JPH03106143A - Communication fault check method in data communication system - Google Patents

Abstract

PURPOSE:To avoid an undetected fault of duplicate address by reading a random number of a resent text and discriminating fault/normal state of communication depending whether the random number is coincident with a random number sent in the case of receiving a text by its own station or not. CONSTITUTION:Communication stations A-D send/receive a packet through a transmission line 5. Then the 1st station A returns (resent text) a random number included in a received text to the 2nd station B, and the 2nd station B receiving the random number discriminates whether or not the random number is coincident with the random number sent by its own station. When plural 2nd stations B exist, the random numbers are dissident except by one station and the station detects a communication fault. Thus, the communication fault is checked by a station sending a random number by returning the random number again to an opposite party station in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Field of Application This invention is applicable to data communication systems in which a large number of communication stations are connected via a single line network such as a packet communication network, in which communication due to duplicate addresses is used. The present invention relates to a communication abnormality testing method for testing abnormalities.

lb) Conventional Technology In communication systems such as the Bakesoto communication network, a large number of communication stations are connected to the same line network, and each station is assigned an individual address. A destination address and a source address are added to the message sent at times &'A }M, and this message is received by all stations. The communication station that receives the message captures and decodes the message only if the destination address is its own address, and sends a reply message to the network.

fc) Problems to be solved by the invention In such a communication network, construction and expansion of the communication network. There have been cases where the same address has been assigned to multiple stations due to an incorrect address setting when changing, or due to someone's intentional manipulation. In such a case, two or more replies are sent to the line network in response to one message sent by a communication station, but since the sending timings of these reply messages are almost synchronized, the messages overlap, The receiving station (the communication station that first sent the message) could not detect that there were multiple stations with the same address. For this reason, there were cases in which it was not possible to receive a reply from the station that truly required a reply, and there was also the drawback that it was difficult to tell whether the received message was from the station to which the address was originally addressed.To solve this problem, Unexamined Japanese Patent Publication 1986
A communication method that includes a random number in the message such as -240734 has also been proposed, but even with this method, if the distance between the receiving station and two stations with overlapping addresses is different, the two stations
There may be a large difference in the voltage level of received messages sent from stations at the same time, and in such cases, only one random number is detected by the transmitting station, and it was discovered that there were multiple stations with the same address. There was a drawback that it could not be done.

In view of these drawbacks, it is an object of the present invention to provide a communication abnormality testing method for a data communication system, which tests for communication abnormalities in a random number transmitting station by sending the random numbers back to the other station.

(Means for solving d1 issues This invention consists of the following steps.

When the second station receives the message from the first station ■ Step of generating an arbitrary random number ■ Step of returning the received message containing this random number to the first station When the second station receives a retransmitted message from the first station, the second station receives a retransmitted message from the first station. ■Step of reading the random number of the retransmitted message and determining whether the communication is abnormal or normal based on whether it matches the random number sent by the received message from the local station fe) Function of the Invention In the communication abnormality inspection method for a data communication system of this invention, Messages are exchanged as described above, but if there are multiple stations (second stations) that have the destination address of the message originally sent by the first station, each station returns the received message. This received message contains a random number uniquely generated by each station, and if the reception levels (voltage levels) of multiple received messages at the first station are similar, mutual interference will cause the received message to The first station can detect a communication abnormality because (at least) the random number part is disturbed (
(See Japanese Patent Application Laid-Open No. 61-240734). However, if the reception level of only one of the multiple received messages is high, the first station captures only this message as the received message,
This telegram signal is ignored as noise. Therefore, in this state, it is not known whether the message received by the first station is the correct message (from the true second station).

Therefore, the first station returns the random number included in the received message to the second station (retransmission message), and the second station receives this random number and checks whether it matches the random number sent by itself. Determine whether or not. If a plurality of second stations exist, the random numbers will not match except for one station, and this station can detect a communication abnormality.

By reporting this communication abnormality to a network control station, etc., this abnormality is transmitted to the entire communication system, and a system without address duplication can be rebuilt.

([1st Embodiment] FIG. 2 is a configuration diagram of a data communication system to which the communication abnormality inspection method of the present invention is applied. This data communication system is a bucket-loading system in which each communication station A to D transmits and receives packets through a transmission path 5. It is a communication system.Each communication station has an A-
The address of C is assigned. Here, as an example of a case where a duplicate address occurs to which the present invention is applied, a case where address (02) is given to two communication stations B and D will be described.

Each communication station has the structure shown in FIG. 3(A). The communication station consists of an application section 6 and a transmission section 7, and the application section 6 is a data terminal device that has the function of variously processing and processing data to be transmitted and received.

This application section 6 is connected to the dual port RAM 17 of the transmission section 7. This dual port RA
M17 has access ports for both the application section 6 and the internal bus 16 of the transmission section 7, and functions as a bus sofa for sending and receiving data. The operation of the transmission section 7 is controlled by the CPU II, and this CPU 1 is connected to the internal bus 1.
It is connected to each part via 6. In addition to the dual port RAM 17, the internal path I6 includes ROM 12, RA
M13. A transmission control section 14, DMA 18, and random number generation section 19 are connected. The CPU 1 controls the transmission section 7 according to the control program in the ROM 12, and sends and receives packets via the transmission control section 14. This transmission control section 1
4 is connected to the transmission line 5. RAM13 is CPU
It is used as a work area for I processing and as a transmitting/receiving bath sofa for sending and receiving packets.

