JPH0550175B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a priority control system in a loop network in which a synchronization signal is supplied to a loop at regular intervals.

With the recent advances in LSI technology and digital technology, distributed control networks, in which switching functions are distributed to each node station, are attracting attention. Furthermore, studies are underway on network architectures that integrate synchronous communications such as voice and asynchronous communications such as data. Among such networks, there is a ``loop type communication system'' described in Patent Application No. 1982-212364, which has a loop-like configuration and a synchronization signal is supplied to the loop at a constant cycle. In this conventional example, integrated communication is provided by providing two levels of priority: reserved communication for voice communication etc. and non-reserved communication for asynchronous communication, and reserved communication is supplied from the clock station. Due to the synchronization signal, non-reservation communications are activated by a reservation end signal also provided by the clock station. However, activating various communications by signals from the clock station is insufficient from the viewpoint of network control decentralization.

An object of the present invention is to provide multi-level priority communication with stronger distributed control and higher reliability.

According to the present invention, in a priority control method in a loop network in which a clock station and a plurality of node stations are connected by a loop and a signal is transmitted in one direction of the loop, a plurality of The clock station sends a synchronization signal to the loop at a constant period longer than the signal propagation time for one round of the loop, and when the synchronization signal is received after going around the loop, the clock station transmits the synchronization signal to the loop. When an idle state on the loop is detected, the transmission right is acquired, and each time the transmission right is acquired, a priority signal having priority information indicating the priority is sent in the order of the priority, and the removing the priority signal from the loop when the priority signal has been received around the loop; It compares the priority information of the signal block it has acquired with the priority of the signal block it wants to transmit, and if the priorities are the same or higher, it starts transmission right acquisition control, and if it acquires the transmission right, it uses the priority information as its own. A priority control system in a loop network is obtained, which is characterized in that signals are sent out in addition to signal blocks.

Next, the present invention will be explained in detail with reference to the drawings. Figure 1 shows the configuration of the loop network.
FIG. 2 shows the configuration of a signal block used in an embodiment of the present invention, and FIG. 3 shows signals on a loop in this embodiment. The loop network of FIG. 1 is comprised of node stations 1, 2, 3, 4, 5, 6 and a clock station 7, interconnected by a loop 8. FIG. 2a shows the synchronization signal and trigger signal sent by the clock station 7, including the preamble PR, start flag SF,
It consists of a synchronization bit SY, priority bits P ₀ and P ₁ and an end flag EF. Figure b
indicates a signal block for communication between node stations.
DA, caller address SA and information field
INFO has been added. FIG. 3 shows the signal on loop 8 at the output of node station 4. The clock station 7 sends out a synchronizing signal F shown in FIG. _2a at a constant period T0. In the synchronization signal F, bit SY is set to 1, and bits P ₀ =P ₁ are set to 0 in order to start communication with the highest priority level, 0. This communication includes, for example, voice communication. There is such a synchronous communication. When the synchronization signal F goes around the loop 8, the clock station 7 removes it, starts transmission right acquisition control, and once the transmission right is acquired, it starts communication with the next highest priority level 1, for example, for call setup. In order to start communication, a trigger signal PR1 with bit SY=0, bit P ₀ =0, and P ₁ =1 is sent out. Similarly, every time the transmission right is acquired within the period T ₀ , the trigger signal PR2 (SY=0, P ₀ =
1, P ₁ =0), and PR3 (SY=0, P ₀ =P ₁ =1). The transmission right acquisition control will be explained later.

