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1、会计学1数字电路英文版第十三单元数字电路英文版第十三单元(dnyun)第一页，共65页。n nBus arbitration The process that prevents two sources from using a bus at the same time.n nBus contention An adverse condition that could occur if two or more devices try to communicate at the same time on a bus.第2页/共65页第二页，共65页。n nController An instrum
2、ent that can specify each of the other instruments on the bus as either a talker or a listener for the purpose of data transfer.n nDCE Data communications equipment.n nDigital-to-analog converter(DAC)n nA device used to convert a digital input to an analog signal.第3页/共65页第三页，共65页。DTE Data terminal e
3、quipment.Flash ADC A simultaneous analog-to-digital converter.Handshaking The process of signal interchange by which two digital devices or systems jointly establish communication.第4页/共65页第四页，共65页。n nHigh-Z The high-impedance state of a tristate circuit in which the output is effectively disconnecte
4、d from the rest of the circuit.n nInterfacing The process of making two or more electronic devices or systems operationally compatible with each other so that they can function properly together.第5页/共65页第五页，共65页。n nISA bus Industry standard architecture bus;an internal parallel bus standard.n nLocal
5、 bus An internal bus that connects the microprocessor to the cache memory,the main memory,the coprocessor,and the PCI bus controller.第6页/共65页第六页，共65页。n nModem A modulator/demodulator for interfacing digital devices to analog transmission systems such as telephone lines.n nPCI bus Peripheral control
6、interconnect bus;an internal parallel bus standard.第7页/共65页第七页，共65页。n nPeripheral A device or instrument that provides communication with a computer or provides auxiliary services or functions for a computer.n nPort The physical interface between a computer and a peripheral.n nSCSI Small computer sy
7、stem interface;an external parallel bus standard.第8页/共65页第八页，共65页。n nSource A sending device on a bus.n nTristate A type of output in logic circuits that exhibits three states:HIGH,LOW,and High-Z.n nUSB Universal serial bus;an external serial bus standard.第9页/共65页第九页，共65页。13.1 DIGITAL AND ANALOG 13.
8、1 DIGITAL AND ANALOG INTERFACINGINTERFACINGAnalog quantities are sometimes called real-world quantities because most physical quantities that we are interested in measuring are analog in nature.2第10页/共65页第十页，共65页。3 Many applications of computers and other digital systems require the input of real-wo
9、rld quantities,such as temperature,speed,position,pressure,and force.第11页/共65页第十一页，共65页。Real-world quantities can even include graphic images.Also,digital systems often must produce outputs to control real-world quantities.第12页/共65页第十二页，共65页。4012345678910111213148976510123415111213141617181920151110
10、11100100010101010110101101111001110111011100110010100111100101010010000001000100第13页/共65页第十三页，共65页。012345678910111213148976510123415111213141617181920155第14页/共65页第十四页，共65页。Application ExamplesAddress busTo interface between the digital and analog worlds,two basic processes are required:analog-to-dig
11、ital(A/D)conversion and digital-to-analog(D/A)conversion.6第15页/共65页第十五页，共65页。7An Electronic Thermostat1AmplifierADCActual temperatureDesired temperatureControl and display logic7894561230.#On/Off Heat/CoolTemperature sensorDigital codeAnalog voltageTo HVAC unit第16页/共65页第十六页，共65页。8CD PlayerAmplifierD
