JPH0550905B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a priority control system for loop networks;
In particular, it relates to a priority control method for loop networks for real-time communication.

[Prior art and its problems]

As a loop network that integrates real-time communication such as voice and video and standby communication such as data and still images, the 1983 IEICE Exchange Study Group SE83
-107 “A Study of High-Speed Synchronous Packet Loops” This network and priority control for providing real-time communication services will be explained. FIG. 4 is a diagram showing an example of the configuration of a general loop network, and FIG. 5 is a diagram showing the operation timing in an example of the conventional priority control method of the loop network.

In Figure 4, the loop network includes trigger station 5, node stations 1, 2,
3 and 4, which are connected by a loop-shaped transmission line 6. As shown in FIG. 5a, the trigger station 5 sends out a trigger signal TG at a constant period T to poll the communication with the highest priority, that is, the immediate communication. In FIG. 5a, node stations 1 and 3 have already acquired the highest priority transmission right, and their respective packet signals PKT1 and PKT3 are sent out. In this network, a node station that wants to newly perform communication with the highest priority first performs transmission with the second priority so as not to interfere with the transmission of a node station that is already communicating with the highest priority. This second priority communication is polled by the polling signal PL after all the highest priority communication is completed. Figure 5a
2 shows a state in which the node stations 2 and 4 transmit their respective packet signals PKT2 and PKT4 at the second priority in order to newly acquire the highest priority. Based on the fact that the node stations 2 and 4 were able to transmit, from the next cycle onwards, they transmit with the highest priority as shown in FIG. 5b. trigger signal
Based on the TG, the node stations 1, . . . , 4 send out packet signals PKT1, .about., PKT4, respectively. In this case, node station 2 is polled before node station 3, but the sum of the time widths of PKT1, ~, PKT4 is guaranteed to be shorter than cycle T in the previous cycle, as shown in Figure 5a. Therefore, the node stations that have already acquired the right to transmit with the highest priority, in this case node stations 1 and 3, will not be unable to transmit. In this way, such a network has the feature that each node station can autonomously control congestion, but the node station that transmits with the second priority will transmit with the highest priority in the next cycle. It is necessary to perform control to increase the priority for transmission. Therefore, if the period T is short, there is a problem in that the control for increasing the priority must be performed at high speed.

[Means for resolving problems]

In the loop network priority control method of the present invention, a trigger station and a plurality of node stations are connected in a loop, and the trigger station sends out a trigger signal to poll the communication with the highest priority at regular intervals, giving the highest priority. When the second priority communication is completed and the next transmission right is acquired, a polling signal is sent to poll the second priority communication.After that, every time the transmission right is acquired within the above period, a polling signal is sent out to poll the second priority communication. In a loop network that sequentially polls, two types of trigger signals, first and second, are provided, and the trigger station sends out the first trigger signal once in a plurality of cycles and sends out the second trigger signal in the remaining cycles. However, the node station that wants to perform new communication with the highest priority will attempt transmission only during the cycle started by the first trigger signal, and when the second priority polling is successful, the next one will be attempted. Communication is performed with the highest priority from any cycle up to and including the cycle that starts with the first trigger signal, and the highest priority is newly acquired in the cycle that starts with the second trigger signal. The trial communication of the desired node station is prohibited, and the trigger station is configured to transmit the first trigger signal only at a cycle that is an integral multiple of the predetermined cycle.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention, in which a indicates a trigger station and b indicates a node station.

In FIG. 1a, the trigger station is comprised of a register 54 and a switch 53 connected in series to the transmission line 6, a control circuit 51, a timer 52, a reception buffer 55, and a transmission buffer 56. On the other hand, as shown in FIG. 1b, the node station includes a register 14, a switch 13, a control circuit 11,
Timer 12, reception buffer 15, transmission buffer 1
6, a detection circuit 17, a priority circuit 18, and an OR gate 19.

The control circuit 51 of the trigger station is a timer 5.
When the start of the cycle T is notified from 2, the switch 53
Connect to the transmission buffer 56 side and connect it to the transmission buffer 56 side.
Send out the signal within.

Figure 2 is a diagram showing an example of the configuration of a signal frame used in this embodiment, and the signal frame has a start delimiter SD
and an end delimiter ED, and consists of two types of trigger signals and bits TG1, TG2, and PL indicating that they are a polling signal, a header HDR such as address information, and an information field INFO. Bit TG1=1 is the period N・N times the period T.
shows the trigger signal TG1 sent out at T, bit
TG2=1 indicates the trigger signal TG2 sent out at other cycles T, and bit PL=1 indicates the polling signal PL sent out within the cycle. The packet signal sent from each node station is TG1.
Identified by =TG2=PL=0. The timer 52 shown in FIG. 1A notifies the control circuit 51 of the start of the period T, and if it is the start of the multi-period N·T, sets only the output 52-1 to 1, bit TG1=
The trigger signal TG1 of 1 is sent out, and in other cycles, only the output 52-2 is set to 1, and bit TG2=
One trigger signal TG2 is sent out. In addition, if the transmission right is acquired within the period after transmitting the trigger signal TG1 or TG2, the output 52-3 is output every time.
polling signal PL with bit PL = 1.
is sent from the transmission buffer 56.

