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CAN-CBX-AIR Manual Rev. 1.1 

CAN-CBX-AIR 

Manual 

to Product C.3050.xx

Document-File: 

Date of Print: 08.07.2005 

PCB version: Rev. 1.0 

Changes in the chapters 

I:\texte\Doku\MANUALS\CAN\CBX\AIR\English\CAN-CBX-AIR_11 .en9 

The changes in the user’s manual listed below affect changes in the hardware as well as changes in the 

description of the facts only. 

Chapter Changes versus previous version 

- First English version 

Technical details are subject to change without notice. 

CAN-CBX-AIR Manual Rev. 1.1


N O T E 

The information in this document has been carefully checked and is believed to be entirely reliable. esd 

makes no warranty of any kind with regard to the material in this document, and assumes no 

responsibility for any errors that may appear in this document. esd reserves the right to make changes 

without notice to this, or any of its products, to improve reliability, performance or design. 

esd assumes no responsibility for the use of any circuitry other than circuitry which is part of a product 

of esd gmbh. 

esd does not convey to the purchaser of the product described herein any license under the patent rights 

of esd gmbh nor the rights of others. 

esd electronic system design gmbh 

Vahrenwalder Str. 207 

30165 Hannover 

Germany 

Phone: +49-511-372 98-0 

Fax: +49-511-372 98-68 

E-mail: info@esd-electronics.com 

Internet: www.esd-electronics.com 

USA / Canada: 

esd electronics Inc. 

12 Elm Street 

Hatfield, MA 01038-0048 

USA 

Phone: +1-800-732-8006 

Fax: +1-800-732-8093 

E-mail: us-sales@esd-electronics.com 

Internet: www.esd-electronics.us

Contents Page 

1. Overview .................................................................... 3 

2. Hardware Installation ......................................................... 4 

2.1 Connecting Diagram .................................................... 4 

2.2 LED- and Connector View ............................................... 5 

2.3 Coding Switch ......................................................... 7 

2.4 Installation of the Module Using Optional In-Rail Bus Connector ................. 9 

2.5 Remove the CAN-CBX Module from the Optional In-Rail Bus .................. 10 

3. Technical Data .............................................................. 11 

3.1 General Technical Data ................................................. 11 

3.2 Microcontroller ....................................................... 11 

3.3 CAN Interface ........................................................ 12 

3.4 Serial Interface ........................................................ 12 

3.5 Radio Communication .................................................. 12 

3.6 Software ............................................................. 13 

3.7 Order Information ..................................................... 13 

4. Description of the Units ....................................................... 14 

4.1 CAN Interface ........................................................ 14 

4.1.1 Interface Circuit ............................................... 14 

4.2 Serial Interfaces ....................................................... 15 

4.2.1 Default Setting of the CAN-CBX-AIR Module ....................... 15 

4.2.2 Configuration ................................................. 15 

4.2.3 Connection of the RS-232-Interface ................................ 15 

5. Configuration of the CAN-CBX-AIR-Module .................................... 16 

5.1 Serial Interface and Coding Switches ...................................... 16 

5.2 Commands ........................................................... 16 

5.3 Change Configuration .................................................. 21 

6. Connector Assignment ....................................................... 22 

6.1 Serial Interface (X100, 9-pin DSUB socket) ................................. 22 

6.2 CAN-Bus (X200, 5-pin COMBICON-Style) ................................ 24 

6.3 CAN and Power Supply Voltage via In-Rail-Bus X210 ....................... 25 

6.4 Power Supply Voltage X500 ............................................. 26 

7. Correctly Wiring Electrically Isolated CAN Networks ............................. 27 

8. CAN-Bus Troubleshooting Guide .............................................. 31 

8.1 Termination .......................................................... 31 

8.2 CAN_H/CAN_L Voltage ............................................... 32 

8.3 Ground ............................................................. 32 

8.4 CAN Transceiver Resistance Test ........................................ 33 

CAN-CBX-AIR Manual Rev. 1.1 1

2 

This page is intentionally left blank. 


