A class of microcontrollers has emerged that provide tailored feature sets aimed at targeted application needs. These application-specific MCUs give embedded systems developers right-sized solutions with the functionality that fits their system requirements.
In contrast to microprocessors, microcontrollers (MCUs) tend to be used for specific applications. But even among MCUs, there’s distinct difference between general purpose MCUs and MCUs that are designed for very specific application segments, or even sub-segments. These application-specific MCUs usually have carefully selected on-chip IP cores and peripherals that meet the requirements unique to an application need.
Responding to needs of embedded systems developers, over the past 12 months MCU vendors have continued to roll out new MCUs that address application needs in industrial control, banking, safety-critical systems and more. While automotive MCUs are, in particular, an extremely active segment of application-specific MCUs, I don’t address automotive MCUs in this article. We covered that topic recently our August Special Feature “IC Solutions Rev Up for Next Gen Auto Designs” (Circuit Cellar 349).
Closed-loop control ranks as one of the most fundamental tasks performed by embedded systems—required in systems ranging from pool pumps to air handling units. Feeding that specific need, Microchip Technology offers its PIC18 Q10 (Figure 1) and ATtiny1607 families, featuring multiple intelligent Core Independent Peripherals (CIPs) that simplify development and enable quick response time to system events. Advancements in the architecture of PIC and AVR 8-bit MCUs have optimized the devices for implementing closed-loop control, enabling systems to offload the CPU to manage more tasks and save power.
Well suited for applications that use closed-loop control, a key advantage of using the PIC18 Q10 and ATtiny1607 MCUs are the CIPs that independently manage tasks and reduce the amount of processing required from the CPU. System designers can also save time and simplify design efforts with the hardware-based CIPs, which significantly reduce the amount of software required to write and validate. Both families have features for functional safety and operate up to 5 V, increasing noise immunity and providing compatibility with the majority of analog output and digital sensors.
Offered in a compact 3 mm x 3 mm 20 pin QFN package, the new ATtiny1607 family is optimized for space-constrained closed-loop control systems such as handheld power tools and remote controls. In addition to the integrated high-speed analog-to-digital converter (ADC) that provides faster conversion of analog signals resulting in deterministic system response, the devices provide improved oscillator accuracy, allowing designers to reduce external components and save costs.
Among the CIPs in the PIC18 Q10 family are the Complementary Waveform Generator (CWG) peripheral, which simplifies complex switching designs, and an integrated Analog-to-Digital Converter with Computation (ADC2) that performs advanced calculations and filtering of data in hardware without any intervention from the core. CIPs such as these allow the CPU to execute more complex tasks, such as Human Machine Interface (HMI) controls, and remain in a low-power mode to conserve power until processing is required.
WATER TOLERANT TOUCH
User interfaces in harsh industrial environments have to contend with factors such as water and other disturbances. To address such needs, in March, NXP Semiconductor announced its 5 V KE1xZ family of MCUs. Based on the Arm Cortex-M0+ core, the MCUs are suited for embedded control systems in harsh electrical environments and provide an integrated CAN controller and capacitive touch from 32 KB flash.
Designed for a wide range of industrial applications, the KE1xZ family offers mixed-signal integration across a range of compact memory variants. The 1-MS/s ADC and FlexTimer modules, combined with NXP’s Freemaster software tools library and Motor Control Application Tuning plugin (MCAT) enable designs of Brushless DC (BLDC) and other motor-control systems.
NXP’s KE1xZ MCU family offers advanced noise immunity, water-tolerant touch and low-power wake-on-touch operation—essential features for the strict electromagnetic compatibility (EMC) standards of the industrial and home appliance markets. NXP’s touch IP, combined with software and tools provide a high level of stability, accuracy and ease of use, with continued responsiveness and functionality through wet conditions. It can sustain 10 V in conducted noise, in alignment with International Electrotechnical Commission (IEC) 6100-4-6 test level 3. NXP enables developers through its MCUXpresso software and tools ecosystem, along with its FRDM-KE15Z and FRDM-TOUCH development platforms (Figure 2).
MCU FOR CONTACTLESS BANKING
Contactless transaction capability is an important application in systems such as banking, identity, transportation and pay-television. In July, STMicroelectronics (ST) announced an MCU aimed directly at that space. The ST31P450 is a dual-interface secure MCU that features the latest 40 nm flash process as well as enhanced RF technologies (Figure 3). The device is built on the proven 32-bit Arm SecurCore SC000 secure processor and meets ISO 7816 and ISO 14443 Type A smart-card and contactless standards. It supports the full range of MIFARE libraries including MIFARE Classic, MIFARE Plus and MIFARE DESFire.
ST’s 40 nm Flash technology creates an ultra-small die for dual-interface use cases such as banking and, with security-enhancing properties, increases safety and fraud prevention. Upgraded RF performance ensures ultra-reliable wireless connections for faster, easier contactless transactions.
