal PR, synchronization flag F ₀
and an end flag EF. At the same time as the transmission of the synchronization signal F is completed, the loop control circuit 15 turns on the switch 17 to the terminal 171 side, and also puts the idle signal supply circuit 16 into operation to supply an idle signal to the output terminal 12 or to make the output terminal 12 non-signal. state. On the other hand, the signal from loop 2 inputted from input terminal 11 is supplied to synchronization flag detection circuit 14 . The synchronization flag detection circuit 14 monitors the signal of this loop 2 and detects the synchronization flag of the synchronization signal F received after going around the loop 2.
Detect F ₀ . The loop control circuit 15 detects the synchronization signal F based on the detection result of the synchronization flag detection circuit 14.
is removed from loop 2, the idle signal supply circuit 16 is rendered inactive. The idle signal supply circuit 16 is the synchronization flag detection circuit 1 in the non-operating state.
4 is supplied to the terminal 171 as it is. Clock station 1 has a period T ₀ as described above.
The synchronizing signal F is sent to the loop 2, and the synchronizing signal F that has gone around the loop is removed from the loop 2.

The node station of FIG. 5 has input terminals 21 corresponding to input terminals 61 and output terminals 62 of FIG.
and an output terminal 22, an idle signal supply circuit 24, a coincidence determination circuit 26, and an address monitor 2.
9, reception control circuit 27, reception buffer 28, OR
Gates 30, 31, AND gate 32, reserved communication control circuit 33, state control circuit 34, counter circuit 35, time-over detection circuit 36, non-reserved communication control circuit 37, flip-flop 38, switch 3
9. Transmission buffer 40, end flag detection circuit 4
1. From the preamble signal monitoring circuit 42 and the input signal, the synchronization flag F ₀ , the preamble signal PR,
It is composed of a signal detection circuit 25 that detects a start flag SF, an end flag EF, a destination address DA, and a sender address SA.

First, communication control for acquiring reservation rights will be explained.

When the state control circuit 34 becomes in a state where the reservation right is desired, the non-reservation communication control circuit 37 is activated by a control signal 342, and the reservation communication control circuit 33 is inhibited by a control signal 341, and the control signal 331 is set to a low level. do.

The counter 35 starts counting based on the end flag EF detected by the signal detection circuit 25,
Synchronization flag F ₀ or start flag SF detected in signal detection circuit 25 via OR gate 30
It is reset by , and the counting operation is stopped. The time-over detection circuit 36 is a counter 35
When the output exceeds a certain value, a time-over signal 361 is supplied to the non-reservation communication control circuit 37.

That is, after the synchronization signal F or the transmission block passes through the signal detection circuit 25, if a no-signal state or an idle signal continues to be input for a time _T1 , a time over signal 361 is supplied to the non-reservation communication control circuit 37. Since the non-reservation communication control circuit 37 is activated by the control signal 342, the control signal 371 is set to high level based on the time-over signal 361. Therefore, the output of the OR gate 31 becomes high level, and the switch 39 is switched from the terminal 391 side to the terminal 392 side.

At the same time that the switch 39 is turned on to the terminal 392 side, the reservation right acquisition block buffered in the transmission buffer 40 is sent to the loop 2 via the output terminal 22. The end flag detection circuit 41 detects the end flag output from the transmission buffer 40 and supplies the detection result to the non-reservation communication control circuit 37. Based on this detection result, the non-reservation communication control circuit 37 sets the control signal 371 to low level and switches the switch 39 to terminal 3.
Turn on the 91 side. That is, the switch 39 is turned on to the terminal 392 side only when the reservation right acquisition block is sent. The reservation right acquisition block thus sent out goes through loop 2 and is supplied to the signal detection circuit 25. The signal detection circuit 25 detects the destination address
When the DA and caller address SA are detected, they are supplied to the address monitor 29. If the destination address DA and the sender address SA are the same and match its own station address, the address monitor 29 recognizes that the reservation right acquisition block it sent has completed its cycle, and sends a control signal 291 to match. The determination circuit 26 is activated. Address monitor 29 activates reception control circuit 27 by control signal 292 when sender address SA matches its own station address. Reception control circuit 2
7 activates the idle signal supply circuit 24. The idle signal supply circuit 24 supplies an idle signal to the terminal 391 (or makes it in a non-signal state), and removes from the loop 2 the reservation right acquisition block that has passed through the loop 2. The reception control circuit 27 becomes inactive due to the end flag EF detected by the signal detection circuit 25, and the idle signal supply circuit 24
to be inactive. Idle signal supply circuit 24
In the non-operating state, the output of the signal detection circuit 25 is directly supplied to the terminal 391. On the other hand, the match determination circuit 26 compares the input reservation right acquisition block through loop 2 with the reservation right acquisition block buffered in the transmission buffer 40, and if they match, it is determined that the reservation right has been acquired. do. This determination result is supplied to the state control circuit 34, which uses control signals 341 and 342 to put the reserved communication control circuit 33 and the non-reserved communication control circuit 37 into a non-operating state. Therefore, the two inputs of the OR gate 31 become low level, and its output also becomes low level.

