15 CAN Flexible Data-Rate (FD) Protocol Module

The CAN Flexible Data-Rate (FD) addresses the increasing demand for bandwidth on CAN buses. The two major enhancements over CAN 2.0B consist of:

An increased data field of up to 64 data bytes (from a maximum eight data bytes for CAN 2.0B)
An option to switch to faster bit rate after the arbitration field

Figure 15-1 shows the possible increase in net bit rate due to the higher Data Bit Rate (DBR) and increased data bytes per frame.

Figure 15-1. Net CAN FD Bit Rate

The CAN FD protocol is defined to allow CAN 2.0 messages and CAN FD messages to co-exist on the same bus. This does not imply that non-CAN FD controllers can be mixed with CAN FD controllers on the same bus. Non-CAN FD controllers will generate error frames while receiving a CAN FD message.