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Digital Fundamentals Tenth Edition Floyd Chapter 1 Floyd, Digital Fundamentals, 10th ed © 2008 Pearson Education Outline • • • • • • 1-1 Digital and Analog Quantities 1-2 Digits, Logic Levels, and Digital Waveforms 1-3 Basic Logic Operations 1-4 Basic System Functions 1-5 Fixed-Function Integrated Circuits 1-6 Test and Measurement Instruments Floyd, Digital Fundamentals, 10th ed Analog Quantities • Most natural quantities that we see are analog and vary continuously. • Digital systems: (1) changes occur discretely Temperature (°F) 100 95 90 85 80 75 70 Time of day 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 A .M . Floyd, Digital Fundamentals, 10th ed P.M . Digital Signal (2) can take values from fix levels (of the Y-axis) only! Floyd, Digital Fundamentals, 10th ed Example Floyd, Digital Fundamentals, 10th ed Digital vs. Analog Signal • Pros: – reduce transmission noise – can process, store, and transmit data more efficiently • Cons: – can only assign discrete values to each point. Signal to send: 2V Transmission Error: 0.3V How about when transmission error is 0.7V? Floyd, Digital Fundamentals, 10th ed Analog signal Domain: 0-5 V Signal received: 2.3V Final error: 0.3V Digital signal Domain: {0,1,2,3,4,5} V Signal received: 2V Final Error: 0V A Complete Digital Systems Analog Input Analog-toDigital Converter (ADC) Digital Processing System Digital-toAnalog Converter (DAC) Computer, Calculator, Watch, Measuring instrument etc. Floyd, Digital Fundamentals, 10th ed Analog Output Analog and Digital Systems Example • Many systems use a mix of analog and digital electronics to take advantage of each technology. • A typical CD player accepts digital data from the CD drive and converts it to an analog signal for amplification. CD drive 10110011101 Digital data Digital-to-analog converter Linear amplifier Analog reproduction of music audio signal Speaker Sound waves Floyd, Digital Fundamentals, 10th ed Digital System Hierarchy Digital Systems Sub Systems Modules Basic Units Circuits Floyd, Digital Fundamentals, 10th ed Latches, Flip-flops Logic Gates Transistors, Resistors, Capacitors Outline • • • • • • 1-1 Digital and Analog Quantities 1-2 Digits, Logic Levels, and Digital Waveforms 1-3 Basic Logic Operations 1-4 Basic System Functions 1-5 Fixed-Function Integrated Circuits 1-6 Test and Measurement Instruments Floyd, Digital Fundamentals, 10th ed Binary Digits and Logic Levels Digital electronics uses circuits that have two states, which are represented by two different voltage levels called HIGH and LOW. The voltages represent numbers in the binary system. VH(max) In binary, a single number is called a bit (for binary digit). A bit can have the value of either a 0 or a 1, depending on if the voltage is HIGH or LOW. HIGH VH(min) Invalid VL(max) LOW VL(min) Floyd, Digital Fundamentals, 10th ed Digital Waveforms • Digital waveforms change between the LOW and HIGH levels. • A positive going pulse is one that goes from a normally LOW logic level to a HIGH level and then back again. • Digital waveforms are made up of a series of pulses. HIGH HIGH Rising or leading edge LOW Falling or trailing edge t0 (a) Positive–going pulse Floyd, Digital Fundamentals, 10th ed t1 Falling or leading edge LOW Rising or trailing edge t0 (b) Negative–going pulse t1 Pulse Actual pulses are not ideal but are described by the rise time, fall time, amplitude, and other characteristics. Overshoot Ringing Droop 90% Amplitude tW 50% Pulse width 10% Ringing Base line Floyd, Digital Fundamentals, 10th ed Undershoot tr tf Rise time Fall time Periodic Pulse Waveforms Periodic pulse waveforms are composed of pulses that repeats in a fixed interval called the period. The frequency is the rate it repeats and is measured in hertz. f 1 T T 1 f The clock is a basic timing signal that is an example of a periodic wave. What is the period of a repetitive wave if f = 3.2 GHz? T Floyd, Digital Fundamentals, 10th ed 1 1 313 ps f 3.2 GHz Pulse Definitions • Repetitive pulse waveforms are described by – – – – frequency and period amplitude (A) pulse width (tW) duty cycle: the ratio of tW to T Volts Amplitude (A) Pulse width (tW) Time Period, T Floyd, Digital Fundamentals, 10th ed Timing Diagrams • A timing diagram is used to show the relationship between two or more digital waveforms, • A diagram like this can be observed directly on a logic analyzer. Clock A B C Floyd, Digital Fundamentals, 10th ed Serial and Parallel Data Data can be transmitted by either serial transfer or parallel transfer. 