Selection of processors in automotive applications
The choice of processors used in automotive systems is affected by many factors. The main selection criteria generally include automotive certification qualification, on-chip integration, performance, price, and energy saving. The quality of software development tools and the availability of software components also affect the choice of processor. Processor suppliers' commitment to their products and future development plans are also important considerations.
Since it is related to life safety, key automotive safety systems such as automobile engines, airbag control and brake systems have very strict reliability and durability requirements for the processor. Therefore, the application of automotive safety systems is the most severe test for processor suppliers. These applications require processors to obtain automotive certification, and these 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 equipment. Although automotive manufacturers and automotive electronic system suppliers also require high-quality components for such applications, the requirements are not as high as critical safety applications. For example, processors used in in-car systems generally do not require automotive certification.
Today, the most demanding automotive signal processing applications are in-car navigation and entertainment systems. This situation may change in a few years, because the new safety system begins to use video and radar processing, and the engine and brake control system will use complex model-based calculation methods. The current popular lookup table reference method will also be complicated Replaced by real-time computing methods.
Integrating appropriate peripherals, memory, and I / O interfaces on the processor helps improve performance and stability, as well as reduce power consumption and system costs. The on-chip integration requirements for automotive applications are very different from other signal processing applications. Therefore, suppliers facing the automotive application market must design their processors specifically for the specific requirements of these applications. Multi-channel analog-to-digital converters are particularly useful for processors for automotive control systems. For example, an engine control system generally receives input signals from dozens of analog sensors.
Attached table: processor types, representative suppliers and processor samples
On-chip flash memory is a key feature for processors for automotive control systems because these systems use large lookup tables and sometimes need to be updated in the field. The look-up table used by the engine control system, for example, contains tens of thousands of calibration points (or similar output values) from various control components (such as fuelers 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 is used for a period of time. On-chip flash memory can use data downloaded from car dealers to update calibration points or other parameters of control algorithms in the field.
Compared with the use of a separate flash memory chip, the biggest benefit of integrating flash memory on the processor is improved system performance and reduced cost. Although integrated on-chip flash memory is valuable to system developers, it is not easy for processor vendors to implement it. Automotive-certified processors require higher temperatures than the mainstream flash memory technology can withstand. It is conceivable that processor suppliers competing in this market often need to invest a lot of resources to develop 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 for specific automotive applications generally integrate network transceivers for related protocols. For example, the Control Area Network (CAN) protocol is generally used for engines and variable speed control networks. The media-oriented system transmission (MOST) protocol is aimed at in-vehicle infotainment applications, such as audio, video, navigation, and communications.
For processors for critical applications, the advanced on-chip debug trace unit is also very useful. This tracking function 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 for global embedded processor debug interfaces defines the interface between software and on-chip debug hardware. The standard was first formulated by the IEEE Industry Standards and Technology Organization (IEEE-ISTO) in 1999 and has been updated to IEEE-ISTO 5001-2003. The developers of this standard hope that it can encourage development tool vendors to add on-chip debug tracking units, or strengthen their support.
In-vehicle information and entertainment systems are the signal processing systems that require the highest computing performance in current automotive applications, mainly because these systems involve video processing and other applications that require powerful signal processing functions. A high-end infotainment system may include a multi-channel audio system, DVD player, GPS navigation system, and hands-free mobile phone, all of which are integrated into one system. Processors for in-car infotainment systems include relatively high-performance DSPs, DSP-enhanced general-purpose processors (GPP), and DSP / GPP hybrid devices. These processors generally operate in the clock rate range of 200 to 750 MHz.
In contrast, processors for critical control systems such as engine and brake control are generally medium-performance processors. Larger chip manufacturing processes (such as 0.18 or 0.25 microns) are easier to meet the requirements of harsh working environments such as high temperatures, and the processing speed requirements of control applications are generally not too high. Therefore, a relatively low maximum processor clock speed (40 to 150 MHz) and a large manufacturing process are the best choices for this type of application. However, the processing performance requirements of these applications are also increasing, and processor vendors must adjust their strategies to achieve higher performance while meeting high-temperature requirements.
