Growing Bit by Bit

Electronics and software represent more than 20% of the cost of today's vehicle and analysts project growth to 35% or even 40% by 2010, so it's no surprise that so-called embedded computing is growing.

Recently introduced 64-bit processors for video and voice recognition applications increase the performance of the 32-bit units typically used in powertrain controllers.

Add more airbags, greater control of seats, doors and windows, and features such as adaptive lighting and advanced driver assistance systems, and it is easy to see how the electronics explosion will continue.

Unlike personal computers that use a high-performance 64-bit microprocessor (MPU) as their central processing unit, the embedded computing in vehicles consists of distributed elements for every system. The computing power comes from microcontrollers (MCUs), digital signal processors (DSPs) and digital signal controllers (DSCs).

Initially, the replacement of a mechanical system with an electronic control typically uses an 8-bit microcontroller. As performance requirements increase to handle more features and respond faster to system inputs, a 16-bit or even 32-bit microcontroller becomes necessary. At the same time, the memory in kilobytes and even megabytes grows to handle the increased software in today's control systems.

The difference between a microprocessor and a microcontroller requires a little clarification.

“A microcontroller is essentially a single chip system with on-chip memory and other system resources,” says Kevin Klein, marketing manager for automotive microcontrollers-Freescale Semiconductor.

“An MPU (microprocessor) typically uses external memory, either flash or DRAM or SRAM, and tends to have more off-chip peripherals surrounding it,” Klein says.

MPUs are becoming popular in the telematics area where there may be a need for external memory, adds Wayne Chavez, applications engineering manager for automotive microcontrollers-Freescale Semiconductor.

Klein admits even Freescale insiders tend to blur the line between how each is defined. Voice recognition and video require a significant amount of memory, though, so auto makers may resort to the use of higher horsepower MPUs instead of MCUs in those applications.

Chris Webber, vice president-automotive, of market research firm Strategy Analytics, sees growth trends for all of the classifications of MCUs. Among them:

Well-established control systems such as powertrain, body electronics and safety started with 8-bit MCUs but a few of today's emerging systems, including hybrid-electric vehicle powertrains and advanced entertainment systems, need the performance of 32-bit MCUs.

Setting the pace for embedded flash memory, Freescale's newest automotive 32-bit MCU, the MPC5566, has three megabytes of on-board flash memory. In the late 1990s or early 2000s, the memory level was about one megabyte in high-end 32-bit machines.

Although tough new tailpipe-emission requirements are driving much of the growth in performance and memory, there are other factors as well, including recent legislation in the U.S. mandating electronic stability control in vehicles and increased demand for features and comfort, says Freescale's Klein.

Freescale has a lot of company in the quest for higher performance and memory capability.

Regarding the amount of integrated memory, Jeff Kelley, Infineon Technologies AG director of marketing for microcontrollers for North America, says, “Our current products in the 32s (bits) are 1.5 and two (megabyte) and products that are in development are headed for threes and fours (megabytes).

These high-memory levels are mainly for powertrain, but there are other vehicle applications. “We are finding out that as we develop these products, stability control systems and high-end safety systems are also looking at similar types of things,” Kelley says.

Infineon's TriCore MCU is a blend of a 32-bit processor with DSP capability that was developed for real-time automotive applications, such as direct injection and valve control in powertrains.

“Today we have a kind of dual-core architecture,” says Bjoern Steurich, senior marketing manager, automotive microcontrollers, Infineon.

Steurich says 64-bit processors are starting to replace 32-bit chips in some applications, but in most situations there will be a transitional step to 32-bit dual-core architectures.

Texas Instruments claims its TMS570 MCU, co-developed with Robert Bosch GmbH, is the first IEC 61508-compliant SIL 3 automotive processor.

The International Electrotechnical Commission's 61508 addresses the components in a safety-related system beginning with a risk analysis to determine the Safety Integrity Level (SIL), that increases exponentially for each level. SIL 3 has a risk reduction factor required of 1,000, which is 10 times higher than a SIL 2 rating providing greater prevention and control of failure even when faults are present.

“It is a dual core approach but not in the sense of host and a co-processor,” says Matthias Poppel, automotive marketing manager-Texas Instruments. “It is two cores of the same kind, and they are running in lock step.”

On consumer desktop computers, chip suppliers use dual cores simply to enhance performance.

“In automotive, we use two cores, but the same software runs on either core. And they are used to compare the results and to make sure there is no failure occurring,” Poppel says.

In spite of the growing need for 32-bit MCUs, 8-bit units are the largest and still-growing portion of embedded automotive computers.

For example, in the past, a rocker switch would have been used for seat-position controls. To add memory-seat capability, a simple 8-bit MCU receives communications from the keyless-entry system to implement a driver-specific seat location, says Willie Fitzgerald, director-automotive marketing, Microchip Technology Inc.

More powerful 16-bit MCUs are satisfying system requirements between the emerging low-cost 8-bit and high-performance 32-bit units.

Electronic parking assist could be a new sweet spot for 16-bit MCUs. That's one of the applications shifting from 8-bit to 16-bit microprocessors, Microchip's Fitzgerald says.

Electronic parking assist systems typically use two to four ultrasonic sensors to detect objects near the vehicle, but some use as many as eight sensors. Processing the additional information drives the requirements into 16-bit territory.

MCUs are not the only embedded computers found on today's vehicles. Math-intensive processing applications, such as advanced driver assistance systems, rely on digital signal processors.

“Image processing is a DSP domain, where a high data stream comes into the device, and then you have pattern recognition, high math-intensive operations, where you really need a very powerful DSP core,” TI's Poppel says.

Another embedded computing category is digital signal controllers, primarily for motor controls.

“Generally, a DSC is a DSP that has been modified to be a little more like a microcontroller,” Freescale's Klein says.

It is a bit easier to program, adding some of the instructions that you would find on a microcontroller that are suited towards actually controlling a system as opposed to doing specific mathematical calculations, Klein says.

One of the more popular applications for a DSC is electronic power steering, where the brushless DC motor's position is calculated based on feedback from steering-wheel position, torque and speed sensors.

The newest embedded computers in vehicles use 64-bit capability to address the stringent requirements of several new systems.

Toshiba Corp. combines a 64-bit CPU and a graphics display controller with a 2D hardware graphics accelerator and video frame-grabber to address high-performance requirements in infotainment.

Designed for applications that combine general-purpose computing with real-time graphics displays, NEC Corp. of America's 64-bit VR Series MIPS-based microprocessors target voice recognition and software video decompression in driver information, infotainment and navigation systems.

The high frame rate of advanced MPEG-4 video coding could require this level of performance.

While MCUs and DSPs have provided the embedded computing in production vehicles, a technology used to reduce development time and cost now is being used for product engineering as well.

Field programmable gate arrays (FPGAs) allow system designers to configure programmable logic blocks and, in some cases, have an embedded MCU core and/or DSP functionality.

Harvey Steele, general manager for the automotive division of Xilinx Inc. says FPGAs are becoming popular in the area of infotainment.

Current applications include telematics, rear-seat entertainment, infotainment head units and initial use in driver assistance. Steele sees growing adoption in driver assistance and instrument clusters in the future.

Freelance writer Randy Frank has been involved in automotive electronics for more than 25 years.

Bits and Bytes for Vehicle Applications