JPH0644761B2 - Token bus LAN analyzer - Google Patents

Description

The present invention relates to an analyzer used for a token bus type LAN (local area network).

[Prior art]

The token bus type LAN is configured to be suitable for communication between devices in a factory, for example, and each device is
It is connected to a shared transmission line (coaxial cable) forming the AN through a tap-off, a modem and a node. There are two types of token bus systems, one is using broadband and the other is using carrier band. In both cases, a coaxial cable is attached with tap-off to connect a modem and a node.

The LAN analyzer takes in data circulating in the LAN and performs various analyzes such as LAN load factor, frame number measurement, and frame interval measurement (JP-A-63-99).
No. 654). Token bus LAN analyzer
It has a modem connected to the coaxial cable via tap-off and processes the data received through this modem,
It stores and analyzes the stored data. The token bus type LAN analyzer also has a function of sending out a data frame through a modem and confirming whether or not the partner device normally operates.

〔Task〕

However, data flowing through the LAN may have bit loss or bit garbled due to the influence of noise, etc.
Therefore, each node may receive abnormal data. In such cases, the node that receives the abnormal data must perform error processing such as detecting the error and retransmitting the data, or displaying in the error message which frame the error occurred in. .

When testing newly designed equipment and software, it is of course necessary to check the operation when normal data is received, but it is also necessary to check the error processing function when abnormal data is received.

In the conventional LAN analyzer, it is possible to send out predetermined data from the data transmission unit to check the operation of the partner device, but since the data transmitter cannot create abnormal data, error processing of the partner device is performed. Unable to check functionality.

[Means for solving the problem and its action]

In order to solve the above problems, the present invention provides a modem connected to a shared transmission line constituting a LAN, a means for processing and storing data received through this modem, and a means for analyzing the stored data. In a token bus system LAN analyzer equipped with a data transmission section for transmitting a data frame through the modem, a part of the data frame transmitted from the data transmission section is selected between the modem and the data transmission section. The error generating circuit for changing the error generating circuit is further provided, and the error generating circuit is further provided with an error generating control section for instructing a section in which an error is generated and an error type.

In the token bus LAN, a data frame having seven sections as shown in FIG. 3 is distributed.
In order from the beginning, SD is start display (1 byte), FC
Is frame control (1 byte), DA is destination advice (6 bytes), SA is source address (6 bytes), Da
ta Unit is information, FCS is a frame check sequence (4 bytes), and ED is an end display (1 byte).
The frame length between SD and ED is 8191 bytes or less.

A normal data frame having the above-mentioned configuration is sent from the data transmitting unit, but the error generating circuit changes the data of a part of the section of the data frame and sends it as data including an error. The section that causes an error and the type of error depend on an instruction from the error generation control unit. For example, the FC data may be erased, or the SA data may be garbled.
By generating an error of any kind in any section of the data frame sent out in this way,
It is possible to check the error processing function of the partner device.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a token bus system LA according to an embodiment of the present invention.
The whole structure of N analyzer is shown. In the figure, 11 is LA
A coaxial cable is a transmission line shared by N, 12 is a tap-off attached to the coaxial cable 11, and 13 is a modem (data transmission modulator / demodulator) connected to the coaxial cable 11 via the tap-off 12. LAN as the modem 13 is a broadband bus system (transmitting 174 to 300 MHz, receiving 5 to 108 MHz)
In the case of, a broadband modem is used, and in the case of a carrier band bus system, a carrier band modem is used.

Next, 14 is a CRC check circuit for error detection, 15 is a filter that selectively passes only frames necessary for analysis,
Reference numeral 16 is a reception signal processing unit that performs conversion from serial data to parallel data, address control for storing parallel data, frame length measurement, and the like, and 17 is composed of a reception data storage unit 18 and a management data storage unit 19. It is a data storage unit. The reception data storage unit 18 stores the parallel data from the reception signal processing unit 16, and the management data storage unit 19 stores the address pointer, frame length, etc. of the parallel data.

Next, 20 is a counter that counts the number of received data frames, and 21 is a frame interval measurement unit that measures the time interval between the received data frames.

Next, 22 to 28 are FC (frame control) type detection units, and 29 to 35 are FC type counters. There are the following seven types of FC.

Claim Token Solid Sex # 1 Solid Sex # 2 Who Follows Set Sex Token Resolve Contention Detectors 22-28 and counters 29-35 detect and count these FCs by type.