12、igital signal processorDigital codePulsesAmplifierAmplifierDACControl On/Off,open/close,play,pause,track,search Laser pick-up headRight channel audio Lift channel audio 第17页/共65页第十七页，共65页。9A Digital Audiotape Player/RecorderAmplifierDigital signal processorAudio inAmplifierAmplifierDACControl On/Off
13、,open/close,play,pause,track,search ADCRight channel audio Lift channel audio Tape driver Magnetic read/write heads Digital code第18页/共65页第十八页，共65页。10 13.2 DIGITAL-TO-ANALOG(13.2 DIGITAL-TO-ANALOG(D/A)CONVERSIOND/A)CONVERSION D/A conversion is an important part of many systems.In this section,we will
14、 examine the theory of operation of two basic types of digital-to-analog converters(DACs)and learn about their performance characteristics.第19页/共65页第十九页，共65页。11The Operational Amplifier+-+-+-Inverting inputNoninverting inputOutput VinVin1Vin2VoutRfRiHigh internalinput RVout(a)Op-amp symbol(c)Op-amp
15、as a comparator(b)Op-amp as an inverting amplifier with gain of Rf/RiRfVout=-VinRi第20页/共65页第二十页，共65页。12Binary-Weighted-Input Digital-to-Analog Converter+-Rf8R4R2RRI1I0I2I3I0=8RVI3=RVI2=2RVI1=4RV+_20232221VVVVVoutI=0IfVout=IfRf第21页/共65页第二十一页，共65页。Figure 14-37Figure 14-37Thomas L.FloydDigital Fundamen
16、tals,8eCopyright 2003 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.第22页/共65页第二十二页，共65页。Figure 14-38 Figure 14-38 Output of the DAC in Figure 14-37.Output of the DAC in Figure 14-37.Thomas L.FloydDigital Fundamentals,8eCopyright 2003 by Pearson Education,Inc.Upper S
17、addle River,New Jersey 07458All rights reserved.第23页/共65页第二十三页，共65页。13The R/2R Ladder Digital-to-Analog Converter+-Rf=2RR8RD02RVoutD1D2D3RRR6R4R2R1R3R5R72R2R2R2RInputs第24页/共65页第二十四页，共65页。14+-Rf=2RD3=1REQ=2RR72RI=2R5V+5V0Vout=-IfRf=-()2R2R5V=-5 V(a)Equivalent circuit for D3=1,D2=0,D1=0,D0=0第25页/共65页第
18、二十五页，共65页。+-Rf=2RD2=1R52RI=2R+5VR7R8REQ=2RR2R+-Rf=2RR72RRRRTHR82.5VVTH2.5VI=00 VVout=-IfRf=-()2R2R2.5V=-2.5 V(b)Equivalent circuit for D3=0,D2=1,D1=0,D0=015第26页/共65页第二十六页，共65页。16I=2R+-Rf=2RR72RRRRTHR81.25VVTH1.25VI=00 VVout=-IfRf=-()2R2R1.25V=-1.25 V(c)Equivalent circuit for D3=0,D2=0,D1=1,D0=0第27页/
19、共65页第二十七页，共65页。17I=2R+-Rf=2RR72RRRRTHR80.625VVTH0.625VI=00 VVout=-IfRf=-()2R=-0.625V2R0.625V(d)Equivalent circuit for D3=0,D2=0,D1=0,D0=1第28页/共65页第二十八页，共65页。n nResolution.The resolution of a DAC is the Resolution.The resolution of a DAC is the reciprocal of the number of discrete steps in the recipr
20、ocal of the number of discrete steps in the output.The total number of discrete steps equals 2output.The total number of discrete steps equals 2n n 1,where n is the number of bits.(4-bit DAC,(1/15)*1,where n is the number of bits.(4-bit DAC,(1/15)*100=6.67%)100=6.67%)第29页/共65页第二十九页，共65页。n nAccuracy.
21、Accuracy is a comparison of the actual Accuracy.Accuracy is a comparison of the actual output of a DAC with the expected output.It is output of a DAC with the expected output.It is expressed as a percentage of a full-scale,or expressed as a percentage of a full-scale,or maximum,output voltage.For ex
22、ample,if a maximum,output voltage.For example,if a convert has a full-scale output of 10 V and the convert has a full-scale output of 10 V and the accuracy is+0.1%,then the maximum error for accuracy is+0.1%,then the maximum error for any output voltage is(10V)(0.001)=10 mV.any output voltage is(10V
23、)(0.001)=10 mV.第30页/共65页第三十页，共65页。n nIdeally,the accuracy should be no worse than+Ideally,the accuracy should be no worse than+of a least significant bit.For an 8-bit converter,of a least significant bit.For an 8-bit converter,the least significant bit is 0.39%of full scale.the least significant bit
