Subject
Year
: Digital System
: 2009
Digital Concept
Chapter 1
Overview
• Digital & Analog Quantities
• Binary Digits, Logic Level & digital waveforms
• Basic logic Operation
3
Digital & Analog Quantities
• An Analog quantity is one having continuous value
• A Digital quantity is one having a discrete set of value
4
Digital & Analog Quantities con’t
• Example an analog electronic system
5
Digital & Analog Quantities con’t
• Example a system using digital and analog method
6
Binary Digits
• Each of the two digits in the binary system, 1 and 0, is called bit
• Generally 1 is represented by the higher voltage, wich we will refer to as a High,
and a 0 is represented by the lower level voltage, wich we will refer to as a Low
7
Logic Levels
VH (max)
HIGH
Binary 1
VH (min)
Unallowed
VL (max)
VL (min)
LOW
Binary 0
• The High value for a certain type of digital
circuit call CMOS may range from 2 V to 3,3V
and the Low value may range from 0 V to 0,8
V. So for example if a voltage of 2,5 is applied,
the circuit will accept it as a high or binary 1. If
a voltage of 0,5 is applied the circuit will
accept it as a Low or binary 0. For this type of
circuit voltage between 0,8 and 2 V are not
accepted.
8
Digital Waveforms
9
Waveforms Characteristics
• In Digital system, all waveforms are synchronized with a basic timing waveforms
called the CLOCK
10
Example
11
Basic Logic Operation
12