JPH0683238B2 - Transmission control method in loop network - Google Patents

Description

The present invention relates to a transmission control system for a trigger station and a node station connected to a loop network.

(Prior art and its problems) In addition to the integration of voice communication and data communication, as a communication method for realizing the integration of high-bandwidth services such as video communication and high-definition images, for example, the 1983 IEICE exchange research There is a loop network described in "Examination of high-speed synchronous packet loops" described in the meeting document SE83-107.

This loop network constitutes a network as shown in FIG. In the figure, the trigger station TS20 sends a polling signal onto the transmission line 24 to perform polling control on the node stations NS21, NS22, NS23. Also, the node stations NS21, NS22, NS23 are
Packets are transmitted and received via the transmission line 24 in accordance with the polling control. These stations are connected by a transmission line 24 in a loop as shown in the figure. (In this specification, the trigger station is abbreviated as TS, and the node station is abbreviated as NS, and TS and NS are collectively referred to as stations.) In this loop network, as shown in FIG. Sends a polling signal (p1 or p2),
Each NS monitors the polling signal passing through the transmission path 24, prepares for packet transmission, and transmits the packet after acquiring the transmission right. For example, in the example of FIG. 7, the NS21 receives the polling signal p1 transmitted by the TS20, acquires the transmission right after passing the signal, and transmits the packet a1. NS22 receives packet a1 after receiving polling signal p1.
After that, the transmission right is acquired and the packet b1 is transmitted. Similarly, NS23 also transmits packet c1.

When the polling signal p1 transmitted by the TS20 makes one round in the transmission line 24 and returns, the TS20 transmits the polling signal p1 to the transmission line 24.
After removing from 24 (the signal removed at each station in the figure is indicated by *) and passing packets a1, b1, c1 transmitted by NS21, NS22 and NS23,
Acquires the right to send, sends the next polling signal p2, NS21
To start sending packet a2. Also, each NS also removes from the transmission line 24 when the packet transmitted by itself returns around the transmission line 24. In this way, the transmitted signal is removed at the transmission source station after passing through the transmission path 24 once.

In the loop network, each station temporarily disconnects the transmission line 24 at the start of signal transmission, transmits the signal in its own station, waits for this signal to go around the transmission line 24, and transmits the same signal. The transmission line 24 is connected again after being removed from the line 24. In this way, each station controls the opening / closing of the transmission path 24 during transmission. Therefore, when a certain station erroneously opens and closes the transmission line 24 due to a code error on the transmission line 24, the transmitted packet is removed at a station before reaching the destination station, Or packet is the transmission line
Despite going through 24 cycles, a failure occurs such as not being removed at the transmission source station, causing an abnormality in the access method of each station. For example, in the example shown in FIG. 8, when the end delimiter indicating the end of the packet appears due to a code error in the middle of the packet a1 transmitted by the NS21, the NS21 that transmitted the packet a1 sends the same packet to the NS21. When the packet has returned through the transmission path 24 and returned, the removal of the packet a1 ends when the end delimiter caused by the code error is detected. Therefore, as indicated by the diagonal lines in FIG. 8, a part of the latter half of the packet a1 is not removed and remains.

On the other hand, NS22 sends the remaining signal to the packet
The transmission line 24 is cut and removed until it is identified as b1 and the end delimiter of the signal indicated by the diagonal lines is detected, and the transmission line 24 is returned to the passing state when the end delimiter is detected. Therefore, even if the packet b1 transmitted by the NS22 goes around the transmission path 24 and returns to the transmission source station NS22, it remains without being removed at the same station and is removed at NS23. Similarly NS
Packet c1 sent by 23 is dropped at TS20 and TS20
Then, the polling signal p2 transmitted by is removed in NS21, and thereafter, an abnormal state in which each source station removes a signal different from the packet transmitted by itself will continue.

(Object of the present invention) The object of the present invention is caused by a code error on a transmission line,
Another object of the present invention is to provide a transmission control method capable of promptly performing normal transmission / reception control even when the transmission / reception control of each station becomes abnormal due to a signal that is not removed even after one round of the transmission path.

