JPH0383431A - Communication equipment for private communication network - Google Patents

Abstract

PURPOSE:To make equal an opportunity to obtain the occupying right of a bus line for respective communication equipments by providing an occupying right possession control part and an operation interval control part to intermittently execute control for obtaining the occupying right of the bus line and shortening the operation interval of the occupying right possession control part with the passage of time. CONSTITUTION:When the occupying right of a bus line B is obtained, it is confirmed by a receiver 20 there is no packet on the bus line B and afterwards, a signal is transmitted to the other communication equipments in order to notify the occupation of the bus line B. When it is made successful to obtain the occupying right, address data are transmitted for specifying the communication equipment as a called party and afterwards, transmission data accumulated in a transmission memory 13 are transmitted. When it is failed to obtain the occupying right, a prescribed value (t) is subtracted from standby time T. When the number of times to fail obtaining the occupying right is increased, the standby time T is subtracted for every prescribed value (t) and accordingly, the standby time T is gradually shortened. Thus, the opportunity to obtain the occupying right is increased and probability for successfully obtain the occupying right is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a communication device for a local area communication network,
In particular, it is used for an Ethernet-type horizontal communication network.

[Prior Art] Conventionally, a local communication network called a local area network (LAN) has been widely used to comprehensively communicate information within a premises. In particular, IEEE802,3 [
Ethernet compliant with X rating (E tl+erneL)
This type of Yokonai communication network is widely used. This Ethernet-type Yokonai communication network connects multiple communication devices called nodes to a two-wire bus line such as a twisted pair wire or coaxial cable, and uses C8MA/CD (Carrier
5ence Multiple Access/Co
11ision Detection) method.

In the C3MA/CD method, the sending node first senses the state of the bus line, confirms that no packets are being sent out on the bus line, and then sends out its own packet. If there is a packet on the bus line, it waits until that packet has been transmitted before transmitting its own packet. It constantly senses the bus line even while sending a packet, and if a signal different from the one it sent appears on the bus line, it determines that the packet has been destroyed and starts retransmitting the packet. At this time, if a plurality of nodes start retransmitting packets at the same time, the signals will collide again, so the node that has an exclusive tank for the bus line will start retransmitting packets. In order to acquire this exclusive tank in advance, the sending node first sends a message to acquire the exclusive tank, and then sends a message to identify the destination node.
Next, data and commands are sent, and when the communication is completed, a message is sent to abandon the exclusive tank and the bus line is released to other nodes.

[Problems to be Solved by the Invention] In the above-mentioned Ethernet-type horizontal communication network, a large amount of data is transmitted at one time from one node, such as in the case of file transfer, and the transmitting node When the number of bus lines is small, the number of transmissions required to acquire a dedicated tank on the bus line is small, resulting in high transmission efficiency. On the other hand, when monitoring and controlling lighting loads in a building that houses many stores or offices, the amount of data transmitted from one node at a time is small and the number of nodes transmitting data is large. In this case, the number of transmissions required to acquire a dedicated tank on the bus line increases, resulting in a decrease in transmission efficiency.

Therefore, a node that has acquired a dedicated tank for a bus line and transmitted data will refrain from transmitting data to acquire a dedicated bus line for a certain waiting period, even if there is data to be sent. , it is preferable to reduce the number of nodes that perform transmission to acquire a dedicated tank on the bus line. However, since the lighting load conditions change all at once in the same building at the start of the work day or during lunch breaks, it is difficult to ensure that all nodes can acquire exclusive use of the bus line and complete data transmission during a certain waiting time. is not limited. In this case, on the one hand, there may be nodes that can acquire a dedicated tank for a bus line many times in a row, and on the other hand, there may be nodes that cannot acquire a dedicated tank for a bus line even once.

The present invention has been made in view of these points, and its purpose is to provide a communication device for the Yokonai communication network that can equalize the chances of acquiring a dedicated bus line tank.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in the figure, a plurality of communication devices NN2. ..., N
i, . In a communication device for a Yokonai communication network that releases transmission data, a transmission unit 11 that sends transmission data onto a bus line B, a transmission control unit 12 that controls the transmission unit 11, and a transmission memory 13 that temporarily stores transmission data. and a dedicated tank acquisition control unit 14 that intermittently performs control to acquire a dedicated tank for bus line B when transmission data exists in the transmission memory 13.
and an operation interval control section 15 that shortens the operation interval of the exclusive tank acquisition control section 14 over time.

[Function] According to the present invention, as described above, the exclusive tank acquisition control section 14 is provided which performs the control for acquiring the exclusive tank of the bus line B intermittently, and the operation interval of this exclusive 11 acquisition control section 14 is adjusted. Since the operation interval control unit 15 is provided to shorten the time interval as time passes, as the time during which a dedicated tank for bus line B cannot be obtained becomes longer, the frequency of control for obtaining a dedicated tank for bus line B increases. . Therefore, it is possible to prevent a situation in which one communication device acquires the exclusive tank of bus line B many times and another communication device is unable to acquire the exclusive tank of bus line B even once. This makes it possible to equalize the chances of acquiring the exclusive tank of B for each communication device.

