【5A版】数字电路英文版

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Bus arbitration The process that prevents two sources from using a bus at the same time. Bus contention An adverse condition that could occur if two or more devices try to communicate at the same time on a bus.
Pulses
Amplifier
Digital signal processor
DAC
Lift channel audio Amplifier
Digital code
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A Digital Audiotape Player/Recorder
Audio in
Control On/Off, open/close,play, pause, track, search
I3
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Figure 14--37
Thomas L. Floyd
Digital Fundamentals, 8e
Copyright ©2003 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458
Figure 14--38 utput of the DAC in Figure 14-37.
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Many applications of computers and other digital systems require the input of real-world quantities, such as temperature, speed, position, pressure, and force.
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+5V D2 =1 R5 2R R8
R REQ =2R Rf =2R
-
2.5V I= 2R VTH RTH R8 2.5V R Rf =2R ≈0 V I =0
+
R
R7 2R
R7 + 2R
Modem A modulator/demodulator for interfacing digital devices to analog transmission systems such as telephone lines. PCI bus Peripheral control interconnect bus; an internal parallel bus standard.
ISA bus Industry standard architecture bus; an internal parallel bus standard. Local bus An internal bus that connects the microprocessor to the cache memory, the main memory, the coprocessor, and the PCI bus controller.
Source A sending device on a bus. Tristate A type of output in logic circuits that exhibits three states: HIGH, LOW, and High-Z. USB Universal serial bus; an external serial bus standard.
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The Operational Amplifier
Inverting input
Vout Rf =Vin Ri
Rf
Vin Ri
+
+
Output
Vout
Vin1 Vin2
+
Vout
Noninverting input
High internal
input R
(a) Op-amp symbol (b) Op-amp as an inverting amplifier with gain of Rf/Ri (c) Op-amp as a comparator
DTE Data terminal equipment. Flash ADC A simultaneous analogto-digital converter. Handshaking The process of signal interchange by which two digital devices or systems jointly establish communication.
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Real-world quantities can even include graphic images. Also, digital systems often must produce outputs to control real-world quantities.
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Inputs D0 R1 2R R4 R
D1
R3 2R R6 R
D2
D3
R2
R5 2R R8 R
R7 Rf =2R 2R
+
Vout
2R
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+5V
D3 =1
R7 2R
5V I = 2R Rf =2R ≈0
+
REQ=2R
5V Vout = -IfRf =-( )2R 2R =-5V
(a) Equivalent circuit for D3=1,D2=0,D1=0,D0=0
Right channel audio Amplifier
ADC
Amplifier
Digital signal processor
Tape driver
DAC
Lift channel audio
Amplifier
Digital code
Magnetic read/write
heads
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§13.2 DIGITAL-TO-ANALOG ( D/A ) CONVERSION D/A conversion is an important part of many systems. In this section, we will examine the theory of operation of two basic types of digital-to-analog converters ( DACs ) and learn about their performance characteristics.
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An Electronic Thermostat
Analog voltage Amplifier Temperature sensor Actual temperature Desired temperature Digital code On/Off Heat/Cool
1
ADC
To HVAC unit
Controller An instrument that can specify each of the other instruments on the bus as either a talker or a listener for the purpose of data transfer. DCE Data communications equipment. Digital-to-analog converter (DAC) A device used to convert a digital input to an analog signal .
§13.1 DIGITAL AND ANALOG INTERFACING Analog quantities are sometimes called real-world quantities because most physical quantities that we are interested in measuring are analog in nature.
CHAPTER 13
INTERFACING
KEY TERMS
Acceptor A receiving device on a bus. Analog-to-digital converter (ADC) A device used to convert an analog signal to digital form. Bus A set of interconnections that interface one or more devices based on a standardized specification.
High-Z The high-impedance state of a tristate circuit in which the output is effectively disconnected from the rest of the circuit. Interfacing The process of making two or more electronic devices or systems operationally compatible with each other so that they can function properly together.
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Binary-Weighted-Input Digital-to-Analog Converter
V I0 = 8R V I1 = 4R V I2 = 2R
I3 = V R 20 V V V V 23 8R
Vout = IfRf
I0
+ +
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22
4R
2R R
Rf If
_
I1
I2 I=0
Vout
Thomas L. Floyd
Digital Fundamentals, 8e
Copyright ©2003 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458
The R/2R Ladder Digital-to-Analog Converter
Peripheral A device or instrument that provides communication with a computer or provides auxiliary services or functions for a computer. Port The physical interface between a computer and a peripheral. SCSI Small computer system interface; an external parallel bus standard.
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Application Examples
To interface between the digital and analog Address bus worlds, two basic processes are required: analog-to-digital ( A/D ) conversion and digital-to-analog ( D/A ) conversion.
Control and display logic
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8
5 2 .
9
6 3 #
0
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CD Player
Control On/Off,
open/close, play,pause, track, search
Right channel audio
Amplifier
Laser pick-up head