12.1 Features

The CAN FD modules have the following features:

General

  • Nominal (Arbitration) Bit Rate up to 1 Mbps
  • Data Bit Rate up to 8 Mbps
  • CAN FD Controller modes:
    • Mixed CAN 2.0B and CAN FD mode
    • CAN 2.0B mode
  • Conforms to ISO11898-1:2015

Message FIFOs

  • Seven FIFOs, Configurable as Transmit or Receive FIFOs
  • One Transmit Queue (TXQ)
  • Transmit Event FIFO (TEF) with 32-Bit Timestamp

Message Transmission

  • Message Transmission Prioritization:
    • Based on priority bit field and/or
    • Message with lowest ID gets transmitted first using the TXQ
  • Programmable Automatic Retransmission Attempts:
    • Unlimited, three attempts or disabled

Message Reception

  • 16 Flexible Filter and Mask Objects
  • Each Object can be Configured to Filter either:
    • Standard ID + first 18 data bits or
    • Extended ID
  • 32-Bit Timestamp
  • The CAN FD Bit Stream Processor (BSP): 
Implements the Medium Access Control of the CAN FD Protocol Described in ISO11898-1:2015. It serializes and deserializes the bit stream, encodes and decodes the CAN FD frames, 
manages the medium access, Acknowledges frames, and detects and signals errors.
  • The TX Handler: Prioritizes the Messages that are Requested for Transmission by the Transmit FIFOs. It uses the RAM interface to fetch the transmit data from RAM and provides them to the BSP for transmission.
  • The BSP: Provides Received Messages to the RX Handler. The RX handler uses acceptance filters to filter out messages that shall be stored in the Receive FIFOs. It uses the RAM interface to store received data into RAM.
  • Each FIFO can be Configured either as a 
Transmit or Receive FIFO: The FIFO control keeps track of the FIFO head and tail, and calculates the user address. In a TX FIFO, the user address points to the address in RAM where the data for the next transmit message shall be stored. In an RX FIFO, the user address points to the address in RAM where the data of the next receive message shall be read. The user notifies the FIFO that a message was written to or read from RAM by incrementing the head/tail of the FIFO.
  • The Transmit Queue (TXQ): A Special Transmit FIFO that Transmits the Messages based on the ID of the Messages Stored in the Queue.
  • The Transmit Event FIFO (TEF): Stores the 
Message IDs of the Transmitted Messages.
  • A Free-Running Time Base Counter: Used to Timestamp Received Messages. Messages in the TEF can also be timestamped.
  • The CAN FD Controller Modules: Generate Interrupts when New Messages are Received or when Messages were Transmitted Successfully.

Figure 12-1 shows the CAN FD system block diagram.

Figure 12-1. CAN FD Module Block Diagram