What are termination requirements for CAN interface?
From the good old basics of transmission line theory we all know that the transmission line has R-L-C properties associated with it. Any signal from transmitter to be reproduced at receiver requires lossless line along with impedance matching between the source and destination. If the source and destination doesn't match, termination resistor need to be used. Termination resistor is also determined by the length of the transmission line between source and destination. CAN is the main interface used in the automotive and industrial markets intensively. If you are using low speed CAN there is no need to terminate the bus as the termination will be done on respective nodes. If you are using high speed CAN, termination of 120 ohms is required. The major difference between low speed and high speed CAN is the baud rate where low speed CAN operates at 250kbps and high speed CAN operates up to 1Mbps. The termination used can be split type or single.
What are some of the electrical requirements of the CAN interface?
CAN typically works with a maximum of 64 nodes. Again the dependency is on speed, bus capacitance, length of the interface. You can use up to 120 nodes as well depending on the characteristics mentioned here. You cannot keep the nodes closer as well to accommodate more number of nodes in network. This disturbs the signal integrity. If we have to use more nodes on application demand we might have to think of bridges which cause delays and disturbs signal integrity. The High-Speed ISO 11898 Standard specifications mention maximum signaling rate of 1 Mbps with a bus length of 40 m and a maximum of 30 nodes.
Is there addressing in CAN interface?
CAN nodes specifically doesn't have a address but the message transmitted between CAN nodes have an identifier. It is the nodes with their intelligence that determines the type of messages they have to deal with. Node of the nodes will transmit messages with the same identifier. CAN2.0A uses 11-bit identifier and CAN2.0B uses 29-bit identifier.
What is the maximum baud rate in CAN interface?
For CAN2.0, maximum baud rate is 1Mbit/sec. With the new CAN FD, baud rate is 15Mbit/sec.
What is the maximum possible physical distance a CAN interface can run?
This is never a straight forward answer. It always depends on the speed at which the interface runs. With a maximum baud rate of 1Mbps, the cable can run up to 40m. With CAN FD the distance is restricted to 10m.
How do you differentiate CAN2.0 and CAN FD packet?
CAN FD uses the same packet format as CAN2.0. It uses a reserve bit to identify the type of it.
Typical message format of CAN:
What are some of the electrical requirements of the CAN interface?
- During design, check if the controller you have has inbuilt transceiver along with CAN controller or you need to accommodate one.
- Verify that there is a common ground between the nodes in CAN network.
- Drivers are open-collector.
CAN typically works with a maximum of 64 nodes. Again the dependency is on speed, bus capacitance, length of the interface. You can use up to 120 nodes as well depending on the characteristics mentioned here. You cannot keep the nodes closer as well to accommodate more number of nodes in network. This disturbs the signal integrity. If we have to use more nodes on application demand we might have to think of bridges which cause delays and disturbs signal integrity. The High-Speed ISO 11898 Standard specifications mention maximum signaling rate of 1 Mbps with a bus length of 40 m and a maximum of 30 nodes.
Is there addressing in CAN interface?
CAN nodes specifically doesn't have a address but the message transmitted between CAN nodes have an identifier. It is the nodes with their intelligence that determines the type of messages they have to deal with. Node of the nodes will transmit messages with the same identifier. CAN2.0A uses 11-bit identifier and CAN2.0B uses 29-bit identifier.
What is the maximum baud rate in CAN interface?
For CAN2.0, maximum baud rate is 1Mbit/sec. With the new CAN FD, baud rate is 15Mbit/sec.
What is the maximum possible physical distance a CAN interface can run?
This is never a straight forward answer. It always depends on the speed at which the interface runs. With a maximum baud rate of 1Mbps, the cable can run up to 40m. With CAN FD the distance is restricted to 10m.
How do you differentiate CAN2.0 and CAN FD packet?
CAN FD uses the same packet format as CAN2.0. It uses a reserve bit to identify the type of it.
Typical message format of CAN:
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