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Selecting the Right Microcontrollers for Your Products: 8-bit v.s 32-bit MCU

This is a world full of controlling and processing, therefore microcontrollers, microprocessors and processors are almost found in every digital device. Comparing to microprocessors and processors, microcontrollers are used more often in general. According to IC Insights, driven by the increased applications of Internet of Things and the rise of automation and embedded control in systems, the revenue of world microcontrollers is estimated to reach USD $21.3 billion in 2023 from USD $17.4 billion in 2018 with a CAGR growth rate of 3.9%; and the unit shipments are projected to reach 38.2 billion in 2023 from 28.1 billion in 2018 with a CAGR growth rate of 6.3%.

 

What are the Bit Sizes for Microcontrollers?

There are 8-bit, 16-bit, and 32-bit microcontroller in terms of bit configuration. 8-bit and 32-bit microcontroller will be discussed in the article since the use cases of 16-bit microcontroller becomes less and less nowadays.

8-bit microcontroller is basically used to execute simple logical operations such as addition, subtraction, multiplication, division, etc.. Comparing to 32-bit microcontroller, 8-bit is way smaller in storage space and its calculating capability is weaker.

Take the first 8-bit microcontroller 8051 architecture which was introduced by Intel in 1981 for instance, it consists of 128 bytes of RAM, 4Kb of ROM storage, and 4 parallel 8-bit ports. Nowadays 8051 microcontrollers have shown a lot of improvements, in Nuvoton, 8 ~ 64KB Flash memory is built in, 2.4 ~ 5.5V operating voltage is widely applied. It is worth noting that 8051 platforms do not support fancy modern programming languages, but support old-fashioned languages which do not have many library or toolchain resources such as assembly or C.

Architecture of the first 8-bit microcontroller 8051 (Source: tutorialspoint)

32-bit microcontroller could be used in more complicated calculations; ARM, Atmel, NXP, Infineon, TI, Renesas and Microchip all have related solutions. Among all, ARM Cortex-M architecture with Cortex-M0, M0+, M1, M3, M4, and M4F is used the most widely. It is worth mentioning that Cortex-M0 is available for free to prototype and commercialize a custom SoC. There are more toolchain resources for Cortex-M0 which support high level programming such as C99 standard.

Different from Cortex-M0, Cortex-M4 contains higher CPU and frequency ability, larger Flash, and DSP implemented. It is considered natural that Cortex-M4 could deal with even more complex workloads.

The architecture of Cortex-M0 (Source: arm)

 

The architecture of Cortex-M4 (Source: arm)

How to Select the Right Microcontroller?

To select a proper microcontroller to design with, one needs to consider the size, system scale, accessibility, cost, latency, RAM efficiency, and the ability of control and process.

Normally 8-bit microcontroller would be applied to a simple and small system while 32-bit microcontroller would be applied to a more complicated system. 8-bit microcontroller has the advantage of cost and small size; but 32-bit microcontroller has the advantage of accessibility. Take Cortex-M architecture for example, due to the support of C++ library, it is easy for designers to write firmware inside it.

For the ability of control and process, 32-bit microcontroller is definitely superior to 8-bit one. Since 8-bit microcontroller could only do simple calculations, it is efficient to deal with interrupt and latency. Moreover, 32-bit microcontroller is capable of controlling more modules or devices; the responsive time would be longer than that of 8-bit one. For RAM efficiency, it depends on the calculation type; 8-bit microcontroller is more efficient in terms of simple calculation while 32-bit microcontroller is more efficient in terms of complicated calculation.

 8-bit MCU32-bit MCU
SizeSmallerSmall
Suitable system scaleSmallMedium
AccessibilitySupport old-fashioned languagesSupport C++ library
CostLowMedium
LatencyShorterLonger
RAM efficiencyEfficient in terms of simple calculationEfficient in terms of complicated calculation
Ability of control and processInferiorSuperior

What are the Applications?

32-bit Cortex-M4 MCU can be applied to industrial automation.

Back in the early days when technology was not so advanced, 8-bit microcontroller was the mainstream in terms of controlling, such as remote control, power switch control, monitor control, volume control, keyboard and mouse control. anything that relates to controlling a single device with a simple commend could be applied with 8-bit microcontroller.

