Digital technology and microcomputers — basics
From ones and zeros to logic gates and the small computer on the circuit board
Analog electronics works with signals that slide smoothly between all values – like the volume on an old radio. Digital electronics, on the other hand, works only with two states: high and low, often called 1 and 0. That simplification sounds like a limitation, but it is actually digital technology's great strength because a signal that can only be two things is far harder to confuse with noise than a signal that can be anything.
§The binary number system
People normally count in the decimal system, but a digital circuit counts in the binary system. Each digit is either 0 or 1, and a group of such digits is called a bit string. Eight bits make a byte, which can represent 256 different values (2 raised to the 8th power). Everything a microcomputer calculates — numbers, text, pictures, sound — is ultimately just patterns of zeros and ones, read and interpreted according to an agreed code.
§Logic gates — the smallest building blocks
A logic gate is a small circuit that takes one or more digital signals in and delivers one digital signal out according to a specific rule. Gates are built up of transistors but you can use them without thinking about the transistors inside — it's the rule itself that's interesting.
| Port | Rule (simplified) |
|---|---|
| AND (OG) | Output is 1 only if both inputs are 1 |
| OR (OR) | Output is 1 if at least one input is 1 |
| NOT (NOT) | The signal is inverted — 1 becomes 0 and vice versa |
| XOR (EITHER-OR) | Output is 1 if the inputs are different |
| NAND / NOR | AND/OR followed by an inversion – very common in practice |
§From gates to memory and counting
If you connect logic gates in certain ways, they can remember a state — this is called a flip-flop, and it's the smallest memory cell in digital electronics. Rows of flip-flops form registers that can hold a number and counter circuits that can count pulses. It's the same basic principle behind everything from a simple digital watch display to the memory in an advanced computer.
§The microcomputer — logic you can programme
Instead of connecting thousands of individual logic gates for each new task, in practice you assemble a finished arithmetic unit, memory and connections to the outside world on one chip: a microcomputer or microcontroller. It typically consists of a processor core (CPU) that executes instructions, memory that stores the program and data, and inputs and outputs (I/O) that connect the chip to sensors, buttons, LEDs and motors. The program — the firmware — determines what the chip should do and can be updated without changing a single component on the board.
- 01CPU — executes the program's instructions step by step
- 02Memory — stores the program itself and the data it works with
- 03I/O pins — connect the chip to sensors, switches, LEDs and motors
- 04Clock—sets the pace everything inside the chip synchronizes according to it.
- 05Firmware — the program that determines the chip's behavior and which can be updated
§The bridge between the analogue and digital world
The reality outside the chip is analog: temperature sound and light flow smoothly. Therefore microcomputers often have an analog-to-digital converter (ADC) built in that translates an analog sensor signal to a digital number the chip can continue to calculate on — and conversely a digital-to-analog converter (DAC) when the result needs to go back into the analog world for example as sound or a control voltage. Understanding this translation is the key to connecting digital logic with the physical world which the course's goal of 'analog RF digital and microcomputer technology' precisely requires that you can connect and troubleshoot in practice.
“A microcomputer is not magic — it's logic gates memory and a program assembled on one small chip.”
— Professional view on digital technology.