1

Chapter 1

Introductory Digital Concepts

2

Chapter Outline

• Digital and Analog Quantities• Binary Digits, Logic Levels, and Digital

Waveforms• Introduction to Basic Logic Operations• Basic Overview of Logic Functions• Fixed-Function Integrated Circuits• Programmable Logic Devices (PLDs)• Introduction to Test Instruments

3

Figure 1--1 Graph of an analog quantity (temperature versus time).

4

Figure 1--2 Sampled-value representation (quantization) of the analog quantity in Figure 1-1. Each value represented by a dot can be digitized by representing it as a digital code that consists of a series of 1s and 0s.

5

Digital Advantages

• Digital Data can be processed/transmitted more efficiently and reliably.

• Storage: can be stored more compactly and reproduced w/ greater accuracy and clarity.

6

Figure 1--3 A basic audio public address system.

Analog Electronic System

7

Figure 1--4 Basic principle of a CD player. Only one channel is shown.

System Using Digital and Analog Methods

8

Binary Digits

• Two digits in BINARY system, 1 and 0, called BIT (Binary digit)

• Positive Logic: HIGH=1, LOW=0

• Negative Logic: LOW=1, HIGH=0

• Code : Groups of bits to represent numbers, letters, symbols, instructions, etc.

9

Figure 1--5 Logic level ranges of voltage for a digital circuit.

Logic Levels

Voltages used to represent 1 and 0.

10

Figure 1--6 Ideal pulses.

Digital Waveforms

Figure 1--7 Nonideal pulse characteristics.

11

Frequency and Period

• Frequency (f) # cycles per sec or Hertz (Hz)

• Period (T) in seconds.

• f=1/T, T = 1/f

12

Figure 1--8 Examples of digital waveforms.

Periodic and Nonperiodic

13

Figure 1--9

Pulse Width and Duty Cycle

Duty Cycle = (tw/T)100 %

14

Figure 1--10 Example of a clock waveform synchronized with a waveform representation of a sequence of bits.

Digital Waveform Carries Binary Information

15

Figure 1--11 Example of a timing diagram.

16

Figure 1--12 Illustration of serial and parallel transfer of binary data. Only the data lines are shown.

Data Transfer

17

Figure 1--15 The basic logic operations and symbols.

Basic Logic Operations and Symbols

18

Figure 1--16 The NOT operation.

NOT Operation

19

Figure 1--17 The AND operation.

AND Operation

20

Figure 1--18 The OR operation.

OR Operation

21

Basic Logic Functions• Comparison Function• Arithmetic Functions• Code conversion function• Encoding function• Decoding function• Data selection function• Data storage function• Counting function

22

Figure 1--19 The comparison function.

Comparison Function

23

Figure 1--20 The addition function.

Arithmetic Function

24

Figure 1--21 An encoder used to encode a calculator keystroke into a binary code for storage or for calculation.

Code Conversion Function: Encoder

25

Figure 1--22 A decoder used to convert a special binary code into a 7-segment decimal readout.

Code Conversion Function: Decoder

26Figure 1--23 Illustration of a basic multiplexing/demultiplexing application.

Data Selection Function

27

Figure 1--24 Example of the operation of a 4-bit serial shift register. Each block represents one storage “cell” or flip-flop.

Data Storage Function

28

Figure 1--25 Example of the operation of a 4-bit parallel shift register.

Data Storage Function

29

Figure 1--26 Illustration of basic counter operation.

Counting Function

30

Figure 1--27 Cutaway view of one type of fixed-function IC package showing the chip mounted inside, with connection to input an output pins.

Fixed-Function Integrated Circuits

31

Figure 1--28 Examples of through-hole and surface-mounted devices. The DIP is larger than the SOIC with the same number of leads. This particular DIP is approximately 0.785 in. long, and the SOIC is approximately 0.385 in. long.

IC Packages

32

Figure 1--29 Examples of SMT package configurations.

33

Figure 1--30 Pin numbering for two standard types of IC packages. Top views are shown.

Pin Numbering

34

Integrated Circuit Technologies

• TTL

• ECL

• CMOS

• NMOS

• SSI and MSI use TTL or CMOS

• VLSI and ULSI use CMOS or NMOS

35

Programmable Logic Devices (PLD)

• Programmable logic devices can replace fixed-function logic - the major advantage is that the logic function of the PLD can be changed without rewiring.

• SPLD (Simple Programmable Logic Devices)

• CPLD (Complex Programmable Logic Devices)

36

Types of SPLD

• PAL (Programmable Array Logic)

• GAL (Generic Array Logic)

• PLA (Programmable Logic Array)

• PROM (Programmable Read-only Memory)

37

Figure 1--32 Typical CPLD packages.

CPLDs are made using 2 to 64 SPLDs

Types of CPLD

38

PLD programming

• Schematic Entry

• Text-Based Entry

39

Test Equipment

• Analog Oscilloscope

• Digital Oscilloscope

• Logic Analyzer

• Logic Probe, Pulser, and Current Probe

• DC Power Supply

• Function Generator

• Digital Multimeter

40

Oscilloscope

41

Figure 1--34 A typical dual-channel digital oscilloscope. Numbers below screen are arbitrary and are shown for illustration only.

42

Figure 1--36 A typical dual-channel analog oscilloscope.

43

Figure 1--37 Typical logic analyzers

Logic Analyzer

44Figure 1--38 Illustration of how a logic probe is used to detect various voltage conditions at a given point in a circuit.

Logic Probe

45

Figure 1--40 Typical test instruments

46Figure 1--41 Simplified basic block diagram for a tablet-counting and bottling control system.

Digital System Application