Microcontroller and Microprocessor – what’s the difference?

Microcontrollers and microprocessors are often found in various electronic devices. Both of these components retrieve commands from memory and perform logical and arithmetic operations, while interacting with input/output devices and other peripherals. So what’s the difference?

Microcontroller

A microcontroller (hereinafter referred to as an MCU) is a microcircuit designed for software control of electronic circuits. An MCU is built on a single chip, housing both the computing unit and ROM and RAM. Additionally, an MCU typically includes input/output ports, timers, an ADC, and serial and parallel interfaces. Some even feature a Wi-Fi/Bluetooth module and NFC support.

The first patent for a microcontroller was issued in 1971 to Texas Instruments. The company’s engineers proposed placing not only a processor but also memory and input/output devices on a chip.

Even though a microcontroller already has everything it needs to operate, it’s sometimes paired with external peripherals. For example, when the internal ROM isn’t sufficient (or simply missing), an external one is connected. This is precisely what happened with the ESP series microcontrollers. The ESP8266 has no onboard memory at all, while the ESP32 has a paltry 448 KB. Therefore, flash memory with a capacity of 1–16 MB is placed inside their housing (or rather, under the heatsink).

So why not build some kind of portable computer based on a microcontroller? The problem is that microcontrollers often have relatively limited computing power. It’s only enough to control, for example, an irrigation system, a microwave, or some kind of machine tool.

For example, one of the most powerful Arduino boards is the Due. It is controlled by a 32-bit AT91SAM3X8E AVR microcontroller with a clock rate of 84 MHz. It has 512 KB of ROM and 96 KB of RAM. The microcontroller has 54 digital GPIOs (12 of which support PWM), 12 analog inputs, and 2 analog outputs (DACs). It also features various interfaces, such as UART, SPI, and I2C.

Despite these modest specifications, microcontrollers are very popular. They are used in applications that don’t require significant computing power, such as robotics, greenhouse controllers, and household appliances.

Microprocessor

With a microprocessor (hereinafter referred to as a microprocessor), things are a little different. It contains an arithmetic logic unit, a synchronization and control unit, a memory unit, registers, and a bus. In other words, the microprocessor contains only what is needed to perform arithmetic and logical operations. All other components (RAM, ROM, input/output devices, interfaces) must be connected externally.

The first microprocessors also appeared in the early 1970s. The 4004 was considered the most popular at the time. This microprocessor was developed by Intel and introduced on November 15, 1971. It had impressive specifications for the time:

• 2300 transistors;
• clock frequency – 740 kHz;
• register and bus bit depth – 4 bits;
• process technology – 10 microns;
• crystal area: — 12 mm².

Incidentally, the 4004 was packaged in a standard DIP-16 package. This microcontroller is the most popular microchip among collectors. Some examples sell for as much as $400 each. Less rare ones cost around $250.

Just a couple of years later, 8-bit microprocessors made it possible to create the first household microcomputers.

Naturally, the advantage here is that a microprocessor can be connected to a variety of peripherals with different characteristics (which isn’t always possible with an MCU). The second main difference between a microprocessor and a microcontroller is that microprocessors have more computing power. They don’t make sense for microwave ovens or smart light bulbs. Microprocessors are used in applications where the computing power of an MCU can’t cope—game consoles, complex computing devices and appliances, and gadgets.

It turns out that to ensure the microprocessor’s functionality, it needs to be connected to at least a minimal set of peripherals. Cons:

1. Size – if in the case of the MC everything is already in one case, then the minimum set of elements for the MP operation takes up more space.
2. Price – usually, the entire “assembly” of components for the microcontroller is much more expensive than the “bare” microcontrollers.

Pros:

1. Performance – Microprocessors have greater performance than microcontrollers.
2. Choice – with a microprocessor, you have the option to choose the components. This will allow you to install peripherals that best suit your needs.

Application

A microcontroller is clearly simple: it requires less hardware, is easier to work with at the software level, and costs start at pennies. But this simplicity also comes at a cost. As mentioned above, a microcontroller cannot provide the high performance of microprocessors. Although microprocessors require external hardware switching and are more complex to operate than microcontrollers, they can easily be used in more complex devices.

However, sometimes there are some clever people online who can fit DOOM and even an NES game emulator into an ESP32 microcontroller.