---
title: "02-combinatorial-logic"
aliases: 
tags: 
- cosc204
- lecture
sr-due: 2022-07-19
sr-interval: 3
sr-ease: 250
---

- [slides](https://blackboard.otago.ac.nz/bbcswebdav/pid-2954102-dt-content-rid-18888626_1/courses/COSC204_S2DNI_2022/L2%20-%20Combinatorial%20Logic.pdf)

# Combinatorial Logic Circuit
> [!Definition]
> Combinatorial Logic Circuit is a circuit whose digital outputs are dependent only on its digital inputs
They can be described using logic expressions and therefore logic gates. We assume the outputs respond immediately^[1]

They can be defined:
- Using a truth table
- Using boolean equations ($Q\ =\ A+\ B$) 
- Using graphical symbols  

- [1 Bit half adder(https://i.imgur.com/mjCVU4I.png)
- 1 Bit full adder: (includes carry input) [](https://i.imgur.com/yu6kS83.png)
 


# Circuit basics:
- current flows + to -
- input to a unit (e.g., LED) is the + end

# Logic Gates
- NOT
- AND
- OR
- NAND
- NOR
- XOR/EOR




[^1] : In real circuits propagation delay must be considered, hence the clock cycle on CPUs