Note that the state control circuit 34 is connected to the signal detection circuit 25.
When the synchronization flag F ₀ is supplied, the control signal 3
42, the non-reservation communication control circuit 37 is reset. At this time, the non-reservation communication control circuit 37 sends the control signal 371 even when the reservation right acquisition block is being sent.
to low level and stop the sending operation.

Further, the idle signal supply circuit 24 is reset by the synchronization flag F ₀ detected by the signal detection circuit 25, and stops supplying the idle signal even when the idle signal is being supplied. This means that when the reservation right acquisition block that has completed one cycle is removed from loop 2, if the reservation right acquisition block is interfered with by the synchronization signal F and the end flag EF is cleared, the supply of the idle signal is stopped. This is to prevent the synchronization signal F from being removed if it continues.

When the reservation right is acquired, the state control circuit 34 waits for the signal detection circuit 25 to detect the next synchronization flag F ₀ and then puts the reservation communication control circuit 33 into the operating state using the control signal 341. flipflop 38
is set by the synchronization flag F ₀ detected by the signal detection circuit 25, and its output Q is supplied to the AND gate 32. When the output Q becomes high level, the AND gate 32 sets the end flag EF detected by the signal detection circuit 25 to the reserved communication control circuit 3.
Supply to 3. The reserved communication control circuit 33 sets the control signal 331 to a high level based on the end flag EF supplied via the AND gate 32. This control signal 331 is supplied to the switch 39 via the OR gate 31, and switches the switch 39 from the terminal 391 side to the terminal 392 side. When the switch 39 is turned on to the terminal 392 side, the transmission block buffered in the transmission buffer 40 is transferred to the terminal 392 with the preamble signal PR at the beginning, as shown in FIG.
2. During the transmission of this preamble signal PR, the signal detection circuit 25 detects the preamble signal PR of the transmission block input from the input terminal 21.
When detecting this, the reservation communication control circuit 33 sets the control signal 331 to low level and switches the switch 39 to terminal 3.
91 side to stop the transmission operation of the transmission buffer 40. By the time the transmission of the preamble signal PR is completed, the signal detection circuit 25 detects the preamble signal
If no PR is detected, transmit buffer 40 sends the remaining transmit block to loop 2 via switch 39 and output terminal 22. The preamble signal monitoring circuit 42 supplies a control signal 421 to the reservation communication control circuit 33 when detecting the end of sending the preamble signal PR. Based on this control signal 421, the reservation communication control circuit 33 uses the control signal 33 even if the signal detection circuit 25 detects the preamble signal PR.
Do not set 1 to low level. This is to prevent the preamble signal PR of its own transmission block from going around the loop 2 and the signal detection circuit 25 detecting this and stopping the transmission operation. When the transmission buffer 40 finishes transmitting the transmission block, the end flag detection circuit 41 detects the completion of the transmission, resets the flip-flop 38, and supplies the detection result to the reserved communication control circuit 33, which receives the control signal. 331 to low level. Therefore, the output of the OR gate 31 becomes low level, and the switch 39 is turned on to the terminal 391 side. Since the output Q of the flip-flop 38 does not become high level until the next synchronization flag _F0 is detected, even if the signal detection circuit 25 detects the end flag EF after sending out the transmission block, the AND
The gate 32 prohibits supply to the reserved communication control circuit 33. In this way, it is detected that there is no signal on the loop after the synchronization signal F has passed, and a transmission block is sent out.

The transmission block received after passing through loop 2 is removed from loop 2 under the control of reception control circuit 27 based on control signal 292. in this case,
A node station identifies a transmission block to be removed based on whether the sender address SA of the transmission block matches its own station address.

