- The S6E2C Series of MCUs have up to 200-MHz operating speeds with floating point unit and integrated flash accelerator.
- Programmable CRC module makes wireless firmware updates easy and safe.
- Integrated solution packages simplify the addition of interfaces, display functionality, touchscreens, and motor control.
Next-generation MCUs enable the Industrial Internet of Things
With the increasing connectivity of machines and production processes in industrial applications, systems developers face changing production conditions. They need to provide flexible and simplified designs in less time and, if possible, at lower cost. High-performance MCUs with large embedded flash and the ability to support new protocols like CAN FD can help to meet these requirements.
The Internet of Things (IoT) demands intelligence and performance of from electronic building blocks and components, which at the same time must operate within a small and/or consistent energy budget. As a result, modern MCUs need to deliver high peak performance at the lowest possible energy consumption, both during operation and in standby mode. In fact, particularly in standby mode, the building blocks should draw only a few microamps of current because in some applications, the MCUs are only reactivated for a short time in order to execute intensive computing operations; for the rest of the time, they remain inactive. Especially in these cases, the designer needs to consider the whole energy budget: not just the maximum performance, which determines the length of execution for computing and the dynamic energy consumption, but the energy consumption in standby mode and the energy consumed during the time spent switching between modes.
It is with these requirements in mind that Spansion developed the S6E2C series of MCUs, part of its FM4 family of products. The new devices have a 200-MHz operating speed with a floating point unit. Embedded flash coupled with an integrated flash accelerator enables operation at up to 200 MHz without wait states. The MCUs combine this performance with a dynamic power consumption of 340 µA/MHz. This permits new degrees of design freedom¾an unused resource can be disconnected from the internal clock pulse, for example, so that it does not create dynamic energy consumption. The FM4 manages with less than 2µA in standby mode (RTC).
Secure OTA updates for firmware
In applications such as automation or machine-to-machine (M2M) communications like smart metering, it is necessary to update the firmware via existing network connections whether via cable or wireless. In this way, a product can be kept up to date or be expanded with further functions without the need for physical access. One example is the retrofitting of new versions of communication protocols. In order to update the firmware securely, the data is transmitted with a supplied CRC code and the target system then checks whether mistakes have crept in during the transfer.
The FM4 MCUs offer a programmable CRC module in hardware that is based on standard polynomials available on the market, but users also can define their own polynomials. After the integrity check, the new firmware can be programmed in the flash memory. This is done by a bootloader that receives the new firmware via any network and that carries out the CRC check and the actual flashing.
In the case of an unstable network connection like wireless, however, there is a risk that the firmware might not arrive completely in a fast transfer to the target system. Guarantee a secure update requires special hardware. The new devices include an operating mode designed for updates to the 2-MB embedded flash. While the incumbent firmware runs from a 1-MB memory, a second -MB memory is being reprogrammed bit by bit (see figure 2). The new firmware is only released and executed at the next system boot, and then only once the programming has successfully completed and verified. At that point, both flash memories swap their roles and can carry out further updates.
New interfaces on the rise
Networking in the industrial environment ranges from classic fieldbuses like CANbus to Ethernet-based buses with a variety of characteristics (e.g.: Profinet, POWERLINK, Modbus TCP, etc.) CANbus, which was originally developed for automotive electronics, has recently experienced an evolution with the introduction of CAN with flexible data rate (CAN FD). The new protocol provides some advantages without the need to change the physical layer. By switching the speed during the data transfer, CAN FD can provide a throughput eight times higher than for the earlier version, while allowing the use of the existing bus topology (see figure 3). The S6E2C series features two CAN channels as well as a CAN-FD channel, making CAN-FD available to the industrial market.