1. Overview 

C 

A 

N 

B 

U 

S 

CAN Connector 

MC1,5/5-GF38 

ME-MAX 

Bus Connector 

Power Connector 

MSTBO 2,5/4- 

G1LKMGY 

Electrical Isolation 

Physical 

CAN 

Layer 

Power Supply 

24 V(DC) 

+5 V= 

DC/DC 

Converter 

LEDs 

+5 V= 

CAN 

Microcontroller 

MB90497 

Transmitter/ 

Receiver 

Serial 

Interface 

Fig. 1: Block diagram of the CAN-CBX-AIR module 

Overview 

Coding Switches 

CAN Baud Rate 

CANopen Node-ID 

DSUB9 

Connector 

The CAN-CBX-AIR module is designed for wireless radio communication of separated CAN networks. 

A CAN-CBX-AIR-Bridge comprises two CAN-CBX-AIR modules. 

The CAN-CBX-AIR module is equipped with a MB90F543 microcontroller, which buffers the CANdata 

in a local SRAM. The firmware is stored in the Flash memory. Parameters are stored in a serial 

EEPROM. 

The power supply voltage and the CAN bus signals can be fed via the In-Rail-bus connector, integrated 

in the mounting rail, or via individual connectors. 

The ISO 11898-compliant CAN interface allows a maximum data transfer rate of 1 Mbit/s. The CAN 

interface is electrically isolated from other units by optocouplers and a DC/DC-converter. 

The CANopen node-ID of the CAN-CBX-AIR module and the CAN bit rate can be easily set via three 

coding switches. 

The serial RS-232 interface for service and development can be connected via a DSUB9 connector. 

CAN-CBX-AIR Manual Rev. 1.1 3 

Antenna 

i

Hardware Installation 

2. Hardware Installation 

2.1 Connecting Diagram 

4 

Fig. 2: Connections of the CAN-CBX-AIR module 

For the signal assignments of the connectors in table form refer to page 22. 


2.2 LED- and Connector View 


Fig. 3: Position of the LEDs and connectors in the front panel 


LED 

Label 

6 


LED 

Color 

LED 

No. 

T yellow 140A Traffic 

R yellow 140B Radio Quality 

C yellow 140C CAN State 

Name LED State Indication 

on transmission in process 

short blinking data package is transmitted or received 

off no data transmission 

on radio signal ok 

blinking 

radio signal disturbed, the worse the signal, 

the faster the blinking 

on CAN-Bus ok 

blinking 

CAN-Bus signal disturbed, the worse the 

signal, the faster the blinking 

P yellow 140D Power on 24 V-power supply voltage 

Table 1: Indication of the LEDs 

During operation the LED state ‘off’ is not defined for the LEDs Radio Quality, CAN State and Power, 

i.e. the LEDs are only off, if the module is turned off. 


2.3 Coding Switch 

Fig. 4: Position of the coding switches 


After switching on the module the position of the coding switches is read and evaluated by the 

firmware. Changes of the settings therefore have to be made before switching on the module, because 

changes of the settings are not determined during operation. 

Node-ID 

The address range of the CAN-CBX-AIR module can be set hexadecimal from 01 h to FF h, i.e. decimal 

from 1 to 255. 

The higher-order bits (higher-order nibble) are set via coding switch HIGH, the lower-order bits are 

set via coding switch LOW. 

Attention: 

Please pay attention that the node-ID of the one module has to correspond with the node-ID of 

the other module! 

For updating the firmware the coding switches have to be set to 00 h. 


Baud rate 

8 


The baud rate can be set with the coding switch BAUD. 

Values from 0 h to F h can be set via the coding switch. The values of the baud rate can be taken from 

the following table: 

Setting Baud rate [Kbit/s] Setting Baud rate [Kbit/s] 

0 1000 8 66.6 

1 666.6 9 50 

2 500 A 33.3 

3 333.3 B 20 

4 250 C 12.5 

5 166 D 10 

6 125 E 800 

7 100 F 

Table 2: Index of the baud rate 

Setting via serial 

configuration 

Note: To select the baud rate via serial configuration (see page 17) the coding switch has to be 

set to F h. 



2.4 Installation of the Module Using Optional In-Rail Bus Connector 

If the CAN bus signals and the power supply voltage shall be fed via the In-Rail bus, please proceed 

as follows: 

Figure 5: Mounting rail with bus connector 

1. Position the In-Rail bus connector on the mounting rail and snap it onto the mounting rail using 

slight pressure. Plug the bus connectors together to contact the communication and power 

signals (in parallel with one). The bus connectors can be plugged together before or after 

mounting the CAN-CBX modules. 