The case where the node station becomes the originating station has been described above, and next, the case where the node station becomes the destination station will be briefly explained. When the destination address DA detected by the signal detection circuit 25 matches its own station address, the address monitor 29 outputs a control signal 29.
2 to the reception control circuit 27, and the reception control circuit 2
7 puts the receiving buffer 28 in the receiving state until the end flag EF is detected. Switch 39 is terminal 3
91 side, the transmission block is supplied to the output terminal 22 as it is and sent to the originating node station. Also, the destination node station replaces the information addressed to the originating node station with the information of the received transmission block, and sends the information to the output terminal 22 without changing the length of the transmission block.
Full-duplex communication such as voice communication may be performed by using a known technique of transmitting the information to the user.

Next, a second embodiment of the present invention will be described.
This embodiment is the same as the first embodiment except for the configuration of the node station. A block diagram of the node station used in this embodiment is shown in FIG. The node station of FIG. 6 has a flip-flop 44 in addition to the node station of FIG.
An AND gate 45 and an OR gate 46 are added, and an interference detection circuit 43 is provided in place of the coincidence determination circuit 26. The communication control in the node station shown in FIG. 6 is the same as the communication control in the node station shown in FIG. 5 except for the procedure up to acquiring the reservation right, so only the procedure for sending out the reservation right acquisition block will be explained.

If you wish to acquire the reservation right, the state control circuit 34
The reservation communication control circuit 33 is activated by the control signal 341.
is brought into a non-operating state, and the non-reservation communication control circuit 37 is brought into an operating state. When the time-over circuit 36 detects that all communications based on reservation rights have been completed in the same manner as in the node station of FIG. 5, it sets the flip-flop 44 and makes the output Q high level. Time over circuit 36 is OR gate 4
A control signal 361 is supplied to the non-reservation communication control circuit 37 via 6 and the AND gate 45, and the non-reservation communication control circuit 37 sets the control signal 371 to high level based on this control signal 361, and switches the switch 39 to the terminal 392 side. The transmission right acquisition block with the preamble signal RR at the beginning is supplied from the transmission buffer 40 to the output terminal 22. During the transmission of the preamble signal RR of the transmission right acquisition block, when the preamble signal PR detected by the signal detection circuit 25 is supplied to the non-reservation communication control circuit 37, the control signal 371 becomes low level and the switch 39 switches to the terminal 3.
91 side and the transmission of the preamble signal is stopped. The transmission right acquisition block is sent when the end flag EF detected by the signal detection circuit 25 is detected by the OR gate 46.
After waiting for the signal to be supplied via the AND gate 45, the non-reservation communication control circuit 37 restarts the communication. When all the preamble signals PR of the transmission block to be sent are supplied to the output terminal 22, the preamble signal monitoring circuit 42 outputs the preamble signal PR.
A control signal 421 indicating the end of PR transmission is supplied to the non-reservation communication control circuit 37. When this control signal is supplied, the non-reservation communication control circuit 37 does not stop sending the reservation right acquisition block even if the preamble signal PR detected by the signal detection circuit 25 is supplied. As explained earlier, this is the preamble signal of the own reservation rights acquisition block that has gone through the cycle.
This is to prevent the transmission operation from being stopped due to PR.
When the transmission of the reservation right acquisition block is completed, the end flag detection circuit 41 detects the end flag EF, resets the flip-flop 44, and supplies the detection result to the non-reservation communication control circuit 37. Based on this detection result, the non-reservation communication control circuit 37 sets the control signal 371 to a low level and ends the transmission control of the reservation right acquisition block. Note that while the reservation right acquisition block is being sent, the signal detection circuit 25 detects the synchronization flag.
When F ₀ is detected, the state control circuit 34 resets the non-reservation communication control circuit 37 in the same manner as the state control circuit 34 of FIG. 5, and the transmission of the reservation right acquisition block is stopped.

In the loop communication system shown in FIG. 1, assume that node stations 3, 5, and 8 have already acquired reservation rights, and node stations 4, 6, and 7 want to newly acquire reservation rights. The loop type communication according to the second embodiment will be explained using the timing chart shown in FIG. 7 at the input terminal 61 and output terminal 62 of. As shown in FIG. 7A-1, the node station 6 attempts to transmit the reservation right acquisition block _S6 at time _T1 after the transmission block _B8 based on the reservation right has passed, but the node station 6 Since the reservation right acquisition block S ₄ is input, the reservation right acquisition block
_S6 is stopped, and after waiting for the reservation right acquisition block _S4 to pass, the reservation right acquisition block _S6 is sent to loop 2 as shown in FIG. 7a-2. As shown in FIG. 7 a-1, the node station 6 confirms that the reservation right acquisition block S ₆ is received after going through loop 2, and acquires the reservation right.
As shown in -2, from loop 2, the reservation right acquisition block _S6 that has been received in one round is removed. The signals of the input terminal 61 and output terminal 62 of the node station 6 when the node stations 4, 6 and 7 acquire the reservation right are shown in FIG. 7 b-1 and b-2, respectively.
Shown below.