Many manufacturers provide ready solution packages that enable a fast start in developing custom applications and are very suitable for quick feasibility studies. The framework of the ‘FM connect Ethernet‘ solution package supports ProfiNET Conformance Class B, Ethernet POWERLINK, Modbus TCP, and web-browser-based user interfaces. Pre-configured Webservers (either uIP or LwIP based) are also available. The use of AJAX objects, for example, enables an existing user interface on a device to be made additionally available via the webserver. Interestingly, entries on both sides can be carried out simultaneously. This means that if a device was accessed by remote maintenance, the adjustment carried out would be immediately visible on the device, and vice versa.
USB made easy
Although hardly new, the USB interface is becoming increasingly popular in industrial applications, in contrast to the good old RS232 interface, which is hardly found any more. USB simplifies securely connecting devices with common PC systems. Users can comfortably log data or update firmware via a standard USB flash memory stick, or simply operate the user interface with a standard keyboard without having to define your own keys.
It’s a powerful technology but also complex. In order to provide an easy entry, Spansion provides a solution package called FM connect USB. The principal element is the USB Wizard. This PC program creates a complete template for the FM4 MCU based on the input of some basic data. In addition to the startup code, it also contains the complete settings for up to two USB interfaces on the host or device, as well as the preferred USB application API.
When the FM4 MCU is the host, mass-storage-class (USB stick drive), keyboard, mouse, and custom classes are available; when the USB interface is set to device mode, LibUSB as well as mass storage classes can be selected from virtual COM ports.
The S6E2C series provides an external bus interface with support from NOR flash, NAND flash, SRAM, and SDRAM memories. One option is the quad SPI (QSPI) interface, which can connect external flash memories from 4 Mbit up to 1 Gbit. The S6E2C SD card interface provides a further possibility. SD cards are very popular by means of their compact dimensions in order to, for example, file graphics data for HMIs. Users can update HMI graphics by simply swapping out the SD card. Naturally SD cards can also be used to log data or parameters. Finally, standard WLAN modules in SD card size are a very comfortable possibility to fit out your own modular applications with WIFI connectivity.
Additional solution options
To simplify integration, the MCU line includes solution packages beyond the previously mentioned FM connect Ethernet and FM connect USB. FM inverter provides algorithms and sample software for operating different inverter motor types with and without encoder or Hall sensor feedback. The S6E2C family also features a trio of multi-function timers that generate complementary pulse-width modulated (PWM) signals, add dead times, trigger the three 12-bit A/D converters, and perform all further motor-driven specific tasks in the hardware. A maximum resolution of 6.25 ns enables improvements to details, creation of asymmetrical PWM and provides an asynchronous emergency stop port for clock-independent emergency shutdown in the case of error.
FM touch provides capacitive touch functionality the complements the MCU’s 32 ports that can be operated as buttons, sliders, scroll wheels, or as an X/Y matrix. The module delivers sensitivity of better than 10 fF, along with automatic offset and crosstalk suppression, while minimizing CPU load and the impact on test application. The package consists of a special firmware library and a caltool–a configuration and set up program for the PC. Sample layouts for touch surfaces and tips for secure designs are complete the package.
Increasingly, industrial products feature TFT-based HMIs, both for functionality and as a product differentiator. The FM color package incorporates the necessary algorithms in order to drive TFTs directly from the MCU. The S6E2C MCUs can drive displays with resolutions as high as WQVGA directly. A tool called the TFT Wizard allows designers to create simple scenarios on the PC and then implement them in practicable firmware for the FM family.
Designed for the IoT, ex-generation MCUs deliver the performance needed for the industrial Internet. A suite of solution packages makes it easy for developers to leverage the functionality of these ARM® Cortex® M-based MCUs to develop prototypes and get better products to market faster. This and the special technical characteristics make these products an interesting alternative in the industrial market where it is all about scalable platforms, fast design times and good technical support.
This article also appears in German language in the magazine EL-info Elektronik Informationen, issue 11/2014.
Spansion(R), the Spansion logo, and combinations thereof, are trademarks and registered trademarks of Spansion LLC in the United States and other countries. ARM and Cortex are registered trademarks of ARM Limited. Other names used are for informational purposes only and may be trademarks of their respective owners.
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