24、 is 0.39%of full scale.The accuracy should be approximately+0.2%.The accuracy should be approximately+0.2%.第31页/共65页第三十一页，共65页。n nLinearity.A linear error is a deviation from the ideal straight-line output of a Linearity.A linear error is a deviation from the ideal straight-line output of a DAC.A sp
25、ecial case is an offset error,which is the amount of output voltage DAC.A special case is an offset error,which is the amount of output voltage when the input bits are all zeros.when the input bits are all zeros.第32页/共65页第三十二页，共65页。n nMonotonicity.A DAC is monotonic if it does not Monotonicity.A DAC
26、 is monotonic if it does not take any reverse steps when it is sequenced over its take any reverse steps when it is sequenced over its entire range of input bits.entire range of input bits.第33页/共65页第三十三页，共65页。n nSettling time.Settling time is normally Settling time.Settling time is normally defined
27、as the it takes a DAC to settle within+defined as the it takes a DAC to settle within+LSB of its final value when a change occurs in LSB of its final value when a change occurs in the input code.(The settling time of a DAC is the the input code.(The settling time of a DAC is the time it takes for th
28、e DACtime it takes for the DAC s analog output settle to s analog output settle to 99.95%of its new value after a digital input has 99.95%of its new value after a digital input has been applied.)been applied.)第34页/共65页第三十四页，共65页。18EXAMPLE 13-2 Determine the resolution,expressed as a percentage,of th
29、e following:(a)An 8-bit DAC (b)a 12-bit DACSolution:(a)For the 8-bit converter,x 100=x 100=0.392%1128-1255(b)For the 12-bit converter,11212-14095x 100=x 100=0.0244%第35页/共65页第三十五页，共65页。n nIf a 4-bit DAC has a 12 V reference applied,calculate each of the following:n n a.step sizen n b.percent resoluti
30、onn n c.the weight of each binary columnn n d.the output voltage when 0010 is appliedn n e.the output voltage when 1011 is applied第36页/共65页第三十六页，共65页。n n a.Step size=V0/2n=12/16=0.75 Vn n b.%Res.=s/size/V0=0.75/12=6.25%n n c.LSB=12V/16=0.75 Vn n 1=12V/8 =1.5 Vn n 1=12V/4 =3.0 Vn n MSB=12V/2 =6.0 Vn
31、n d.0010=1.5 Vn n e.1011=8.25 V第37页/共65页第三十七页，共65页。n nIf an 8-bit DAC has a 10 V reference applied,calculate each of the following:n n a.step sizen n b.percent resolutionn n c.the weight of each binary columnn n d.the output voltage when 0000 0101 is appliedn n e.the output voltage when 1011 0111 is
32、 applied第38页/共65页第三十八页，共65页。n n a.Step size=V0/2n=10/256=0.039 Vn n b.%Res.=s/size/V0=0.039/10=0.39%n n c.LSB=10V/256 =0.039 Vn n 1=10V/128 =0.078 Vn n 2=10V/64 =0.156 Vn n 3=10V/32 =0.3125Vn n 4=10V/16 =0.625 Vn n 5=10V/8 =1.25 Vn n 6=10V/4 =2.5 Vn n MSB=10V/2 =5 V第39页/共65页第三十九页，共65页。n n n n d.0000
33、 0101=0.195 Vn n e.1011 0111=7.137 V第40页/共65页第四十页，共65页。13.3 ANALOG TO DIGITAL(A/D)13.3 ANALOG TO DIGITAL(A/D)CONVERSIONCONVERSIONFlash(Simultaneous)Analog-to-Digital Converter:Disadvantages:too many comparatorsAdvantages:fast conversion time19第41页/共65页第四十一页，共65页。67543210124+_+_+_+_+_+_+_RRRRRRRROp a
34、mp comparatorsD0D1D2+VREFSampling pulsesParallel binary outputPriority encoderAnalog input20第42页/共65页第四十二页，共65页。n n 7 6 5 4 3 2 1 0 4 2 1 7 6 5 4 3 2 1 0 4 2 1n n0 to 0.9 V 0 0 0 0 0 0 0 0 0 0 00 to 0.9 V 0 0 0 0 0 0 0 0 0 0 0n n1 to 1.9 V 0 0 0 0 0 0 1 0 0 0 11 to 1.9 V 0 0 0 0 0 0 1 0 0 0 1n n2 to
35、 2.9 V 0 0 0 0 0 1 1 0 0 1 02 to 2.9 V 0 0 0 0 0 1 1 0 0 1 0n n3 to 3.9 V 0 0 0 0 1 1 1 0 0 1 13 to 3.9 V 0 0 0 0 1 1 1 0 0 1 1n n4 to 4.9 V 0 0 0 1 1 1 1 0 1 0 04 to 4.9 V 0 0 0 1 1 1 1 0 1 0 0n n5 to 5.9 V 0 0 1 1 1 1 1 0 1 0 15 to 5.9 V 0 0 1 1 1 1 1 0 1 0 1n n6 to 6.9 V 0 1 1 1 1 1 1 1 1 1 06 to
