What is a combinational circuit? And why should we learn how to design those circuits? In this lecture, 1
answering these questions, I will introduce you to these types of circuits. 2
A combination circuit is a logical circuit whose outputs depend only on the state of its inputs. 3
Therefore, it doesn't have any memories or circuits (such as feedbacks) that use some data from the 4
past. 5
Any changes on the input states may have an impact on the output after a delay. 6
These are examples of combinational circuits. 7
Simple arithmetic and logical expressions are examples of combinational circuits as their outputs only 8
depend on the value of their inputs. 9
Some of the software programming structures such as if-else, loops, and switch-case also can be synthesised 10
into combinational circuits. 11
Combinational circuits can be used to implement a wide range of applications, some of them are shown 12
in this slide. 13
These applications can be categorised into five groups: controllers, arithmetic and logical 14
expressions, data transmission circuits, code conversions, and as a basic block in sequential 15
circuits. 16
Combinational controllers can directly drive simple matrix keyboards, LEDs, and displays such 17
as a 7-segment. Arithmetic and logical expressions can include additions, multiplications, divisions, 18
and comparators. 19
Examples for data transmission circuits are multiplexers and demultiplexers. 20
BCD encoders and decoders are examples of code conversions. 21
Also, sequential circuits are built on top of the combinational circuits. 22
In other words, combinational 23
circuits are the basic blocks in designing different types of sequential circuits. 24
Timing is one of the main factors in designing a high-performance digital circuit. 25
So the question is What is the delay in a computational circuit, and how can we measure that? 26
These are the questions that will be answered in the next lecture. 27
These are our takeaway messages. 28
•A combinational circuit can have m binary inputs and n binary outputs. •The outputs of a combinational 29
logic circuit only depend on the state of its inputs. 30
Now the quiz question. Which circuit can be combinational? 31
Traffic light controller, 4-bit integer multiplier, Binary counter, A three-layer perceptron neural 32
network, A recurrent neural network