A microcontroller (MCU) is a full computer built on a chip. They are used for a specific application and are normally found as part of embedded systems. MCUs execute the commands of the program by storing values in memory, by fetching values from memory and storage, and by controlling peripherals according to the statements of the program.

MCUs are employed in devices that need human interaction or human control. Evolution of computer technology is closely tied to the development of MCUs. Two main reasons for their development include improvements in integrated circuit (IC) design and fabrication, such as complimentary metal-oxide semiconductor (CMOS) and very large scale integration (VLSI) technology, and improvements in memory technologies. Modern semiconductors have revolutionized computing; large amounts of memory, fast operating speeds, and reduced power, size, and cost with a small ship are now possible.

Examples of common MCUs are the clock in a kitchen oven, and the IC that signals to open a car door when the handle is touched. MCUs are used in devices that need human interaction or human control.

Components

The accompanying figure shows the main components of an MCU and their interrelations. The most important components are the central processing unit (CPU), memory unit, mass storage, and input and output ports. Other important components for the operation of MCU include the program counter, clock oscillator, power supply circuitry, and program and source code.

CPU: The CPU is the brain of the microcontroller and its most important component. It is an extremely useful digital electronic circuit. If the CPU is entirely contained in an IC package it is also called a microprocessor (MPU).

Memory unit: In an MCU, memory stores data and instructions code. Mainly, there are two types of memory in a typical MCU: ROM and RAM memory. Other types of memory such as Flash or EEPROM memory is used in some MCUs.

Mass storage: All MCUs need to have access to electronics hardware to store information. The information includes program instructions (source code), executables, images, documents, numbers, strings, and other data.

I/O ports: The input/output ports are electronic connectors (pins) that connect with peripherals outside the MCU. Peripherals include devices such as keyboards, monitors, serial communication devices, printers, and all type of devices. To enhance the storage and memory capabilities of the MCU it is possible to add extra external storage or extra external memory using the I/O ports.

Manufacture

All MCUs are electronic devices built in a chip with standard fabrication techniques used in the manufacturing of all ICs. An MCU is a computer in a chip, and its form factor is an IC.

Specifications

MCU Family (Width of Data Bus)

MCU family refers to the size of the data bus. The data bus is the number of bits that can transferred at the same time. Based on this specification, there are families known as 8-bit, 16-bit, 32-bit, 64-bit, and so on. The higher the size of the bus, the faster data transfer is for the MCU.

Clock Rate

All MCUs need a clock (oscillator) to operate. At intervals the MCU performs an operation or executes a command. Faster devices have higher clock rates. Clock rate is measured in megahertz (MHz) or "tics" per second.

Memory

The installed memory is important because it will hold the source code of the operating program and will store temporary instructions and data. An MCU with big memory can perform faster. This is similar to a personal computer, where more memory means faster operations.

Supply Voltage

This parameter is important when the MCU is part of an embedded system. A low power requirement means that system energy can be used to drive more devices.

Types and Number of Ports

The number of input and output ports is important if you plan to drive many devices with the MCU. Also, the type of port is essential, because this will allow you to drive specific devices. Some of the port types include:

• CAN, controlled area network
• SPI., serial peripheral interface
• I2C, inter-integrated circuits
• USB, universal serial ports

Image credit:

Texas Instruments