36、 6.9 V 0 1 1 1 1 1 1 1 1 1 0n n7 V or Greater 1 1 1 1 1 1 1 1 1 1 17 V or Greater 1 1 1 1 1 1 1 1 1 1 1n nVREF=8 V R=1 k第43页/共65页第四十三页，共65页。第44页/共65页第四十四页，共65页。012345678912345678101112tV100110111110101 010000001 011 101110 111EXAMPLE 13-321第45页/共65页第四十五页，共65页。22 Related Problem:13-3:010,100,101,110,
37、110,111,110,110,101,100,011,010,000,000,001,001,010,011,100,101,110,110,111,111,第46页/共65页第四十六页，共65页。23CLKStairstep-Ramp Analog-to-Digital ConverterCLEARENQ6Q7Q5Q4Q3Q2Q1Q0D6D7D5D4D3D2D1D0D6D7D5D4D3D2D1D0LatchCTR DIV 256DACControl circuitStairstep reference voltageAnalog inputComparatorC+_第47页/共65页第四十
38、七页，共65页。24CLKTracking Analog-to-Digital ConverterDOWNENQ6Q7Q5Q4Q3Q2Q1Q0D6D7D5D4D3D2D1D0D6D7D5D4D3D2D1D0LatchCounterDACControl circuitAnalog inputComparatorC+_UP第48页/共65页第四十八页，共65页。40123456789101112131489765101234151112131416171819201525第49页/共65页第四十九页，共65页。26D6D7D5D4D3D2D1D0CounterLatchesCControl log
39、icRamp generatorAnalog inputCLKComparatorResetENtVRamp+_CLEARBinary or BCD output第50页/共65页第五十页，共65页。第51页/共65页第五十一页，共65页。第52页/共65页第五十二页，共65页。第53页/共65页第五十三页，共65页。第54页/共65页第五十四页，共65页。Chapter 13:Interfacingn nTrue/Falsen n1.A light bulb and switch are examples of an analog circuit.n n2.A D/A converter c
40、hanges something like temperature variations into a digital quantity.第55页/共65页第五十五页，共65页。n n3.An operational amplifier is used as a comparator.n n4.An eight-bit D/A converter has a resolution of 0.125.n n5.The primary disadvantage of the flash A/D converter is the large number of comparators require
41、d.第56页/共65页第五十六页，共65页。n n6.When the analog input to a tracking A/D converter is at a constant level,the digital output will oscillate.n n7.The RS-232-C is a serial data transfer system.第57页/共65页第五十七页，共65页。Multiple ChoiceMultiple Choicen n11.Which of the following characterizes an analog quantity?n n
42、 a.Discrete levels represent changes in a quantity.n n b.Its values follow a logarithmic response curve.n n c.Can be described with a finite number of steps.n n d.Has a continuous set of values over a given range.第58页/共65页第五十八页，共65页。n n12.An analog-to-digital converter has a four-bit output.How many
43、 analog values can it represent?n n a.4n n b.1/4n n c.16n n d.0.0625第59页/共65页第五十九页，共65页。n n13.An analog quantity varies from 0-7V and is input to a 6-bit A/D coverter.What analog value is represented by each step on the digital output?n n a.0.111Vn n b.1.17Vn n c.0.109Vn n d.0.875V第60页/共65页第六十页，共65页
44、。n n14.What function is performed by the block labeled X in Figure 13-1?n n a.Analog-to-digital conversion.n n b.Digital-to-analog conversion.n n c.Audio ON/OFF control.n n d.Power supply for the audio amplifier.第61页/共65页第六十一页，共65页。ControlTape driveDigital signal processing YXAudio inAudio out第62页/共
45、65页第六十二页，共65页。n n15.Which of the equations below expresses the voltage gain relationship for an operational amplifier?n n a.Vout=Vin/Avn n b.Vout/Vin=Rout/Rinn n c.Vin/Vout=Rout/Rinn n d.Vout/Vin=-Rf/Rin第63页/共65页第六十三页，共65页。n n16.What is the inverting input on an op-amp referred to as,and why?n n a.V
46、irtual ground;because it is connected to common.n n b.The(-)input;to distinguish it from the other input.n n c.Virtual ground;because it has approximately zero volts on it with respect to the non-inverting terminal.n n d.Common input;because it is connected to the negative terminal of the power supply,which is in turn connected to circuit common.第64页/共65页第六十四页，共65页。感谢您的观看(gunkn)！第65页/共65页第六十五页，共65页。