1. 1 digital circuit overview 1
The development of electronic technology
1. 1.2 digital signal 1
1. 1.3 Digital Circuit 2
1. 1.4 Classification and learning methods of digital circuits 3
1.2 digital system and code system 3
1.2. 1 digital system 3
1.2.2 binary code 5
1.2.3 Character and number code 6
Basic operations of 1.3 logical algebra 7
1.3. 1 and operation 7
1.3.2 or operation 8
1.3.3 Non-operation 8
1.4 logic function 9
The representation of 1.4. 1 logic function 10
1.4.2 Basic formulas and rules of logic algebra 1 1
1.4.3 Simplification of logical functions
1.5 knowledge expansion 14
Karnaugh map simplification method of logic function 14
Summary 16
Exercise 16
Chapter II Logic Gate Circuit 19
2. 1 switching characteristics of diodes and triodes 19
2. Switching characteristics of1.1diode 19
2. 1.2 switching characteristics of triode 20
2.2 basic logic gate 2 1
2.2. 1 diode and gate 2 1
2.2.2 diode or gate 2 1
2.2.3 Triode NOT gate circuit 22
2.2.4 DTL NAND gate circuit 22
2.3 TTL integrated gate circuit 22
2. 3. 1 TTL NAND gate basics 22
2.3.2 Introduction of TTL Gate Integrated Chip 27
2.4 CMOS integrated gate circuit 29
2.4. 1 CMOS not gate 30
2.4.2 other CMOS gate circuits 30
2. 4. 3 CMOS logic gate series 3 1
2.5 Knowledge development 32
2.5. 1 other TTL gates 32
2.5.2 Processing of Input and Output of Integrated Gate 34
2.6 Experiment 36
Gate logic function and test 36
2.7 Training 38
TTL NAND gate parameter test 38
Summary 40
Exercise 40
Chapter III Combinatorial Logic Circuits 43
3. 1 combinational logic circuit analysis 43
3. 1. 1 Functional description of combinational logic circuit 43
3. 1.2 Analysis method of combinational logic circuit 43
3.2 Design method of combinational logic circuit 45
3.3 Encoder 46
3.3. 1 common encoder 47
3.3.2 Priority Encoder 48
3.3.3 Extension of Encoder 50
3.4 Decoder 5 1
Binary decoder 5 1
3.4.2 Extension of Decoder 52
3.4.3 The data distributor 53 consists of a decoder.
The display decoder 53
3.5 Data Selector 56
Select 1 data selector 56
3.5.2 Integrated data selector 57
3.5.3 Application of Data Selector
3.6 Adder 58
3.6. 1 half adder 58
Full adder 59
3.6.3 Application of Adder
3.7 Numerical comparator 6 1
3.7. 1 1 digital comparator 6 1
3.7.2 Integrated digital comparator 62
3.7.3 Application of Numerical Comparator 62
3.8 Knowledge development 63
Competition adventure of combinational logic circuit 63
3.8.2 Scale combinational logic module and its application 65
3.9 Experiment 67
Functional test of combinational logic circuit 67
3. 10 training 68
3. 10. 1 Three-variable combinational logic circuit design 68
3. 10.2 decoding display circuit design 69
Summary 70
Exercise 70
Chapter 4 Integration Trigger 74
4. 1 basic RS flip-flop 74
4. 1. 1 Circuit structure and working principle 74
4. Function description method of1.2 flip-flop 76
4.2 synchronous RS flip-flop 77
4.3 master-slave JK flip-flop 78
4.4 edge d flip-flop 80
4.5 T flip-flop 82
4.6 Application of Trigger 82
4.7 Integrated Trigger 84
4.8 Knowledge development 87
4.8. 1 flip-flop logic function conversion 87
4.8.2 CMOS edge D flip-flop 89
4.9 Experiment 90
Integrated flip-flop logic function test 90
Summary 93
Exercise 94
The fifth chapter sequential logic circuit 97
5. 1 overview 97
5.2 Counter 100
The counter is a logic circuit to realize this operation. In the digital system, the counter mainly counts the number of pulses to realize the functions of measurement, counting and control, and also has the function of frequency division. The counter consists of a basic counting unit and some control gates. The counting unit consists of a series of various triggers with the function of storing information, such as rs trigger, T trigger, D trigger and JK trigger. Counters are widely used in digital systems, such as counting instruction addresses in the controller of an electronic computer to take out the next instruction in sequence, recording the number of additions and subtractions in multiplication and division in an arithmetic unit, and counting pulses in a digital instrument. Counter can be used to display the working status of products. Generally speaking, it is mainly used to indicate how many copies of folding and matching work have been completed. Its main index lies in the number of digits of the counter, generally 3 digits and 4 digits. Obviously, a 3-bit counter can display 999 at most, and a 4-bit counter can display nine thousand nine hundred and ninety-nine at most.