2. Place the CAN-CBX module with the DIN rail guideway on the top edge of the mounting rail. 

Figure 6 : Mounting CAN-CBX modules 

3. Swivel the CAN-CBX module onto the mounting rail in pressing the module downwards 


10 


according to the arrow as shown in figure 6. The housing is mechanically guided by the DIN 

rail bus connector. 

4. When mounting the CAN-CBX module the metal foot catch snaps on the bottom edge of the 

mounting rail. Now the module is mounted on the mounting rail and connected to the In-Rail 

bus via the bus connector. Connect the bus connectors and the In-Rail bus if not already done. 

Figure 7: Mounted CAN-CBX module 

2.5 Remove the CAN-CBX Module from the Optional In-Rail Bus 

If the CAN-CBX module is connected to the In-Rail bus please proceed as follows: 

Release the module from the mounting rail in moving the foot catch (see figure 7) downwards (e.g. with 

a screwdriver). Now the module is detached from the bottom edge of the mounting rail and can be 

removed. 

Note: It is possible to remove entire individual devices from the whole without interrupting the 

In-Rail bus connection, because the contact chain will not be interrupted. 


3. Technical Data 

3.1 General Technical Data 

Power supply voltage 

Connectors 

Temperature range 


nominal voltage 24 V/DC ±10%, 

current consumption (at 20 C): 60 mA (typically) 

X100 (DSUB9, socket) - Serial interface 

X200 (5-pin COMBICON connector) - CAN interface 

X210 (ME-MAX-TRAG5, Phoenix Contact TBUS-connector) - 

CAN interface and power supply voltage via In-Rail-Bus 

X300 (SMA-coaxial-socket, Multicomp, inner conductor : female) - 

antenna connector 

X500 (4-pol.COMBICON plug with spring-cage connection) - 24Vpower 

supply voltage 

0...50 C ambient temperature 

(-20 C ... +70 C on request) 

Humidity max. 90%, non-condensing 

Dimensions 

Weight approx. 125 g 

3.2 Microcontroller 

Microcontroller MB90F543 

Memory 

width: 22 mm, height: 100 mm, depth: 115 mm 

(including hat rail mounting and connector projection, but without 

antenna) 

SRAM: internal in MB90F543, 6 Kbyte 

Flash-EPROM: internal in MB90F543, 128 Kbyte 

EEPROM: serial SPI-EEPROM 



3.3 CAN Interface 

Number of CAN interfaces 1 x CAN 

Connection 

12 

CAN controller 

Electrical isolation of CAN 

interfaces from other units 

Physical CAN Layer 

3.4 Serial Interface 

Controller MB90F543 

Interface 

5-pol. COMBICON with spring-cage connection 

or via Phoenix Contact TBUS-connector (In-Rail-Bus) 

MB90F543, CAN 2.0A/B, 

11- and 29-bit CAN identifier 

Connection 9-pin DSUB socket 

3.5 Radio Communication 

Antenna connector 

(at CAN-CBX-AIR) 

via optocouplers and DC/DC-converter 

reference voltage: 300 V/DC, 250 V/AC 

Transmitting frequency 2.44 GHz (ISM-band) 

Transceiver 

Antenna 

Range 

CAN-CBX-AIR CAN-CBX-AIR 

Physical Layer according to ISO 11898, 

transfer rate programmable from 10 Kbit/s up to 1 Mbit/s 

RS-232, 

only the signals TxD, RxD and GND are supported 

SMA-connector, coaxial socket (inner conductor: female) 

typical peak power output: + 2 dBm, 

typical Rx sensitivity for BER = 10 -4 : - 80 dBm 

connector of the antenna: coaxial SMA-connector 

(inner conductor: male), 

impedance: 50 Ohm nominal, 

antenna gain: 2.0 dBi 

in open field approx. 15 m 


3.6 Software 

Update update option via serial interface 

3.7 Order Information 

CAN-CBX-AIR 


Type Properties Order No. 

CAN-CBX-AIR-Bridge 

Wireless CAN-Bridge 

CAN according to ISO 11898, bit rate up to 1 Mbit/s, 

electrically isolated, 2.4 GHz ISM-band, 24 V/DC, 

hat rail mounting 

2x C.3050.02, 

Transfer range in open field approx. 15 m 

C.3050.02 

C.3050.04 

CAN-CBX-AIR-ME Manual in English 1*) C.3050.21 

CAN-CBX-AIR-ENG 

Engineering Manual in English 2*) 

Contents: Circuit diagrams, PCB top overlay drawing, 

data sheets of significant components 

1*) If module and manual are ordered together, the manual is free of charge. 

