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Recommended practice

CiA has released part 1 of the CiA 601-1 CAN FD node and system design recommended practice. The series 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 (Photo: CiA)

PART 1 OF THE SERIES 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).

Part 1 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 by 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, which 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.

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