Automotive applications are particularly price sensitive. Processor suppliers have to develop highly integrated dedicated processors to reduce system costs. Although automotive applications are price sensitive, the automotive qualification process is expensive, and these costs increase chip costs. As a result, automotive qualified processors are generally more expensive than non-certified similar products. In automotive signal processing systems, energy efficiency is generally not a major issue. Only when the engine is running and the battery charging system is started, the engine, chassis and brake control systems are in working condition.
Nevertheless, energy efficiency is also important in certain applications. Some systems are working when the engine is turned off, and their power consumption must be low so that battery power consumption does not affect engine startup. For example, in-vehicle infotainment equipment is one such application. There are also systems that must be sealed well so as not to be affected by the external environment. In this case, the packaging of such systems may affect heat dissipation, so the power consumption cannot be too large.
Signal processors for automotive applications
In today's automotive systems, there are many types of chips used to complete signal processing tasks, from 8-bit MCU to DSP to FPGA. In systems where signal processing plays an important role, 8-bit and 16-bit MCUs are now not commonly used because of their limited processing performance. To reduce costs, system developers often choose processors with just enough performance. However, for some applications, it is wise to reserve some performance space, especially the in-car infotainment system, which can benefit from the flexibility of this performance space, because some functional applications (such as voice recognition, navigation and audio Control) has not been fully developed when choosing a processor.
32-bit embedded general-purpose processors (GPP) are generally used in automotive signal processing control systems with moderate performance requirements. The processors of this grade generally adopt the RISC structure, and the instructions used are simple, ordinary, and there are almost no parallel instructions. GPP is particularly effective in algorithmic processing that emphasizes decision and control flow changes, but in many cases its signal processing performance is also good. In addition, GPP is also a good compilation object. Compared with some special DSP structures that are difficult to compile, GPP compiled code is quite effective. Popular 32-bit GPP structures (such as MIPS, ARM, and PowerPC) have been widely used in automotive and non-automotive applications.
The advantages brought by the widespread market recognition include a rich supply of third-party software components and strong development tool support. Processors in this category include Texas Instruments' TMS470 series (based on the ARM7 core) and Freescale's MPC500 series (based on the PowerPC core). Both processors integrate automotive-specific peripherals on a 32-bit general-purpose processor core. Freescale's MPC500 series processors integrate peripherals, memory, and dedicated I / O interfaces, mainly for engine and variable speed control applications, with large-capacity flash memory, multiple CAN interfaces, a Nexus debug interface, and multiple ADCs , And multiple advanced timing modules.
DSP, DSP / GPP hybrid devices and DSP-enhanced GPP are generally used in in-car infotainment systems and control systems that require signal processing functions. These processors have special functions, including multi-accumulation hardware, large-capacity storage bandwidth, and instructions that use multi-run algorithms. Taken together, these features can greatly speed up digital signal processing algorithms, much faster than GPP at the same clock rate.
The DSP / GPP hybrid device and DSP enhanced GPP are intended to integrate the best features of DSP and GPP: the signal processing function of DSP and the high efficiency of GPP in decision-intensive algorithms and compiled code. This combination of functions is especially important for systems that require both signal processing and decision processing. Such processors include Texas Instruments ’TMS320C2000 series, Freescale ’s MC56F83xx series, Renesas’ SH7760, and Analog Devices ’ADSP-BF53x (Blackfin series).
FPGAs do not seem to be suitable for automotive processing applications because they have always been known for being expensive. However, in recent years, FPGA vendors have introduced a series of low-cost, high-efficiency devices, making FPGAs an option for automotive systems. Unlike traditional fixed-structure processors (such as DSP and GPP), FPGAs are not restricted by a pre-set instruction set. In contrast, FPGAs can provide system designers with great design flexibility in order to develop processing structures suitable for specific applications.
Because FPGA has powerful parallel processing capability, its signal processing speed is faster than the fastest fixed structure processor. But high performance comes at a price: the development cost of FPGA-based signal processing systems is much higher than the cost of fixed-structure software development. Although the role of FPGA in automotive systems will gradually expand, it is currently mainly used for the interface of in-vehicle infotainment systems. Of course, once the FPGA enters the automotive system, it will have more other uses and may replace the functions of other system components.