In addition, the ST31P450 features new low-power cryptographic engines that minimize the energy budget and ensure superior product performance at low RF-field strength while executing cryptographic operations. The ST31P450 also comes with optimized loading firmware that makes life easier for card provisioners, offering post-issuance capability. The MCU and its associated cryptographic libraries, are expected to achieve Common Criteria EAL5+, as well as EMVCo and CUP (China UnionPay) certifications within the coming months. The ST31P450, with 450 KB non-volatile memory (NVM) and 10 KB RAM on-chip, is in production now.
Safety-critical systems—any system where failures could cause harm to life and limb—have special requirements beyond those of other embedded systems. To address such needs at the MCU level, Infineon Technologies decided on a collaborative effort. In February, Infineon announced an effort with Xilinx and Xylon to produce a new Xylon IP core called logiHSSL. It enables high-speed communication between Infineon’s AURIX TC2xx and TC3xx MCUs (Figure 4) and Xilinx’ SoC, MPSoC and FPGA devices via the Infineon High Speed Serial Link (HSSL). This serial link supports baudrates of up to 320 Mbaud at a net payload data-rate of up to 84%.
The HSSL is an Infineon native interface that is low-cost in regard to pin-count because it requires only five pins—two LVDS with two pins each and one CLK pin. So far, the HSSL interface is used to exchange data between AURIX devices and customer ASICs for performance or functional extension.
Now, the new IP core will allow system developers to combine safety and security provided by AURIX with the wide range of functional possibilities brought to the table by the Xilinx devices. Linked devices can access and control each other’s internal and connected resources through the HSSL
To support development activities, the partners are offering a starter kit. It includes a Xilinx evaluation kit, an Infineon AURIX evaluation board and a Xylon FMC board. Kit deliverables include the reference design with the test software application, Xylon’s logicBRICKS evaluation licenses, documentation and technical support.
MCUS FOR SERVO CONTROL
MCUs play many roles in industrial applications. But there are several specific systems that have unique requirements. With that in mind, in May Renesas Electronics introduced the RX72T Group of 32-bit motor control MCUs with dedicated hardware accelerator IP to perform the complex, high-speed computations required for motor control in robots and other industrial equipment (Figure 5). According to the company, the RX72T Group provides superior performance, achieving an 1160 CoreMark score as measured by EEMBC Benchmarks—the highest level for a 5 V MCU operating at 200 MHz.
Servo systems are becoming increasingly popular and the demand for compact industrial robots is also rising, says Renesas. To implement the complex motions required by industrial robots, high-precision control of the position, direction, speed, and torque of the motor is required. The RX72T MCUs include dedicated accelerator hardware that enables the high-speed position control and speed control calculations required for implementing servo motor control in compact industrial robots. This allows the current control loop calculation to be performed in less than 1.5 µs, providing a new option for users to independently develop servo systems where previously they only had the option of purchasing existing servo systems.
Implementing calculations in software can require excessive computing time. However, completely hardware-based calculations can adversely affect the flexibility to implement unique user control operations. With the RX72T MCUs, Renesas resolves the issue by implementing only the single-precision floating point trigonometric function (sin, cos, arctan, hypot) and a register bank save function in hardware as dedicated IP. This retains the flexibility while increasing the calculation speed. Furthermore, the register bank save function increases the speed and precision of interrupt handling, improving the device computation performance. The MCUs also include 200 MHz PWM inverter control timers with up to 4 channels of 3-phase control, 2 channels of 5-phase control or 10 channels of single-phase control.
MCUs WITH EtherCAT
Also targeting industrial systems, in June Texas Instruments (TI) introduced new communications capabilities on its C2000 MCUs. C2000 F2838x 32-bit MCUs enable designers to use a single chip to implement connectivity, including EtherCAT, Ethernet and Controller Area Network with Flexible Data Rate (CAN FD), in AC servo drives and other industrial systems.
Systems with communication interfaces often require an external ASIC or dedicated host control microprocessor, which limits the flexibility of the design architecture, adds complexity and takes up space on the board. The new C2000 F2838x MCUs do not require an external ASIC, therefore, reducing overall solution size and bill of materials.
By integrating three industrial communication protocols, the F2838x MCUs give designers the ability to tailor one MCU to the unique needs of each system. A key component in achieving this is a new connectivity manager, an Arm Cortex-M4-based subsystem, which offloads processing-intensive communications and optimizes connectivity. In addition to these capabilities, C2000 F2838x MCUs offer enhanced real-time control performance and higher flexibility than previous C2000 series MCUs.
For electrically isolated architectures, the new MCUs use a fast serial interface with eight receiving channels to facilitate chip-to-chip communication at up to 200 Mbps using minimal pins. Designers can build on this high level of integration in CAN FD designs and quickly increase the number of available CAN FD ports by pairing the F2838x with a TI system basis chip (SBC), such as the TCAN4550 SBC with integrated CAN FD controller and transceiver.
Infineon Technologies | www.infineon.com
Microchip Technology | www.microchip.com
NXP Semiconductor | www.nxp.com
Renesas Electronics | www.renesas.com
STMicroelectronics | www.st.com
Texas Instruments | www.ti.com
PUBLISHED IN CIRCUIT CELLAR MAGAZINE • OCTOBER 2019 #351 – Get a PDF of the issue