(Structure of the Invention) According to the present invention, it is composed of one trigger station and a plurality of node stations, these stations are connected in a loop by a transmission line, and the trigger station transmits a polling signal to the transmission line, A transmission control method of a loop network for controlling transmission to the node station, wherein the trigger station comprises a switch provided in series with the transmission line for opening and closing the transmission line, and a round trip propagation of the transmission line. A timer for notifying the elapse of a fixed time determined based on time, the trigger station and the node station,
A first detector for detecting the start of a signal block passing through the transmission path and a second detector for detecting the end of the signal block
And a flip-flop set by the detection output of the first detection unit and reset by the detection output of the second detection unit. In the trigger station and the node station, the flip-flop of When the detection output of the first detection section becomes active when the positive logic output is active, or when the negative logic output of the flip-flop is active, the detection output of the second detection section becomes active. If the trigger station cannot acquire the transmission right, after the signal passing through the transmission path passes,
While the timer is started, the transmission path is kept in a disconnected state by the switch until the lapse of the fixed time is recognized, and the polling signal is transmitted after the timer notifies the lapse of the fixed time. A transmission control method in a loop network is obtained.

(Detailed Description of Configuration) The transmission control method of the loop network according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of the trigger station TS20 according to the present invention. In the figure, the signal on the transmission path 24 is bypassed to the adjacent NS21 via the switch 1 when the TS20 is not transmitting, and the SD detection unit 3 that detects the start delimiter (SD) of the packet and the packet It is input to the ED detection unit 4 that detects the end delimiter (ED) and the idle state detection unit 2 that monitors the state on the transmission line 24 and detects the idle state of the transmission line 24 immediately after passing the ED. When the idle state detector 2 detects the idle state of the transmission line 24 immediately after passing through the ED, the output 2-1 of the same is activated. The delimiter abnormality detection unit 5 monitors each delimiter detection output from the SD detection unit 3 and the ED detection unit 4, and when the occurrence or disappearance of the delimiter due to a code error on the transmission line 24 is detected, the output of the same unit 5- Activate 1 The output 5-1 of the delimiter abnormality detection unit 5 is inverted by the inverter 11 and input to the AND gate 9. That is, the AND gate 9 activates the output of the same section when the transmission line 24 enters the idle state without any abnormality in the detection of the delimiter. The access control unit 6 sets a polling signal in the transmission register 8 in advance, and
Switch 1 when the output of D-gate 9 becomes active
Is connected to the transmission register 8 side to transmit a polling signal. The timer 7 is a timer for notifying a fixed time determined based on the one-cycle delay time of the transmission path 24, and the control of this timer will be described later.

Further, FIG. 2 shows the trigger station TS shown in FIG.
The configuration of the delimiter abnormality detection unit 5 in 20 is shown. The flip-flop 50 in the figure is the SD detection output 3-1 from the SD detection unit 3.
Is set by the ED detection section 4 and reset by the ED detection output 4-1 from the ED detection section 4, and the initial value is preset by the output 7-1 from the timer 7. The initial values at this time are Q = 0 and = 1. Therefore, once the flip-flop 50 is preset, the AND gate 51 operates as the S signal from the SD detector 3.
When the SD detection output is received and the SD detection output is subsequently received after the flip-flop 50 is set, it becomes active. Similarly, the AND gate 52 receives the ED detection output from the ED detection unit 4 and continues after the flip-flop 50 is reset.
When ED detection output is received, it becomes active. Each like this
The output of the AND gate has the same delimiter consecutive
When passing through, it becomes active and detects an error in delimiter detection. The flip-flop 54 is set by the output of the OR gate 53 which takes the logical sum of the AND gates 51 and 52, and notifies the abnormal state of delimiter detection. The output 5-1 is reset by the output 7-1 of the timer 7.