2*) This manual is liable for costs, please contact our support. 

C.3050.25 


14 

CRX0 

Description of the Units 

4. Description of the Units 

4.1 CAN Interface 

4.1.1 Interface Circuit 

10K 

CTX0 GND 

to 

Microcontroller 

DC/DC 

S7U-0505 

VCC 

+ + 

VC05D150 

5V 

10µF 

GND 

- 

5V 

- 

CAN_GND 

VCC 

GND 

VCCin 

IN 

GNDin 

VCCout 

OUT 

2.2M 

2.2nF/250V~ 

Optical Coupler 

HCPL7710 

ENABLE 

GNDout 

VCCout 

OUT 

ENABLE 

GNDout 

Optical Coupler 

HCPL7710 

VCCin 

IN 

GNDin 

+5V 

+5V 

TX 

VDD 

BUSL 

RX BUSH 

R/GND 

+5V 

CAN Transceiver 

TJA1050 

GND 

CAN-bus driver 

+5V 

ADD-On option (X7-X8) for other Physical Layers 

Fig. 8: Circuit of the CAN interface 

Reference potential M24 

Power supply voltage P24 

CAN_GND 

CAN_H 

CAN_L 

X210 

In-Rail-Bus 

X200 

MC1,5/5-GF-3,81 

CAN_L 

CAN_H 

CAN_GND 

Shield 

n.c. 

4T, 4B 

5T, 5B 

3T, 3B 

1T, 1B 

2T, 2B 


2 

4 

1 

3 

5

4.2 Serial Interfaces 

4.2.1 Default Setting of the CAN-CBX-AIR Module 

Bit rate: 9600 Baud 

Data bits: 8 

Parity: no 

Stop bit: 1 

Handshake: no 

4.2.2 Configuration 

TxD 

RxD 

GND 

3 

2 

TxD 

RxD 

5 GND 

Description of the Units 

The serial interface is controlled by the MB90F543 microcontroller. 

The bit rate is 9600 Baud. Set the user’s terminal / PC to this value. The bit rate of the CAN-CBX-AIR 

module can not be changed. 

4.2.3 Connection of the RS-232-Interface 

Below, the wiring of the serial interface is shown. The figure is used to explain the short terms of the 

signals as used in the chapter Connector Assignments. The signal description is given exemplary for 

the connection of the CAN-CBX-AIR to a PC. 

Note: For the connection of the CAN-CBX-AIR module to the RS-232 interface of the PC a 

nullmodem is necessary (if not already considered by the configuration of the serial lines). 

local 

signalterms 

CAN-CBX-AIR 

(Terminal, DEE) 

pin numbers of the 9-pole DSUB connector 

of the CAN-CBX-AIR module 

pin number of the 9-pole DSUB connector 

of the CAN-CBX-AIR module 

PC 

(Modem, DÜE) 

Fig. 9: Connecting diagram of the RS-232 interface 


3 

2 

5

Configuration 

5. Configuration of the CAN-CBX-AIR-Module 

This chapter describes the procedure for the configuration of the CAN-CBX-AIR, which can easily be 

done e.g. by means of the program ‘Hyperterminal’ of Windows. 

5.1 Serial Interface and Coding Switches 

The serial interface of the PC has to be configured with the values which are described in chapter 

Default Setting of CAN-CBX-Modules, (see page 15). 

Attention: The settings of the coding switches are only read by the firmware when the module 

is switched on. Thus changes of the settings have to be made before switching on 

the module. Changes of the settings during operation have no effect (see page 7). 

5.2 Commands 

After the power supply has been switched on the CAN-CBX-AIR module wakes up and puts out a 

message in the hyperterminal. 

Now you can enter the commands directly and acknowledge with >EnterEnter< 

output: B0 : 6 


Configuration 

Bn:HexIndex The baud rate can only be set via software, if the coding switch is set to the 

value F h when the module is switched on. 

