CAN Bus adaptor with a 9-pin male D-Sub connector

D-sub 9 pin 120 Ohm termination adapter

Terminal Resistor 120 Ohm, DB9, CAN Bus  

Termination resistance of CAN bus

CAN-bus communication

How to match the termination resistance of CAN bus  ?

According to the ISO 11898 specification, in order to enhance the reliability of CAN-bus communication, the two endpoints of the CAN-bus network usually need to add a termination matching resistance of 120Ω

The size of the terminal matching resistance is determined by the characteristic impedance of the transmission cable. For example, if the characteristic impedance of the twisted pair is 120Ω, the two terminals on the bus should also be equipped with a 120Ω terminal resistance.

In addition, in long-distance communication, the resistance of the terminal resistor sometimes needs to be increased to ensure the normal communication.

CAN belongs to the category of field bus, which is a serial communication network that effectively supports distributed control or real-time control.

Compared with many RS-485 distributed control systems based on R line, the distributed control system based on CAN bus has obvious advantages in the following aspects.
 

The CAN bus is connected to the physical bus through the two output terminals CANH and CANL of the CAN transceiver interface chip 82C250, and the state of the CANH terminal can only be a high level or a floating state, and the CANL terminal can only be a low level or a floating state.

This ensures that there will be no phenomenon in the RS-485 network, that is, when there is an error in the system and multiple nodes send data to the bus at the same time, the bus will be short-circuited, thereby damaging some nodes.

Moreover, the CAN node has the function of automatically turning off the output in the case of serious errors, so that the operation of other nodes on the bus is not affected, so as to ensure that there will be no problems in the network