The node station 6 is connected to the seventh node by the method described above.
Even if the reservation right acquisition block _S6 is sent as shown in Figure c-2, if it is received as block _S6 ' due to interference from the synchronization signal F as shown in Figure 7c-1, the node Station 6 cannot acquire reservation rights. In this embodiment, even if the node station desiring to acquire the reservation right detects that all communication based on the reservation right has ended, it waits to send out the reservation right acquisition block until loop 2 is in a no-signal state. Interference between acquisition blocks can be avoided.

The operation of the node station from sending out the reservation right acquisition block to acquiring the reservation right will be explained using FIG. The address monitor 29 detects its own reservation right acquisition block that has gone around the loop 2 using the same method as explained in the first embodiment, and uses the control signal 291 to detect the interference detection circuit 43.
Start. The interference detection circuit 43 detects the synchronization flag _F0 and the end flag EF detected by the signal detection circuit 25.
When the end flag EF is detected before the synchronization flag F ₀ , it is determined that the reservation right has been acquired, and when the synchronization flag F ₀ is detected before the end flag EF, it is determined that the reservation right has not been acquired. The status control circuit 34 is notified of this fact. Further, the own reservation right acquisition block that has gone through one cycle is removed from loop 2 using the same method as explained in the first embodiment.

A third embodiment of the present invention will be described. Note that this embodiment is characterized by the transmission control of the reservation right acquisition block, and the other transmission controls are the same as in the other embodiments, so the explanation will be limited to the reservation right acquisition method. In the first embodiment, the node station transmits a reservation right acquisition block after detecting that all communication based on the reservation right has ended, and in the second embodiment, the node station sends out a reservation right acquisition block to the input terminal of another node station. When a reservation right acquisition block is input, it waits for its passage and sends its own reservation right acquisition block. In contrast, in this embodiment, when it becomes possible to send out the reservation right acquisition block, the time until the next synchronization signal F passes is calculated, and the synchronization is performed while the reservation right acquisition block goes around the loop. It is determined whether or not there will be interference from signal F, and only when it is determined that there will be no interference, a reservation right acquisition block is sent out.

FIG. 8 shows a block diagram of the node station used in this embodiment. The node station in FIG. 8 is the same as the node station in FIG. 6, except that a time measurement circuit 47 is added and the interference detection circuit 43 in FIG. 6 is no longer necessary.
Since the node station shown in FIG. 8 differs from the first and second embodiments only in the procedure for transmitting the reservation right acquisition block, only the procedure for transmitting the reservation right acquisition block will be explained. Details of the time measurement circuit 47 are shown in FIG.
The time measurement circuit 47 shown in FIG. 9 includes a counter 473 that counts in synchronization with the synchronization flag F ₀ , a reservation right acquisition determination circuit 474 and an AND gate 475. The reservation right acquisition determination circuit 474 detects the rise of the control signal 371 of the non-reservation communication control circuit 33, inputs the output of the counter 473 at the time of the rise, and determines the loop occupation time based on the length of the reservation right acquisition block to be sent. It is determined whether the calculated time and the transmission delay time in the loop are shorter than the time until the next synchronization signal F passes, or whether it is shorter than a certain period of time, and if it is short, the control signal 476 from low level to high level. Therefore, the output 471 of AND gate 475
becomes high level and is supplied to the switch 39 via the OR gate 31, and transmission of the reservation right acquisition block is started. When the reservation right acquisition determination circuit 474 is notified by the control signal 421 of the preamble signal detection circuit 42 that the transmission of the preamble signal of its own transmission right acquisition block has ended, the reservation right acquisition determination circuit 474 determines that the reservation right has been acquired by the control signal 472. 34. When a preamble signal from another node station is supplied from the input terminal 21 when transmitting its own preamble signal, the control signal 371
becomes low level. Reservation right acquisition determination circuit 474
When detecting this fall of the control signal 371, it sets the control signal 476 to low level and returns to the initial state. Note that the reservation right acquisition block that has gone through the loop is removed from the loop by the method described above.