FIG. 3 shows a node station NS21, 22, according to the present invention.
The structure inside 23 is shown. In the figure, the signal on the transmission line 24 is bypassed to the adjacent NS or TS20 via the switch 1 when the NS is not transmitting, and the SD detection unit 3, which detects the start delimiter (SD) of the packet, ED detector 4 for detecting the end delimiter (ED) of the packet and the transmission path
It is input to the idle state detection unit 2 that monitors the state on 24 and detects the idle state of the transmission path 24 immediately after passing through the ED, and the polling signal detection unit 12 that detects the polling signal transmitted from the TS 20. The delimiter abnormality detection unit 5'monitors each delimiter detection output from the SD detection unit 3 and the ED detection unit 4, and when the occurrence or disappearance of the delimiter due to a code error is detected, the output 5'-1 of the unit is activated. To The output 5'-1 of the delimiter abnormality detection unit 5'is inverted by the inverter 11 and input to the AND gate 9. That is, the AND gate 9 activates the output of the same section when the transmission line 24 is in the idle state without any abnormality in the detection of the delimiter. The access control unit 6'sets the signal packet to be transmitted in the transmission register 8 and, after receiving the polling signal,
When the AND gate 9 is activated, the switch 1 is connected to the transmission register 8 side to transmit a packet. The timer 7'is a timer for notifying a fixed time specified based on the round trip delay time of the transmission line 24, and the control of this timer will be described later.

The internal structure of the delimiter abnormality detecting section 5'is shown in FIG.
Although it is the same as the delimiter abnormality detection unit 5 in the TS20, in the case of the above example, the presets and resets of the internal flip-flops 50 and 54 were performed by the output 7-1 of the timer 7 in the TS20. The delimiter abnormality detection unit 5'of each NS
, The output 12-1 from the polling signal detector 12 causes the flip-flop 50 in the delimiter abnormality detector 5 ',
Preset and reset 54.

(Embodiment) An embodiment of the present invention will be described based on the configurations of the trigger station TS20 and the node stations NS21, 22, 23 described above.

FIG. 4 shows a frame structure of a polling signal transmitted by the TS20 and a packet transmitted by each NS. These signals consist of the address of the source station of the signal, the address of the receiving station and the control information of the frame, a header part (HDR) that contains polling information for each NS, and a message part (INFO) that transmits the communication content. Before and after this, a start delimiter (SD) and an end delimiter (ED) indicating the start and end of the signal are added, packetized and transmitted on the transmission 24. The header part has a PL bit indicating that it is a polling signal transmitted by the TS20. That is, PL = 1 indicates the polling signal transmitted by TS20, PL
= 0 indicates a packet transmitted by each NS.

As shown in Fig. 4, the end delimiter (E
D) is added, and all stations send ED and end the transmission. Also, the signal received first from the upstream side of the transmission line 24 after each station finishes transmission is the signal transmitted by itself after the circuit has made one round in the transmission line 24 under normal conditions, and in FIG. , TS20 first sends polling signal p1 that it has sent after the end of transmission.
And NS21, NS22, and NS23 respectively receive the packets a1, b1, and c1 first transmitted by themselves after the end of transmission. Therefore, each station can recognize that the end delimiter (ED) detected first by monitoring the transmission line 24 after the end of transmission is the signal indicating the end of the packet transmitted by itself, and the removal of the packet transmitted by itself is It is performed until the end delimiter (ED) is detected after the end of transmission.

FIG. 5 shows an abnormal state as described with reference to FIG. 8, that is, when an end delimiter (ED) occurs due to a code error in the transmission line 24 as indicated by a black mark in the middle of the packet a1 transmitted by NS21. 7 shows a signal flow on the transmission line 24 when the transmission control according to the present invention is performed. An embodiment will be described below with reference to FIG.

At the start of polling control, the access control unit 6 in the TS20 stores the polling signal p1 in the transmission register 8, activates the output 6-1 and connects the switch 1 to the output terminal of the transmission register 8 to transmit the polling signal p1. To start. After the TS20 starts the polling control as described above, the access control unit 6 detects the idle state of the transmission path 24 immediately after passing the ED and the delimiter abnormality detection in the normal state when the access control unit 6 normally operates. If the output 5-1 of the unit 5 is inactive, the polling signal is repeatedly transmitted.

