Kvaser proposes backward-compatible, high-bandwidth CAN version
As automotive software applications require more bandwidth for data communications among ECUs inside the car, a new, speedier version of the venerable CAN bus is currently under development by CAN inventor Bosch GmbH. This version, CAN FD, will provide 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 is not compatible with existing CAN controllers; systems and modules have to be re-designed.
At the 14th International CAN Conference in Paris, Kvaser pressed ahead by introducing CAN-EF. This version achieves 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 backwards compatibility with existing CAN infrastructure.
According to Kvaser president Lars-Berno Fredriksson, CAN-EF could facilitate the industry’s move to CAN-FD. Since the development and standardization of CAN-FD is expected quite a while – currently the flexible data rate CAN is in the process of being integrated within ISO 11898-1 – 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 information visit www.can-cia.org
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