In this embodiment, c-1 and c-2 in FIG.
Since the transmission of a reservation right acquisition block that is subject to interference from the synchronization signal _F as shown in FIG. . Furthermore, since the signal sent to the loop is not interfered with by other signals on the loop, communication between node stations that is not based on reservation rights can be performed using the same method as the transmission and reception of reservation right acquisition blocks.

However, the block of data to be sent has the configuration shown in FIG. 2a.

The timing diagram in this case is shown in Figure 10 a-1, a.
-2. Note that D ₆ in the figure indicates a data block sent from the node station 6 that is not based on a reservation right.

At this time, a control signal 472 indicating reservation right acquisition is sent.
is supplied from the time measurement circuit 47 to the state control circuit 34, but the state determination circuit 34 ignores this.

The above has been explained using the transmission block, the reservation right acquisition block, and the synchronization signal shown in FIGS. 2a, b, and c, respectively. However, as shown in FIG. may be given to each block, and only the synchronizing signal shown in FIG. Destination address DA and sender address SA of synchronization signal
Both are the clock station address.
In this case, the signal detection circuit 25 detects SY=1 instead of detecting the synchronization flag _F0 .

A fourth embodiment of the present invention will be described. In the three embodiments described above, each node station monitored the termination of communication based on the reservation right, but in this embodiment, only one specific node station has this monitoring function, and this node station When the end of communication based on the right is detected, a reservation right communication end signal is sent to the loop and removed after completing one cycle.

The other node stations wait for the reservation right communication end signal to pass and then send out their own reservation right acquisition blocks. In the loop communication system shown in Figure 1,
As an example, assume that node stations 3, 5, and 8 have already acquired reservation rights, node stations 4 and 6 wish to acquire reservation rights, and node station 3 is the above-mentioned specific node station. The operation of the station 6 will be explained using the dimming diagram shown in FIG.

When the no-signal period continues for a time _T1 after the transmission block _B8 has passed, the node station 3 determines that the communication based on the reservation right has ended, and sends a reservation right communication end signal M to the loop. Following passage of the reservation right communication end signal M, the node station 4 sends out a reservation right acquisition block _S4 . When the node station 6 receives the reservation right communication end signal M and the subsequent reservation right acquisition block _S4 as shown in FIG. 12 a-1, it acquires the reservation right as shown in FIG. 12 a-2. After waiting for block _S4 to pass, reservation right acquisition block _S6 is sent to loop 2. When the reservation right acquisition block _S6 completes one cycle without being interfered with by the synchronization signal F, the node station 6 acquires the reservation right.

The configuration of the signal block used in this example is as follows.
As shown in the figure. The transmission block inserts the data to be communicated into the information area, and the reservation right acquisition block inserts the aforementioned dummy signal DMY into the information area.
Bit SY indicates whether the signal block is a synchronous signal.
Bit MC indicates whether the signal block is the reservation right communication end signal M.

The configuration of the node station that sends the reservation right communication end signal M with MC=1 is the non-reservation communication control circuit 3.
Since it is the same as the node station shown in FIG. 5 except for the function 7, it will be explained using FIG. The non-reservation communication control circuit 37 is always in an operating state, and the time-over detection circuit 36 notifies the non-reservation communication control circuit 37 of the termination of all communications based on reservation rights using a control signal 361. The non-reservation communication control circuit 37 sets the control signal 371 to high level and supplies the reservation right communication end signal M in the transmission buffer 40 to the output terminal 22 via the switch 39. Reservation right communication end signal M
Then, SY=0, MC=1, and the destination address DA and sender address SA are the own station address. If this node station desires to acquire the reservation right, it sets the reservation right acquisition block to SY=0 and MC=1, adds reservation right communication termination information to the reservation right acquisition block, and sends it out. That is, the signal block sent out is a reservation right acquisition block for this node station, and becomes a reservation right communication end signal M for other node stations.