Part (B) of the same figure shows a partial configuration diagram of the RAM 13.

M1 is a transmitting/receiving buffer in which the packets to be transmitted and the received packets are temporarily stored. M2 is a transmission random number storage area in which the random number used when this communication station sends out a response packet is stored. Further, M3 is a received random number storage area, in which the random number included in the received retransmission message is stored.

Further, the DMA 18 is a device having a function of transferring data received by the transmission control unit 14 to a specified address.

The random number generator 19 has a function of generating random numbers. Here, FIG. 4 shows the structure of packets sent and received between each communication station. First, the general structure of a packet will be explained with reference to FIG. General Bagasoto is PR. SD, DA, CF
, SA DATA FCSED. Here, PR is a preamble signal used for receiver synchronization. SD is a start delay ξ that indicates the start of a frame. DA is a destination station address in which an address indicating a destination is stored. CF is a control field indicating the type of frame. SA is the source address where the address indicating the source is stored, DAT
A is the area of actual data required for each frame. F.C.S.
is an area where a frame check sequence is stored, and ED is an end delimiter indicating the end of the frame.

Hereinafter, packets exchanged when data is transmitted from communication station A having address (01) to communication station B having address (02) with reference to (B) to (D) in the same figure will be explained.

FIG. 2B shows an example of a normal bucket (including data) transmitted from communication station A to communication station B. The destination station address DA is ((+2)), the source address SA is (o1), and CF is "20" indicating a normal message.

FIG. 2C shows a response packet sent by the station at address (02) to the effect that it has received the bucket message from communication station A. This response bucket corresponds to the received message of the present invention. In this case, DA is (01), . S
A is (02). Further, CF is "22" indicating a response packet. In this message, a random number generated by the random number generator l9 is written in the DATA area.

When communication station A normally receives the response packet ((C) in the same figure), the retransmission packet (retransmission message) sent back to this station is shown in (D) in the same figure. DA is (02) and SA is (0■). Also, CF is “2” which indicates a retransmitted packet.
1". The random number received in the above response bucket is written as is in the DATA area of this packet.

Here, when communication station 8 transmits the bucket note shown in the figure (B) to communication station B (address (02)), address (
After the station 02) receives the packet, it transmits a response packet to communication station A. Here, address (0
2) is redundantly given to communication stations B and D, response packets from communication stations B and D appear on transmission line 5 almost simultaneously.

When multiple messages appear on the transmission line L at the same time in this way, the signals of those messages usually collide and errors occur in the packets, resulting in a communication error, which allows duplicate addresses to be discovered. However, address (02)
If the signal level of one packet is sufficiently higher than the signal level of the other packet due to a difference in distance between the two receiving stations (ii!l receiving station A), these messages will collide. However, only signals with high levels are extracted as signals, and telegram signals with low levels are removed as noise.

In order to prevent this detection omission, communication station A uses the address (02
) The random value sent by the response bucket is sent back as is (retransmission packet). In the case of this embodiment, communication station A sends out the random number of either communication station B or communication station D in a retransmission packet, but the other communication station receives the random number of its own station and the retransmission packet. The random numbers obtained do not match. Duplicate addresses can be detected based on this mismatch.

The operation of the communication station at address (02) in this embodiment will be explained using the flowcharts in FIGS. 1(A) and 1(B).

First, (A) in the same figure shows the operation when sending a response bucket. When a packet is received from communication station A, the data of this packet is sent to the application section 6 (dual port R
AM17) and obtains a random number value from the random number generator 19 (n1). This random value is sent to the reception buffer Ml.
(n2), and this random value is stored in the transmission random value storage area M2 (n3). Thereafter, the response packet set in the transmission/reception buffer M1 is transmitted to the communication station A (n4).

When a retransmission packet is sent from communication station A in response to this response packet, the operation shown in FIG. 3B is executed. First, the random number included in the received retransmission packet is stored in the received random number storage area M3 (n5). This random value is compared with the value stored in the transmission random value storage area M2 (n
6), if they match, the process ends normally. If there is a mismatch, the application unit 6 is notified (n?) that there is a communication error due to the duplicate address, and the process ends abnormally. (g) Effects of the Invention As described above, by using the communication abnormality inspection method for a data communication system of the present invention, even though packets collided, one signal level was sufficiently higher than the other signal level. Due to normal reception on the receiving side,
It is possible to eliminate the risk that duplicate address abnormalities will not be detected.

This makes it possible to eliminate communication confusion caused by duplicate addresses that often occur in large-scale data communication systems, and to maintain the reliability of the communication system.

FIG. 3 is a diagram illustrating the structure of packets to be transmitted.

A-D one communication station, 5 one transmission line, 191 Random number generator.

Claims (1)

[Claims] (1) When the second station receives a message from the first station, (a) Generating an arbitrary random number (b) Returning the received message containing this random number to the first station. Step: When the first station receives the received message from the second station, (c) reads a random number in the received message and returns a retransmission message containing this random number to the second station. When a retransmitted message is received from the station, (d) reading the random number of the retransmitted message and determining whether the communication is abnormal or normal based on whether it matches the random number sent by the own station in the received message. A communication abnormality inspection method for a data communication system.