1 CAN Bus Overview

CAN is a 2-wire differential communications interface which has its physical layer defined by the ISO 11898-2 standard. The physical layer consists of the CAN transceiver and the twisted pair cabling that connects all the CAN nodes together. The two lines connecting the CAN transceiver to the cabling are referred to as CANH and CANL. It is also recommended to terminate the CANH and CANL lines with a split termination to avoid signal reflections and high frequency noise. Figure 1-1 illustrates the typical CAN bus setup.

The CAN protocol can come in many different flavors and speeds. These flavors include:

• Low speed (LS CAN): Up to 125 kbps
• High speed (HS CAN): Up to 1 Mbps
• Flexible data rate (CAN FD): Up to 5 Mbps
• Signal Improved capable CAN (CAN SIC): Up to 8 Mbps
• CAN XL: Up to 10-20 Mbps (not yet released)