CANwatch - EMS Dr. Thomas Wünsche
Contents
1. 9 3 2 Absolute Limiting Values 10 3 3 Nominal values 10 3 4 Evaluation characteristics 11 4 Small CAN Troubleshooting Guide 12 User Manual iil iv User Manual CANwatch CAN Physical Layer Analyser CAN Physical Layer Analyser CANwatch 1 Overview 1 1 Attributes e Analyser for the physical layer of CAN based systems e Designed for systems according to ISO 11898 high speed e Diagnosis of signal shape and level e Indication of the percent frequency of error frames e Easy operation usable by installers and plant operators e LED display for error indication 1 2 General Description CANwatch is an analyser supporting easy de tection of errors during installation and operati on of CAN networks CANwatch monitors the analogue signals on the bus and detects er rors like e g invalid levels overshoots slow slopes and short circuits of signal lines to supply lines Besides the diagnosis of problems during in stallation CANwatch allows recognition of sig nal deficiencies below the level causing failu res This allows preventive error recognition and thus an increase in the availability of auto mated systems CANwatch offers an easy solution for installers and plant operators for detection and correcti on of errors on the physical layer of a CAN ba sed system Until now this was usually left to CAN specialists using expensive and bulky hardware equipment2. 1 3 Ordering Information 12 10 001 20 CANwatch CAN physical layer analyser for rail mount application with LED display User Manual User Manual CANwatch CAN Physical Layer Analyser CAN Physical Layer Analyser CANwatch 2 Operation 2 1 Measuring Principle CANwatch is a passive device whose function is based on the analysis of static and dynamic parameters of the CAN signal The evaluation of the signal shape is mainly based on the dif ference level between the signals CAN High and CAN Low The protocol based information of the CAN telegrams has no influence on the function of the device except error frames and therefore CANwatch is suitable for all CAN based higher layer protocols 2 2 Connection Attention Connection CANwatch has two Sub D 9 plugs for the con nection to the CAN The CAN connector is also used for the power supply of CANwatch CAN bus cables can alternatively be plugged into connector 1 upper left plug or connector 2 upper right plug Optional extensions in the planning stage can be operated at con nector 1 exclusively In addition to the contacts for CAN signal and supply CANwatch uses additional control lines These are also connected to the Sub D plugs The corresponding contacts may only be con nected to permitted accessories connection to other signals may cause permanent damage of CANwatch or other devices Initialisation For the analysis process
3. CAN Physical Layer Analyser CANwatch User Manual Sonnenhang 3 f D 85304 IImm nster Tel 49 8441 490260 THOMAS WUNSCHE Fax 49 8441 81860 CAN Physical Layer Analyser CANwatch Documentation for CANwatch version 1 2 Documentation date November 2004 No part of this document or the software described herein may be reproduced in any form without prior written agreement from EMS Dr Thomas Winsche For technical assistance please contact EMS Dr Thomas Wunsche Sonnenhang 3 D 85304 IImmUnster Tel 49 8441 490260 Fax 49 8441 81860 Email support ems wuensche com Our products are continuously improved Due to this fact specifications may be changed at any time and without announcement WARNING 5 CANwatch and software may not be used in applications where damage to life health or private property may result from failures in or caused by these components ii User Manual CANwatch CAN Physical Layer Analyser CAN Physical Layer Analyser CANwatch Content THIS PAGE INTENTIONALLY LEFT BLANK 1 Overview 1 11 Attributes 0 1 12 General Description 1 1 3 Ordering Information 2 2 Operation Kalaw KAKAMBAL 3 2 1 Measuring Principle 3 22 CONNEC ON s ose s sorit caci a diosa 3 2 3 Display 2 4 8 2428224 db ee 4 2 4 Guidelines for Interpretation 7 3 Technical Data 9 3 1 Configuration of Connectors
