MCU Selection Guide: What to Look for in a Microcontroller?
Open the datasheet of a microcontroller, usually, you will find more than 300 pages in front of you. It is time-consuming and inefficient to read the pages one after one, hence knowing which specifications are important is very necessary and helpful. In this article, TECHDesign will introduce the most essential specifications when choosing a microcontroller, which are core, clock frequency, memory size, input/output, power mode, communication protocol, and security.
The core and core numbers of a microcontroller determine its features and powerfulness. The popular microcontroller cores are the Cortex-M series from Arm, 8051 series from Intel, PIC series from Microchip, and AVR series from Atmel. Among them, Arm Cortex-M and 8-bit 8051 series are used the most often.
The clock frequency of a microcontroller directly determines its throughput. The higher the clock frequency is, the speedy the microcontroller performs. High-frequency microcontrollers are suitable for supporting intensive computing requirements (such as DSP function). One of the leading microcontroller suppliers Nuvoton provides NUC505 and M481/482/483/484/485/487 series with clock frequencies more than 100MHz.
A microcontroller is equipped with RAM for data storage and Flash memory for program storage. With various memory sizes, microcontrollers can be used to run with different systems. The following table indicates the functions that microcontrollers with various memory sizes can support.
|<32KB||Logic controlling only, usually run without OS or lite-weight RTOS|
|32～64KB||Capable of controlling low-speed communication protocols, such as UART, I2C, CAN, BLE, ZigBee, etc.|
|64～128KB||Capable of TCP socket programming|
|128～256KB||Fully capable of TCP communications|
|≧256KB||Run with 7-segment displays or even a small LCD panel|
|≧512KB||Not many microcontrollers support 512K+ memory, but if they do, they can run with a user-friendly LCD panel, like a QVGA or VGA panel|
I/O (Input/Output) pins in a microcontroller generally refer to GPIO (general purpose input and output) pins that can be configured into input, output, or bidirectional. Confirming the numbers of I/O pins required for your application will help you choose suitable microcontrollers. Besides, rather than having DACs (Digital to Analog Converters), most microcontrollers are equipped with ADCs (Analog to Digital Converters) to read analog inputs. Therefore, check if the microcontroller has a built-in DAC when you need an analog output.
There are several power modes in a microcontroller, and each of them represents different functions enabled. For instance, in most microcontrollers of Nuvoton, Normal mode, Idle mode, and Power-down mode are provided. the CPU clock and peripherals can be enabled or disabled in Normal mode; when the microcontroller enters Idle mode, the peripherals can still work with the CPU clock is disabled. In Power-down mode, the system (does not need to work for a long time); most clocks and peripherals are disabled. Various Power-down modes refer to the power-saving capability of a microcontroller; in Nuvoton M251/M252 series, Power-down mode can be classified into Normal Power-down mode, Deep Power-down mode, and Fast Wake-up Power-down mode with different power consumption levels.
Communication protocols are one of the critical specifications of a microcontroller. The more protocols a microcontroller supports, the more communication capabilities it performs. I2C (Inter Integrated Circuit), SPI (Serial Peripheral Interface), USB (Universal Serial Bus), UART (Universal Asynchronous Receiver Transmitter), and CAN (Controller Area Network) are commonly used protocols that help microcontrollers communicate with other devices.
I2C uses 2 bus lines including SDA (Serial Data Line) and SCL (Serial Clock Line) to transmit data between devices; SPI uses 4 bus lines including SCLK (Serial Clock), MOSI (Master Out Slave In), MISO (Master In Slave Out), and CS/SS (Chip/Slave Select) to transmit data, USB can transmit a huge amount of data with its speedy characteristic, and UART is designed for sequential communication, nowadays usually fits low-speed peripherals like debugging ports, low-speed modems, etc.
Another protocol CAN is popular in automotive applications, industrial automation, elevator systems, building automation, etc., for its capability of long-distance transmission (yet low speed), error detection, and no need of hosts.
The security of a microcontroller becomes important as cyberattacks are getting serious. Multiple security solutions have been introduced by different companies to protect the data, firmware, and system functions, and Arm TrustZone is a popular one that has been widely used in microcontrollers. The concept of it is to partition a microcontroller into trusted and non-trusted views, and everything is protected in the trusted view. Nuvoton NuMicro M2351 and M2354 microcontroller series are the implementations of the TrustZone.
Shop for Microcontrollers at TECHDesign
The basic specifications of a microcontroller have been introduced above. It is necessary to check all these specifications when selecting a suitable microcontroller for use. But before that, it is way more important to select a trustworthy microcontroller supplier, such as Nuvoton, the world-leading microcontroller manufacturer that has expertise in the developments of microcontrollers, microprocessors, and other kinds of ICs. At TECHDesign, Nuvoton has provided a complete product portfolio of microcontrollers, hence, come shop for microcontrollers here now!