1 serial t0 0 t1 1 t2 1 t3 0 0 t 4 t 5 t6 1 0 t7 Computer Modem 1 Computer Printer 0 1 1 0 parallel 0 1 0 t0 Floyd, Digital Fundamentals, 10th ed t1 Outline • • • • • • 1-1 Digital and Analog Quantities 1-2 Digits, Logic Levels, and Digital Waveforms 1-3 Basic Logic Operations 1-4 Basic System Functions 1-5 Fixed-Function Integrated Circuits 1-6 Test and Measurement Instruments Floyd, Digital Fundamentals, 10th ed Basic Logic Operations True only if all input conditions are true. True only if one or more input conditions are true. Indicates the opposite condition. Floyd, Digital Fundamentals, 10th ed Basic System Functions • AND, OR, and NOT elements can be combined to form various logic functions. A few examples are: The comparison function A Comparator A> B Two binary numbers A= B B A< B Adder Basic arithmetic functions A Two binary numbers B Carry in Floyd, Digital Fundamentals, 10th ed Outputs Cin Σ Cout Sum Carry out Basic System Functions HIGH The encoding function 7 4 8 5 9 6 1 2 3 0 . +/– 9 8 7 6 5 4 3 2 1 0 Encoder Binary code for 9 used for storage and/or computation Calculator keypad The decoding function Decoder Binary input 7-segment display Floyd, Digital Fundamentals, 10th ed Basic System Functions The data selection function Multiplexer A ∆t1 B Demultiplexer Data from A to D Data from B to E Data from C to F Data from A to D ∆ t1 ∆ t2 ∆ t3 ∆t 1 D ∆t1 E ∆t2 ∆t2 ∆t3 ∆t3 Switching sequence control input Switching sequence control input C Floyd, Digital Fundamentals, 10th ed F Basic System Functions The counting function Counter 1 2 3 4 Input pulses 5 Floyd, Digital Fundamentals, 10th ed Parallel output lines Binary code for 1 Binary code for 2 Binary code for 3 Binary code for 4 Binary code for 5 Sequence of binary codes that represent the number of input pulses counted. Outline • • • • • • 1-1 Digital and Analog Quantities 1-2 Digits, Logic Levels, and Digital Waveforms 1-3 Basic Logic Operations 1-4 Basic System Functions 1-5 Fixed-Function Integrated Circuits 1-6 Test and Measurement Instruments Floyd, Digital Fundamentals, 10th ed Integrated Circuits Cutaway view of DIP (Dual-In-line Pins) chip: Chip Plastic case Pins DIPs are popular for laboratory experiments with logic. Floyd, Digital Fundamentals, 10th ed Integrated Circuits Laboratory prototyping. The circuit is wired using DIP chips and tested. Testing can be done by a computer connected to the system. DIP chips Floyd, Digital Fundamentals, 10th ed Integrated Circuits Pin 1 Dual in-line package Floyd, Digital Fundamentals, 10th ed Small outline IC (SOIC) Outline • • • • • • 1-1 Digital and Analog Quantities 1-2 Digits, Logic Levels, and Digital Waveforms 1-3 Basic Logic Operations 1-4 Basic System Functions 1-5 Fixed-Function Integrated Circuits 1-6 Test and Measurement Instruments Floyd, Digital Fundamentals, 10th ed Test and Measurement Instruments The front panel controls for a general-purpose oscilloscope can be divided into four major groups. VERTICAL CH 1 CH 2 HORIZONTAL TRIGGER BOTH SLOPE Ð POSITION POSITION VOLTS/DIV VOLTS/DIV + LEVEL POSITION SEC/DIV SOURCE CH 1 CH 2 5V 2 mV 5V 2 mV 5s 5 ns EXT LINE COUPLING COUPLING AC-DC-GND AC-DC-GND TRIG COUP DC DISPLAY PROBE COMP 5V INTENSITY Floyd, Digital Fundamentals, 10th ed CH 1 CH 2 EXT TRIG AC Test and Measurement Instruments The logic analyzer can display multiple channels of digital information or show data in tabular form. Floyd, Digital Fundamentals, 10th ed Test and Measurement Instruments The Digital Multimeter (DMM) can make three basic electrical measurements. 0.01 V OFF V Hz V Voltage Resistance Current mV A Range Autorange Touc h/Hold Floyd, Digital Fundamentals, 10th ed 1s V 40 m A COM Fused DMMs are useful for • checking power supply voltages • verifying resistors • testing continuity 1s 10 A Programmable Logic Devices (PLDs) • an alternative to fixed function devices. • can be programmed for a specific purpose. • cost less and use less board space • e.g.: programmable logic array with AND and OR gates Programmable AND array Floyd, Digital Fundamentals, 10th ed Fixed OR array and output logic Selected Key Terms Analog Being continuous or having continuous values. Digital Related to digits or discrete quantities; having a set of discrete values. Binary Having two values or states; describes a number system that has a base of two and utilizes 1 and 0 as its digits. Bit A binary digit, which can be a 1 or a 0. Pulse A sudden change from one level to another, followed after a time, called the pulse width, by a sudden change back to the original level. Floyd, Digital Fundamentals, 10th ed Selected Key Terms Clock A basic timing signal in a digital system; a periodic waveform used to synchronize actions. Gate A logic circuit that performs a basic logic operations such as AND or OR. NOT A basic logic function that performs inversion. AND A basic logic operation in which a true (HIGH) output occurs only when all input conditions are true (HIGH). OR A basic logic operation in which a true (HIGH) output occurs when when one or more of the input conditions are true (HIGH). Floyd, Digital Fundamentals, 10th ed Selected Key Terms Fixed-function A category of digital integrated circuits having functions that logic cannot be altered. Programmable A category of digital integrated circuits capable of being logic programmed to perform specified functions. Floyd, Digital Fundamentals, 10th ed