After this reservation right communication end signal M goes around loop 2, it is removed from loop 2 by the method described above.
The coincidence determination circuit 26 notifies the state control circuit 34 of whether or not the reservation right has been acquired in response to the reservation right communication end signal M in the same way as for the reservation right acquisition block. If it is inside, it will recognize that the reservation right has been acquired, and if it is not reserved, it will be ignored. Note that the passage of the synchronization signal F is detected by detecting bit SY=1 in the signal detection circuit 25. Similarly, in the clock station 1 shown in FIG. 4 in this embodiment, when the synchronization flag detection circuit 14 detects bit SY=1, it removes the synchronization signal F that has gone through one cycle from the loop 2. In the node station shown in FIG. 5, the coincidence determination circuit 26 determines whether or not a reservation right has been acquired, but the interference detection circuit 43 shown in FIG. 6 used in the second embodiment may also be used. The configuration of the node station in this case is shown in FIG. In the node station shown in FIG. 14, the interference detection circuit 43 detects that the end flag EF of its own reservation right acquisition block, which has been received in one round, is
The state control circuit 3 determines whether or not the reservation right has been acquired based on whether or not it is received before the synchronization signal of SY=1.
Notify 4.

FIG. 15 shows an example of the configuration of a node station that does not send out the reservation right communication end signal M used in this embodiment. The node station of FIG. 15 is the same as the node station of FIG. 6 except that flip-flop 44 is set by bit MC=1 detected by signal detection circuit 25. However, the flip-flop 44 is set by the MC=1 bit of the passing signal detected by the signal detection circuit 25, and reset by the end flag EF of its own transmission signal detected by the end flag detection circuit 41. Therefore, after this node station detects passage of the reservation right communication end signal M,
When loop 2 becomes non-signaled, it sends out a reservation right acquisition block.

A fifth embodiment of the present invention will be described. Fourth
In the embodiment described above, a specific node station sent the reservation right communication end signal M, whereas in this embodiment, the clock station 1 has this function.
Transmission/reception control in this embodiment will be explained using the timing diagram of FIG. 16 showing signals at the input terminal 11 and output terminal 12 of the clock station 1.
Clock station 1 sends a synchronizing signal F to loop 21 with period T ₀ as shown in FIG. 16a-2. This synchronization signal F _is input to node station 1 in one cycle as shown in FIG _. B ₈ is input.

Clock station 1 receives the synchronization signal F after one cycle.
is removed from loop 2, and the transmission block
Immediately after detecting a no-signal state after passing _B8 , a reservation right communication end signal M is sent. This reservation right communication end signal M is removed after going through loop 2.

A block diagram of the clock station 1 used in this embodiment is shown in FIG.

First, transmission and reception control for the synchronization signal F will be explained. The synchronization signal supply circuit 50 sets the control signal 501 to a high level at a cycle _T0 and sends out the synchronization signal F in the transmission buffer 40 via the switch 39, and when the end flag detection circuit 41 notifies that the transmission of the synchronization signal F has ended. Control signal 501 is set to low level. The reception control circuit 27 activates the idle signal supply circuit 24 when the control signal 501 becomes high level. The idle signal supply circuit 24 continues to output the idle signal until the signal detection circuit 25 detects the end flag EF and the reception control circuit 27 is notified of the detection result. Therefore, after sending out the synchronization signal F, an idle signal is supplied to the output terminal 12 until the synchronization signal F is received after one cycle, and the synchronization signal F after one cycle is also removed from the loop 2.

Next, the transmission and reception control for the reservation right communication end signal M will be explained.

The clock station 1 has a reservation communication control circuit 3.
3, a flip-flop 38, an AND gate 32, and a preamble signal monitoring circuit 42.
This has the same configuration as the transmission control circuit of the transmission block based on the reservation right possessed by the node station shown in FIG. Therefore, clock station 1 transmits subsequent transmission blocks B ₃ , B ₅ and B ₈ based on reservation rights, as shown in FIG. 16a-2, in the same manner as the communication based on reservation rights. A reservation right communication end signal M of the buffer 40 is sent to the loop 2 via the output terminal 22. The reservation right communication end signal M that has gone around is removed from loop 2 in the same way as the node station in FIG. 8 removes its own transmission block that has gone around again from loop 2.

The node station used in this embodiment is the same as the node station shown in FIG. 15 used in the fourth embodiment, and acquires its own reservation right when the loop 2 signal disappears after the reservation right communication end signal M passes. Send a block.

