A microcontroller can be seen as a small computer, and this is because of the essential components inside of it; the Central Processing Unit (CPU), the Random-Access Memory (RAM), the Flash Memory, the Serial Bus Interface, the Input/Output Ports (I/O Ports), and in many cases, the Electrical Erasable Programmable Read-Only Memory (EEPROM). Figure 1 shows a great diagram of the main parts and also other parts in the microcontroller. Let’s dive into each of these components and see how they work inside the microcontroller. This is the figure of the inside part of a microcontroller.
The CPU, sometimes called a processor or microprocessor, controls
all of the instructions/data flow that it receives. You can think of it as the
brains of the system, processing all the data input it receives and executes
the required instructions. Its two main components are the Arithmetic Logic
Unit (ALU), which performs arithmetic and logical operations, and the Control
Unit (CU), which handles all of the processor’s instruction executions. Figure
2 shows a usual "machine cycle" that the CPU goes through.
RAM (Random Access Memory) is a component
that temporarily stores data, and can be accessed quickly. It provides quick
read-and-write access to the storage device. This differs from most other
memories as it takes longer for data to be extracted since the data isn’t
readily available. You can see it as RAM having access to the surface of data –
easily reachable – but anything that dives deeper will require a different type
of memory. RAM improves total system performance because it allows the
microcontroller to work with more information at the same time. Since RAM is
temporary data, its content is always erased when the microcontroller is shut
down.
Flash Memory is a type of
non-volatile memory that, unlike RAM, retains its data for an extended period,
even if the microcontroller is turned off. This keeps the saved program that
you might have uploaded to the microcontroller. Flash Memory writes to a
“block” or “sector” at a time, so if you need to just re-write one byte, Flash
Memory will need to re-write the whole block that the byte is in, which can
wear out quicker.
EEPROM is like Flash Memory, being a
non-volatile memory and retaining its data even after shutdown. The difference
is that, while Flash Memory re-writes a “block” of bytes, EEPROM can re-write
any specific byte at any time. This extends the life of EEPROM compared to
Flash Memory, but also means that it is more expensive.
A
Serial Bus Interface is the serial communication in the microcontroller,
sending data one bit at a time. With microcontroller boards, it connects ICs
with signal traces on a printed circuit board (PCB). For ICs, they use serial
bus to transfer data to reduce the number of pins in a package making them more
cost effective. Examples of serial buses in ICs are SPIs or I2Cs.
I/O
ports are what the microcontroller uses to connect to real-world applications.
Inputs receive changes in the real-world, from temperature sensing, to motion
sensing, to push buttons, and much more. The input then goes to the CPU and
decides what to do with that information. When it’s time to do a certain
command based on a certain value from the input, it sends a signal to the
output ports, where it can range from a simple LED light going off, to running
a motor for a certain part, to many more. Figure 3 shows some common input and
output components.