Next, a reception control unit 36 stores the measured number of frames, frame interval, FC type count value, etc. in the management data storage unit 19 through the bus controller 37. The storage of the above-mentioned address pointer and frame length in the management data storage unit 19 is also performed under the control of the reception control unit 36. The reception control unit 36 includes a CPU 68000, ROM, RA
It can be configured by a microcomputer including M.

The received data is processed and stored as described above, and the stored data is analyzed by the main control unit 38. Main control unit
Reference numeral 38 denotes a microcomputer including, for example, a CPU 80286, ROM and RAM, to which various peripheral devices (keyboard, display, floppy disk drive, etc.) 39 are connected via a controller 40. The main control unit 38 refers to various data stored in the received data storage unit 18 and the management data storage unit 19 by inputting from the keyboard, and performs necessary analysis.

Next, 41 is a data transmission unit. This data transmitter 41
Is for sending the data created by the main control unit 38 in accordance with a predetermined format.The data sent from here is converted into an analog signal by the modem 13 and sent to the partner device via the coaxial cable 11, Used for checking the operation of equipment.

The above is the general configuration of the conventional token bus type LAN analyzer, but the present invention is such a LAN analyzer that a data frame sent from the data transmitting unit 41 between the modem 13 and the data transmitting unit 41. Error circuit that selectively changes the data in some sections of the
51 is provided, and further, the error generation circuit 51 is provided with an error generation control section 52 for instructing a section in which an error is generated and an error type.

The error generating circuit 51 is configured, for example, as shown in FIG. The delay circuit 53 delays the data frame sent from the data transmission unit 41 by 2 bytes (may be longer than that), thereby gaining time for producing an error. The SD detection unit 54 detects the SD of the data frame sent from the data transmission unit 41, and the FC detection unit 55 and the byte counter.
It is intended to synchronize 57. The FC detector 55 detects the FC of the data frame sent from the data transmitter 41,
The FC select circuit 56 selects the type of FC that causes an error according to an instruction from the error generation control unit 52. The byte counter 57 is the next SD / FC / DA / S.
A pulse for the A select control unit 58 is created. The select control unit 58 selects which section of SD, FC, DA, or SA the error occurs in according to an instruction from the error generation control unit 52, and the timing and width of the error (pulse loss, garbled bit, etc.). It controls things like. The ED detection unit 59 detects the ED of the data frame sent from the data transmission unit 41, and the ED select control unit 60 causes an error when an error occurs in the ED according to an instruction from the error generation control unit 52 ( Pulse loss, garbled bit, etc.) and the timing and width are controlled. The error section select circuit 61 uses SD, FC, DA, SA,
It is to select which section of the ED causes the error.

The error section select circuit 61 outputs a signal that causes a specific error in a specific section of the data frame by the operation of the above circuits. This signal is synchronized with the data frame sent from the delay circuit 53 with a delay of 2 bytes. When this signal enters the gate 62, the data frame passing through the gate 62 contains a specific error in a specific section. Can be remade. In this way, a data frame containing an error is output from the gate 62, which is converted into an analog signal by the modem 13 and LA is output.
Sent to N. Therefore, it is possible to check how the device that receives such abnormal data operates and whether the error processing function of the device surely works.

〔The invention's effect〕

As described above, the LAN analyzer according to the present invention is
When transmitting a data frame, it is possible to include a desired type of error in the desired section of the data frame, so check how the device that receives the abnormal data including the error behaves. You can
Further, when a newly designed device or software is incorporated in the LAN, the error handling function can be debugged reliably in a short period of time.

[Brief description of drawings]

FIG. 1 shows a token bus system LA according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an embodiment of an N analyzer, FIG. 2 is a block diagram showing a concrete example of an error generating circuit of the analyzer, and FIG. 3 is an explanatory diagram showing a structure of a token bus system data frame. 11: coaxial cable, 12: tap-off, 13: modem, 41:
Data transmission unit, 51: error generation circuit, 52: error generation control unit.

Claims (1)

[Claims] 1. A modem connected to a shared transmission line constituting a LAN (Local Area Network), and a means for processing and storing data received through the modem.
In a token bus system LAN analyzer equipped with a means for analyzing stored data and a data transmission unit for transmitting a data frame through the modem, a data frame transmitted from the data transmission unit is provided between the modem and the data transmission unit. A token bus that is provided with an error generation circuit that selectively changes data in some sections, and further has an error generation control unit that instructs the error generation circuit and the type of the error generation section. Method LAN analyzer.