ST Rolls 32-bit MCU Aimed at Cost-conscious 8-bit System Designs
With its new microcontroller offering, STMicroelectronics hopes to bring 32-bit computing into 8-bit applications.
As low-cost, low-power embedded electronics become more popular, there is also a demand for greater performance out of these devices. Historically, a low-power device may design in an 8-bit microcontroller (MCU) to keep cost and power consumption down, but this comes at a tradeoff of performance.
Now, STMicroelectronics (ST) is aiming to change this narrative with a new family of MCUs. Late last week, ST announced its STM32C0 family of 32-bit MCUs, a suite of products that it says are its most affordable yet.
The entry-level STM32C0 is aimed at cost-sensitive applications. Image use courtesy of STMicroelectronics
In this article, we’ll take a look at why 8-bit MCUs are preferred in low-cost, low-power electronics, and how, with its newest MCU family, ST hopes to change that narrative with its latest 32-bit offering.
STM32C0 Family Knocks Down Tradeoffs
According to ST, the new STM32C0 family of MCUs are designed to merge all of the benefits of 8-bit and 32-bit computing. Namely, ST wants to create a path for designers to use 32-bit MCUs in applications where only 8-bit options would have previously been feasible.
To do this, ST designed the STM32C0 family to be extremely cheap, calling them the lowest-cost 32-bit MCUs on the market. According to the datasheet, the new MCU family is also very low power, consuming under a maximum of 5 mA from a 3.0 V source. Despite claims of affordability, it’s important to note that ST includes no price range information about the STM32C0 in its announcement.
Block diagram of the STM32C0 family. Image used courtesy of STMicroelectronics
Beyond the power and cost, the MCU family also offers some appreciable performance specifications. Built around a 48 MHz Arm Cortex M0+ core, the STM32C0 family features up to 32 KB of flash memory, 12 KB of SRAM, and also integrates important circuit blocks such as a 12-bit, 0.4 µs analog-to-digital converter (ADC).
To further support low-power operation, the MCU also features a number of low-power modes, including sleep and stop modes which are capable of current consumption beneath 2 mA and in the microamp range respectively.
8-bit versus 32-bit
ST’s new MCU raises the question of how to decide between 8-bit and 32-bit MCU solutions. Indeed, when it comes to selecting a MCU, one of the most significant specifications is its data width. Data width, which defines the maximum number of bits of data that can be processed at once, is an important indicator of the functionality of the MCU.
Beyond simply defining how many bits of data can be operated on, the data width of a MCU also sets the upper limit of much of its functionality. For example, data width also determines the maximum memory locations that can be addressed and the size of its registers.
8-bit versus 32-bit microcontrollers. Image used courtesy of SEA Company
An 8-bit MCU is a type of MCU that uses an 8-bit data bus, meaning it can process 8 bits of data at a time. This means that it can handle values between 0 and 255 (or -128 and 127 in the case of signed values) in a single operation. A 32-bit MCU uses a 32-bit data bus and can handle values between 0 and 4,294,967,295 (or -2,147,483,648 and 2,147,483,647 in the case of signed values) in a single operation.
In general, 8-bit MCUs have a smaller instruction set and simpler instruction architecture than 32-bit MCUs. This means that they require fewer clock cycles to execute the same instruction, resulting in less power consumption and lower cost. Because of this low processing power and cost, 8-bit MCUs are often used in simple, low-cost applications such as consumer electronics, appliances, and toys.
On the other hand, 32-bit MCUs have a larger instruction set and more complex instruction architecture than 8-bit MCUs. This means that they require more clock cycles to execute the same instruction, resulting in more power consumption and higher cost.
All that said, they are more powerful and have more memory than 8-bit MCUs, lending them to more complex applications such as industrial automation, medical devices, and automotive systems.
A Future of Low Cost 32-bit Designs?
According to ST, the company hopes that this new line of MCUs will help create a future where inexpensive, low-power electronics can still offer exceptional performance and functionality.
