JPH0550177B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication initiation method in a loop network in which a clock station sends a synchronization signal to a loop at regular intervals.

A loop network in which a clock station sends a synchronizing signal to a loop at regular intervals is disclosed in Patent Application No. 1982-212364. Communication in such a network will be explained using FIGS. 1 and 2. The loop network in FIG. 1 consists of a clock station 7 and node stations 1, 2, 3, 4, 5, and 6, each connected by a loop 8. Figure 2a,
b and c indicate the output signals of clock station 7 and node stations 1 and 6, respectively. The clock station 7 receives a synchronizing signal F at a constant period _T0 .
Send out. The node station 1 sends out a signal block _B1 following the synchronization signal F, as shown in FIG. 2b. As shown in FIG. 2c, node station 6 also sends out signal block B 6 following the synchronization signal F supplied from upstream of loop 8 and signal blocks B ₁ , B ₃ , B ₄ of node stations 1, 3, and ₄ . do. Since the clock station ₇ always sends out the synchronization signal F in the period T0, each node station finishes sending out the signal block before the timer operating in synchronization therewith indicates the elapse of the period _T0 . For example, node station 6 is
As shown in Figure c, the time indicated by the timer (T ₀ −△)
Sending ends at . However, if the time Δ is smaller than the time τ ₁ for the signal to go around the loop 8, the following problem occurs. Now the signal block
Assume that the destination of _B6 is node station 1. As _shown in FIG.
At the same time, the continuously supplied signal block is passed through as is. Note that the time position of the removed synchronization signal is indicated by a broken line. However, the period
When T ₀ has elapsed, the synchronization signal F is sent out regardless of the presence or absence of a signal on the loop. In this case, since Δ<τ _{1 ,} the synchronizing signal F is sent out before the entire signal block B ₆ has elapsed.
is interfered with by the synchronizing signal F and is output as a signal block B ₆ '. Therefore, as shown in FIG. 2b, the node station 1 is supplied with the signal block B ₆ ' and cannot communicate properly.

In this way, if each node station does not know the time it takes for a signal to go around the loop, even if its own timer finishes transmitting before the period _T0 has elapsed, it will be interfered with by the synchronization signal F and will spoil smooth communication services. Sometimes.

An object of the present invention is to prevent the signal block of inter-node communication from being interfered with by the synchronization signal F.

According to the present invention, a loop network is constructed of one clock station and a plurality of node stations, and the clock station sends out a synchronization signal to the loop at a constant period longer than the signal propagation time for one round of the loop, and the synchronization signal circulates around the loop network. In the communication control system in the work, the node station operates a timer in synchronization with the passage of the synchronization signal, and acquires the transmission right by detecting an idle state on the loop after the synchronization signal passes. When the control is started and the transmission right is acquired, a signal block for loop propagation time detection is transmitted and received to detect the loop propagation time, and then the transmission right acquisition control is started, and when the transmission right is acquired, the signal block is transmitted and received for detecting the loop propagation time. If a block is transmitted and the timer outputs a time obtained by subtracting the loop propagation time from the period or a certain margin time from the time during the transmission right acquisition control or at the time of the transmission, the transmission right is A communication control system in a loop network characterized by acquisition control or stopping the transmission is obtained.

Next, the present invention will be explained in detail with reference to the drawings. A first embodiment of the present invention will be explained using the loop network shown in FIG. 1 and the timing diagram shown in FIG. 3. When each node station acquires the transmission right within a time TL shorter than the period T ₀ , for example, TL=T ₀ /2, it transmits a signal block TM for detecting the propagation signal τ ₁ of the loop 8, and then transmits the signal block TM. Communication with other node stations is not performed until transmission and reception of the node station is completed. For example, when _the node station 6 is newly accommodated in the loop network, the node station 6 controls acquisition of the transmission right, but as shown in _FIG . If acquired, the signal block TM will not be sent.
When the transmission right is acquired at time T ₂ (T ₂ <TL) within a certain period, the signal block TM is generated as shown in Figure 3.
Send out. Since the time TL is smaller than the period _T0 , the signal block TM goes around the loop 8 without being interfered with by the synchronization signal F. In this way, each node station knows the time τ ₁ to go around the loop 8 of the signal block TM. From now on, if the transmission of a signal block addressed to another node station is completed before the timer reaches (T ₀ -τ ₁ ), this signal block will not be interfered with by the synchronization signal.