4. CANwatch is connec ted to the bus via connector 1 or 2 After suc cessful initialisation of the processor the devi ce performs a test of the LEDs These are si multaneously switched on for a short period of time about 0 5 sec Thereafter CANwatch starts with the determination of the baud rate The other measurements level test testing for over undershoots slow slopes error frames are started after the determination of the baud rate and repeated cyclically as long as CAN watch is connected to the supply voltage 2 3 Display CANwatch shows the result of the analysis on a display consisting of twelve LEDs Each LED represents a bus state or a warning The mea ning of the different displays is as follows CAN Ok CANwatch sets this LED with each recognized telegram and resets it cyclically During normal operation this LED will be flickering according to telegram traffic the brighter it lights the more telegrams are evaluated EMS Dr Thomas Wunsche 3 User Manual CANwatch CAN Physical Layer Analyser CAN Physical Layer Analyser CANwatch Serious CAN Failure CANwatch lights this LED to indicate basic er rors on the CAN e g short circuit of GND and CAN High or CAN Low respectively CAN High locked This LED is activated if CANwatch recognizes a short circuit of the CAN High line to a fixed level This is assumed by the actual software at levels of the CAN High signal of about OV against groun
5. was registe red The valid range of recessive levels for re ceiver nodes is specified between 1V and 0 5V Error Frame Display The indication of the error frames is the per centage of errors compared to the number of registered telegrams E g 0 1 1 errors means that the number of error frames related to the number of registered and evaluated te legrams is 0 1 1 The display is divided into the ranges 0 1 1 1 5 5 100 User Manual User Manual CANwatch CAN Physical Layer Analyser CAN Physical Layer Analyser CANwatch Invalid Termination The LED Invalid Termination is not supported at present Invalid bus termination can be re cognised from signal deformations over un dershoots invalid dominant level invalid re cessive level 2 4 Guidelines for Interpretation Flash Codes An absolute statement regarding the function of a CAN net in the broad range between correct signals and severely disturbed signals is not possible Therefore results from evalua tions of CANwatch should not be used for de cisions between valid and invalid but as hints on possible problems If CANwatch gives a warning concerning critical signal shapes the communication on the bus is not definitely dis turbed The LEDs Invalid Dominant Level Invalid Recessive Level Slow slopes Over Un dershoots and the LEDs for the frequency of error frames indicate the time of error events by m
6. an be caused by e Too high line resistance e Too many or faulty termination resistors e Output resists in the transceiver drivers e Mislead currents Invalid Recessive Levels Invalid recessive levels may be caused by e missing termination resistors e Mislead currents Invalid Bus Termination Under certain conditions invalid bus termina tion may be detected by measuring DC resis tance The following cases have to be dis tinguished e The terminating resistors are totally missing e Only one bus termination resistor is installed e More than two bus termination resistors are installed A reliable indication of correct termination can not be given through measurement of DC re sistance E g there is no possibility to recogni ze placement of both resistors at the same end of a cable Other termination errors may arise from the to pology of the net A reliable statement concerning valid termina tion has to consider the high frequency behavi our This may be achieved by evaluation of the signal shapes by means of the indicators Slow Slopes and Over Undershoots User Manual 13 User Manual
7. d The LED remains set until the failure is no longer detected after a new eva luation or a difference signal occurs between CAN High and CAN Low This test is perfor med with a cycle time of about 6 seconds CAN Low locked This LED is activated if CANwatch recognizes a short circuit of the CAN Low line to a fixed level This is assumed by the actual software at levels of the CAN Low signal of about OV against ground The LED remains set until the failure is no longer detected after a new eva luation or a difference signal occurs between CAN High and CAN Low This test is perfor med with a cycle time of about 6 seconds Over Undershoots CANwatch lights this LED if the CAN differen ce signal of a registered telegram is affected by over undershoots in a degree that undis turbed communication on the bus can no lon ger be guaranteed Slow Slopes If CANwatch sets this LED the CAN difference signal of a registered telegrams is affected by slow signal slopes in a degree that undistur bed communication on the bus can no longer be guaranteed Invalid Dominant Level If CANwatch lights this LED a telegram with dominant level above or below the threshold level of ISO 11898 was registered The valid range of dominant levels for receiver nodes is specified between 0 9V and 5V Invalid Recessive Level If CANwatch activates this LED a telegram with recessive level above or below the permit ted level according to ISO 11898
