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CAN with flexible Data Rate improved CAN

More than 20 years after introducing CAN, communication requirements have increased and CAN has reached it's bandwidth limits in some application fields. To improve CAN regarding bandwidth Bosch has specified the improved CAN data link layer protocol, called CAN FD. The idea behind CAN FD is that after the arbitration phase of classic CAN the data rate can be increased. The data bits are transferred with a higher bit rate than in the arbitration phase when a transmitter has won the bus arbitration. The speed is limited only by the CAN transceiver signal delay and the signal delay on the cable.
Besides the increased bit speed the new CAN FD allows date frames up to 64 bytes compared with the maximum of 8 bytes with classic CAN.

The ISO TC22 SC3 WG1 is currently working to integrate CAN FD in the ISO 11898-1 standard as an optional feature, than called ISO CAN FD. An CiA Newsletter article explains what is the difference between the original BOSCH non-ISO CAN FD and the upcoming ISO CAN FD protocol.

For more information see the Bosch CAN FD Specification Version 1.0 or the older CAN-FD Whitepaper (V1.1) . Official introduced by BOSCH at the 13th international CAN Conference in March 2012.
Since May 2012 the new M_CAN manual contains specific information on CAN FD used in this FPGA IP.

CiA provides information on CAN FD and organizes world wide events to promote it. CiA has a short introduction here.

The CAN FD protocol was recently enhanced regarding the CRC weakness in the original Bosch paper. The CiA White Paper explains why and how (“Summary of the discussion regarding the CAN FD CRC i ssue”). The new frame format has 5 bits more, three stuff bit counter bits, one parity bit for the counter and one additional stuff bit.

The Linux CAN device driver can4linux supports this frame format already in it's 'virtual' mode. The same is true for the SocketCAN approach. Since May 2014 a version of can4linux is available with real hardware support for the IFI non-ISO CAN FD controller.

Kvaser demonstrates CAN FD capability

CiA explains CAN FD

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