FIG. 4 shows the loop interface section of each node station used in this embodiment, and FIG. 5 shows the configuration of the signal block. The loop interface in FIG. 4, the input terminal 10 connected to the loop 8,
It has an output terminal 11, a switch 12, a buffer 13, a transmission buffer 14, a control circuit 15,
18, a synchronization signal detection circuit 16, and a timer 17. FIG. 5a shows the structure of the synchronization signal F, which is composed of a preamble PR, a start flag SF, a synchronization bit SY, and an end flag EF. Bit SY=1 indicates a synchronization signal. Fifth
Figure b shows the signal block TM and the destination address
DA and caller address SA are added. Fifth
Figure c shows a signal block for inter-node communication, to which an information field INFO is added. Note that the signal blocks in FIGS. 5b and 5c have bit SY=0.

The timer 17 operates in synchronization with the synchronizing signal F of bit SY=1 shown in FIG.
18. The control circuit 15 receives the control signal 19
When initialized by
The signal block TM of FIG. 5b is stored in . Note that the destination address DA of this signal block TM is
Set the sender address SA to your own address.
The control circuit 15 monitors the signal block from the upstream of the loop 8 supplied from the buffer 13, and when it detects the end flag EF, turns on the switch 12 to the transmission buffer 14 side and starts transmitting from the preamble PR. When it detects that a signal block preamble is supplied from upstream during the transmission of the preamble PR, the switch 12 is turned on to the loop 8 side and transmission is stopped. Then, waiting for the end flag EF of this signal block to pass, the series of controls is repeated, and the preamble PR of the signal block TM is
If no preamble for another signal block is supplied from the buffer 13 during transmission of the signal block TM, it acquires the transmission right and transmits the remaining part of the signal block TM. The control circuit 15 performs the above-described transmission control while the output of the timer 17 is smaller than TL, but when it becomes larger than TL, it stops this control and waits for the next synchronization signal F to pass before restarting. If the transmission right is acquired before the timer 17 reaches TL, the signal block TM is sent out, and the time τ ₁ required for this signal block TM to go around the loop 8 and be received is measured. This time τ ₁
is derived from the difference in the output value of the timer 17 when the signal block TM is sent and received. The control circuit 15 notifies the control circuit 18 of the measured time τ ₁ . Note that the switch 12 is returned to the loop 8 side at the same time as the reception ends. Even when the control circuit 18 is initialized by the control signal 19, it does not start up immediately, but waits for notification of time τ ₁ from the control circuit 15 before starting up. When a transmission request occurs, the control circuit 18 stores the signal block shown in FIG. However, the transmission control in the control circuit 18 is performed only until the output of the timer 17 reaches (T ₀ -τ ₁ ). Also, the timer (T ₀ −
τ ₁ ), the transmission ends.

A second embodiment of the present invention will be described using FIGS. 1, 6, and 7. FIG. 6 shows the signals on loop 8, and FIG. 7 shows the signal blocks used in this embodiment. This signal block has priority bits P ₀ ,
P ₁ is added, and Fig. 7 a, b, and c show the synchronization signal, trigger signal, and signal block, respectively.
TM indicates a signal block for inter-node communication. Priority control in this embodiment will be briefly explained. Clock station 7 sends out a synchronization signal F with period _T0 . This synchronization signal F
is bit SY=1 and P ₀ =P ₁ =0 in order to trigger a synchronization signal for communication with the highest priority, such as voice communication. When the clock station 7 acquires the transmission right within the period T ₀ using exactly the same control as the transmission right acquisition control of the node station shown in the first embodiment, SY=
0, P ₀ = 0, P ₁ = 1, and then a high priority communication is activated.
Thereafter, a trigger signal PR2 with priorities P ₀ =1 and P ₁ =0 and a trigger signal P ₃ with priorities P ₀ =P ₁ =1 are sent out in the same manner. Each node station monitors the priority bits P ₀ and P ₁ of passing signal blocks including synchronization signals and trigger signals, and determines whether the priority level of the signal lock to be transmitted by itself is (P ₀ ,
If the priority level is equal to or higher than the priority level given by P ₁ ), this signal block is sent out. Note that the priority bits P ₀ and P ₁ of this signal block are copied from the bits P ₀ and P ₁ of the signal block that passed immediately before.

