Driving Forces for MCUs Continue to Evolve
As electronics systems proliferate in vehicles, 32-bit MCUs are increasingly deployed in vehicular systems, but Caroline Hayes reports that 16-bit MCUs still have a role to play.
The driverless car may still be some way away in practical terms, but semi-autonomous driving features in cars—such as self-parking, advanced cruise controls and collision-avoidance systems—are increasing the role of controllers and sensors in new vehicles.
The number of cars around the world continues to escalate. By 2011, there were over one billion cars on the roads (Ward’s Auto figures) and the number keeps rising. Internet statistics company Statista predicts that there will be 72.94million vehicles sold this year alone, compared to just under 65 million in 2012.
The electric content in vehicles is significant—around 40 percent in traditional, combustion engine cars and up to 75 percent in Electric Vehicles (EVs) and Hybrid EVs (HEVs). Of these electronics components, microcontroller units (MCUs) are used to operate power windows, airbags, lamps, doors and seat controls, and more powerful MCUs are being specified for use within the connected car, as driver and passengers expect to access the Internet for information, entertainment and for vehicle safety and comfort features.
The Rise of ADAS
The increase in functions which has been fueling demand for high precision, embedded processing systems and Internet connectivity has also led to an increase in 32-bit MCUs to manage engine management transmission, anti-lock braking systems, electric power steering, active suspension and ADAS (Advanced Driver Assistance Systems). This last category is one of the automotive market’s fastest growing segments, forecast to achieve a CAGR (Compound Annual Growth Rate) of 14% from 2012 to 2020 (ABI Research) and to be worth an estimated $261 billion by 2020.
Reflecting the mixture of technologies involved in initially high-end vehicles but which migrate to mid-range cars, Freescale has collaborated with wireless semiconductor specialist Broadcom to develop processors based on Freescale’s 32bit Qorivva MPC5606E MCU and Broadcom’s BroadR-Reach automotive Ethernet PHY (physical layer) transceiver.
Qorivva is the family name for Freescale’s 32-bit MCUs based on its Power Architecture. While all members of the MPC57xxx family are ISO 26262-compliant for automotive functional safety, the MPC56xxx MCU family has only selected models that comply with the functional safety standard.
The blending of the MPC5606E MCU with Broadcom’s automotive Ethernet technology represents the combination of disciplines that drivers and passengers expect in vehicles today. Ethernet allows multiple in-vehicle systems to access information simultaneously over a single, unshielded twisted pair cable at up to 100Mbit/s. It also reduces weight, to improve performance by eliminating shielding cabling.
The MPC5606E MCU supports video data, at 8/10/12-bit per data word, audio data, with six stereo channels, RADAR data and serial communication interfaces.
The processors are designed for use in 360° camera systems and camera-based assisted parking systems as part of a vehicle’s ADAS. The combination of the image compression features found in the Qorivva MPC5606E device and the time stamping and transmission capabilities of the BroadR-Reach PHY allow vision compression and real-time broadcast of video and audio data over the Ethernet throughout the vehicle.
The 8×8mm package contributes to a reduction in size of automotive camera modules by up to 50 percent, says the company, allowing cameras small enough to be placed in the front grill, the bumper or wing mirror.
While increased processing performance is driving 32-bit MCU growth to as much as 25 percent of the processing power in vehicles, there is still a role for 16-bit MCUs.
Communication and Power
The leader in automotive microcontroller, Renesas, commands 40% market share (IHS figures) and has recently introduced its 16-bit RL78/F15 series which can be used for Engine Control Units (ECUs) controlling power windows, airbags, lamp, doors and seats.
There are 36 models in the low power family, but equally important to power consumption is the ability to adapt as vehicle specifications change. These changes may come about due to market conditions, sometimes due to legislation. They may require changes or upgrades to the ECU, while software additions or changes may be required due to system development.
Using a common software across multiple ECUs makes the MCUs efficient and portable. RL78/F15 MCUs are compatible with the company’s RL78/F13 and RL78/F14 families, which means that a common software can be used across multiple ECUs to reduce development and certification time in the event of changes or upgrades.
Models in the RL78/F15 series have two Controlled Area Network (CAN) channels, which allow CAN communication to be used independently for control and diagnostics. Depending on the MCU model chosen, there are up to three hardware Local Interconnect Network (LIN) channels, for applications requiring centralized control of communication, such as body control modules (BCMs). There is also support of Inter Equipment Bus (IEBus) to accommodate car audio applications.
Mass production of the RL78/F15 is scheduled for July 2016.
With increased data traffic, the car has become a potential security risk. As a result, more MCUs are equipped with encryption as well as memory and CAN interfaces. One such is the 32-bit PIC32MZ EF from Microchip. Made up of 24 devices, the family is high performance, boasting 330 DMIPS and 3.28 CoreMarks/MHz, sufficient for the processing power required by today’s vehicular systems. There is also up to 2Mbyte of Flash, 512kByte RAM and for connectivity within the vehicle, there is a first amongst the company’s PCI MCUs—a high-speed USB Media Access Control / PHY (MAC/PHY), together with a 10/100 Ethernet MAC and dual CAN ports.
To protect data, a hardware crypto engine has a random number generator for Advanced Encryption Standard (AES), Triple Data Encryption Standard (3DES), SHA (Secure Hash Algorithm (SHA), Maximum Distance Separable (MDS) and keyed-hash message authentication code (HMAC) encryption/decryption and authentication.
The intelligent, connected car is clearly driving the demand for 32-bit MCUs, yet there are also challenges to protect data and networks from attacks. Consumers, carmakers, as well as government organizations via legislation, play a role in shaping the car of the future.
Plans continue to expand driver-assist features to develop “smart,” fully autonomous or driverless vehicles over the next 10 years. MCUs will have a role to play in that development.
Caroline Hayes has been a journalist, covering the electronics sector for over 20 years. She has worked on many titles, most recently the pan-European magazine, EPN. Now a freelance journalist, she contributes news, features, interviews and profiles for electronics journals in Europe and the U.S.