As time goes by, the coming of IoT era brings more automatically controlled applications and somehow 8-bit microcontroller is not enough to be used in some scenarios. Generally speaking, new IoT applications are mostly applied with 32-bit microcontrollers due to the consideration of specific control and future scalability.

To further divide 32-bit microcontroller thoroughly, Cortex-M0 and M4 are used for more explanations. 32-bit Cortex-M0 microcontroller suits controlling multiple connections without TCP/IP capability such as light bulb control, power supply control, hardware control, card reader control, sensor control. Another example is Bluetooth related application; this microcontroller could control Bluetooth and communicate with Bluetooth module at the same time.

For 32-bit Cortex-M4 microcontroller, even more complex calculations such as multimedia control could be applied. This microcontroller could control multiple connections at the same time with TCP/IP capability. For instance, it could control a device with Bluetooth, NFC and cellular connection abilities, and it could control other peripherals as well. Basically, the related applications of Cortex-M4 microcontroller include motor control, automotive, power management, embedded audio and industrial automation.

 8-bit MCU32-bit MCU
Cortex-M0
32-bit MCU
Cortex-M4
ApplicationRemote control, power switch control, monitor control, volume control, keyboard and mouse controlLight bulb control, power supply control, hardware control, card reader control, sensor controlMotor control, automotive, power management, embedded audio and industrial automation
TCP/IP AbilityNNY

*TCP/IP capability requires additional connectivity peripherals and software stack

 

What is mentioned above explains the development trend of microcontrollers. Overall, applications of 8-bit microcontroller are old but the market demand is stable; it is also cost-effective on bare-metal devices. On the other hand, applications of 32-bit microcontroller are rising and the market demand is growing.

 

Nuvoton Provides Complete Product Lines

Here now at TechDesign, Nuvoton offers complete 8-bit and 32-bit microcontroller products for consumers. The 8-bit microcontrollers are with 2.4 ~ 5.5V operating voltage, -40°C ~ 85°C working temperature, high noise immunity and a rich set of I/O. there are N78 and W78 series for standard 8051; N76E and N79E series for low pin count microcontrollers; MS51 series for industrial use; ML51 series for low power function; ML54 and N76E series for LCD application. Besides, all of them are pin-compatible with traditional 8051.

 

8-bit MCU family of Nuvoton (Source: Nuvoton)

 

At Nuvoton, 32-bit microcontroller families are complete as well. For ARM Cortex-M0 based microcontrollers, Mini series, M05* series, NUC029 and M031 series are all for advanced applications, and only M031 series have a built with 512KB Flash memory; NUC series are for supporting USB and CAN I/O; Nano series are for ultra-low power function. All of them are with high accuracy oscillator and high noise immunity; provide wide operating voltage from 2.1V to 5.5V and industrial temperature from – 40 °C to 105 °C.

Cortex-M0 MCU family of Nuvoton (Source: Nuvoton)

 

Moreover, for ARM Cortex-M4 based microcontrollers, there is NuMicro high performance family with FPU and DSP extension. Among them, M45* series are with 5V operating voltage, 72MHz CPU, up to 256 KB Flash memory, 32 KB SRAM memory, and Quad-SPI interface. M480 series are with 192MHz CPU, up to 512 KB dual bank Flash memory, 160 KB SRAM memory, and Quad-SPI interface with XIP (Execute in Place), 16-bit I80 QVGA LCD. NUC505 series are with 100 MHz CPU, up to 2048 KB SPI Flash memory, 128 KB SRAM, and audio interface.

Cortex-M4 MCU family of Nuvoton (Source: Nuvoton)

 

Conclusion

In conclusion, 8-bit microcontroller could be used to execute logical operations in a relatively small system. The applications for it are traditional applications such as remote control, monitor control, keyboard and mouse control, etc., any application related to control a single device with a simple commend.

For cost-sensitive applications that require more computing power, 32-bit Cortex-M0 microcontroller would be a great fit. It could control multiple connections at the same time, such as power supply control, hardware control, and sensor control. In addition, if TCP/IP capability and more connections are needed, 32-bit Cortex-M4 microcontroller is recommended to use. The applications consist of motor control, power management, embedded audio and industrial automation.

Nuvoton provides complete microcontroller products for multiple applications. Visit TechDesign and find the right microcontroller for your product now!

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