BOB·半岛

Automobiles are undergoing a baptism of digital revolution: the era of pure mechanical systems and analog electronics is gone forever. Today's cars are digital cars, equipped with dozens or even hundreds of embedded processors that are interconnected through digital networks to control and optimize the operation of almost every system inside the car. Future cars will integrate more processors as advanced applications and performance require more complex signal processing algorithms, including safety, engine and exhaust emission control, driver car interaction interfaces, and in car information and entertainment systems.

The automotive market requires processor suppliers to make long-term commitments. For example, car manufacturers sometimes require their suppliers to provide a supply commitment of up to 10-15 years for a certain processor product. Below, we will explore various types of processors for automotive digital signal processing applications, as well as their advantages and disadvantages. In addition, we will also analyze the impact of special requirements for automotive applications on processors targeting the automotive market.

Appendix: Processor Types, Representative Suppliers, and Processor Samples;

Selection of processors in automotive applications

The selection of processors used in automotive systems is influenced by various factors. The main selection criteria generally include automotive certification qualifications, on-chip integration, performance, price, and energy efficiency. The quality of software development tools and the availability of software components can also affect the selection of processors. The commitment of processor suppliers to their products and future development plans are also important considerations.

Due to the importance of life safety, critical automotive safety systems such as engines, airbag control, and braking systems have very strict requirements for processor reliability and durability. Therefore, the application of automotive safety systems is the most severe test for processor suppliers. These applications require processors to obtain automotive certification qualifications, and these types of processors require specialized design, manufacturing, packaging, and testing methods.

There are many non critical signal processing automotive systems that also require a large number of processors, such as in car navigation and entertainment devices. Although automobile manufacturers and electronic system suppliers also require high-quality components for such applications, the requirements are not as high as those for critical safety applications. For example, processors used for in car systems generally do not require automotive certification qualifications.

Nowadays, the most performance demanding automotive signal processing applications are in car navigation and entertainment systems. In a few years, this situation may change as new security systems begin to use video and radar processing, and the engine and brake control systems will adopt complex model-based calculation methods. The currently popular lookup table reference method will also be replaced by complex real-time calculation methods.

Integrating appropriate peripherals, memory, and I/O interfaces on the processor can help improve performance and stability, as well as reduce power consumption and system costs. The on-chip integration requirements for automotive applications differ significantly from other signal processing applications. Therefore, suppliers targeting the automotive application market must design their processors specifically for the special requirements of these applications. Multi channel analog-to-digital converters are particularly useful for processors facing automotive control systems. For example, an engine control system typically receives input signals from dozens of analog sensors.

For processors facing automotive control systems, on-chip flash memory is a key feature as these systems require large lookup tables and sometimes on-site updates. The lookup table used in engine control systems contains tens of thousands of calibration points (or similar output values) from various control components, such as fuel dispensers and ignition coils. Calibration point data is generally determined in the laboratory before the car leaves the factory, but some calibration points may need to be adjusted after the car has been in use for a period of time. On chip flash memory can be used to update calibration points or other parameters of control algorithms on-site using data downloaded from car dealerships.

The biggest advantage of integrating flash memory into a processor compared to using a separate flash chip is the improvement in system performance and cost reduction. Although integrated on-chip flash memory is valuable to system developers, it is not easy for processor vendors to implement it. Automotive certified processors have higher requirements for high temperatures than mainstream flash memory technology can withstand. It can be imagined that processor suppliers competing in this market often need to invest significant resources in developing flash memory technology that can work stably on automotive systems.

Digital network transceivers facilitate communication between processors in distributed systems. There are various network protocols for different automotive systems. Processors designed for specific automotive applications typically integrate network transceivers with relevant protocols. For example, the Control Domain Network (CAN) protocol is generally used for engine and transmission control networks. The Media oriented System Transport (MOST) protocol is designed for in car entertainment applications such as audio, video, navigation, and communication.

For processors targeting critical applications, advanced on-chip debug tracing units are also very useful. This tracking feature can provide system developers with detailed processor, software, and operating system status information, which is particularly useful for verification and debugging. The Nexus 5001 Forum standard defines the interface between software and on-chip debugging hardware for global embedded processor debugging interfaces. This standard was first developed by the IEEE Industry Standards and Technology Organization (IEEE-ISTO) in 1999 and has now been updated to IEEE-ISTO 5001-2003. The developers of this standard hope that it can encourage development tool suppliers to add on-chip debugging trace units or strengthen support for it.