[Examples] Examples of the present invention will be described below with reference to the drawings. Figure 1(a) shows the overall configuration of an Ethernet-type horizontal communication network. In Figure 1(a), B is a bus line.
It consists of two-wire transmission lines such as twisted bare wires or coaxial cables. N,,N2. ...Ni, ..., Nj,
... are communication devices called nodes, and are connected to bus line B. Each communication device Ni includes a transmitter 10, a receiver 20, and a collision detector 30. The transmission source communication device Ni uses the receiver 20 to sense the state of the bus line B, and when it confirms that no packet I is being sent on the bus line B, the transmitter 10 sends out its own packet. If there is a packet on bus line B, it waits until that packet has been transmitted before transmitting its own packet. The bus line B is always sensed even during the sending of the bage soto, and if a signal different from the signal sent out appears on the bus line B, the collision detector 30 detects a collision of signals, and the transmitter 10 Instructs to retransmit the packet. At this time, if another communication device starts retransmitting the packet at the same time, the signals will collide again, so the sending communication device Ni first acquires the exclusive tank for bus line B in order to acquire it in advance. , then sends a message to identify the communication bag WNi (≠Ni) of the other party, then sends data and commands, and
When the communication is completed, a transmission is made to abandon the exclusive tank, and the bus line B is released to other communication devices.

FIG. 1(b) shows the configuration of the transmitter 10.

The transmitter 11 has a function of sending data to be transmitted to the bus line B. The transmission control unit 12 controls the protocol of the transmission unit 11 and the like. The transmission memory 13 is a buffer memory that temporarily stores transmission data, and is, for example, a FIFO″rti
has been completed. The exclusive tank acquisition control unit 14 is connected to the transmission memory 13
If there is transmission data on the bus line B, control is performed intermittently to acquire a dedicated tank for the bus line B. The operation interval control section 15 performs control to shorten the operation interval of the exclusive tank acquisition control section 14 as time passes.

FIG. 2 is a flowchart showing the operation of this embodiment.

In #1, it is determined whether transmission data exists in the transmission memory 13. If there is no transmission data in the transmission memory 13, wait until the transmission data is input into the transmission memory 13.
If there is transmission data in the transmission memory 13, after waiting for the waiting time T to elapse in #2, the exclusive tank acquisition control unit 1
4 to perform control for acquiring a dedicated tank for bus line B.

To acquire a dedicated tank for bus line B, after confirming with the receiver 20 that there are no packets on bus line B,
A signal is sent to notify other communication devices that bus line B is occupied. As a result, other communication devices can detect that bus line B is occupied, and therefore do not perform any transmission to obtain an exclusive tank until they are informed that bus line B has been released. If two or more communication devices simultaneously perform transmissions for acquiring the exclusive tank, the signals will collide on bus line B, and the acquisition of the exclusive tank will fail. In #4, it is determined whether or not the exclusive tank has been successfully acquired. If the exclusive tank is successfully acquired, address data for specifying the communication device of the other party is transmitted in step #5, and then the transmission data stored in the transmission memory 13 is transmitted.

Then, a signal for notifying the release of bus line B is transmitted to other communication devices. Next, in #6, the waiting time T is set to the initial value Ts, and the process returns to #1. If acquisition of the exclusive tank fails, a predetermined value t is subtracted from the waiting time T in #7. In #8, it is determined whether or not the exclusive tank acquisition has failed I(times in a row). If the number of exclusive tank acquisition failures is less than the number of times, the process returns to #1. If the number of exclusive tank acquisition failures increases, , in #7, the waiting time T is subtracted by a predetermined value t, so the waiting time T in #2 gradually becomes shorter.This increases the chances of acquiring a dedicated tank, and increases the probability of successfully acquiring a dedicated tank. Furthermore, if bus line B is particularly busy, the number of communication devices with short standby time T will increase, and the chances of acquiring a private tank will actually decrease, so the number of failures to acquire a private tank will increase. When reaching the second period, a reset operation is performed in #9 and the state returns to the m-phase state.This increases the possibility that another communication device can acquire the exclusive tank.

[Effects of the Invention] According to the present invention, in a communication device of a yokonai communication network in which a plurality of communication devices are connected to a bus line, the interval at which control is performed to acquire an exclusive tank of the bus line can be shortened as time passes. This has the effect that each communication device has an equal chance of acquiring a dedicated bus line.

[Brief explanation of drawings]

Fig. 1 (a) is a block diagram showing the overall configuration of an embodiment of the present invention, Fig. 1 (b) is a block diagram showing the main part of the tank bottom, and Fig. 2 is a block diagram for explaining the operation of the same. It is a flowchart. B is a bus line, N, , N2..., N i,...
, Nj, ... are communication devices, 10 is a transmitter, 11 is a transmission section, 12 is a transmission control section, 13 is a transmission memory, 14 is a proprietary II acquisition control section, 15 is an operation interval control section, 20 is a receiver , 30 is a collision detector.

Claims (1)

[Claims] (1) A local communication network in which multiple communication devices are connected to a bus line, and the communication device that has acquired exclusive rights to the bus line monopolizes the bus line during communication, and releases the bus line after communication is completed. In a communication device, there is a transmission unit that sends transmission data onto a bus line, a transmission control unit that controls the transmission unit, a transmission memory that temporarily stores the transmission data, and a transmission unit that sends transmission data onto the bus line when the transmission data exists in the transmission memory. an exclusive right acquisition control section that intermittently performs control to acquire exclusive right of the exclusive right acquisition control section; and an operation interval control section that shortens the operation interval of the exclusive right acquisition control section as time passes. communication equipment.