Next, FIG. 3 is a diagram showing the operation timing in this embodiment, and FIG.
Indicates PL. The trigger signal TG1 is sent out in the first period T of the multi-period N·T. Acquisition control of the highest priority is permitted only in this cycle. That is, a node station that wishes to transmit with the highest priority transmits the packet signal PKT with the second priority given by the next polling signal. Figure a
In this case, node stations 1 and 3 have already acquired the highest priority and send out packet signals PKT1 and PKT3, and node stations 2 and 4 transmit packet signals PKT2 and PKT4 to acquire the highest priority, respectively.
This shows a situation in which the data is sent with the second priority. In other periods T starting with the trigger signal TG2, control for obtaining the highest priority is prohibited. Therefore, even if a packet signal can be transmitted with the second priority, transmission with the highest priority is not permitted. That is, no node station will newly acquire the highest priority until the next trigger signal TG1 is supplied. Therefore, unlike the conventional example, the node stations 2 and 4 that have transmitted the packet signals PKT2 and PKT4 with the second priority and obtained the highest priority do not need to transmit with the highest priority in the next cycle. FIG. 3b shows a situation in which node station 4 starts transmitting at the highest priority from the third cycle, and node station 2 starts transmitting at the highest priority from the first cycle of the next multi-cycle.

Next, the operation of the node station shown in FIG. 1b will be explained. The detection circuit 17 monitors the bits TG1, TG2 and PL of the passing signal frame, and when detecting the bit TG=1, that is, the trigger signal TG1, initializes the timer 12 with the control signal 17-1. This causes the control circuit 11 to know the start of the multi-period N·T. Furthermore, when bit TG2=1 is detected, the control signal 17-2 causes the next period T
The control circuit 11 is notified of the start of the process via the timer 12. On the other hand, the priority circuit 18 is initialized by the control signals 17-1 and 17-2 via the OR gate 19, and indicates the highest priority, and changes the priority to 1 every time it detects bit PL=1, that is, the polling signal PL. Lower it one by one. When the timer 12 indicates the first cycle of the multi-cycle N·T and the priority circuit 18 indicates the second priority, the control circuit 11 of the node station that wants to perform communication with the highest priority transmits data in the transmission buffer 16. Once the packet signal to be transmitted is installed on the switch 13 and access rights to the transmission path 6 are obtained
is connected to the transmission buffer 16 side, and sends out a packet signal. If the transmission is successful, the control circuit 11
raises the priority to be sent by one and sets it to the highest priority before the next multi cycle. Furthermore, if the transmission is not possible, the highest priority cannot be obtained. Further retries are made at the start of the next multi-period.

〔Effect of the invention〕

As explained above, in the present invention, even if the transmission is performed at the second priority in the first cycle of a multi-cycle and the highest priority is acquired, the transmission from the second priority is performed by the start of the next multi-cycle. Since the priority level can be increased by one level and the highest priority level can be set as the priority level of the packet signal to be transmitted, priority control does not need to be performed at a high speed and can be performed at a lower speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a diagram showing an example of the structure of a signal frame used in this embodiment, FIG. 3 is a diagram showing operation timing in this embodiment, and FIG. 4 is a diagram showing an example of the structure of a general loop network. FIG. 5 is a diagram showing the operation timing of an example of a conventional loop network priority control system. 1, 2, 3, 4...node station, 5...
...Trigger station, 6...Transmission line, 11,5
1... Control circuit, 12, 52... Timer, 13,
53...Switch, 14, 54...Register, 1
5, 55... Reception buffer, 16, 56... Transmission buffer, 17... Detection circuit, 18... Priority circuit, 19... OR gate.

Claims (1)

[Scope of Claims] 1. A trigger station and a plurality of node stations are connected in a loop, and the trigger station sends out a trigger signal to poll the highest priority communication at a constant cycle, and the highest priority communication is terminated. Then, when it acquires the transmission right, it sends out a polling signal to poll the second priority communication.After that, every time it acquires the transmission right within the above period, it sends out a polling signal and polls the lower priority communications in order. In the workpiece, two types of trigger signals, first and second, are provided, and the trigger station sends out the first trigger signal once in a plurality of cycles, and sends out the second trigger signal in the remaining cycles. A node station with which a new communication is to be performed will attempt transmission during polling of the second priority only in the cycle started by the first trigger signal, and if transmission is successful, the next first trigger signal will be sent. The node station that communicates with the highest priority from any cycle up to and including the cycle that starts with the signal, and that wants to newly acquire the highest priority in the cycle that starts with the second trigger signal. A loop network priority control method characterized by prohibiting trial communications. 2. The loop network priority control method according to claim 1, wherein the trigger station constantly sends out the first trigger signal at a cycle that is an integral multiple of the cycle. priority control method.