The present invention will be specifically explained using FIG. As shown in the figure, following the synchronization signal F, the signal block _B2 of the node station 2 with priority level 0 passes, and then the trigger signal PP1 passes. At this time, signal block B ₂ is bit P ₀
=P ₁ =0. Each node station constantly monitors the priority level of the signal blocks passing through it. When the clock station 7 detects the end of the priority level 0 communication, it sends out a trigger signal PR1. Now, after the trigger signal PR1 passes through the node station 4 (arrow A in Fig. 3),
Assume that a priority level 1 transmission request occurs. At this time, signal block B1 with priority 1 is passing through, and node station 4 compares the priority level given by signal block B1 with the priority level of its own transmission request, and since both levels are the same, it performs transmission right acquisition control. Start. When the end flag EF of the signal block B1 is detected, the preamble PR is sent to the loop 8. At the same time, the signal supplied from upstream is monitored.
In this case, since the preable PR of signal block B3 is supplied, transmission is stopped and signal block B3 is passed. Signal block B3 also has bits P ₀ = 0, P ₁
=1, which is the same as the priority level of the transmission request of the node station 4, so when the node station 4 detects the end flag EF of the signal block B3, it starts transmission right acquisition control again. in this case,
Since no preamble is supplied from the upstream side of the loop 8 while the preamble PR is being transmitted, it acquires the transmission right and transmits a signal block B41 whose structure is shown in FIG. 2b. The priority level of signal block B41 is set to the same bits P ₀ =0 and P ₁ =1 as the signal block B3 that passed immediately before. In this way, the priority level setting function is not concentrated on the signal PR1 but is distributed over all signal blocks, so higher reliability can be obtained. For example, even if bits P ₀ and P ₁ of the trigger signal PR1 cause a code error during loop propagation, if the bits of the signal block B ₃ are correct, the priority level of the loop is maintained correctly.

Next, suppose that a request for transmission of priority level 2 occurs in node station 4 while signal block B6 from node station 6 is passing through (indicated by arrow B in FIG. 3). At this time, loop 8
The priority level is 2, which is the same as the transmission request, so after detecting the end flag EF of the signal block B6, the node station 4 starts transmission right acquisition control. However, the trigger signal continues from upstream.
Since PR3 is supplied, transmission right acquisition control is stopped. Since the priority level 3 (P ₀ =P ₁ =1) given by the trigger signal PR3 is lower than the priority level 2 of this transmission request, transmission right acquisition control is restarted after the trigger signal PR3 passes. In this case, since no signal block is supplied from upstream, the node station 4 acquires the transmission right and sends out the signal block B42. However, although the priority level of this transmission request is 2, the signal block B42 is transmitted with bits P ₀ =1, P ₁ =1, and the priority level set to 3. This is because node stations downstream from node station 4 are given priority level 3.

Next, the configuration of the loop interface section of each node station and clock station 7 is shown in FIGS. 4 and 5, and its operation will be explained.

The node station has an input terminal 10 and an output terminal 11 connected to a loop 8, and when not transmitting, a signal block from upstream supplied from the input terminal 10 is supplied to the output terminal 11 via a buffer 12 and a switch 30. and sent to the downstream node station of loop 8. Signal detection circuit 14
detects the preamble PR, start flag SF, bit SY, priority bits _P0 , _P1 , end flag EF, destination address DA, and caller address SA of the signal block supplied from buffer 12,
When bit SY=1 is detected, the timer 17 is reset and other detection results are sent to the control circuit 13.
supply to. The control circuit 13
A priority level PRI is supplied to the priority comparison circuit 16 based on P ₀ and P ₁ . When a certain transmission request occurs, the control circuit 13 stores a signal block in the transmission buffer 18. The priority comparison circuit 16 compares the priority level of the signal block in the transmission buffer 18 with the priority level PRI supplied from the control circuit 13, and determines whether the priority level of this signal block is higher or both levels are the same. If so, the control circuit 13 is notified accordingly. Priority comparison circuit 1
6 performs this control every time the priority level PRI is updated. Based on this notification and when the signal detection circuit 14 detects the end flag EF, the control circuit 13 activates the switch 30 using a control signal 131.
Send the buffer to the 18 side and turn on the preamble
Start sending PR. When the signal detection circuit 14 detects the preamble PR during this transmission, the control circuit 13 returns the switch 30 to the loop 8 side and stops transmission, waits for the end flag EF to be detected, and then performs the above transmission. Resume rights acquisition control. If the signal detection circuit 14 does not detect a preamble PR while transmitting its own preamble PR, it acquires the transmission right, and the control circuit 13 transmits the control signal 132.
This controls the priority comparison circuit 16 to write the priority level PRI into the priority bit of the signal block in the transmission buffer 18. A signal block with priority level PRI is therefore applied to the output terminal. The control circuit 13 waits for the sending signal detection circuit 14 of this signal block to detect the end flag EF and returns the switch 30 to the loop 8 side. Therefore, all signal blocks are removed from the loop 8 after completing one round at the originating node station. When the timer 17 notifies the passage of the period T ₀ or the passage of a period of time minus a certain margin time from the period T ₀ , the control circuit 13 stops the transmission right acquisition control,
Or, if it is in progress, end the transmission and timer 17
Wait until SY is reset by SY=1. In addition,
When the signal detection circuit 14 detects the same destination address DA as its own address, the reception buffer 15
and receives the supplied signal block.

