Solid-State Memory Addresses Navigation, Infotainment and ADAS Needs

Beyond the capabilities of industrial NAND Flash, automotive NAND Flash features advanced data-care management, diagnostic, protection and security features. By Rolf Schroeder, Swissbit.

Offering fashionable looks, do-anything features and always-connected convenience, the smartphone has come to rival the car as a popular plaything and status symbol. Cars could now be fighting back, as Internet-based infotainment and advanced driver assistance systems improve the comfort and “cool factor” of today’s latest models. Just around the corner, V2X communication promises to make driving even safer and more engaging.

Some say the modern car is becoming very much like a smartphone, or even an IoT device. Car makers can benefit from this trend by exploiting greater scope to create new features, apply updates cost-effectively over the air, and establish new revenue streams by building ecosystems in partnership with selected service providers. Connected cars can also help improve safety for other road users, lower emissions in town centres and help drivers find parking and local amenities more easily and quickly. In addition, authorities can enforce traffic laws and apply usage-based tariffs more easily and at lower cost.

On the other hand, comparison with smartphones raises important new questions such as the potential for hacker attacks. These could range from data theft to taking over part or all of the vehicle remotely. Security specialists in the US have demonstrated remote wireless exploits aimed at vulnerable connected vehicles, including identifying the vehicle type, pinpointing its location by capturing GPS data, and successfully sending malicious commands to systems such as wipers, climate control, transmission and brakes. As a result, car makers are moving to make vehicle systems more resistant to remote wireless tampering.

To maximise the benefits of the connected car, while minimising risks, the automotive industry needs electronic technologies that are robust enough to meet industry quality standards and customers’ reliability and lifetime expectations, and capable of supporting security policies that will safeguard not only personal data but also life and limb.

More Data Means More Storage

The increasingly connected nature of cars means that they handle more data and, consequently, require more storage. In-car systems such as infotainment, navigation, Advanced Driver Assistance Systems (ADAS) and black-box recorders, must provide plentiful storage for personal content, map data and event information such as location and sensor data to aid accident investigations. As more and more video or radar-based driver-assistance systems, as well as V2X communication is built into next-generation vehicles, reliance on non-volatile storage is set to increase significantly.

High-density NAND Flash has emerged as the preferred storage for these applications, and is available for automotive uses in the form of eMMC (embedded Multi-Media Card) chips, CompactFlash, SD or micro-SD cards, or as Solid-State Drives (SSD) such as PATA/SATA or mSATA drives.

Solid-state memory faces significant challenges to maintain data integrity in the automotive environment. Temperature is a well-known and important factor governing data retention of Flash, even when devices are located in the dashboard or a head unit in the cabin. Although ambient temperatures can be expected to remain within the industrial range of -40°C to 85°C, in-car electronics can be exposed to harsh temperatures almost continuously. This, and the way the memory is accessed by systems and users, can significantly impair data retention. To enhance performance, automotive Flash devices implement additional special measures.

Overcoming Memory Limitations

The expected working lifetime of a car is considerably longer than that of a laptop or desktop computer and so the long-term performance of the on-board storage must match that of other core systems. However, data retention in particular is known to deteriorate over time. For conventional Flash, loss of data-retention capability also accelerates with increasing operating temperature. Figure 1 illustrates temperature-related retention-loss acceleration. For 19nm MLC (Multi-Level Cell) NAND the acceleration factors for retention degradation are 6.5 at 55°C and a fatal 168 at 85°C which means that stored data is definitely corrupted after a few months without additional countermeasures.

Some automotive NAND-Flash memories, such as Swissbit S-45 and S-450 SD/SDHC cards, have introduced automatic read refresh to counteract temperature-related retention loss. This enables the memory to guarantee retention even at peak temperature levels.

Other capabilities that are critical in automotive applications include power-fail protection and read-disturb resistance. A navigation system, for example, may need frequent read access to the same page, but this may cause errors in the cells of neighbouring pages. Autonomous data care such as read-disturb management, requiring no intervention from the host system, is effective in eliminating errors in read-intensive applications, and so enhances data integrity.

Sensitive electronics can also be vulnerable to noise and instability that characterise the automotive electrical environment. The battery voltage can dip by more than 50% during engine cranking, for example, and systems can also be exposed to surges and spikes as large inductive loads such as fans and pumps are frequently switched on and off to perform various functions in the cabin, engine bay and other areas. Data retention must also be guaranteed in the event of sudden power failure, which may occur if the battery becomes disconnected such as during an accident.

Power-fail protection varies widely among industrial Flash devices. The best dedicated automotive memories protect against all power-fail conditions through a combination of firmware redundancy, data redundancy, and built-in voltage monitoring that blocks access if the supply voltage falls below a defined threshold.

Swissbit builds extra diagnostic features into its automotive memories, which provide detailed system information that can be used to provide early failure warnings. This allows pre-emptive replacement, avoiding unexpected system failures. Devices are subjected to 100% full-temperature test and screening prior to shipping in order to ensure optimum reliability.

Moreover, ADAS systems are now imposing their own specific requirements on automotive-systems designers by introducing extra storage-related performance requirements over and above the basic need for data integrity. Whereas traditional navigation systems need only to read map data, ADAS requires high-resolution map data and dynamic traffic information. This leads to the need for incremental updates. For the storage device this means frequently writing a large quantity of small data packages into memory. In the future, V2X will intensify these challenges. Building on its experience in the broadband and telecom industries, Swissbit has implemented special page-based firmware in automotive memories such as the S-45, which is better suited to incremental changes than the traditional block-based method.

Superior Security

Automotive memory also has a major role in ensuring the security of the on-board electronics, to protect the owner’s personal data and digital rights, protect the intellectual property and revenue of car makers and service providers, and to prevent malicious take-over of on-board systems.

A number of hardware features can be implemented in automotive Flash memory to help overcome the weaknesses of software-only security. Swissbit, for example, has embedded a smart card chip as a secure element in selected memories of its PS-100u high-security Flash family. The smart card chip communicates via an industry-standard ISO 7816 interface, and allows data to be stored securely or be encrypted through secure methods according standards like Java Card and Global Platform. This prevents unauthorised applications gaining access to sensitive data, thereby helping to block theft or replacement with malicious code. All devices feature a standardised security interface, which enables partners and solution providers to build applications on various platforms. The smart card chip is certified to EAL 5+ according to the international Common Criteria (CC), a level that ensures extremely high security as far as commercial systems are concerned. Figure 2 illustrates the structure of a secure MicroSD card with the optional smart card chip as secure element.

The automotive industry needs high-density storage to meet its underlying objectives, which are to deliver connected cars that are more compelling for customers, open up new revenue streams from sales of connected services, and improve performance and safety. At the same time, in-vehicle systems must be rugged in order to withstand the harsh automotive environment and deliver reliable service for the lifetime of the vehicle. In addition, growing realisation of the security implications of the connected-car revolution is raising demand for integrated hardware-based encryption and authentication.

Memory and storage devices are now appearing that specifically meet the needs of automotive applications with advanced data-care management, diagnostic, protection and security features. This is taking automotive memory well beyond what was previously used in general industrial applications.

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