Binary counter 100
5.2.2 Integrated binary counter 103
5.3 Register 106
5.3. 1 shift register 106
shift register
The data in the shift register can be shifted to the right or left one bit at a time under the action of shift pulse. The data can be input and output in parallel, input and output in parallel, and output in parallel, which is very flexible and widely used.
At present, there are many commonly used integrated shift registers, such as 74 164, 74 165, 74 166 and 74595, all of which are eight-bit unidirectional shift registers, and 74 195 is a four-bit unidirectional shift register, 746544.
5.3.2 Integrated Register 108
5.4 knowledge expansion 1 10
5.4. 1 decimal counter 1 10
5.4.2 Digital register 1 13
5.4.3 Asynchronous sequential logic circuit analysis 1 14
5.4.4 Medium-scale sequential logic circuit 1 15
5.5 Experiment 1 16
Counting, decoding and display circuit 1 16
5.6 Training 1 18
5.6. 1 counter 1 18 function test
5.6.2 Functional test of register 120
Summary 12 1
Exercise 12 1
Chapter VI Generation and Transformation of Pulse Waveform 124
6. 1 ordinary pulse waveform 124
6.2 555 timer 125
6.2. Circuit structure and working principle of1.555 timer 125
6.2.2 Functions of 555 Timer 126
6.3 Schmidt trigger 127
Schmitt trigger also has two stable states, but different from general trigger, Schmitt trigger adopts potential trigger mode, and its state is maintained by input signal potential; Schmidt trigger has different threshold voltages for negative falling and positive rising input signals.
The gate circuit has a threshold voltage. When the input voltage rises from low level to threshold voltage or falls from high level to threshold voltage, the state of the circuit will change. Schmidt trigger is a special gate circuit. Different from ordinary gate circuits, Schmitt trigger has two threshold voltages, which are called positive threshold voltage and negative threshold voltage respectively. The input voltage that changes the circuit state when the input signal rises from low level to high level is called positive threshold voltage, and the input voltage that changes the circuit state when the input signal falls from high level to low level is called negative threshold voltage. The difference between the positive threshold voltage and the negative threshold voltage is called the return difference voltage.
It is a threshold switching circuit with abrupt input and output characteristics. This circuit is designed to prevent the slight change of input voltage (below a certain threshold) from causing the change of output voltage.
By using the positive feedback in the process of Schmidt trigger state transition, the periodic signal with slow edge change can be transformed into a rectangular pulse signal with steep edge. As long as the amplitude of the input signal is greater than vt+, a rectangular pulse signal with the same frequency can be obtained at the output of Schmidt trigger.
When the input voltage changes from low to high and reaches V+, the output voltage changes suddenly, while the input voltage Vi changes from high to low and reaches V-, so the output voltage changes slowly. It can be seen that it is especially suitable for circuits that need a certain delay when starting.
Rectangular pulses obtained from sensors often have waveform distortion after transmission. When the capacitance on the transmission line is large, the rising edge of the waveform will obviously slow down; When the transmission line is long and the impedance of the receiving end does not match the impedance of the transmission line, oscillation will occur at the rising and falling edges of the waveform; When other pulse signals are superimposed on rectangular pulse signals through distributed capacitors between wires or public power lines, additional noise will appear on the signals. In any case, the ideal rectangular pulse waveform can be obtained by Schmidt inverse trigger shaping. As long as the vt+ and vt- of Schmidt trigger are set properly, satisfactory shaping effect can be obtained.
6.4 monostable trigger 129
1. The monostable trigger has only one steady state and one transient state.
2. Under the action of external pulse, monostable trigger can change from steady state to transient state.
3. Due to the function of RC delay link in the circuit, the transient state is maintained for a period of time and then returns to the original steady state, and the time to maintain the transient state depends on the parameter value of RC.
6.5 multivibrator 133
Multi-oscillator: by using deep positive feedback, two electronic devices are alternately switched through resistance-capacitance coupling, from
And a self-excited oscillator generating a square wave output. Usually used as a square wave generator.
