# BINARY LOGIC – LOGIC 0 AND LOGIC 1

Here you will learn about different types of signals that exist and binary logic levels in microcontrollers.

We live in a world where all natural signal presents are analog in nature but for our convenience we convert them into digital signals.

Electronics systems are of two kinds – analog system and digital system.

• Analog waves are continuous and smooth while Digital waves are square, stepping, and discrete.
• Voltage and/or current value in analog systems can take infinite values in a given range while, Voltage and/or current levels in a digital system are assumed to be switched from one value to another means have finite distinct values.

Check out difference in figures shown below –

## BINARY LOGIC – LOGIC 0 OR LOGIC 1

Digital electronics depend on binary logic to store, process, and transmit data or information. Binary Logic refers to one of two states – either ON or OFF.

In digital electronics we generally use binary systems, in binary we work with only yes and no means either signal present or not. Digital systems are also called logic systems, because each type of digital system follows a certain set of logic rules.

Binary means two hence it has two independent symbols that are ‘1’ and ‘0’. Where‘1’ means high voltage level (high signal) & ‘0’ means low voltage level (low signal) (no voltage level = 0V).

Binary is a number system similar to the decimal number system but as the decimal system has 10 unique symbols zero to nine (0,1,2,3,4,5,6,7,8,9), binary system has two unique symbols (0,1).

For example – If threshold (TH) voltage for circuit is 5V then logic state 1 denotes 5V and if threshold (TH) voltage is 3.3V then logic 1 denotes 3.3V. Logic state 0 denotes signal is either zero (0) voltage or less than threshold voltage.

This is just an example in the next tutorial you will find exact logic levels for controllers which are based on TTL and CMOS logic

The strength of a signal is usually defined by its voltage level. TTL or Transistor-Transistor Logic is the most common standard. As technology grows we want to work with the devices which consume less power (voltage/current). Now, C-MOS is also in trend which works on 3.3V.

## ACTIVE LOW AND ACTIVE HIGH

When you start working with IC’s, microcontrollers or microprocessors you will always hear terms like active low and active high, what does they mean? So not making it complicated the answer is simple, pins of microcontroller/IC’s are by default set by manufacture as active high or active low pins.

If a pin is active high means it will work when it gets a high signal (usually 3.3V/5V). For example in an IC reset pin (suppose 14) is active high so as we give high signal to the IC pin 14 it will reset the IC just by signal we don’t need to reset manually.

In the same way as if a pin is active low, it will work when we give it a low signal (ground) otherwise it will not work.

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TTL LOGIC LEVELS 