For example, with the emergence of using FPGAs to implement "soft" processor cores, like Altera's Nios II and Xilinx's MicroBlaze (both are 32-bit RISC processor cores), microprocessors may use FPGAs more Implementation, not a separate chip. This saves costs, because the soft core can be customized (designers can include and exclude certain features, and can also choose between functions and resource consumption), and it is also easy to implement and use FPGA-specific dedicated hardware (such as a specific algorithm accelerator) Interface.
Digital signal processors are everywhere in the car
With the increasing electric and electronic control of automotive applications, digital signal processing will be everywhere in the car. Those applications that have already adopted digital signal processing will increase the computational load, thus promoting the development of a new generation of high-performance automotive processors. For example, Freescale's new MCP5554 processor runs twice as fast as its previous generation MPC566, and the new SIMD instruction execution function can further improve its signal processing performance.
New applications of digital signal processing in the automotive field include both computationally intensive applications that require high signal processing performance (such as lane tracking systems) and applications that require only general processing performance (such as tire pressure monitoring systems-TPMS). Processors for automotive signal processing applications have a wide range of performance and will tend to be more diverse in the future. High-end applications such as video-based security and infotainment systems will require higher signal processing performance, while low-end applications such as TPMS require energy-efficient and efficient processing performance.
More processors, wider performance range, when will this trend end? Maybe you have to wait until the embedded processor penetrates every corner of the automotive system. Imagine this scenario: In addition to the air pressure monitor integrated into each tire (new cars will be mandatory), each tire also has a built-in processor for collecting and forwarding information about its status and performance. For example, the tire may automatically issue a warning: "This is the front right tire. I noticed that the road surface is wet, but my tread pattern is not deep enough to cope with this situation."
You may think this is a bit too advanced, but the use of more processors in automotive systems will be an irreversible trend. Given the decreasing cost of semiconductor products and the potential benefits of smart car devices, it is foreseeable that one day our cars will be equipped with smart tires.
The choice of processors used in automotive systems is affected by many factors. The main selection criteria generally include automotive certification qualification, on-chip integration, performance, price, and energy saving. The quality of software development tools and the availability of software components also affect the choice of processor. Processor suppliers' commitment to their products and future development plans are also important considerations.
Since it is related to life safety, key automotive safety systems such as automobile engines, airbag control and brake systems have very strict reliability and durability requirements for the processor. Therefore, the application of automotive safety systems is the most severe test for processor suppliers. These applications require processors to obtain automotive certification, and these 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 equipment. Although automotive manufacturers and automotive electronic system suppliers also require high-quality components for such applications, the requirements are not as high as critical safety applications. For example, processors used in in-car systems generally do not require automotive certification.
Today, the most demanding automotive signal processing applications are in-car navigation and entertainment systems. This situation may change in a few years, because the new safety system begins to use video and radar processing, and the engine and brake control system will use complex model-based calculation methods. The current popular lookup table reference method will also be complicated Replaced by real-time computing methods.
Integrating appropriate peripherals, memory, and I / O interfaces on the processor helps improve performance and stability, as well as reduce power consumption and system costs. The on-chip integration requirements for automotive applications are very different from other signal processing applications. Therefore, suppliers facing the automotive application market must design their processors specifically for the specific requirements of these applications. Multi-channel analog-to-digital converters are particularly useful for processors for automotive control systems. For example, an engine control system generally receives input signals from dozens of analog sensors.
Attached table: processor types, representative suppliers and processor samples
On-chip flash memory is a key feature for processors for automotive control systems because these systems use large lookup tables and sometimes need to be updated in the field. The look-up table used by the engine control system, for example, contains tens of thousands of calibration points (or similar output values) from various control components (such as fuelers 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 is used for a period of time. On-chip flash memory can use data downloaded from car dealers to update calibration points or other parameters of control algorithms in the field.
