CAN FD node and system design recommended practice.

The nonprofit CAN in Automation (CiA) association has released part 1 of the CiA 601-1 CAN FD node and system design recommended practice. The CiA 601 series of guidelines and recommendations fills the gap between the ISO standards for CAN FD and the system design specifications. 

Sampling of a recessive bit at the transmitting node with and without transmitting node delay compensation (Source: CiA)

This provides specifications and guidelines on the physical layer interface design for automotive electronic control units and non-automotive devices supporting the CAN FD data link layer as defined in ISO 11898-1. The related CAN high-speed physical layer is defined in the harmonized ISO 11898-2 standard, which includes the specification of high-speed transceivers with low-power mode (formerly known as ISO 11898-5) and/or with selective wake-up functionality (formerly known as ISO 11898-6).

It is released as a Draft Standard Proposal (DSP). It specifies the Tx delay symmetry and the Rx delay symmetry requirements as well as the recessive bit-time at the receiving node’s RxD pin for different bit-rates (1 Mbit/s, 2 Mbit/s, and 5 Mbit/s). Rules of thumb on how to calculate the transmitting node delay with and without galvanic isolation are also included. Part 1 will be updated frequently depending on the experiences coming from prototype developments of OEMs and CAN FD plug-fests organized by CiA. The document is also available for non-members on request for review purposes. In particular, carmakers and Tier 1 suppliers are invited to submit comments and further recommendations to be evaluated and discussed in the CiA Interest Group (IG) “CAN FD”.

Part 2 (host controller interface recommendation) and Part 3 (system design specification) are still under development. Part 4 is also in preparation. It introduces and specifies a ringing suppression technology intended for star and hybrid topologies. These parts will be released as a DSP when the “CAN FD” group has observed and implemented all pending comments.