In the example of FIG. 5, the TS20 removes the polling signal p1 after transmitting the polling signal p1 when the signal goes around the transmission line 24 and returns to the own station. (Note that the signals removed at each station are indicated by *.) Then, the polling signal p1
After detecting the ED, the output 6-1 is made inactive, the switch 1 is connected to the transmission line 24 side, the transmission line 24 is returned to the connected state, and the packets a1, b1, c1 are passed. At this time TS20 is a packet
In order to continuously detect the end delimiter (ED) caused by a code error shown by a black mark in the middle of a1 and the end delimiter (ED) originally added to the packet a1, the delimiter abnormality detection unit 5 in the TS20 detects the delimiter. To detect abnormalities.

When TS20 detects a delimiter and the output 5-1 of the delimiter abnormality detection unit 5 becomes active, the output of the AND gate 9 does not become active and the transmission right even when the idle state detection unit 2 detects the idle state. Cannot be obtained. That is, the TS 20 does not transmit the next polling signal even if the transmission line 24 becomes idle after the packet c1 passes. On the other hand, when the output 5-1 of the delimiter abnormality detection unit 5 is in the active state and the idle state detection unit 2 detects the idle state of the transmission line 24 immediately after the packet c1 passes, the AND gate 10
Output becomes active. At this time, the access control unit 6
When it is detected that the output of the AND gate 10 has become active, the switch 1 is used to hold the transmission line 24 in the disconnected state.
This is because when the end delimiter (ED) occurs due to a code error, the signal that is not removed even if the transmission path 24 makes one round as described in the example of FIG. 8 is removed in the TS20.

Further, the timer 7 is a timer for measuring the time during which the TS 20 holds the disconnection state of the transmission line 24, and is started at the same time when the output of the AND gate 10 becomes active, and is determined based on the round-trip propagation time of the transmission line 24. The elapse of a certain time t1 is measured.
The timer 7 activates its output 7-1 after the elapse of a fixed time t1. The value of this t1 shall be equal to or slightly larger than the round-trip propagation time of the transmission line 24, so that all the signals left on the transmission line 24 within this time t1 are removed. To do.

On the other hand, each NS transmits after receiving the polling signal transmitted by TS20. Access control unit 6'in NS shown in FIG.
Sets a packet to be transmitted to its own NS in the transmission register 8 when there is a transmission request, and when the output of the AND gate 9 becomes active, that is, the output 5'-1 of the delimiter abnormality detection unit 5'is Inactive state and idle state detection unit 2
When the idle state of the transmission line 24 is detected, the transmission right is acquired, the output 6'-1 is activated, the switch 1 is connected to the transmission register 8 side, and the packet is transmitted. The access control unit 6 ′ waits for the passage of the end delimiter (ED) that first passes through the transmission path after finishing the transmission of the packet, and then this ED
Immediately after passing through the switch, the output 6'-1 is deactivated and the switch 1
Is connected to the transmission line 24 side and returned to the passing state. Further, in case the ED is not detected due to a code error in the ED, the access control unit 6 ′ puts the switch 1 into the passing state even if the ED is not detected when a certain time has passed after the end of the packet transmission of the own station. return. Therefore, the access control unit 6'activates the output 6'-2 at the end of packet transmission and sets the transmission line 6'-2.
A timer 7'for notifying the elapse of the fixed time t1 specified based on the 24 round-trip delay time is started. The set value t1 of the timer 7'is the same as the set value of the timer 7 in the TS20. After the transmission is completed, the access control unit 6'starts the timer 7 ', and when the output 7'-1 of the timer 7'becomes active and the elapse of a certain time t1 is known, the switch 1 is unconditionally returned to the passing state.

In FIG. 5, when the NS21 receives the polling signal p1, the boring signal detection unit 12 detects it and the delimiter abnormality detection unit 5'is initialized, and immediately after the polling signal p1 has passed, the transmission right is acquired and the packet a1 is transmitted. To do. After this, transmission line 24
When the same packet returns after one round, the perspective part of the packet a1 is set to the transmission line 24 in order to detect the ED generated in the middle of the packet and complete the removal as described in FIG.
Remain in. At this time, the NS21 continuously receives two EDs as well as the TS20, so that the delimiter abnormality detection unit 5'in its own station
Detects an error in the delimiter.