Compared with the use of a separate flash memory chip, the biggest benefit of integrating flash memory on the processor is improved system performance and reduced cost. Although integrated on-chip flash memory is valuable to system developers, it is not easy for processor vendors to implement it. Automotive-certified processors require higher temperatures than the mainstream flash memory technology can withstand. It is conceivable that processor suppliers competing in this market often need to invest a lot of resources to develop 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 for specific automotive applications generally integrate network transceivers for related protocols. For example, the Control Area Network (CAN) protocol is generally used for engines and variable speed control networks. The media-oriented system transmission (MOST) protocol is aimed at in-vehicle infotainment applications, such as audio, video, navigation, and communications.
For processors for critical applications, the advanced on-chip debug trace unit is also very useful. This tracking function 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 for global embedded processor debug interfaces defines the interface between software and on-chip debug hardware. The standard was first formulated by the IEEE Industry Standards and Technology Organization (IEEE-ISTO) in 1999 and has been updated to IEEE-ISTO 5001-2003. The developers of this standard hope that it can encourage development tool vendors to add on-chip debug tracking units, or strengthen their support.
In-vehicle information and entertainment systems are the signal processing systems that require the highest computing performance in current automotive applications, mainly because these systems involve video processing and other applications that require powerful signal processing functions. A high-end infotainment system may include a multi-channel audio system, DVD player, GPS navigation system, and hands-free mobile phone, all of which are integrated into one system. Processors for in-car infotainment systems include relatively high-performance DSPs, DSP-enhanced general-purpose processors (GPP), and DSP / GPP hybrid devices. These processors generally operate in the clock rate range of 200 to 750 MHz.
In contrast, processors for critical control systems such as engine and brake control are generally medium-performance processors. Larger chip manufacturing processes (such as 0.18 or 0.25 microns) are easier to meet the requirements of harsh working environments such as high temperatures, and the processing speed requirements of control applications are generally not too high. Therefore, a relatively low maximum processor clock speed (40 to 150 MHz) and a large manufacturing process are the best choices for this type of application. However, the processing performance requirements of these applications are also increasing, and processor vendors must adjust their strategies to achieve higher performance while meeting high-temperature requirements.
Automotive applications are particularly price sensitive. Processor suppliers have to develop highly integrated dedicated processors to reduce system costs. Although automotive applications are price sensitive, the automotive qualification process is expensive, and these costs increase chip costs. As a result, automotive qualified processors are generally more expensive than non-certified similar products. In automotive signal processing systems, energy efficiency is generally not a major issue. Only when the engine is running and the battery charging system is started, the engine, chassis and brake control systems are in working condition.
Nevertheless, energy efficiency is also important in certain applications. Some systems are working when the engine is turned off, and their power consumption must be low so that battery power consumption does not affect engine startup. For example, in-vehicle infotainment equipment is one such application. There are also systems that must be sealed well so as not to be affected by the external environment. In this case, the packaging of such systems may affect heat dissipation, so the power consumption cannot be too large.
Signal processors for automotive applications
In today's automotive systems, there are many types of chips used to complete signal processing tasks, from 8-bit MCU to DSP to FPGA. In systems where signal processing plays an important role, 8-bit and 16-bit MCUs are now not commonly used because of their limited processing performance. To reduce costs, system developers often choose processors with just enough performance. However, for some applications, it is wise to reserve some performance space, especially the in-car infotainment system, which can benefit from the flexibility of this performance space, because some functional applications (such as voice recognition, navigation and audio Control) has not been fully developed when choosing a processor.
32-bit embedded general-purpose processors (GPP) are generally used in automotive signal processing control systems with moderate performance requirements. The processors of this grade generally adopt the RISC structure, and the instructions used are simple, ordinary, and there are almost no parallel instructions. GPP is particularly effective in algorithmic processing that emphasizes decision and control flow changes, but in many cases its signal processing performance is also good. In addition, GPP is also a good compilation object. Compared with some special DSP structures that are difficult to compile, GPP compiled code is quite effective. Popular 32-bit GPP structures (such as MIPS, ARM, and PowerPC) have been widely used in automotive and non-automotive applications.
