With the rapid development of the Internet of Things, many devices that were not connected to the network in the past also gradually need to integrate communication module functions. Conversely, the number and harmfulness of security threats are also on the rise. Therefore, the microcontroller must meet a series of requirements, including reducing footprint, reducing power consumption, enhancing security, and providing timely over-the-air (OTA) firmware updates.
The rapid progress of Internet technology and various sensor technologies has promoted the development of the Internet of Things, giving birth to a large number of devices covering a wide range of uses. According to the data released by the market forecast company, it is estimated that by 2022, the market size of IoT devices is expected to grow to US$1 trillion. Edge devices integrate communication modules for different standards and specific sensor modules (depending on the application and purpose of the IoT device), the size is shrinking, and more functions will be implemented. Therefore, the microcontrollers in these devices must meet the needs of the market, including not only existing requirements such as high performance and low power consumption, but also a more compact package size and a smaller footprint. In addition, application development also needs to add value-added functions to provide IoT support, and develop program codes to handle protocol stacks of various communication interfaces. This will increase the control complexity and code size, which means that the microcontroller not only needs a powerful CPU, but also sufficient large-capacity flash ROM and RAM. From the perspective of hardware designers, product series have become more diversified. In order to reduce development costs, it is necessary to use a specially optimized platform design, and use general-purpose circuit board development as much as possible to achieve compatibility of pin layout and shape. . Therefore, a microcontroller with a high specification and a small package is an ideal choice. As the name suggests, Internet of Things devices use Internet connections, and more and more people realize that the security of the Internet of Things devices themselves (that is, edge devices) must be ensured. In recent years, cyber attacks using IoT devices connected to the Internet as gateways have become increasingly rampant, and there have also been incidents of using security vulnerabilities to hijack devices or using devices for monitoring. This makes implementing appropriate security measures an important issue. Without proper security measures, equipment will always face various risks such as hacker attacks and hijacking. In order to solve such problems, security measures must be introduced on the edge devices that act as endpoints. This also highlights the importance of overall life cycle management, including ensuring safe program writing during initial manufacturing and transportation, and the need for security patches to fix problems in program code after entering the market. The conventional method is to add special safety equipment to the traditional controller, and consult the technical experts in the safety field to design the system. However, for edge devices, due to cost constraints, a shorter development cycle (TAT) is required, and these implementation methods are very difficult. Therefore, we want to integrate safety functions into the microcontroller.
Small footprint and high performance
With the development of compact modules, the central microcontroller responsible for function control must adopt a small footprint package. For example, the space occupied by microcontrollers of various communication module product series on the market is usually 10 x 10 mm, but a package of 5 x 5 mm or smaller is urgently needed. In addition to reducing the footprint of the package, a larger ROM capacity is needed to support various applications, and enough RAM to handle the protocol stack. These product series should be able to allow users to select the appropriate memory capacity according to the scale of the application. In traditional microcontrollers, memory capacity and small package volume need to be weighed, and it is difficult to balance them. Therefore, the current small package controllers on the market are mainly 1 MB ROM/256 KB RAM products. Through the industry-leading 40nmFlash process technology, we can expand the RX651 product series and add new products with a 4.5 x 4.5 mm package, 2MB internal flash ROM and 640 KB RAM. Compared with the smallest 7.0 x 7.0 mm product in the 32-bit MCU RX651 series that has been mass-produced, its footprint has been reduced by 60%, which allows us to more flexibly meet market needs. Our product lineup is strong, covering from 512KB to 2 MB of internal flash ROM, from 256 KB to 640 KB of RAM. The 64-pin product in a small package achieves pin compatibility between all memory configurations, which helps customers use common components and circuit board designs to create product series based on the platform.
Root of Trust in Embedded System
When developing embedded systems, to implement security functions in hardware and software, senior development and technical personnel with these skills are required, and the high cost will become another obstacle. In addition, it is not easy to get end users to recognize the value of security. If the security functions in certain applications are obviously very important, such as in financial transactions and confidential information processing, the market will regard strong security as value-added content, and a lot of development resources and costs are usually invested. In these markets, the use of dedicated chips to achieve strong security has always been a common practice. In recent years, the development of the Internet of Things has prompted more and more manufacturers to consider implementing security features, even extending to devices that were not connected to the Internet in the past. However, due to the lack of safety experience, equipment manufacturers are usually more familiar with traditional microcontrollers, and it has become a reasonable approach to use general-purpose microcontrollers to implement powerful security functions. This has also become a requirement for edge device development. In addition, when IoT devices are connected to the network, the cloud or server may not be able to ensure security, or the access point that acts as a relay point for data transmission and reception may not be able to ensure security. Therefore, IoT edge devices as endpoints must have integrated security functions. In order to achieve this goal, the edge device should have a root of trust component, so that the device itself can ensure safe operation. The RX651 microcontroller implements the root of trust in the hardware, provides the Trusted Secure IP (TSIP) function to protect key data, prevents key leakage and provides memory protection functions to prevent authorized programs from being tampered with. RX651 1.5 MB and 2 MB flash memory products, integrated Trusted Secure IP (TSIP) dedicated hardware IP, used to manage keys, prevent illegal access to keys, and can hide these keys through index information to keep them safe The ground is stored in the internal ROM.
In addition, the memory protection function in all RX651 products allows zone protection to be enabled for the internal flash memory. This ensures that the code is stored in a dedicated memory area that cannot be rewritten from the outside. Since the security code that detects malicious code can be protected in this way, comprehensive security is achieved. RX651 series products using TSIP do not need to rely on dedicated security chips. Utilize the TSIP hardware function and characteristic of general-purpose microcontroller itself, establish strong security.
The Trusted Secure IP of RX651 not only supports common key encryption methods such as AES and 3DES, but also supports RSA asymmetric encryption required for SSL/TLS communication. The encrypted communication required to connect to different cloud services can be implemented based on hardware, so that high throughput can be achieved without increasing CPU load.
Simple firmware update
The function of updating the firmware through the network can be regarded as a crucial feature of the Internet of Things devices. It allows users to continue to add new functions to the product after the product is released, fix application errors, and enhance the safety of the product. As network attack methods continue to evolve, users must patch existing products. With traditional microcontrollers, it is generally necessary to download new firmware to a dedicated backup memory area and execute a dedicated update program to perform firmware update. In addition to requiring the controller to provide a separate backup memory, this method must also stop the original work of the system when downloading or updating the system. As a processor for IoT applications, we hope to deploy a backup area in the built-in memory and implement background downloads.
The 2 MB and 1.5 MB flash memory versions of RX651 provide Dual Bank function and support background operation (BGO). Therefore, we only need to use the internal flash memory to update the firmware without stopping the system. The Dual Bank function can divide the internal flash memory into two independent storage areas, one area is used for program execution and the other area is used for downloading firmware. Using the BGO function, while the program code can be executed, the new firmware is received through the communication interface and written into the firmware download area. When the background writing process is completed, the execution area switching register will be set, and the reset will be executed, the execution area and the download area will be exchanged, and the new firmware will start to run. The boot program can include steps to check whether the firmware is damaged, and if necessary, you can easily restore to the old version of the firmware.
