JPS6080337A - Access control system in bus type local area network - Google Patents

Abstract

PURPOSE:To attain transmission of a data packet in the order of reservation without collision by providing a signal directivity detecting circuit and allowing the own communication node to detect whether or not data collides with the node with priority to perform sequentially reservation from the node with priority. CONSTITUTION:The access of a communication node 3 to a transmission line 1 consists of a reservation mode and a transfer mode. The communication node 3 having a transmission request confirms an idle transmission line 1, transmits a packet and when a collision detection circuit 6 detects a collision, a signal directivity circuit 7 performs logical operation based on the data received by three passive taps 4 to detect with which reservation packet from left or right node the data collides and the reservation packet is retransmitted only when the own node has the highest priority at the outermost end, for example. After the reservation packet from the left mode passes through, the other node increments the reservation number by one and transmits again the reservation packet. When all the reservations is finished, the data packet is transmitted in the order of reserved number.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field to which the invention pertains) The present invention provides an access control method that realizes highly efficient use in a no-su type local area network. To improve the performance of local Corrier networks, a similar method is r C8MA.
/CD-DCR method" (described in Information Processing Society of Japan Distributed Processing System Study Group Materials 13-3pp, 1-pp, 10.1982). This method requires signal transmission in only one direction, and requires a directional accessor to control the direction of signal transmission and reception. A directional accessor must be realized using an optical splitter/combiner. However, optical branching/coupling devices have large losses, the number of devices that can be passively connected to one optical transmission line is limited to seven, and communication nodes must send and receive signals in both left and right directions, making control complex. There was a drawback. Furthermore, when implementing a directional accessor with an amplification function to compensate for the above-mentioned loss, a branch/add connection is used in which the transmission line is once drawn into the directional accessor, which has the disadvantage of lowering reliability.

(Object of the Invention) The present invention eliminates the use of directional signals, eliminates the need for a directional accessor by providing a passive directionality detection circuit, and separates reservation motes and forwarding motes. The purpose of the present invention is to realize highly reliable, expandable, and easily controllable local area network by guaranteeing the reservation of the highest priority communication notebook in the event of a signal collision.

(Structure and operation of the invention) FIG. 1 shows an example of the overall structure of a lotus-shaped local area network according to the present invention, where ] is a transmission path, 2 is a terminator for terminating signals on the transmission path, and 3 is for communication processing. The communication node 4 is a passive tap that does not have an amplification function.

FIG. 2 is a block diagram showing the configuration of the communication node 3 in FIG. 1, where 5 is a signal transmitting/receiving circuit that sends and receives signals on the transmission path, and 6 is a collision detection circuit that detects signal collisions on the transmission path. , 7 is a signal direction detection circuit for detecting the direction of a signal on a transmission path, 8 is a communication node that performs overall communication processing including collision control, and 9 is a communication main device (for example, a divider, communication terminals, etc.). One iGnote 3 is connected to the transmission line 1 at three points by passive taps 4, with the central passive tap 4 used for both sending and receiving newsletters, and the left and right passive taps 4 used only for receiving.

However, the intervals between the center and the left and right passive taps shall be equal.

FIG. 3 shows a detailed (N+) signal transmitting/receiving circuit 5 in FIG.
10 is a block diagram showing the configuration of the receiver, nH, iu
12 is a protection circuit, and 13 is an insulation circuit. The protection circuit 12 prevents the transmitter 11 from failing and continuing to emit high-level signals, thereby interfering with other communication nodes. This is a disconnection circuit. The insulating circuit 13 is a necessary circuit because the ground potentials of the transmission line and the communication node are different.

Also, a is the received signal at the left passive tap, b is the received signal at the center passive tap, C is the transmitted signal at the center passive tap, and d
is the received signal at the right passive tap.

FIG. 4 is a block diagram showing a detailed configuration of the collision detection circuit 6 in FIG. 2, and 14 is an exclusive OR circuit. When transmitting a signal at its own communication node, by taking the exclusive OR of the received signal at the central passive tap and 3c at the transmitter, if there is a signal sent from another communication node, a signal e indicating signal collision is generated. Output.

