JPS6285531A - Control system for priority of loop network - Google Patents

Abstract

PURPOSE:To control priority at a low speed by performing the transmission for acquisition of the transmission right of the highest priority only in the cycle where a trigger station transmits the 1st trigger signal and performing no trial in the cycle where the 2nd trigger signal is transmitted. CONSTITUTION:A detecting circuit 17 of a node station monitors the bit of a passing signal frame and initializes a timer 12 by a control signal 17-1 when a trigger signal is detected. Thus a control circuit 11 knows the start of a multiple cycle. Here the circuit 11 of the node station where the communication is desired with the highest priority sets a packet signal to be sent into a transmission buffer 16 when the timer 12 shows the first cycle of the multiple cycle and also a priority circuit 18 shows the second priority. Then a switch 13 is connected to the buffer 16 when the access right is acquired to a transmission line 6 and the packet signal is transmitted. When this transmission is successful, the circuit 11 rises the priority to be sent by a rank before the next multiple cycle is set. Thus the highest priority is set.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a priority control method for a loop network, particularly to a priority control method for a loop network for real-time communication.

[Prior art and its problems]

Established in 1937 as a loop network that integrates real-time communications such as audio and video, and time-consuming communications such as data and still images.
There is one described in ``Study of High-Speed Synchronous Packet Loose 5E8B-107R'' by the Institute of Electronics and Communication Engineers Exchange Study Group 5E8B-107R. This network and priority control for providing real-time communication services will be explained. FIG. 4 is a diagram showing an example of the -it configuration of a general loop network, and FIG. 5 is a diagram showing operation timing in an example of a conventional loop network priority control method.

In FIG. 4, the loop network consists of a trigger station 5 and node stations 1, 2, and 3.degree. 4, which are connected by a loop-shaped transmission line 6. The trigger station 5 operates at a constant period T as shown in FIG. 5(a).
The trigger signal TG is sent out to poll the communication with the highest priority, that is, the immediate communication. In FIG. 5(a), node station 1.3 has already acquired the highest priority transmission right, and its respective bucket 1 signals PKTI, PKT3 are sent out. In this network, a node station that newly wishes to perform Rfl-priority communication first performs transmission with second priority so as not to interfere with the transmission of a node station that is already conducting communication with highest priority. This second priority communication is polled by the polling signal PL after all the highest priority communication is completed. FIG. 5(a) shows a state in which node station 2.4 has transmitted the respective packet signals PKT2.PKT4 at the second priority in order to newly acquire the highest priority. Based on the fact that node station 4 was successfully transmitted, from the next cycle onward, transmission is performed with the highest priority as shown in FIG. 5(b).Based on the trigger signal TG, node station 1.~.

4 sends out packet signals PKTI, -, PKT4, respectively. In this case, node station 2 is polled before node station 3, but PKTl,
~, the sum of the time widths of PKT4 is shorter than the period T.
As shown in Figure 5 (a), this is guaranteed in the previous cycle, so 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, the Kagaru network has the feature that each node station can perform autonomous comparison control, but the node station that transmits with the second priority will receive the highest priority in the next cycle. It is necessary to perform control to increase the priority so that it can be transmitted at the same time.

Therefore, if the period T is short, there is a problem that the control for increasing the priority must be performed at high speed.

[Means for solving 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 at regular intervals to poll the communication with the highest priority. During the cycle, polling is performed using polling signals in order of communication starting with the highest priority.A node station that wants to perform a new communication with the highest priority attempts transmission with the second priority, and if the transmission is successful, it is given the highest priority. In a loop network that acquires the transmission right of a certain period and performs transmission with the highest priority from the next cycle, first and second trigger signals are provided as the trigger signal, and the trigger station transmits the first trigger signal. A node station that wishes to perform a new transmission with the highest priority only in a period performs a transmission attempt to acquire the highest priority transmission right,
The trial is not performed in the cycle in which the second trigger signal is transmitted, and the 1-trigger station transmits the first trigger signal only in a cycle that is an integral multiple of the fixed 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, (a)
(b) is a block diagram showing a trigger station, and (b) is a block diagram showing a node station.

In FIG. 1(a), the trigger station is the transmission line 6.
A resistor connected in series with 5.4. switch 53;
Control circuit 51. Timer 52. Receive buffer 55. It consists of a transmission buffer 56.

On the other hand, as shown in FIG. 1(b), the node station registers 14. Switch 13. Control circuit 11, timer 12. Receive buffer 15. Transmission buffer 16. Detection circuit 17. When the control circuit 51 of the equipped trigger station consisting of the priority circuit 18 and one OR gate is notified of the start of the period T by the timer 52, it connects the switch 53 to the transmission buffer 56 side and transmits the signal in the transmission buffer 56. Send.

