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  • Ten Daily Electronic Common Sense-Section 124

    What should you watch out for when using a select signal assignment statement in VHDL?

    • When using the selection signal assignment statement in VHDL, you should pay attention to the following points:
      1. Only when the value of the selection condition expression meets a certain selection condition. It is possible to assign the value of the expression preceding the selection condition to the target signal.
      2. The expressions in the selection signal assignment statement all contain when clauses.
      3. The selection signal assignment statement is a parallel description statement, so it cannot be used inside the process.
      4. Since the judgment of the selection condition in the selection signal assignment statement is carried out simultaneously. Therefore, overlapping of selection criteria is not allowed here.
      5. The selection condition in the selection signal assignment statement does not allow incomplete coverage.

    What is the beam divergence angle?

    Beam divergence is a measure that can be measured in the far field to determine how much the beam has been expanded compared to the original radius.
    In laser physics, the beam divergence half-angle can be obtained from the ratio of the expanded beam radius to the axial distance measured in the far-field region.

    What are the counters divided into working principles and usage?

    Counters are divided into many types according to their working principles and usage conditions, such as traveling wave counters, synchronous counters, counters of various bases (such as binary counters, decimal counters, etc.).

    What are the advantages of asymmetric cryptosystems?

    1. Key distribution is simple.、
    2. The amount of keys kept in secret is reduced. Each smart card only needs to keep its own decryption key secretly.
    3. The emergence of the public key makes the asymmetric cryptosystem adaptable to the open use environment.
    4. Digital signature can be realized.

    What is the definition of PCM?

    PCM is used to graft an analog signal (such as voice) onto a 64kbps digital bit stream for transmission. PCM converts continuous analog signals into discrete digital signals. In digital audio, the pulse code development method is commonly used, which is the so-called PCM (PULSECODEMODULATION).
    PCM code is the abbreviation of PulseCodeModulation, also known as pulse code modulation. It is one of the encoding methods of digital communication. The main process of encoding is to sample analog signals such as voice and image at regular intervals to make them discretized. At the same time, the sampling value is rounded and quantized according to the hierarchical unit, and the sampling value is represented by a set of binary codes to represent the amplitude of the sampling pulse.
    The biggest advantage of PCM encoding is good sound quality, but the biggest disadvantage is its large size. Our common AudioCD uses PCM encoding, and the capacity of a disc can only hold 72 minutes of music information.
    The PCM method is completed by three basic steps of sampling, quantization and coding. After the audio signal is band-limited filtered by the low-pass filter, the PCM modulation is completed by the three steps of sampling, quantization and encoding to realize A/D change. The formed PCM digital signal is recorded on the recording medium after error correction coding and modulation.
    The recording media of digital audio include laser discs and cassette tapes. During playback, the digital signal taken out from the recording medium is demodulated, error-corrected, etc. processed. It is restored to a PCM digital signal and restored to an analog audio signal by a D/A converter and a low-pass filter. The decoder that converts the CD-PCM digital signal into an analog signal is called a CD-PCM decoder.

    What is a dark Resistors?

    The resistance value measured by the photoresistor at room temperature and after a certain period of time when it is completely dark is called dark resistance.

    What is the design purpose of the semi-reliable transmission algorithm?

    • Minimize the number of packets that need to be transmitted per unit of application data.
    • Minimize the time required to transfer an entire generation of data from the source node to the destination node. Thereby minimizing the end-to-end latency of the application and the number of generations in the network.
    • Minimize the delay of packets from creation to transmission. Therefore, the information in the sent data packet is timely and useful to the downstream node.

    What are the main components of the DS18B20 internal structure?

    The internal structure of DS18B20 is mainly composed of 4 parts:
    64-bit lithography ROM, temperature sensor, non-volatile temperature alarm trigger TH and TL, configuration register.

    What are the main technical features of the TPS7510x?

    1. Because there is no need to use internal switching signals, the influence of electromagnetic interference (EMI) is eliminated;
    2. The output current matching accuracy is: 2%;
    3. Common cathode structure, driving up to 4 LEDs with a power of 25mA each;
    4. In lithium In ion battery applications, the typical voltage drop of 28mV extends the available power supply range;
    5. PWM signal is used for brightness control, and each group of LEDs (two LEDs in each group. Two groups in total) has independent start-up and PWM brightness control functions;
    6. Optional external resistors allow for high accuracy and features such as programmable current. The default LED current can save external components;
    7. Use innovative factory EEPROM programming technology. The default value can be set in the range of 3 ~ 10mA (step increment is 1mA);
    8. With over-current and overheating protection functions.

    What is the main purpose of the session layer?

    On the basis of the transport layer, some functions of coordinating dialogue are added.
    It manages conversations between processes on different hosts.


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