By means of command Bn: you can select the bit rate of the CAN net with the 

net number n, with: n= 0 for net 0 

If values between 0 h and F h are read for the HexIndex, the bit rate is configured 

according to the following table: 

HexIndex Baud rate [Kbit/s] HexIndex Baud rate [Kbit/s] 

0 1000 8 66.6 

1 666.6 9 50 

2 500 A 33.3 

3 333.3 B 20 

4 250 C 12.5 

5 166 D 10 

6 125 E 800 

7 100 F reserved 

Table 3: Index of the baud rate 

In the following example the bit rate of net 0 (n=0) is to be configured to 

10 Kbit/s. From Table 3 you get the HexIndex = D. Your input therefore is as 

follows: 

Input : B0:D >Enter< 

Bn:8000yyzz Alternatively you can configure the bit-timing register of the MB90F543 

component used, directly. In this case the register value for the bit-timing 

registers BTR0 and BTR1 is specified directly. 

Here is: n: 0... net number 

yy: value for BTR0 

zz: value for BTR1 

Please refer to the manuals of the controller MB90F543 for the correct way to 

determine the bit timing and the bit rate from the register values. 

The manual can e.g. be downloaded from the Fujitsu-Homepage: 

http://www.fme.gsdc.de/gsdc.htm?products/mb90495g.htm 

Choose the ‘MB90F540/545G Series Hardware Manual VX-xx’. 


Configuration 

I0:ID Net 0 I1:ID Net 1 

This command assigns an identifier of CAN-net 1 to an identifier of CAN-net 0. 

The identifier ID Net 0, which is received by the local CAN net, is transmitted 

with identifier ID Net 1 on the CAN net which is connected via the transmission 

path. 

18 

Note: 

If you want to configure 29-bit CAN identifier (value range bit 28...bit 0), bit 29 

has to be set to indicate the 29-bit identifier to the system (20000000 h according 

to CANopen)! 

In the example below the 29 bit identifier 3456789 h of the net 0 is mapped to the 

11-bit identifier 543 h of net 1. 

Input: I0:23456789 I1:543 >Enter< 

In the following example the 11-bit identifier ID Net 0 = 200 h is mapped to the 

11-bit identifier ID Netz 1 = 300 h. 

Input: I0:200 I1:300 >Enter< 


Configuration 

M0:1:zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz 

With this command masks for 29-bit identifiers can be defined. 

This way all identifiers of particular areas of identifiers can be assigned. 

Here is: 0: 0... net in which the identifiers are to be received 

1: 1... net in which the filtered CAN frames are to be 

transmitted: always 1 for the net transmitted 

via the transmission path. 

z...z: 0,1,x... mask 

0: the according bit has to be logically 0 

1: the according bit has to be logically 1 

x: the status of the according bit does not 

matter 

Attention: Please note that the bits are numbered from right to left. 

The first bit from the left is therefore bit 30! 

The mask must always have the full length of 30 bits (29 bits + 30th bit to 

distinguish between 11-bit and 29-bit identifiers). 

The first bit is the distinction bit, the following bit is the MSB of the CAN 

identifier, etc. 

Bit 30 Meaning 

0 11-bit identifier 

1 29-bit identifier 

x 11- and 29-bit identifier 

In the following example only the odd identifiers between 0 h and FF h are let 

through from net 0 to net 1: 

Input: M0:1:0000000000000000000000xxxxxxx1 

>Enter< 

If more than one mask has been defined for one direction, one identifier has to 

pass all masks (AND links) in order to be mapped in the other net. At the 

moment 2 masks are possible for each direction. 


Configuration 

The current configuration of the CAN-CBX-AIR module from the previous examples can be displayed 

by means of command R. 

20 

Input: R >Enter< 

Output: B0:6 

I0:200 I1:300 

I0:23456789 I1:543 

M0:1:0000000000000000000000xxxxxxx1 

E After the configuration has been successfully completed, the configured data is 

stored in the configuration memory by means of command E. Only after the 

data have been stored the changes become effective. 

The CAN-CBX-AIR module is now in RUN status and meets the desired bridge 

function. 

Input: E >Enter< 

C You can delete a configuration again by means of the command C. The 

command deletes all identifier assignments and resets the CAN bit rates to the 

default value of HexIndex 6, that is a bit rate of 125 Kbit/s. The configuration 

memory is also deleted. 

Input: C >Enter< 


5.3 Change Configuration 

Configuration 

It is not possible to modify single parameters of an existing configuration. You have to call the 

command C (see page 20) to clear all parameters. After that you have to configure the CAN-CBX-AIR 

again with the correct parameters. Do not forget to call the command E to store the new data to the 

configuration memory after the configuration. 