FIG. 2 is a diagram showing an example of the configuration of a signal frame used in this embodiment. The signal frame is delimited by a start delimiter SD and an end delimiter ED, and includes two types of bits TGI indicating that the signal is a trigger signal and a polling signal. TG2 and PL
, a header HDR containing address information, and an information field INFO. Bit TG 1 = 1 is period T
Bit TG2 = 1 indicates a trigger signal TGI sent out at a period N - T that is N times N - T, bit TG2 = 1 indicates a trigger signal TG2 sent out at any other period T, and bit PL = 1 indicates a polling signal sent out within the period T. Signal PL is shown. Packet signals sent from each node station are TG1=TG2=P
It is identified by L=0. Timer 5 shown in FIG. 1(a)
2 notifies the control circuit 51 of the start of the period T, and if it is the start of the multi-period NT, only the output 52-1 is set to 1 and a trigger signal TG1 with bit TG 1 = 1 is sent out; In each cycle, only the output 52-2 is set to 1, and a trigger signal TG2 with bit TG2=1 is sent out.

Further, when the transmission right is acquired within the period after sending out the trigger signal TGI or TG2, only the output 52-3 is set to 1 and a polling signal PL with bit PL=1 is sent out from the sending buffer 56 each time.

Next, FIG. 3 is a diagram showing the operation timing in this embodiment, and FIG. 3(a) shows the trigger signals TGI, TG2 and the polling signal PL in the multi-period NT. A trigger signal TGI is sent out in the first period T of the multi-period NT. Acquisition control of the highest priority is permitted only in this cycle.

That is, a node station desiring to transmit with the highest priority transmits the packet signal PKT with the second priority given by the next polling signal. In the same figure (a), node station 1.3 has already acquired the highest priority and sends out packet signals PKTI and PKT3, and node stations 2 and 4 each transmit packet signals PKT2 and PKT4 in order to acquire the highest priority. This shows a situation in which transmission is performed with the second priority. In other cycles T starting with the trigger signal TG2, control to obtain the highest priority is prohibited. Therefore, the second priority Even if a packet signal can be transmitted at the second node, transmission at the highest priority is not permitted.In other words, no node station newly acquires the highest priority until the next trigger signal TGI is supplied.Therefore, the second Unlike the conventional example, the node station 2.4 that transmits the packet signals PKT2.PKT4 with the highest priority and has acquired the highest priority does not need to transmit with the highest priority in the next cycle. Fig. 3(b) shows a situation in which node station 4 starts transmission with the highest priority from the third period, and node station 2 starts transmission with the highest priority from the first period of the next multi-period.

Next, the operation of the node station shown in FIG. 1(b) will be explained. The detection circuit 17 monitors bits TGI, TG2 and PL of the passing signal frame, and detects bit TG.
When l = 1, that is, when the trigger signal TG1 is detected, the timer 12 is initialized to 1 by the control signal 17-1. This causes the control circuit 11 to know the start of the multi-period NT. Also, when bit TG2-1 is detected, control signals 17-2
The control circuit 1 starts the next cycle T via the timer 12.
Notify 1. On the other hand, the priority circuit 18 is initialized by a control signal 17-1, 17-2 through one OR gate, indicates the highest priority, and every time it detects a pin I-P L = 1, that is, a polling signal PL. Lower the priority variation one by one. The control circuit 11 of the node station that wants to perform communication with the highest priority has a timer 12 set to a multi-period N.TL.
near) fi indicates the first cycle, and the priority circuit 18 indicates the second cycle.
When the priority is indicated, a packet signal to be transmitted is set in the transmission buffer 16, and when access rights to the transmission line 6 are obtained, the switch 13 is connected to the transmission buffer 16 side and the packet signal is transmitted. 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 fails, the highest priority cannot be obtained. If you want to try again, wait for the start of the next multi cycle.

〔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. 1
Since it is sufficient to increase the priority by one priority and set the highest priority as the priority of the packet signal to be transmitted, there is no need to perform priority control at high speed, and there is an effect that it can be performed at a lower speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of the configuration of a signal frame used in this embodiment, and FIG.
4 is a diagram showing an example of the configuration of a general loop network. FIG. 5 is a diagram showing the operation timing of an example of a conventional loop network priority control method. be. 1.2, 3.4... Node station, 5... Trigger station, 6... Transmission line, 11.51...
Control circuit, 12.52...Timer, 13.53...
switch, 14.54... register, ], 5.55.
...Receive buffer, 16.56...Send buffer, 1
7...Detection circuit, 18...Priority circuit, ]9...
OR gate.・Town Agent Patent Attorney Susumu Uchihara 5/Pa No. Z

Claims (2)

[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 at a constant cycle, polls the highest priority communication, and within the cycle, the high priority communication The node station that wants to perform a new communication with the highest priority will perform a transmission attempt with the second highest priority, and if the transmission is successful, it will acquire the highest priority transmission right and perform the next transmission. In a loop network that performs transmission with the highest priority from cycle to cycle, first and second trigger signals are provided as the trigger signal, and the highest priority is newly transmitted only in the cycle in which the trigger station sends out the first trigger signal. Priority control of a loop network, characterized in that a node station desiring to transmit makes a transmission attempt to acquire the highest priority transmission right, and does not make the above attempt in the period in which the second trigger signal is sent. method. (2) In the loop network priority control system as set forth in claim (1), the loop network is characterized in that the trigger station sends out the first trigger signal only at a cycle that is an integral multiple of a certain cycle. priority control method.