FIG. 18 shows a block diagram of a clock station 1 used in a sixth embodiment of the present invention. 18th
The clock station 1 shown in the figure is the clock station shown in FIG. 17 to which the function of a node station is added. That is, the reception buffer 28
and an interference detection circuit 43 are added. 1st
When the clock station 1 in FIG. 8 has acquired the reservation right as a function of a node station, the clock station 1 in FIG.
Set MC to 0, insert data for inter-station communication into the information area, and set the destination address DA to the address of the data destination node station. If you wish to acquire the reservation right, change the signal block shown in Figure 13 to SY=0,
Set MC=1 and add a dummy signal to the information area.
Insert DMY. That is, the setting of bits SY and MC indicates that the signal block to be sent is the synchronization signal F or the reservation right communication end signal M, and also functions as a transmission block or reservation right acquisition block based on the reservation right. This signal block is sent to loop 2 in the same manner as the clock station of FIG. 17, and is removed after going through loop 2. The interference detection circuit 43 determines whether or not a reservation right has been acquired using the same method as in the node station shown in FIG. 14, and notifies the synchronization signal supply circuit 50 of the determination result. The receiving buffer 28 receives and buffers the data block addressed to itself. The node station shown in FIG. 15 is used as in the fifth embodiment.

In the fourth, fifth, and sixth embodiments, each node station, like the node station in FIG. 8 used in the third embodiment, determines whether or not it is possible to send a reservation right acquisition block. A configuration may be adopted in which reservation rights are acquired when possible.

In this case, as shown in FIG.
7 is provided at the input of the OR gate 31. FIGS. 19 and 20 are block diagrams in which the node station of FIG. 15 and the clock station of FIG. 18 having the functions of the node station have the above functions. In the node station shown in FIG. 19, the time measurement circuit 47 detects that when the control signal 371 of the non-reservation communication control circuit 37 becomes high level, the reservation right acquisition block to be sent receives interference from the synchronization signal F on loop 2. It is determined whether or not this is the case, and the determination result 472 is notified to the state control circuit 34.
In the clock station shown in FIG. 20, the time measuring circuit 47 supplies the determination result 472 to the state control circuit 34 based on the control signal 331 of the reservation communication control circuit 33 that controls the transmission of the reservation right communication end signal M. . In this case, in addition to determining whether the reservation right communication end signal M can be sent, the time measurement circuit 47 determines whether the dummy signal DMY can be inserted into the reservation right communication end signal M if the reservation right acquisition is desired. judge. Based on the control signal 472, the state control circuit 34 determines whether the reservation right communication end signal M can be sent to the reservation communication control circuit 33, and whether a dummy signal DMY for acquiring the reservation right should be inserted. If the dummy signal DMY can be inserted, that is, if the reservation right is acquired, the synchronization signal supply circuit 50 is notified of whether or not the dummy signal DMY can be inserted. Notify that it should be inserted into the information area of F.

In this way, when each node station has the time measurement circuit 47, the signal on loop 2 is not interfered with by the synchronization signal F, as in the third embodiment using the node station in FIG. Instead of reservation right acquisition blocks, data blocks can be sent for communication between node stations that are not based on reservation rights.

In the above explanation, a communication system consisting of stations physically connected in a loop as shown in FIG. It can also be applied to systems.

That is, in the communication system of FIG. 1, node station 2 can communicate after node station 1 finishes communication, node station 3 can communicate after node station 2 finishes communication, and so on in a predetermined order. Therefore, in rotation, all node stations have the right to communicate. As long as this order is determined physically or logically, the physical form of the transmission path connecting the node stations in the present invention is not limited.

As described above, according to the present invention, each node station can autonomously determine whether or not a reservation right has been acquired, and the length of a transmission block in communication based on a reservation right can also be made variable. It is also possible to provide communication between stations that is not based on authority, the load on the clock station is reduced, and a highly reliable and flexible loop communication system can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the loop communication system of the present invention, and FIG.
1 is a configuration diagram of a signal block used in an embodiment of
FIG. 3 is a timing diagram of the node station according to the first embodiment of the present invention, and FIGS. 4 and 5 are block diagrams of the clock station and node station used in the first embodiment of the present invention. , FIG. 6 is a block diagram of a node station used in a second embodiment of the present invention, FIG. 7 is a timing diagram of the node station of FIG. 6, and FIG. 8 is a block diagram of a node station used in a third embodiment of the present invention. This is a node station used in an example, and FIG. 9 shows a time measurement circuit 47 used in the node station in FIG.
FIG. 10 is a timing diagram of the node station of FIG. 8, and FIGS. 11a, b, and c are diagrams of signal blocks used in the first, second, and third embodiments of the present invention. 12 is a timing diagram of the node station according to the fourth embodiment of the present invention, and FIG. 13 is a diagram of the configuration of a signal block used in the fourth embodiment of the present invention. , 14 and 15 are block diagrams of a particular node station and other node stations used in the fourth embodiment of the present invention, and FIG. 16 is a block diagram of a specific node station and other node stations used in the fourth embodiment of the present invention. FIG. 17 is a block diagram of the clock station used in the fifth embodiment of the present invention, and FIG. 18 is a block diagram of the clock station used in the sixth embodiment of the present invention. 19 and 20 are block diagrams of a node station and a clock station used in yet another embodiment. Figure 1, Figure 4, Figure 5, Figure 6, Figure 8, Figure 9, Figure 14, Figure 15, Figure 17, Figure 18.
19 and 20, 1 is the clock station, 2 is the loop, 3, 4, 5, 6,
7 and 8 are node stations, 14 is a synchronization flag detection circuit, 15 is a loop control circuit, 16 and 2
4 is an idle signal supply circuit, 17 and 39 are switches, 18 and 40 are transmission buffers, 25 is a signal detection circuit, 26 is a coincidence judgment circuit, 27 is a reception control circuit, 28 is a reception buffer, 30, 31, 32,
45 and 46 are gates, 33 is a reservation communication control circuit, 34 is a state control circuit, 35 is a counter circuit,
36 is a time-over detection circuit, 37 is a non-reservation communication control circuit, 38 and 44 are flip-flops, 4
1 is an end flag detection circuit, 42 is a preamble signal monitoring circuit, 43 is an interference detection circuit, 47 is a time measurement circuit, 473 is a counter, 474 is a reservation right acquisition determination circuit, 475 is a gate, and 50 is a synchronization signal supply circuit 50 are shown respectively.