FIG. 5 shows a detailed configuration of the signal directionality detection circuit 7 in FIG. 2.
6 is a NOT circuit, and 17 is an OR circuit. Delay circuit 15
Let the delay time at τ9 be equal to the transmission delay time of the interval between passive taps, and the received signal d of the right passive tap at time t is the right direction signal 1R(t) and the left direction signal 1. (1
) is +n(t)+IL(t), and the received signal at the center tap is l11(t+τD)+i, (t-
τD). b after passing through the delay circuit 15 and inversion circuit 16
The signal becomes -1□(t)=i, , (t-2τ9), and the output signal g from the OR circuit 17 is l H(j) l I
, (t~2τD), there is only a leftward signal. In other words, a signal sent from a communication node located on the left side of the own communication node can be detected by the output signal g, and a signal sent from a communication node located on the right side can be detected similarly by the output signal f. This makes it possible to determine whether the own communication node is located at the leftmost end or the rightmost end among the communication nodes that have caused a signal collision.

FIG. 6 is a block diagram showing the detailed configuration of the communication node 8 in FIG.
1 is a memory, 22 is a common bus, 2 is an input/output interface for sending and receiving uke data, and h is an input/output signal with the communication main device 9.

The operation of the access control system according to the present invention using the configuration shown in FIGS. 2 to 6 will be described. Access to the transmission path by a communication node consists of two modes: reservation mode and transfer mode.

(1) Reservation mode A node that has transmission data transmits a reservation bucket and reserves the right to transmit data packets.

In the case of a reservation packet collision, all colliding communication nodes continue to send reservation packets until all reservations are completed.

(II) Transfer mode The communication node transmits data packets in the reservation order in the reservation mote.

The detailed operating algorithm in this mode is shown below. Note that the highest priority communication node can be either the leftmost or rightmost communication node, but since the operating algorithm is exactly the same, only the case of the leftmost communication node will be described here.

(1) Reservation mode■ A communication node without a transmission request always monitors the transmission path, and if a signal is detected, it enters a waiting state for the reservation mode (■) to end. If there is a transmission request, please use the reservation number - 1 as ■
Move to.

■ In the wait state for reservation mode to end, even if a transmission request occurs within the communication node, it is suppressed. Immediately after detecting the 0 reservation mode end signal 1 after all reservations have been completed, the transfer mode shifts to the data bucket reception state (2).

■ In the sending state, after confirming that the transmission path is free, the reserved packet is sent. If a signal is received from another communication node (collision detected) during transmission, the transmission is immediately stopped and the process moves to (3). If the transmission is completed normally, the 1 reservation mode end signal 1 is immediately sent out continuously, and the transfer mode moves to the "data packet transmission state (A)" of ■.

(2) From the time of data transmission, the transmission path is monitored at a time interval of 2×(maximum propagation delay time), and it is determined whether the colliding partner communication node is located on the left or right side of the own communication node. If the own communication node is at the leftmost position, proceed to ■; otherwise, proceed to ■.

■ Resend the reservation bucket. When the transmission path is monitored and the 0 reservation mode end signal I is detected, the process shifts to the "data packet transmission state (B)" of the transfer mode.

■ After the reservation packet passes through the leftmost communication node, return to ■ as reservation number - reservation number + 1.

(11) Transfer mode■ In the data packet reception state, even if a transmission request occurs in the communication node, it is suppressed until the transfer mode ends, and the transmission path is constantly monitored and only data packets addressed to the own communication node are received. ``If transfer mode end signal 1 is detected, return to reservation mode ■.

■ [Data packet transmission status (A) J: (Reservation number - 1) data packets on the transmission path.