The clock station in FIG. 5 has an input terminal 20 and an output terminal 21 connected to a loop 8, as well as a buffer 22, a signal detection circuit 24, a control circuit 23, a priority setting circuit 26, a timer 27, and a transmission buffer 28. It consists of

The timer 27 sets bit SY of the signal block in the transmission buffer 28 to 1 every cycle T ₀ and supplies this time information to the control circuit 24. Based on this time information, the control circuit 24 sets the priority level 0 to the priority setting circuit 26.
(P ₀ =P ₁ =0) is controlled to be written into the signal block, and the control signal 231 turns on the switch 31 to the transmission buffer 28 side to send out the signal block in the transmission buffer 28, that is, the synchronization signal F. This synchronizing signal F is removed from the loop 8 by the same method as in the node station of FIG. 4 after going around the loop 8. The clock station 7 starts transmission right acquisition control at the same time as the removal, and blocks the signal block in the transmission buffer 28, that is, the preamble PR of the trigger signal PR1.
Send out. If the signal detection circuit 24 does not detect the preamble PR during transmission, it acquires the transmission right and transmits the trigger signal PR1. Trigger signal PR1 bit
P ₀ and P ₁ are set to P ₀ =0 and P ₁ =1 by the priority setting circuit 26 based on the control signal 232 of the control circuit 23 prior to this sending.
If the signal detection circuit 24 detects the preamble PR while transmitting the preamble PR, the control circuit 23
returns the switch 31 to the loop 8 side, and resumes transmission right acquisition control after detecting the end flag EF of the passing signal block. Note that bit SY of the trigger signal PR1 is not set by the timer 27, so SY=0. The trigger signal PR1 is removed after passing through the loop 8. Similarly, the trigger signal is
Send and remove PR2 and PR3.

As described above, according to the present invention, all signal blocks sent to the loop have priority level information, so high reliability can be obtained, and when the priority level is set to multiple levels, the transmission of the priority level on the loop is Even if a request occurs, it can be transmitted while maintaining the priority level on the loop.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a loop network according to the present invention, FIG. 2 is a diagram showing the configuration of a signal block used in an embodiment of the present invention, FIG. 3 is a timing diagram in this embodiment, and FIG. FIG. 5 is a block diagram showing the configuration of the node station and clock station used in this embodiment. In the figure, 1, 2, 3, 4, 5, and 6 are node stations, 7 is a clock station, 8 is a loop, 12, 15, 18, 22, and 28 are buffers, and 14 and 24 are signal detection circuits 13 and 23. The control circuit includes a priority comparison circuit 16, a priority setting circuit 26, and timers 17 and 27.

Claims (1)

[Scope of Claims] 1. A priority control method in a loop network in which a clock station and a plurality of node stations are connected by a loop and a signal is transmitted in one direction of the loop, wherein a plurality of node stations are connected to each other in communication in the loop network. The clock station sends a synchronization signal to the loop at a constant period longer than the signal propagation time for one round of the loop, and when the synchronization signal is received after going around the loop, the clock station transmits the synchronization signal to the loop. removed from the loop, and upon detecting an idle state on the loop, acquires a transmission right, and each time it acquires the transmission right, sends a priority signal having priority information indicating the priority in the order of the highest priority, removing the priority signal from the loop when the priority signal is received after passing through the loop; and the node station transmits the priority information or the other node station after passing the priority signal. The priority information of the received signal block and the priority of the signal block to be transmitted are compared, and if the priorities are the same or higher, transmission right acquisition control is started, and if the transmission right is acquired, the priority information is automatically transmitted. A priority control method in a loop network characterized by transmitting a signal in addition to a signal block.