background image

© 

National Instruments Corp.

7

NI 9882 Operating Instructions

CAN Bus Topology and Termination

A CAN bus consists of two or more CAN nodes cabled together. 
The CAN_H and CAN_L pins of each node are connected to the 
main CAN bus cable through a short connection known as a “stub.” 
The pair of signal wires, CAN_H and CAN_L, constitutes a 
transmission line. If the transmission line is not terminated, 
each signal change on the bus causes reflections that may cause 
communication errors. Because the CAN bus is bidirectional, both 
ends of the cable must be terminated. However, this requirement 
does not mean that every node on the bus should have a termination 
resistor; only the two nodes at the far end of the cable should have 
termination resistors.

Figure 1 shows a simplified diagram of a CAN bus with multiple 
CAN nodes and proper termination resistor (R

t

) locations.

Summary of Contents for NI 9882

Page 1: ...OPERATING INSTRUCTIONS NI 9882 1 Port DeviceNet Module...

Page 2: ...tware is available at ni com downloads Note The safety guidelines and specifications in this document are specific to the NI 9882 The other components in your system may not meet the same safety ratin...

Page 3: ...tentially explosive environment Not following these guidelines may result in serious injury or death Caution Do not disconnect I O side wires or connectors unless power has been switched off or the ar...

Page 4: ...Certificate No 07 ATEX 0626664X Each module is marked II 3G and is suitable for use in Zone 2 hazardous locations Wiring the NI 9882 The NI 9882 has one 9 pin male D Sub connector that provides conne...

Page 5: ...ower supply marked LPS with the NI 9882 The NI 9882 requires an external power supply in the range of 9 to 30 V to operate Supply power to the NI 9882 VSUP pin Note Power on VSUP is required for Devic...

Page 6: ...NI 9882 Operating Instructions 6 ni com Table 1 Pin Assignments for the NI 9882 Connector Pin Signal 1 No Connection NC 2 CAN_L 3 COM 4 NC 5 SHLD 6 COM 7 CAN_H 8 NC 9 VSUP 6 7 8 9 1 2 3 4 5...

Page 7: ...a transmission line If the transmission line is not terminated each signal change on the bus causes reflections that may cause communication errors Because the CAN bus is bidirectional both ends of th...

Page 8: ...erating Instructions 8 ni com Figure 1 CAN Bus Topology and Termination Resistor Locations CAN Node CAN Node CAN Node Rt Rt CAN Node CAN_H CAN_L CAN_H CAN_L CAN_H CAN_L CAN_H CAN_L Bus Cable Length St...

Page 9: ...f connecting the NI 9882 directly to one CAN node Figure 2 Connecting the NI 9882 to a CAN Device Cabling Requirements for the NI 9882 This section deals with cabling specifications termination resist...

Page 10: ...istors Rt should match the nominal impedance of the CAN cable and therefore comply with the values in Table 3 The onboard software selectable termination has a nominal value of 120 If you are not usin...

Page 11: ...viceNet specifications ISO 11898 specifies 40 m total cable length with a maximum stub length of 0 3 m for a bit rate of 1 Mb s The ISO 11898 specification says that significantly longer cable lengths...

Page 12: ...signal quality below ISO 11898 signal level specifications The NI 9882 electrical characteristics allow at least 110 CAN ports on a network NI 9882 Hardware Overview The NI 9882 has one full featured...

Page 13: ...ystem in software In sleep mode the system consumes less power and may dissipate less heat When a system is in sleep mode you cannot communicate with the modules Refer to the Specifications section fo...

Page 14: ...wise noted High Speed CAN Characteristics Transceiver NXP PCA82C251T Max baud rate 1 Mbps CAN_H CAN_L bus lines voltage 27 to 40 VDC Supply voltage range VSUP CAN 9 to 30 VDC MTBF Contact NI for Bellc...

Page 15: ...its Port to COM 27 to 40 VDC max Measurement Category I Measurement Category I is for measurements performed on circuits not directly connected to the electrical distribution system referred to as MAI...

Page 16: ...nnect to signals or use for measurements within Measurement Categories II III or IV Isolation Voltages Port to earth ground Withstand 1000 Vrms verified by a 5 s dielectric withstand test Continuous 6...

Page 17: ...S UL Class I Division 2 Groups A B C D T4 Class I Zone 2 AEx nA II T4 Canada C UL Class I Division 2 Groups A B C D T4 Class I Zone 2 Ex nA II T4 Europe DEMKO Ex nA II T4 Environmental Refer to the in...

Page 18: ...Maximum altitude 2 000 m Indoor use only Shock and Vibration To meet these specifications you must panel mount the CompactRIO system Operating vibration random IEC 60068 2 64 5 grms 10 to 500 Hz Opera...

Page 19: ...laboratory use EN 61326 IEC 61326 Class A emissions Basic immunity EN 55011 CISPR 11 Group 1 Class A emissions AS NZS CISPR 11 Group 1 Class A emissions FCC 47 CFR Part 15B Class A emissions ICES 001...

Page 20: ...f Conformity DoC for additional regulatory compliance information To obtain product certifications and the DoC for this product visit ni com certification search by model number or product line and cl...

Page 21: ...cument Waste Electrical and Electronic Equipment WEEE EU Customers At the end of the product life cycle all products must be sent to a WEEE recycling center For more information about WEEE recycling c...

Page 22: ...ments also has offices located around the world to help address your support needs For telephone support in the United States create your service request at ni com support and follow the calling instr...

Page 23: ...466 New Zealand 0800 553 322 Norway 47 0 66 90 76 60 Poland 48 22 328 90 10 Portugal 351 210 311 210 Russia 7 495 783 6851 Singapore 1800 226 5886 Slovenia 386 3 425 42 00 South Africa 27 0 11 805 81...

Page 24: ...to the Trademark Information at ni com trademarks for other National Instruments trademarks Other product and company names mentioned herein are trademarks or trade names of their respective companie...

Reviews: