Experience of digital circuit training Part I: Digital electronic technology is a subject closely related to theory and practice. If we only rely on theory, we will have a headache. If you rely on experiments, the effect will be different. In particular, the experiment of digital electronic technology allows us to verify the theory in the book and design by ourselves, which is conducive to cultivating our practical design ability and hands-on ability.

Through the experiment of digital electronic technology, we have not only done several experiments, but also learned the experimental technology. We should master the experimental methods, that is, the method of testing the theory by experiments, the method of seeking the relationship between physical quantities, and the method of seeking the best scheme. Mastering these methods is more important than doing a few experiments.

In the experiment of digital electronic technology, according to the given experimental instruments, experimental principles and some requirements, we can design the experimental scheme and steps, draw the experimental circuit diagram, and then measure and get the results.

In the process of digital electronic technology experiment, we also encountered various problems, and we will take corresponding measures to solve these problems, such as:

1, the line is not available-check whether the line is available with a logic pen;

2. Chip damage-use a chip detector to detect whether the chip is available normally and its type;

3. In some experiments, oscilloscopes are used, which requires us to use oscilloscopes correctly and familiarly. Through learning, we learned how to adjust the instrument to make the waveform easy to observe and how to read the relevant parameters on the oscilloscope. For example, in the final exam experiment "555 time base circuit and its application", we can read the transient time Tw of multivibrator, Tph and monostable trigger, sometimes because of the problem of access line, which can be solved by switching to the original line.

At the same time, we have also learned many lessons:

1. If there is a problem during the experiment, don't blindly remove all the wires and reconnect them. This not only wastes time, but also fails to exercise our hands and brains.

At this time, we should calm down and calmly analyze the problem, which link may exist, such as the incorrect experimental principle or the need to modify the experimental circuit. Only in this way can our ability be improved.

2. In the process of experiment, you should learn to cooperate, and you can't just do it yourself or not participate at all.

3. During the experiment, we should learn from each other, learn from the methods and strengths of outstanding students, and learn to consult the instructor humbly. Of course, this should be based on our own independent thinking.

The experiment of digital electronic technology is conducive to mastering the knowledge system and learning methods, stimulating our learning initiative, enhancing our self-confidence, cultivating our innovative ability and learning ability, and consolidating and transferring book knowledge and skills. Through the practice in the experiment of digital electronic technology, I have gained a lot!

The second experience of digital circuit training: first, before learning

Digital circuit experiment is an experiment to learn and test the theory of digital circuit. It is also the first professional-related experimental course that our electronic science and technology major has come into contact with. I feel that it will be a very difficult course for people who are not good at hands-on like me.

However, I clearly realize that digital electronic technology is a subject closely related to theory and practice. If you only rely on theory, you may be confused, but there is no practice. It is undoubtedly meaningful to study this course. If I use experiments, the effect will be different, especially the experiment of digital electronic technology, which allows me to verify the theory in the book and design it myself, which is conducive to cultivating my practical design ability and hands-on ability.

No one will attend the meeting and no one will be born. Although my hands-on ability is poor, I treat this course with a good attitude of serious study. I believe I can get a good exercise by studying.

Second, study.

In the digital circuit experiment class, we first learned to use Multisim software to simulate the circuit. At first, the teacher really didn't understand anything, and the students around him helped to complete the experimental tasks assigned by the teacher. But later, if you do more, you will gradually understand. Although it was a bad start, you managed to catch up. With this software, we can do a simulation exercise on the computer first when designing the circuit. If there is something wrong with the design, it can be improved first, so as not to burn out the components unnecessarily and greatly reduce the waste of resources. After learning to simulate, we went into the laboratory and conducted a series of "real gun combat". At the beginning, it was the same. We were at a loss and burned two components. The main reason is that I am too careless and always connect the circuit backwards, which makes the components emit a "stench". Here, I am deeply sorry! The teacher said, "I'm afraid you can't burn out the components, but I'm afraid you dare not do it." The teacher's words gave me great encouragement! Over time, I slowly found pleasure in the experiment, especially in welding circuits. I used to hate learning circuits, and I was afraid to get in touch with the reality related to "electricity", even if it was only a simple series-parallel circuit in junior high school. However, under the leadership of our teacher Peng, I actually began to be willing to weld the circuit myself. At first, I just held a try attitude, and my hands were shaking all the time when I held the soldering iron. But slowly, slowly, I actually enjoy it. The first experiment of welding the small fan failed. The small fan didn't turn, but it really completed a loop. It was really great!

Third, after studying.

Time flies, and the experimental course of digital electricity is coming to an end. Looking back on the learning process, there are bitter and sweet. Through learning, I have the following experiences:

1, if the line is blocked, you can use a logic pen to check whether the line is available; Check for open circuit and poor wire connection.

Remember to be anxious when you experiment. When encountering problems, don't blindly tear down all the wires and reconnect them. This will not only not exercise your hands and brain, but also waste time. At this time, it is necessary to calm down and seriously think, calmly analyze the problem and correct it in time.

3. We should learn from each other during the experiment, learn from the methods and strengths of outstanding students, and learn to consult the instructor humbly. Of course, this should be based on our own independent thinking.

In the process of experiment, we should learn to cooperate, instead of just doing it ourselves or not participating at all.

Fourth, teaching opinions.

Teacher Peng's humor added a lot of fun to the course, and he made us complete the experimental task in a relaxed and happy atmosphere. The teacher's careful teaching also made us interested in the experimental class that we didn't like originally, so as to learn digital circuits better and cultivate our hands-on ability. I believe that with strong interest, we can better complete the next course!

If there is anything wrong with this course, I only have a small opinion, that is, whether it can be divided into two groups, so that no one will make a fool of themselves and everyone can devote themselves to the joy of welding circuits. One semester's experimental course study increased my confidence in learning professional knowledge. It's not really difficult to weld a circuit, as long as you study hard enough. Finally, thank the teacher for his careful teaching for a semester!

Experience of digital circuit training Part III: In the process of doing gymnastics with experimental equipment, I got a better understanding of theoretical knowledge (half adder and full adder), and really achieved the purpose of guiding theory to practice and testing theory in practice.

Several points that should be paid special attention to in experimental operation:

(1) The target chip selected at the beginning of the project must correspond to the chip on the experimental board.

(2) When connecting the circuit, pay attention to ensure that the line is connected with the port, and be careful not to pull it into the dashed box of the device graphic symbol.

(3) There can only be one entity name of the top-level file. Note that the symbol file cannot be the same as the entity name of the top-level file.

(4) When saving the waveform file, pay attention to that the file name must be consistent with the project name, because when creating a waveform file for a project for many times, it is necessary to pay attention to that the file name should be consistent with the project name when saving, otherwise the correct simulation results cannot be obtained.

(5) The setting of the simulation time region and the setting of the input waveform period must be coordinated, otherwise the obtained waveform may be inconvenient to observe or make mistakes.

Experience: When a novice uses a new software, he must do a good preview before the experiment and be careful in the specific experimental operation. For example, when setting pushpins, you must "sit in the right position". I used to spend a lot of time on this. All kinds of problems encountered in the experiment are basically solved by themselves, which greatly improves and exercises their ability to solve problems independently. In a word, I benefited a lot from this experiment.

Experience of digital circuit training Part IV: Digital circuit can also be called logic circuit, and it is called (&; ), or (> = 1), NOT (O), XOR (= 1), XOR (=) and so on.

Logic circuits can be divided into combinational logic circuits and sequential logic circuits. Combinatorial logic circuit means that the output state at a certain moment only depends on the input state at that moment, and has nothing to do with the past state of the circuit.

TTL and CMOS circuit: TTL is the abbreviation of transistor input transistor output logic, which uses 5V power supply. CMOS circuit consists of PMOS transistor and NMOS transistor (the source of which is generally grounded), and the power supply voltage range is wide, from 1.2V to 18V.

CMOS push-pull output: When the output level is high, the N tube is turned off and the P tube is turned on; When the output level is low, the N tube is turned on and the P tube is turned off. The output resistance is small, so the driving ability is strong.

The drain of CMOS gate is open: the P tube is removed, and the output can be directly connected to realize the function of line and function. If CMOS transistors are directly connected together, then when one output is high and the other output is low, the P transistor and the N transistor are turned on at the same time, and the current is very large, which may burn out the transistors. When a single tube is on, only the channel is on, and the current is very small. If both tubes are conductive, a current loop is formed and the current is large.

Input-output high impedance: add a P2 tube and N2 tube at the drains of P 1 and N 1. When high impedance is to be configured, the P2 tube and N2 tube are not conductive, thus achieving a high impedance state.

Static current: the current under the condition of input stateless inversion (high-low level conversion).

Dynamic current: the power consumption generated by the circuit in the process of logic state switching, including instantaneous conduction power consumption and load capacitor charging and discharging power consumption. The rising edge and falling edge of the gate circuit are inevitable, so when the input voltage reaches Vt from high to low or from low to high, the two transistors are turned on at the same time, resulting in peak current. Loss depends on input waveform (CMOS process), power supply voltage and repetition frequency of input signal. The charging and discharging of circuit load capacitance is also a large part.

ESD protection: electrostatic discharge, electrostatic discharge.

Input-output buffer: it is a buffer, not a buffer, nor a CMOS gate circuit. The function of input buffer is mainly 1, TTL/CMOS level conversion interface; 2. Filter external input signal noise. The function of the output buffer is to increase the driving ability.

Matching input mode is not necessarily more power-saving than output mode: input mode will open input buffer and output mode will open output buffer.

Notes on reading and writing GPIO data registers on TESEO:

When configured as an ordinary GPIO, if configured as an output port, the write data register will directly output this level, and the read data register is actually the last written value in the read latch. If it is configured as an input port and pull-up and pull-down are enabled, the write data register is configured with a pull-up resistor, and the read data register is a buffer for the read input pin, which returns the current level of the pin. Some platforms have a special status register. Whether the current pin is configured as an input or an output, reading the special status register will return the current level of the pin.

The boot state of the pin is the state when the pin is powered on or hard restarted, and the state after reset release is the reset state, which may be different from the state. Utar0 _ tx of TESEO is boot 1, and the signal of this pin will be latched at power-on or hard restart, so that it can be used for default register mapping when reset is released.

Power supply voltage configuration of IO: IO pins belong to different IO rings, and different IO rings can input different voltages. When CPU judges the logic level of IO, it will compare it with the level of IO ring (multiplied by the coefficient of high and low levels).

Swing in digital circuit: input swing and output swing. Input swing refers to the difference between the lowest input high level and the highest input low level, output swing refers to the difference between the lowest output high level and the highest output low level, and TTL swing is small.

In the sequential logic circuit, if the input clock stops, the power consumption of the whole circuit is very low, because the output of many small units in the sequential logic circuit is driven by the clock, and when the clock stops, it is basically a high impedance state. If the power supply of the whole module is cut off, it will save more electricity.

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If the serial communication circuit is turned off, the general RX line will be at low level. If a high level is detected, an interrupt will occur. At this point, the serial port can be restarted, but the first byte is not in the serial port register, so the data will be lost.