Multi-oscillator is a kind of self-excited oscillator which can generate rectangular wave, also known as rectangular wave generator. "Multi-harmonic" means that rectangular waves contain rich higher harmonic components in addition to fundamental components. The multivibrator has no steady state, only two transients. When working, the state of the circuit automatically alternates between these two transients, thus generating rectangular wave pulse signals, which are often used as pulse signal sources and clock signals in sequential circuits.
When the circuit is just connected to the power supply, both transistors are turned off. However, when the base voltages of these two transistors rise together, one of them must be turned on first because it is impossible to control the turn-on delay of each transistor during the transistor manufacturing process. Therefore, this circuit will enter one of the states and ensure continuous oscillation.
Roughly speaking, the duration of the first state (output high potential) is related to R 1 and C 1, and the duration of the second state is related to R2 and C2. Because R 1, R2, C 1 and C2 can be freely configured, the vibration and compression period and duty ratio can be freely determined.
However, the duration of each state is determined by the initial state of the capacitor (voltage across the capacitor) at the beginning of charging, which is related to the discharge amount in the previous state; The discharge amount in the previous stage is determined by the resistors R 1 and R4 through which the current flows and the duration of the discharge process. In short, it takes a long time to charge the capacitor when the circuit is just started (generally speaking, both ends of the capacitor are completely discharged when it is not started), but the duration of each stage will become shorter and tend to be stable afterwards.
Because the multivibrator uses the charging process of current to control the period, the oscillation period is also related to the amount of current flowing out of the multivibrator at the output end.
Due to the influence of various uncertain factors on the oscillation period of multivibrator, in practice, more accurate timing integrated circuits are usually used to replace simple multivibrator circuits.
6.6 Application of 555 Timer 135
6.7 knowledge development 136
Pulse shaping circuit composed of integrated gate 136
6.8 experiment 137
Generation and shaping of pulse waveform 137
6.9 Training 139
Design and Application of 555 Timer 139
Summary 140
Exercise 14 1
Chapter VII Digital/Analog and Analog/Digital Converter 143
7. 1 DAC 143
7. Basic principle of1.1DAC143
7. 1.2 switching network 144
7. 1.3 analog switch 145
7. Main technical indicators of1.4 D/A converter 145
7. 1.5 integrated digital-to-analog converter 146
7.2 A/D converter 148
7.2. 1 sample and hold 148
Quantization and coding 149
7.2.3 Ordinary ADC 149
7.2.4 Main technical indicators of A/D converter 15 1
7.2.5 Integrated ADC 152
7.3 knowledge development 153
7.3. 1 data acquisition control system: pressure
Temperature controller 153
7.3.2 Common D/A converters and A/D
Converter introduction 154
Summary 157
Exercise 157
Chapter 8 Memory and Programmable Logic Devices 160
8. 1 memory 160
8. 1. 1 random access memory 160
8. 1.2 ROM 165
8.2 programmable logic device 169
8.2. 1 Characteristics and representation of programmable logic devices 169
8.2.2 Programmable array logic 170
Generic array logic (GAL) 17 1
8.3 Introduction of CPLD, FPGA and System Programming Technology 173
8.3. Introduction to1CPLD173
8.3.2 Introduction of FPGA173
8.3.3 ISP technical introduction 174
Summary 174
Exercise 174
Chapter 9 Comprehensive Training of Digital Circuits 177
9. 1 Functional analysis of digital circuit system5438+077
9. 1. 1 taxi meter circuit 177
9. 1.2 digital responder circuit 18 1
9.2 debugging of digital circuit system 183
9.2. 1 General steps of circuit debugging 183
9.2.2 Problems in Circuit Debugging 184
9.3 Diagnosis and elimination of digital circuit faults 185
9.4 Comprehensive Training 189
9.4. Analysis and design of1transponder 189
9.4.2 Assembly of Digital Multimeter 190
Summary 196
Exercise 197
Appendix A Introduction to Electronic Design Automation 198
Appendix B Comparison of New and Old Graphical Symbols of Digital Circuits 206
Appendix C Common IC Model and Pin Diagram 208
Appendix dtll74 Series Device Introduction 2 1 1
Appendix E Introduction of CD45 Series Equipment 2 15
Appendix F Introduction of CD40 Series Equipment 2 17
Appendix introduction of G A/D and D/A conversion devices 220
Appendix H Introduction to Storage Devices 225
Reference 227
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