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CAN Newsletter magazine

One solution for complex CAN architectures

The Polish company DCD-Semi provides the DCAN FD IP core for implementation of standalone CAN (FD) controllers. The company’s CAN-All ecosystem considers automotive safety standards and expands towards CAN XL.

DCAN FD block diagram (Source: DCD-Semi)

The complete article is published in the June issue of the CAN Newsletter magazine 2022. This is just an excerpt.

In 1997 at a computer expo Bill Gates did say a joke: “If GM had kept up with technology like the computer industry has, we would be driving 25-$ cars that got 1000 miles to the gallon”. GM did not wait with a response saying that with the same car characteristics “your car would crash twice a day”. 20 years ago, both statements built tensions between the automotive and computer industries. Nowadays we can see a different relationship between them. Every modern car is equipped with an on-board computer, multiple sensors, cameras, and safety systems. Lights, brakes, engine(s), even air-conditioning – all of these devices built in modern cars – are supervised by sensors and controlled by micro-controllers. And, this is where the CAN network is a vital part of (almost) every automotive being.

CAN was originally designed to significantly save on copper, because it did reduce the number of connections between devices, creating a global net inside the vehicle. Its story begins in the Robert Bosch company in 1983. By now it was further developed and standardized. In 2012, an improved version of CAN, the CAN with Flexible Data-Rate has been released to support greater loads without extending transmission time. Currently, another CAN successor is under development. CAN XL, supporting even greater loads and introducing new transmission features, such as PWM coding – seems to become “apple of daddy’s eye” not only for automotive.

CAN did expand over the physical layer. Today when saying CAN, you may expect both hardware and software, covering the physical layer, data link layer, and application layer. More medium-dependent interface sub-layers may also be introduced. CAN is a complete environment, providing many standard mechanisms ensuring faster product development. The end-user may easily replace an old CAN controller without reinventing the design because the succeeding CAN protocols are all backward compatible.

Over the decades carmakers introduced a lot of measures to save lives (Source: Autoweek.com)

Automotive IP cores provider

DCD-Semi (Poland) masters automotive IP cores (e.g. DCAN FD) since 1999. That’s why the CAN-ALL ecosystem is a natural step of development based on experience gained with the biggest and the most innovative automotive companies. During these two decades the company developed more than 70 different architectures, which were successfully implemented in more than 750 000 000 electronic devices around the globe. CAN-ALL is already proven in dozens of events and production designs. The verification is based, on more than two decades of market experience and thousands of automotive implementations with such companies as Volkswagen and Toyota.

The DCAN-FD IP core is designed in accordance with the ISO 11898-1:2015 standard. It does support CAN FD frames and the Classical CAN frames to provide backward compatibility. The IP supports up to 64-byte data frames. A CAN FD frame consists of the arbitration phase and the data phase. Between them, there is a dedicated BRS (bit rate switch) bit, which enables to increase the data bit rate while transferring payload. The bit rate switch takes place exactly between segment 1 and segment 2 of the BRS bit. This functionality is fully supported by the DCAN-FD. The data-phase bit rate may be up to 8 Mbit/s.

ISO 26262 standards overview (Source: ISO)

The DCAN offers an advanced hardware frame filtering with multiple filter banks. To enable maximal throughput the IP can be equipped with multiple transmission buffers, so that the next CAN frames may be loaded while the current one is transmitted. The IP is also capable of receiving multiple frames inside the internal FIFO memory before reading them. This functionality might be also used with a DMA (direct memory access) controller. All CAN frame types are supported: data frame, remote frame, error passive and error active frames, as well as the overload frame.

For the transfer error detection and handling, the DCAN offers a sophisticated error management logic as a self-test capability. It can be both an active CAN participant and a listener. After multiple transmission errors and reaching of the error passive state, a device is cut-off from the network to avoid disturbance of the CAN traffic. To achieve a lower power consumption while CAN is in the idle state, the IP can be set to sleep mode and waked up, if a transfer occurs. Additionally, the IP core offers many more features and can be tailored to the project needs, basing on customer’s design requirements. The company’s experience and the team spirit have led to creation of an advanced, fast, architecture-independent IP core design.

Functional safety – 21st century approach to system design

Even the best engineer makes mistakes. Over the decades of car manufacturing (Benz Patent Motor Car, model no. 1 was reported in July 1886) did happen a lot. Many people died, but the lessons have been learned. The carmakers introduced hydraulic brakes for better deaccelerating, seat belts and airbags for better driver and passenger protection, lidars, cameras and blind-spot motors for the safety of all road users. Now, different introduced AI (artificial intelligence) applications should help the driver. Nowadays the manufacturers have to think about pedestrians’ safety, too.

The scope of the car-influenced elements expands pretty fast. In 1934 GM performed the first crash test to gain better real-life information about car safety. Vehicle safety standards evolved, and today’s cars are safer than ever before. This wouldn’t be possible without a tight cooperation between the automotive and electronics industry. The biggest issue is that one cannot rely on the design itself. It can work as designed but still lead to an accident, because of the wrong design assumptions. A car can be stuffed with plenty of safety features, but their cooperation can fail. The vehicle can have advanced software supervising system, but the bad coding practices or compiler bugs can still lead to an unexpected behavior.

To change the whole conception, design, manufacturing, and decommissioning process (the product lifetime) the ISO 26262 standard has been introduced. The main goal is to mitigate risks (systematic failures and random hardware failures) by providing appropriate requirements and processes.

CAN-All fulfills the automotive safety requirements according to ISO-26262, ASIL-B (Source: DCD-Semi)

When trying to describe the standard in just one sentence – it ensures that the design is fully controlled at every step. Management is the key. Not only the design matters but also the project management. A project manager and competent, trained team members shall be drafted. Each product mastered within the project must be supervised: stored under a version control system, the author of each modification must be specified with the description of the change and date, the change must be reviewed by other team members. It is very important to establish best practices to be used in each project, specify the work products that need to be created, and plan each activity.

The project begins with the concept phase where proper safety goals must be defined. In the next step, proper functional safety concepts have to be defined to realize the safety goals. Then the proper functional safety requirements must be defined to realize the functional safety concepts. After that, the proper technical safety concepts must be defined to realize the functional safety requirements.

Then in the next step, proper technical safety requirements have to be defined to realize the technical safety concepts. The concepts and requirements are then used for the definition of safety mechanisms and assumptions of use, emphasized further in safety metrics calculation.

If you would like to read the full article, you can download it free of charge or you download the entire magazine.

cw

Publish date
2022-06-28
Company

CAN Newsletter June 2022
DCD-Semi

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