The advantages brought by the widespread market recognition include a rich supply of third-party software components and strong development tool support. Processors in this category include Texas Instruments' TMS470 series (based on the ARM7 core) and Freescale's MPC500 series (based on the PowerPC core). Both processors integrate automotive-specific peripherals on a 32-bit general-purpose processor core. Freescale's MPC500 series processors integrate peripherals, memory, and dedicated I / O interfaces, mainly for engine and variable speed control applications, with large-capacity flash memory, multiple CAN interfaces, a Nexus debug interface, and multiple ADCs , And multiple advanced timing modules.
DSP, DSP / GPP hybrid devices and DSP-enhanced GPP are generally used in in-car infotainment systems and control systems that require signal processing functions. These processors have special functions, including multi-accumulation hardware, large-capacity storage bandwidth, and instructions that use multi-run algorithms. Taken together, these features can greatly speed up digital signal processing algorithms, much faster than GPP at the same clock rate.
The DSP / GPP hybrid device and DSP enhanced GPP are intended to integrate the best features of DSP and GPP: the signal processing function of DSP and the high efficiency of GPP in decision-intensive algorithms and compiled code. This combination of functions is especially important for systems that require both signal processing and decision processing. Such processors include Texas Instruments ’TMS320C2000 series, Freescale ’s MC56F83xx series, Renesas’ SH7760, and Analog Devices ’ADSP-BF53x (Blackfin series).
FPGAs do not seem to be suitable for automotive processing applications because they have always been known for being expensive. However, in recent years, FPGA vendors have introduced a series of low-cost, high-efficiency devices, making FPGAs an option for automotive systems. Unlike traditional fixed-structure processors (such as DSP and GPP), FPGAs are not restricted by a pre-set instruction set. In contrast, FPGAs can provide system designers with great design flexibility in order to develop processing structures suitable for specific applications.
Because FPGA has powerful parallel processing capability, its signal processing speed is faster than the fastest fixed structure processor. But high performance comes at a price: the development cost of FPGA-based signal processing systems is much higher than the cost of fixed-structure software development. Although the role of FPGA in automotive systems will gradually expand, it is currently mainly used for the interface of in-vehicle infotainment systems. Of course, once the FPGA enters the automotive system, it will have more other uses and may replace the functions of other system components.
For example, with the emergence of using FPGAs to implement "soft" processor cores, like Altera's Nios II and Xilinx's MicroBlaze (both are 32-bit RISC processor cores), microprocessors may use FPGAs more Implementation, not a separate chip. This saves costs, because the soft core can be customized (designers can include and exclude certain features, and can also choose between functions and resource consumption), and it is also easy to implement and use FPGA-specific dedicated hardware (such as a specific algorithm accelerator) Interface.
Digital signal processors are everywhere in the car
With the increasing electric and electronic control of automotive applications, digital signal processing will be everywhere in the car. Those applications that have already adopted digital signal processing will increase the computational load, thus promoting the development of a new generation of high-performance automotive processors. For example, Freescale's new MCP5554 processor runs twice as fast as its previous generation MPC566, and the new SIMD instruction execution function can further improve its signal processing performance.
New applications of digital signal processing in the automotive field include both computationally intensive applications that require high signal processing performance (such as lane tracking systems) and applications that require only general processing performance (such as tire pressure monitoring systems-TPMS). Processors for automotive signal processing applications have a wide range of performance and will tend to be more diverse in the future. High-end applications such as video-based security and infotainment systems will require higher signal processing performance, while low-end applications such as TPMS require energy-efficient and efficient processing performance.
More processors, wider performance range, when will this trend end? Maybe you have to wait until the embedded processor penetrates every corner of the automotive system. Imagine this scenario: In addition to the air pressure monitor integrated into each tire (new cars will be mandatory), each tire also has a built-in processor for collecting and forwarding information about its status and performance. For example, the tire may automatically issue a warning: "This is the front right tire. I noticed that the road surface is wet, but my tread pattern is not deep enough to cope with this situation."
You may think this is a bit too advanced, but the use of more processors in automotive systems will be an irreversible trend. Given the decreasing cost of semiconductor products and the potential benefits of smart car devices, it is foreseeable that one day our cars will be equipped with smart tires.
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