22 

Connector Assignment 

6. Connector Assignment 

6.1 Serial Interface (X100, 9-pin DSUB socket) 

Pin Position: 

Pin Assignment: 

Signal Pin Signal 

- 1 

RxD (Input) 2 

TxD (Output) 3 

- 4 

GND 5 

9-pin DSUB socket 

Signal description: 

RxD/TxD ... receive and transmit data 

GND ... reference potential 

- ... reserved 

6 - 

7 - 

8 - 

9 - 


Connecting cable for the serial interface 

5 4 3 2 1 

9 8 7 6 

P1: 

(PC) 

1 

2 

3 

4 

5 

6 

7 

8 

9 


Below the connecting cable of the serial interface (RS-232) of the CAN-CBX-AIR module to a PC is 

shown. 

P1 

DSUB female 

9-pole 

P2: 

(CAN-CBX-AIR Module) 

1 

RxD 

2 RxD 

TxD 

3 TxD 


GND 

5 4 3 2 1 

9 8 7 6 

4 

5 

6 

7 

8 

9 

GND 

P2 

DSUB female 

9-pole 

local signal 

names used 

at CAN-CBX-Module


6.2 CAN-Bus (X200, 5-pin COMBICON-Style) 

The CAN-Bus connector can have spring-cage connections or screw connections. Wires with a cross 

section of up to 2.5 mm² fit in the terminal blocks. 


24 

Pin Position: Pin Assignment: 

1 

2 

3 

4 

5 

Pin Signal 

1 CAN_GND 

2 CAN_L 

3 Shield 

4 CAN_H 

5 n.c. 

CAN_L, CAN_H ... CAN signals 

CAN_GND ... reference potential of the local CAN physical layer 

Shield ... shielding 

(connected with the shield contact of the case, which has a connection to the 

mounting rail) 

n.c. ... not connected 

Adapter Cable from 5-pin Mini-Combicon (with spring-cage-connection) to 9-pin DSUB: 

The 9-pin DSUB 

connector is 

assigned in 

accordance with 

CiA DS 102. 


6.3 CAN and Power Supply Voltage via In-Rail-Bus X210 

Connector: Bus connector MEMAX 

ME 22,5 TBUS 1,5/5-ST-3,81 KMGY 


Pin Position: 


Pin Signal 

5 M24 (GND) 

4 P24 (+24 V) 

3 CAN_GND 

2 CAN_L 

1 CAN_H 

S FE (PE_GND) 

CAN_L, 

CAN_H ... CAN signals 

CAN_GND ... reference potential of the local CAN physical layers 

P24... power supply voltage +24 V 

M24... reference potential 

FE... functional earth contact (EMC) 




6.4 Power Supply Voltage X500 

Connector type: Mini-Combicon connector, MSTBO 2,5/4-G1LKMGY 

26 

Pin Position: 


Pin 4 3 2 1 

Signal - - 

Refer to the connecting diagram (page 4). 


P24... power supply voltage +24 V 

M24... reference potential 

M24 

(GND) 

P24 

(+ 24 V) 


CAN_H 

CAN_L 

CAN_GND 

Shielded wire with 

transposed wires 

120 Ohm 

DSUB9 connector 

(female or male) 

CAN_GND 

DSUB9 connector 

(female or male) 

pin designation 

(at wire shield) 

pin designation 

1 

2 

n.c. 

CAN_L 

n.c. 1 

2 

3 

3 

4 n.c. 

n.c. 4 

5 n.c. 

n.c. 5 

6 

7 

n.c. 

CAN_H 

n.c. 6 

7 

8 n.c. 

n.c. 8 

9 n.c. 

n.c. 9 

connector case n.c. 

n.c. connector case 

n.c. = not connected 

Wiring 

7. Correctly Wiring Electrically Isolated CAN Networks 

Generally all instructions applying for wiring regarding an electromagnetic compatible installation, 

wiring, cross sections of wires, material to be used, minimum distances, lightning protection, etc. have 

to be followed. 

The following general rules for the CAN wiring must be followed: 

1. 

2. 

3. 

A CAN net must not branch (exception: short dead-end feeders) and has to be terminated 

by the wave impedance of the wire (generally 120 W ±10%) at both ends (between the 

signals CAN_L and CAN_H and not at GND)! 

A CAN data wire requires two twisted wires and a wire to conduct the reference potential 

(CAN_GND)! 

For this the shield of the wire should be used! 

The reference potential CAN_GND has to be connected to the earth potential (PE) at one 

point. Exactly one connection to earth has to be established! 

