Question

Simply list out the three parts of a port in the context of embedded microcontrollers.

Answer 1

A microcontroller (MCU for microcontroller unit) is a small computer on a single metal-oxide-semiconductor (MOS) integrated circuit (IC) chip. In modern terminology, it is similar to, but less sophisticated than, a system on a chip (SoC); a SoC may include a microcontroller as one of its components. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals.
Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, toys and other embedded systems. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes.

A Microcontroller is a VLSI (Very Large Scale Integration) Integrated Circuit (IC) that contains electronic computing unit and logic unit (combinedly known as CPU), Memory (Program Memory and Data Memory), I/O Ports (Input / Output Ports) and few other components integrated on a single chip.

The following image shows the Basic Structure of a Microcontroller.

From the above image, you can understand that the three important (or major) components of a Microcontroller are:

• The CPU (Central Processing Unit)
• The Memory and
• The I/O Ports

This doesn’t mean that other components are of less importance. But these can be considered as supporting devices. We will now see each of the Basic Components of a Microcontroller mentioned in the above structure.

CPU

Central Processing Unit or CPU is the brain of the Microcontroller. It consists of an Arithmetic Logic Unit (ALU) and a Control Unit (CU). A CPU reads, decodes and executes instructions to perform Arithmetic, Logic and Data Transfer operations.

Memory

Any Computational System requires two types of Memory: Program Memory and Data Memory. Program Memory, as the name suggests, contains the program i.e. the instructions to be executed by the CPU. Data Memory on the other hand, is required to store temporary data while executing the instructions.

Usually, Program Memory is a Read Only Memory or ROM and the Data Memory is a Random Access Memory or RAM. Data Memory is sometimes called as Read Write Memory (R/W M).

I/O Ports

The interface for the Microcontroller to the external world is provided by the I/O Ports or Input/Output Ports. Inputs device like Switches, Keypads, etc. provide information from the user to the CPU in the form of Binary Data.

The CPU, upon receiving the data from the input devices, executes appropriate instructions and gives response through Output Devices like LEDs, Displays, Printers, etc.

Bus

Another important component of a Microcontroller, but rarely discussed is the System Bus. A System bus is a group of connecting wire that connect the CPU with other peripherals like Memory, I/O Ports and other supporting components.

Timers/Counters

One of the important components of a Microcontroller are the Timers and Counters. They provide the operations of Time Delays and counting external events. Additionally, Timers and Counters can provide Function Generation, Pulse Width Modulation, Clock Control, etc.

Serial Port

One of the important requirement of a Microcontroller is to communicate with other device and peripherals (external). Serial Port proves such interface through serial communication. Most common serial communication implemented in Microcontrollers is UART.

Interrupts

A very important feature of a Microcontroller is Interrupts and its Interrupt Handling Mechanism. Interrupts can be external, internal, hardware related or software related.

ADC (Analog to Digital Converter)

Analog to Digital Converter or ADC is a circuit that converts Analog signals to Digital Signals. The ADC Circuit forms the interface between the external Analog Input devices and the CPU of the Microcontroller. Almost all sensors are analog devices and the analog data from these sensors must be converted in to digital data for the CPU to understand.

DAC (Digital to Analog Converter)

DIgital to Analog Converter or DAC is a circuit, that works in contrast to an ADC i.e. it converts Digital Signals to Analog Signals. DAC forms the bridge between the CPU of the Microcontroller and the external analog devices.