(However, this operation is not necessary when the reservation number is -1), immediately sends the data packet, and then sends the ``transfer mode end signal n'' to switch to the reservation mode.
Return to

■ “Data packet transmission status (B) J: Transmission path”
- to confirm the passage of (reservation number - 1) data packets, immediately send the data packets, monitor the transmission path, and when detecting the 7 transfer mode end signal 1, switch to the reservation mode.
Return to

7 and 8 are flowcharts showing the operation algorithm in the above access control method.
The figure shows the reservation mode, and FIG. 8 shows the transfer mode.

(Effects of the Invention) As described in detail above, the access control method in a lotus-shaped local area network according to the present invention achieves the following effects by implementing it using the above configuration and operation algorithm.

I) The performance of the lotus-shaped local area network is improved by dividing the access mode into two, limiting signal collision to reserved motes only, and ensuring that the highest priority communication node can always be reserved in the event of a collision.・Efficiency improves.

11) The position detection function of collision communication node 1 in this access method is based on the bidirectional transmission path and passive connection of the communication node.
1, the reliability, expandability, and ease of control, which are the characteristics of conventional bus-type local area networks, are not lost.

111) Since the transfer mode interval is variable, the data packet length in each communication node may be variable, and mixed transmission of long and deep packets is possible.

IV) Since signal collision does not occur in the transfer mode, one long Paqueso transmission (for example, image data) can be efficiently realized.

By applying the access control method of the present invention, in addition to data communication services, voice, image, etc. This has the advantage of improving the performance of low-power area networks, where the degree of integration and complexity of heterogeneous networks is increasing.

[Brief explanation of the drawing]

FIG. 1 is an example of the overall configuration of a bus type local area network according to the present invention, FIG. 2 is a block diagram showing the configuration of communication node 1, FIG. 3 is a block diagram showing the configuration of the signal transmission/reception circuit in FIG. 4 is a block diagram showing the configuration of the collision detection circuit in FIG. 2, FIG. 5 is a block diagram showing the configuration of the signal directionality detection circuit in FIG. 2, and FIG. 6 is the configuration of the communication node 8 in FIG. 2. 7 and 8 are flowcharts of operational algorithms in the access control system. ] ... Transmission line, 2 ... Terminator, 3
・・・・・・Communication node, 4. Hit passive Kunobu,
5-... Signal transmission/reception circuit, 6...
Collision detection circuit, 7... Signal directionality detection circuit, 8... Communication node, 9......
Main communication device, 10...Receiver, 11...Transmitter, 12...Protection circuit, 13...Isolation circuit, ]4...Exclusive OR circuit, 15
-...Delay circuit, 16...NOT circuit, 17...OR circuit, 18...
...Input/output cover sofa for communication control, 19...
・・Transmission interface, 20 ・・・・・・Professional Seven So”), 21 ・・・・・Memory, 22 ・・・
Song/Common Lotus, 23-/Sending/receiving data input/output interface 0 Patent applicant Nippon Telegraph and Telephone Public Corporation Fig. 2 Fig. 3 Fig. 4

Claims (1)

[Claims] A transmission path as a communication medium, a terminator that terminates a signal applied to the transmission path, a signal transmission/reception circuit that sends and receives signals to and from the transmission path, a collision detection circuit that detects signal collision on the transmission path, and a signal A communication node consisting of a signal direction detection circuit for detecting the position of a sending node, a communication control circuit for performing communication processing, a communication main device such as a computer, and a communication terminal, and passively connecting the communication node to a transmission path. In a bus-type local area network consisting of passive taps with no amplification function, there is an access mote with two modes: a reservation mode and a transfer mode. The bucket collision detection circuit detects the collision, and the signal direction detection circuit recognizes whether the colliding communication node is located on the left or right side of its own communication node.
or the rightmost terminal) realizes the reservation when the next transmission path is free, and the remaining communication nodes sequentially realize the reservation in the same way.
All collided communication notes will be transferred to transfer mode after the reservation is completed.
An access control method in a bus-type local area network, characterized in that each reserved communication notebook transmits data packets in the order of reservation without collision.