In the above priority control, the second priority (P ₀ =0,
(corresponding to P ₁ =1) is given. Therefore, for example, when the node station 5 wants to send out a signal block TM, a trigger signal is sent as shown in FIG.
After passing through RR1, it acquires the transmission right and transmits. Since this transmission is performed prior to the communication triggered by the trigger signals PR2 and PR3, the node station 5 promptly adjusts the propagation delay time τ ₁ of the loop 8.
You can know. Knowing the time τ ₁ allows inter-node communication to be performed, so that, for example, a signal block B ₅ can be sent out based on the trigger signal PR 3 as shown in FIG. In addition, the fifth
In the figure, signal blocks B ₁ , B ₂ , B ₆ and B ₃ represent signal blocks sent out from node stations 1, 2, 6 and 3, respectively.

The operation of the loop interface section of each node station in this embodiment will be explained using FIG. Control circuit 1 activated by control signal 19
5 starts the same transmission right acquisition control as in the first embodiment when it detects bits P ₀ = 0, P ₁ = 1 of the signal block supplied from the buffer 13, and when the transmission right is acquired, the buffer 14 The stored signal block TM is sent to the output terminal 11 via the switch 12. When the control circuit 15 measures the time τ ₁ , it notifies the control circuit 18 . The control circuit 18 is activated based on this notification. Thereafter, inter-node communication is performed in the same manner as in the first embodiment.

In the first and second embodiments, after the timer ₁₇ outputs (T ₀ - τ ₁ ), the communication is controlled to end. ₀ −ατ ₁ −τ ₀ ), the communication may be terminated.

In this way, according to the invention, the loop delay time can be known in advance of inter-node communication, and based on this, it is possible to prevent signal blocks in inter-node communication from being interfered with by synchronization signals. It is possible to provide smooth communication services.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a nop network, and FIG. 2 is a timing diagram for a conventional loop network. 3 and 6 are timing diagrams in the first and second embodiments of the present invention, and FIGS. 5 and 7 are diagrams showing the configuration of signal blocks used in the first and second embodiments. FIG. 4 is a block diagram showing the loop interface section of the node station used in the first and second embodiments. In Figures 1 and 4, 1, 2, 3, 4,
5 and 6 are node stations, 7 is a clock station, 8 is a loop, 13 and 14 are buffers,
15 and 18 are control circuits, 16 is a synchronization signal detection circuit, and 17 is a timer.

Claims (1)

[Claims] 1. A communication control system in a loop network consisting of one clock station and a plurality of node stations, in which the clock station sends out a synchronization signal to the loop at a constant period longer than the signal propagation time for one loop, and the synchronization signal circulates. wherein the node station operates a timer in synchronization with the passage of the synchronization signal, and starts transmission right acquisition control to acquire the transmission right by detecting an idle state on the loop after the passage of the synchronization signal; When the transmission right is acquired, the loop propagation time is detected by transmitting and receiving a signal block for loop propagation time detection, and then the transmission right acquisition control is started, and when the transmission right is acquired, the signal block is transmitted, When the timer outputs a time obtained by subtracting the loop propagation time from the cycle or a time obtained by subtracting a certain margin time from the time during the transmission right acquisition control or the transmission, the transmission right acquisition control or the transmission A communication control method in a loop network characterized by stopping.