8. eans of flash codes Repeated Indications When CANwatch detects an error the corre sponding LED lights up The error indication is done by four different LED states LED state flashing mode meaning o error happened lt 1 second ago quickly 100ms on error happened flashing 100ms off lt 5 seconds ago slowly 100ms on error happened flashing 300ms off gt 5 seconds ago off no error It may happen that one error causes several error indications at the same time If e g a sig nal line is drawn to a fixed potential and this causes invalid levels in addition the LEDs CAN High locked or CAN Low locked and in valid dominant level or invalid recessive level will light up User Manual User Manual CANwatch CAN Physical Layer Analyser CAN Physical Layer Analyser CANwatch 3 Technical Data 3 1 Configuration of Connectors Pin Configuration Connector 1 Connector 1 is made up of a Sub D 9 plug configured to comply with CiA DS 102 version 2 0 In addition to this specification contacts are used for additional purposes Pin Signal Description reserved by CiA CAN L CAN Low bus line 1 2 3 CAN GND Ground 4 S1 Control line do not connect 5 S2 Control line do not connect GND optional ground CAN_H CAN High bus line S3 Control line do not connect 9 V CAN Power supply Hint The pins 2 3 6 7 9
9. ed to telegrams with standard format and one byte of data Erfassungsrate a S 10 20 50 100 125 250 500 800 1000 Baudrate kBit s Percentage of registered telegrams depending on the baud rate Busload50 constant distance of telegrams ____ Busload 10 constant distance of telegrams To support troubleshooting of CAN networks the following list includes possible reasons for errors indicated by CANwatch Over Undershoots The diagnosis indication of over undershoots can be triggered by the following installation defects e Impedance mismatch with resulting re flections number and position of termi nation resistors bus topology e Interferences with strong electric or magnetic fields near cables e g cau sed by electric motors power lines Interferences are not over undershoots in a classical sense but the effects on the signal shape are quite similar Slow Slopes Slow slopes can be caused by correlation of several parameters Influence on slopes re sults from e Capacitance cables devices e Resistance line and drivers filter in ductivities e Slow slope settings in the transmitter User Manual 11 12 User Manual CANwatch CAN Physical Layer Analyser CAN Physical Layer Analyser CANwatch Short Circuits Short circuits can be caused by e Damage of the bus cables e Wiring errors Invalid Dominant Levels Invalid dominant levels c
10. of connector 1 are con nected with the corresponding pins of connec tor 2 The shields of both Sub D plugs are connected to each other 3 2 Absolute Limiting Values Attention Exceeding the specified limiting values my cause permanent damage on CANwatch Parameter Min Max Unit Storage temperature 20 80 C Operating temperature 0 60 C Power supply Pin 9 100 35 V Input voltage Pin 2 7 2 7 V Due to requirements of measurement techno logy the inputs of CANwatch are not equipped with overvoltage protection including ESD Connection to overvoltage and electrostatic discharge must be avoided 3 3 Nominal values Parameter Min Max Unit Supply voltage Pin 9 10 30 V V CAN Attention The control lines are reserved for compatible accessories and may not be connected to sig Current consumption 20 65 mA nals of the system which is to be tested Pin 9 V CAN 24V Input voltage 2 7 V Pin Configuration Connector 2 Pins 2 7 According to connector 1 however the pins 4 baud rates 10 1000 kBit s 5 8 control lines S1 S3 are not used User Manual 9 10 User Manual CANwatch CAN Physical Layer Analyser CAN Physical Layer Analyser CANwatch 3 4 Evaluation characteristics 4 Small CAN Troubleshooting Guide The number of telegrams that CANwatch can maximally register and evaluate are shown in the figure The values are relat
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