Claims (1)

[Claims] 1. In a loop communication system in which a clock station and a plurality of node stations are connected by a loop and a signal is transmitted through the loop in one direction, the clock station transmits a synchronization signal at regular intervals. When the synchronization signal sent to the loop is received after going around the loop, the synchronization signal is removed from the loop, and the node station that has acquired the reservation right is placed in an idle state on the loop after the synchronization signal passes. When the node station detects the synchronization signal, it sends the transmission block to the loop, and when the transmission block has gone around the loop and is received, it removes the transmission block from the loop and acquires the reservation right. A reservation having a length equal to or longer than the length of a transmission block that is periodically transmitted based on the reservation right when it is detected that the idle state on the loop has continued for a longer time than the signal propagation time of one round of the loop after passing through. A loop type communication system characterized in that a right acquisition signal block is sent to the loop, and when all the reservation right acquisition signal blocks are received after going around the loop, the reservation right is acquired. 2. When the node station attempting to acquire the reservation right detects that the idle state on the loop has continued for a time longer than the signal propagation time for one round of the loop after the passage of the synchronization signal, the node station that wants to acquire the reservation right If the remaining time is equal to or longer than the loop occupation time of the reservation acquisition signal block, which has a length equal to or longer than the length of the transmission block periodically transmitted based on the reservation right, the reservation right is acquired. 2. The loop type communication system according to claim 1, wherein a signal block is transmitted to said loop, and when all signal blocks are received after going around said loop, a reservation right is acquired. 3. In a loop communication system in which a clock station and a plurality of node stations are connected by a loop and a signal is transmitted in one direction on the loop, the clock station sends a synchronization signal to the loop at regular intervals. When the synchronization signal is received after going around the loop, the synchronization signal is removed from the loop, and a specific station among the clock station and the node station transmits the signal when the idle state of the loop is around the loop. If it detects that the loop idle continuation state is longer than the signal propagation time for one round of the loop after passing the synchronization signal, it sends a reservation right communication end signal to the loop. The node station that has acquired the reservation right transfers the transmission block to the loop when it detects an idle state on the loop after passing the synchronization signal. When the sending block is received after going around the loop, the node station that intends to remove the sending block from the loop and acquire the reservation right monitors the loop after the reservation right communication end signal has passed. When an idle state is detected, a reservation right acquisition signal block having a length equal to or longer than the length of the transmission block sent synchronously based on the reservation right is sent to the loop, and all the blocks are received after going around the loop. A loop communication system characterized by acquiring reservation rights when 4 The node station attempting to acquire the reservation right monitors the loop after the reservation right communication end signal has passed, and periodically calculates the remaining time until the start of the cycle when an idle state is detected based on the reservation right. If the length is the same as or longer than the loop occupation time of the reservation right acquisition signal block, which has the same or longer length as the transmission block to be sent, the reservation right acquisition signal block is sent to the loop and the reservation right acquisition signal block is sent to the loop. Claim 3 characterized in that the reservation right is acquired when all the messages have been received in one cycle.
Loop communication system as described.