On 12th November 2013, Kvaser presented CAN EF (Controller Area Network – Enhanced Format) to attendees of the 14th International CAN Conference in Paris, France. CAN-EF proposes an intermediate step between CAN and the new high performance CAN with Flexible Data Rate (CAN FD) solution that is in the process of being integrated within ISO 11898-1. The proposal was put forward for industry discussion within the context of Hardware Development Manager Kent Lennartsson’s paper entitled ‘How to implement and utilize high bit-rate in your system’.
CAN FD provides a highly efficient method of increasing CAN data throughput, by increasing the number of bytes in each CAN-frame (from 8 to 64 bytes), whilst making the CAN-frames shorter. However, this technology cannot be used with existing CAN controllers. In contrast, CAN EF offers higher data-rate communication than CAN by packing the extra bits into the CAN-frames in such way that they can be received by legacy CAN controllers, ensuring full backwards compatibility with existing CAN infrastructure.
Commented Lars-Berno Fredriksson, president of Kvaser AB: “On the one hand, CAN FD provides a high bit rate, but on the other hand, it is not backwards compatible with the current version of CAN. Systems and modules have to be redesigned to take advantage of CAN FD. We see that CAN EF could facilitate the industry’s move to CAN FD. The reality is that it will take time for the industry to switch to what is an entirely new communications standard; CAN EF could give CAN users quicker and simpler access to greater data rates in the meantime.”
The performance of CAN EF would be within the range of 50-90% of CAN FD in similar circumstances. Kent Lennartsson, Kvaser’s Hardware Development Manager, says: “From a silicon vendor’s point of view, a great deal of the logic would be common across CAN, CAN EF and CAN FD, making it possible to combine all logic into one unit with a minor increase in gate count compared to CAN FD.”
CAN EF works by hiding the high-speed data from the legacy CAN modules, allowing CAN EF modules to be installed into any system to communicate at a higher bit-rate without interfering with any connected CAN-module in use today. This would allow users to replace modules gradually to achieve a progressive increase in data throughput, rather than suddenly render all existing CAN modules and service tools obsolete. For example, in truck applications where J1939 is employed at 250 kBit/s, CAN EF would facilitate an increase in data throughput, without altering the basic bit rate.
CAN EF requires no physical layer modification, but like CAN FD, certain physical architectures will limit its highest usable bit-rate. CAN EF communication could co-exist with CAN FD, potentially allowing CAN EF to act as a technically compatible bridge technology between the existing CAN standard and the future high performance CAN FD protocol.
For further technical information, please contact Kent Lennartsson at [email protected] The paper presented at the ICC is available from the CAN in Automation (CAN-CiA) head office. Please visit www.can-cia.org for more details.