The access control unit 6'in the NS21 is the delimiter abnormality detection unit 5 '
When the output 5'-1 of 1 is active, the transmission right cannot be acquired. Therefore, NS21 does not transmit a packet after passing packets b1 and c1. Similarly, NS22 also detects an anomaly in the delimiter, so it does not transmit a packet, and NS23 cannot transmit it because TS20 has not newly transmitted a polling signal to transmission line 24.

As described above, the TS20 does not send a polling signal after passing the packet c1 and does not send a polling signal for a time t1.
Keeping 24 disconnected, during this time the packet c1 left unremoved in NS23 passes TS20 and at this time the transmission line 24
Removed from. Then, after the time t1, the TS20 transmits a polling signal p2 to newly start polling control. Each NS detects the polling signal p2 and at the same time initializes the delimiter abnormality detection unit 5'in its own station to resume normal transmission control and transmit packets a2 and b2. The value of t1 used in the above examples is, for example, Patent Application No. Sho 58-0.
It can be measured according to the method described in the specification of 55438 "Communication control method in loop network".

(Effects of the Invention) As described above, a code error on the transmission line 24 causes an end delimiter (ED) in the middle of a packet, which causes an abnormality in the subsequent transmission / reception control and makes a round trip on the transmission line 24. If a signal that cannot be removed is generated even after that, each NS detects that there is an abnormality in ED detection and does not transmit any packets thereafter, while TS20 detects that there is an abnormality in ED detection. Then, after all the signals on the transmission line 24 have passed, the transmission line
24 is kept in a disconnected state until a certain time t1 elapses, signals passing before the certain time t1 elapses, that is, all signals that have not been removed by NS are removed, and a new signal is obtained after a certain time t1 elapses. Since the polling control is started by transmitting the polling signal to the device, it is possible to immediately return to the normal transmission control.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration inside a trigger station TS20 which constitutes a loop network, FIG. 2 is a diagram showing a configuration inside a node station NS21, 22, 23 which constitutes a loop network, and FIG. 3 is a diagram showing inside each station. FIG. 4 is a diagram showing a configuration inside the delimiter abnormality detection unit, FIG. 4 is a diagram showing a frame configuration of a signal transmitted by each station, FIG. 5, and FIG.
FIG. 8 and FIG. 8 show signal flows, and FIG. 6 is a diagram showing a configuration of a loop network. In the figure, 1 is a switch, 2 is an idle state detection unit,
3 is an SD detection unit, 4 is an ED detection unit, 5 and 5'is a delimiter abnormality detection unit 5, 6 and 6'is an access control unit, 7 and 7'is a timer, 8 is a transmission register, 9 and 10 are AND gates. , 11 is an inverter, 24 is a transmission line, 20 is a trigger station (TS), 21, 22 and 23 are node stations (N
S) is shown.

Claims (1)

[Claims] 1. A trigger station and a plurality of node stations, each station being connected in a loop by a transmission line, said trigger station transmitting a polling signal to said transmission line, to said node station. A transmission control method of a loop network for performing transmission control, wherein the trigger station is determined based on a switch provided in series with the transmission path for opening and closing the transmission path, and a round trip time of the transmission path. And a timer for notifying the passage of a fixed time, the trigger station and the node station,
A first detector for detecting the start of a signal block passing through the transmission path and a second detector for detecting the end of the signal block
And a flip-flop set by the detection output of the first detection unit and reset by the detection output of the second detection unit. In the trigger station and the node station, the flip-flop of When the detection output of the first detection section becomes active when the positive logic output is active, or when the negative logic output of the flip-flop is active, the detection output of the second detection section becomes active. If the trigger station cannot acquire the transmission right, after the signal passing through the transmission path passes,
While the timer is started, the transmission path is kept in a disconnected state by the switch until the lapse of the fixed time is recognized, and the polling signal is transmitted after the timer notifies the lapse of the fixed time. Transmission control method in loop network.