4. The bit rate has to be adapted to the wire length. 

5. Dead-end feeders have to kept as short as possible (l < 0.3 m)! 

6. 

7. 

8. 

When using double shielded wires the external shield has to be connected to the earth 

potential (PE) at one point. There must be not more than one connection to earth. 

A suitable type of wire (wave impedance ca. 120 ±10%) has to be used and the voltage 

loss in the wire has to be considered! 

CAN wires should not be laid directly next to disturbing sources. If this cannot be avoided, 

double shielded wires are preferable. 

Wire structure Signal assignment of wire and connection of earthing and terminator 

CAN wire with connectors 

Figure: Structure and connection of wire 


120 Ohm 

earth (PE)

Cabling 

28 

Wiring 

for devices which have only one CAN connector per net use T-connector and dead-end feeder 

(shorter than 0.3 m) (available as accessory) 

CAN-Board 

Net 1 

e.g. PCI/405, 

CAN-USB, 

VME-CAN2, etc. 

Net 2 

Connecting 

CAN_GND to 

Protective Conductor PE 

Terminator 

PE 

with PE Connector 

T-Connector 

Order-no.: C.1311.03 

l < 0,3 m 

Terminal Resistance 

CAN-CBM- 

DIO8 

T-Connector 

C.1311.03 

CAN-Cable 

Order-no.: C.1323.03 

l < 0,3 m 

CAN-CBM- 

AI4 

T-Connector 

C.1311.03 

CAN-Cable 

Order-no.: C.1323.03 

CAN_H 

CAN_L 

CAN_GND 

l < 0,3 m 

CAN-CBM- 

COM1 

T-Connector 

C.1311.03 

Female Connector 

Male Connector 

Male Terminator 

(Order-no.: C.1302.01) 

Female Terminator 

(Order-no.: C.1301.01) 

l < 0,3 m 

CAN-Cable 

Order-no.: C.1323.03 

Figure: Example for correct wiring (when using single shielded wires) 

use external terminator, because this can later be found again more easily! 

T-Connector 

C.1311.03 

Terminator 

l < 0,3 m 

e.g. 

CAN-SPS Interface 

CSC595/2 

or 

CAN-PC Board 

9-pin DSUB-terminator with male and female contacts and earth terminal are available as 

accessories 

Earthing 

CAN_GND has to be conducted in the CAN wire, because the individual esd modules are 

electrically isolated from each other! 

CAN_GND has to be connected to the earth potential (PE) at exactly one point in the net! 

each CAN user without electrically isolated interface works as an earthing, therefore: do not 

connect more than one user without potential separation! 

Earthing CAN e.g. be made at a connector 


Wire Length 

Wiring 

Optical couplers are delaying the CAN signals. By using fast optical couplers and testing each 

board at 1 Mbit/s, however, esd CAN guarantee a reachable length of 37 m at 1 Mbit/s for most 

esd CAN modules within a closed net without impedance disturbances like e.g. longer dead-end 

feeders. (Exception: CAN-CBM-DIO8, -AI4 and AO4 (these modules work only up to 10 m with 

1 Mbit/s)) 

Bit rate 

[Kbit/s] 

1000 

800 

666.6 

500 

333.3 

250 

166 

125 

100 

66.6 

50 

33.3 

20 

12.5 

10 

Typical values of reachable 

wire length with esd 

interface l max [m] 

37 

59 

80 

130 

180 

270 

420 

570 

710 

1000 

1400 

2000 

3600 

5400 

7300 

CiA recommendations 

(07/95) for reachable wire 

lengths l min [m] 

25 

50 

- 

100 

- 

250 

- 

500 

650 

- 

1000 

- 

2500 

- 

5000 

Table: Reachable wire lengths depending on the bit rate when using esd-CAN interfaces 


Wiring 

Examples for CAN Wires 

30 

Manufacturer Type of wire 

U.I. LAPP GmbH 

Schulze-Delitzsch-Straße 25 

70565 Stuttgart 

Germany 

www.lappkabel.de 

ConCab GmbH 

Äußerer Eichwald 

74535 Mainhardt 

Germany 

www.concab.de 

SAB Bröckskes GmbH&Co. KG 

Grefrather Straße 204-212b 

41749 Viersen 

Germany 

www.sab-brockskes.de 

e.g. 

