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    What are the specific steps for applying a VHDL design state machine?

    The specific steps of applying the VHDL design state machine are as follows: determine the number of states, the condition of state transition, and the assignment of each state output signal according to the system requirements, and draw a state transition diagram; write the VHDL design procedure of the state machine according to the state transition diagram; use EDAThe tool performs simulation verification on the function of the state machine.

    What are the components of the wireless sensor network system architecture?

    The architecture of a wireless sensor network system consists of three parts: layered network communication protocol, network management platform, and application support.

    What are the main features of the switch current circuit?

    1. The circuit contains only MOSFETs and can be fabricated using a standard digital CMOS process compatible with digital circuits so that new advances in digital CMOS processes can be directly utilized, and it is easy to integrate with digital circuits on the same chip. Switched capacitor circuits, on the other hand, need to make floating capacitors with both plates not grounded. For example, in the aforementioned various switched capacitor unit circuits, the capacitors are connected across the output terminal and the input terminal of the operational amplifier, which makes it necessary to add some process steps to manufacture the switched capacitor circuit.
    2. A lower power supply voltage can be used. Because the switched current circuit uses the current as the signal carrier, the amplitude of the signal change is not directly limited by the power supply voltage, so it has the potential to work at a low power supply voltage. However, since MOS switches are still voltage controlled, careful design is required when implementing low power supplies.
    3. Compared with the switched capacitor circuit, the switched current circuit does not need a high-voltage gain amplifier, and each node in its signal path is a low-impedance node so that the switched current circuit can work at high frequencies.
    4. The circuit structure is relatively simple and regular, and it is easy to design automation.
    5. The degree of circuit matching is high, and the clock feedthrough introduced by the switch is the main problem that affects the performance of the switch current circuit.

    What are the main features of fiber optic sensors compared to conventional sensors?

    • Compared with traditional sensors, the main features of optical fiber sensors are:
      1. Anti-electromagnetic interference, electrical insulation, and intrinsic safety: Since optical fiber sensors use light waves to transmit information, and optical fibers are electrically insulating transmission media, they are not immune to strong Electromagnetic interference does not affect the external electromagnetic field. In addition, the weak optical signal transmitted in the optical fiber will not generate electric spark, which is safe and reliable.
      2. High sensitivity: The optical fiber sensor based on phase modulation and interference technology has extremely high sensitivity.
      3. Light weight, small volume, and variable shape: In addition to the characteristics of light weight and small volume, optical fiber also has the advantage of being windable. Therefore, various optical fiber sensors with different shapes and sizes can be made by using optical fibers.
      4. Wide range of measurement objects: At present, there are different performances for measuring temperature, pressure, displacement, speed, acceleration, liquid level, flow rate, vibration, underwater sound, current, electric field, magnetic field, voltage, impurity content, liquid concentration, nuclear radiation Fiber optic sensors of various physical and chemical quantities are used in the field.
      5. Small influence on the measured medium: This is extremely beneficial for applications in the field of medicine and biology.
      6. Continuous distributed measurement can be carried out, which is convenient for multiplexing and network formation: it is beneficial to form a telemetry network and an optical fiber sensor network with the existing optical communication technology.

    Briefly describe the characteristics of the Thumb instruction?

    Compared with the ARM instruction set, the operand of the data processing instruction in the Thumb instruction set is still 32 bits, and the instruction address is also 32 bits, but the Thumb instruction set is 16 bits of instruction length, and most of the Thumb instructions are unconditionally executed.

    What are the test methods for electrical characteristics of contact IC cards?

    • VCC contact
    • I / () contact
    • CLK contact
    • RST contact
    • VPP contact

    The MCU and ASIC are the control units of the reader. What is its function?

    1. Communicate with the master in parallel or serial mode (USB) and execute commands from the master.
    2. Communicate with the IC card through the high-frequency interface.
    3. Realizing parity and/or CRC check of communication data between card machines.
    4. Encoding and encrypting data transmitted to the IC card, decrypting and decoding data from the IC card.
    5. Perform anti-collision processing of multiple cards simultaneously entering the reader’s RF field.
    6. Realize mutual identification between card machines.

    What types of inverters can be classified according to the nature of DC power?

    Can be divided into voltage type inverters and current type inverters.

    Sensor information fusion classification:

    1. Combination: A processing method in which multiple sensors are combined into parallel or complementary ways to obtain multiple sets of data output. It is the most basic way. The problems involved include the coordination and synthesis of output methods and the selection of sensors. applied at the hardware level.
    2. Synthesis: An effective method for obtaining clear information in information optimization processing. Example: In virtual reality technology, two separate cameras are used to capture two images of different sides of an object at the same time, and combining the two images can restore an accurate image of a three-dimensional object.
    3. Fusion: When the sensor data sets are correlated or the sensor data is correlated with the knowledge model inside the system, a new expression of information is generated.
    4. Correlation: Obtaining certain results by processing sensor information requires not only single-item information processing but also processing through correlation to learn the relationship between sensor data sets, to obtain correct information, and eliminate useless and wrong information. Purpose of correlation processing: Synthesize and optimize information from processes such as recognition, prediction, learning, and memory.

    What are the features of the SIM card?

    • Store user-related data
    • User PIN operation and management
    • User identity authentication
    • Security algorithm and key in SIM card


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