UNITRONIC ®-BUS CAN UL/CSA (UL/CSA approved) 

UNITRONIC ®-BUS-FD P CAN UL/CSA (UL/CSA approved) 

e.g. 

BUS-PVC-C (1 x 2 x 0,22 mm²) Order No.: 93 022 016 (UL appr.) 

BUS-Schleppflex-PUR-C (1 x 2 x 0,25 mm²) Order No.: 94 025 016 (UL appr.) 

e.g. 

SABIX ® CB 620 (1 x 2 x 0,25 mm²) Order No.: 56202251 

CB 627 (1 x 2 x 0,25 mm²) Order No.: 06272251 (UL appr.) 

Note: Completely configured CAN wires can be ordered from esd. 


8. CAN-Bus Troubleshooting Guide 

CAN-Bus Troubleshooting Guide 

The CAN-Bus Troubleshooting Guide is a guide to find and eliminate the most frequent hardware-error 

causes in the wiring of CAN-networks. 

120 

CAN_H 

CAN_L 

CAN_GND 

8.1 Termination 

Figure: Simplified diagram of a CAN network 

CAN_H 

CAN_L 

CAN_GND 

2 3 

V V 

The termination is used to match impedance of a node to the impedance of the transmission line being 

used. When impedance is mismatched, the transmitted signal is not completely absorbed by the load 

and a portion is reflected back into the transmission line. If the source, transmission line and load 

impedance are equal these reflections are eliminated. This test measures the series resistance of the 

CAN data pair conductors and the attached terminating resistors. 

To test it, please 

1. Turn off all power supplies of the attached CAN nodes. 

2. Measure the DC resistance between CAN_H and CAN_L at the middle and ends of 

the network 1 (see figure above). 

The measured value should be between 50 and 70 . 

If the value is below 50 , please make sure that: 

- there is no short circuit between CAN_H and CAN_L wiring 

- there are not more than two terminating resistors 

- the nodes do not have faulty transceivers. 

If the value is higher than 70 , please make sure that: 

- there are no open circuits in CAN_H or CAN_L wiring 

- your bus system has two terminating resistors (one at each end) and that they are 120 each. 


120 

 

1


8.2 CAN_H/CAN_L Voltage 

Each node contains a CAN transceiver that outputs differential signals. When the network 

communication is idle the CAN_H and CAN_L voltages are approximately 2.5 volts. Faulty 

transceivers can cause the idle voltages to vary and disrupt network communication. 

To test for faulty transceivers, please 

1. Turn on all supplies. 

2. Stop all network communication. 

3. Measure the DC voltage between CAN_H and GND 2 (see figure above). 

4. Measure the DC voltage between CAN_L and GND 3 (see figure above). 

32 

Normally the voltage should be between 2.0 V and 4.0 V. 

If it is lower than 2.0 V or higher than 4.0 V, it is possible that one or more nodes have faulty 

transceivers. For a voltage lower than 2.0 V please check CAN_H and CAN_L conductors for 

continuity. For a voltage higher than 4.0 V, please check for excessive voltage. 

To find the node with a faulty transceiver please test the CAN transceiver resistance (see next page). 

8.3 Ground 

The shield of the CAN network has to be grounded at only one location. This test will indicate if the 

shielding is grounded in several places. 

To test it, please 

1. Disconnect the shield wire from the ground. 

2. Measure the DC resistance between Shield and ground. 

3. Connect Shield wire to ground. 

The resistance should be higher than 1 M . If it is lower, please search for additional grounding of 

the shield wires. 


8.4 CAN Transceiver Resistance Test 


CAN transceivers have one circuit that controls CAN_H and another circuit that controls CAN_L. 

Experience has shown that electrical damage to one or both of the circuits may increase the leakage 

current in these circuits. 

To measure the current leakage through the CAN circuits, please use an ohm-meter and: 

1. Disconnect the node from the network. Leave the node unpowered 4 (see figure below). 

2. Measure the DC resistance between CAN_H and CAN_GND 5 (see figure below). 

3. Measure the DC resistance between CAN_L and CAN_GND 6 (see figure below). 

Normally the resistance should be between 1 M and 4 M . If it is not within this range, the CAN 

transceiver is probably faulty. 

CAN-Node 

CAN- 

Transceiver 

CAN_H 

CAN_L 

CAN_GND 

Power 

4 Disconnect 

Power ! 

5 6 


 

 

Disconnect 

CAN ! 

Figure: Simplified diagram of a CAN node 

4

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