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    The biggest feature of Modelsim is its powerful debugging features. Which are the main types?

    • The biggest feature of Modelsim is its powerful debugging functions, which mainly include the following:
      1. Advanced data flow window, which can quickly trace the causes of errors or indeterminate states.
      2. Performance analysis tools help analyze performance bottlenecks and accelerate simulation.
      3. The code coverage detection ensures the completeness of the test.
      4. Waveform comparison function of multiple modes.
      5. The advanced Signal Spy function can easily access the underlying signals in VHDL, Verilog or a hybrid design of the two.
      6. Support encrypted IP.
      7. Co-simulation with Simulink of MATLAB can be realized.

    What are the characteristics of the netX network controller?

    netX is a highly integrated network controller produced by Hilscher in Germany. The company was founded in 1986 by Hans-Jurgen Hilscher and is headquartered in Hattersheim, Germany. The company initially consisted of a team of experts dedicated to electronics and control technology, and success in this field established the company’s qualification as a service provider in the field of systems engineering. Based on early experience, Hilscher turned its focus to the fieldbus and industrial Ethernet markets in the early 1990s. At present, the company is engaged in industrial communication technology, and has become a leading manufacturer of industrial communication products and technical service providers in this field. At the end of 2005, Hilscher launched the network control chip – netX, which represents the future of industrial communication. 
    netX has a new system optimization structure, suitable for industrial communication and large-scale data throughput. Each communication channel is composed of 3 freely configurable ALUs, and different fieldbus and real-time Ethernet systems can be implemented through the command set and its structure. The internal 32-bit ARM is used as the CPU core, and the main frequency is 200MHz.
    The characteristics of netX are: 1) A unified communication platform. 2) Full integration strategy from fieldbus to real-time Ethernet. 3) A monolithic solution with integrated communication controller. 4) Open technology.

    What are the advantages and disadvantages of multi-cell series multilevel inverter topology?

    1. The DC side adopts independent DC voltage sources, and no voltage equalization is required.
    2. It has the characteristics of modular structure; the design, manufacture and installation are convenient; the low-voltage and small-capacity inverter technology based on it is mature, easy to control, and the system has high reliability.
    3. For the same number of levels, the number of components required for the series structure is the least.
    4. Since there is no limitation of capacitors and clamping diodes, the number of levels of the series structure can be increased accordingly. As a result, higher voltage and lower harmonic requirements can be achieved. The disadvantage of the series structure is that it requires multiple independent DC power supplies. If the method of uncontrollable rectifier bridge is used to realize it, a phase-shifting transformer with complex structure needs to be designed.

    What are the classifications of automotive sensors?

    1. Sensors are classified according to whether they need additional energy or not, and can be divided into two types: active sensors and passive sensors.
    2. According to the signal conversion relationship, it can be divided into: sensors that are converted from one kind of non-electricity to another kind of non-electricity, such as elastic sensitive elements and pneumatic sensors; sensors that are converted from non-electricity to electricity, such as thermocouple temperature sensors , Piezoelectric accelerometer, etc.
    3. According to different types of input, it can be divided into displacement, velocity, acceleration, angular displacement, angular velocity, force, torque, pressure, vacuum, and temperature.
    4. According to the working principle of the sensor, there are Resistive, capacitive, strain, inductive, photoelectric, photosensitive, piezoelectric and pyroelectric sensors, etc.
    5. According to the form of sensor output signal, there are two types of analog and digital sensors.
    6. Various automobile sensors can be divided into two categories according to their functions: one is the sensors that enable drivers and maintenance personnel to understand the status of various parts of the automobile, such as temperature, vehicle speed, engine speed, and fluid pressure sensors. The other type is the sensor used to control the running state of the car, such as throttle position sensor, wheel speed sensor, deceleration sensor, yaw rate sensor, etc.

    What is the principle of RFID positioning?

    RFID positioning technology belongs to a kind of wireless communication positioning technology. Wireless positioning was originally used in navigation and positioning systems. According to the changes of the received signal strength, phase, time, frequency and other parameters of the radio navigation station, the user can calculate his position through a certain algorithm. In recent years, with the rapid development of personal mobile communications, direct use of mobile station positioning has become an important aspect of third-generation mobile communications. In some application scenarios that provide location information for a large number of indoor targets (such as personnel supervision, tracking of valuables, etc.). Whether it is GPRS or mobile communication network, there are shortcomings such as weak wireless signal and large interference, which will lead to low positioning accuracy or inability to locate. Therefore, the use of RFID-based information transmission technology to manage location information has become a research hotspot.

    From the address calculation method of the addressing mode, there are several forms of load/store instructions?

    • Zero offset
    • Front index offset
    • Program relative offset
    • Post index offset

    What are the main performance indicators of integrated op amps?

    1. Open-loop differential mode voltage gain Aud. When there is no external connection between the output terminal and the input terminal of the integrated operational amplifier, the ratio of the output voltage to the input voltage. Defined as the open-loop differential mode voltage gain, that is, Aud=U0/ui. The larger the open-loop differential mode voltage gain Aud of the integrated op amp, the better, and the open-loop voltage gain of the ideal op amp Aud→∞.
    2. The maximum output voltage Uopp. Under the specified power supply voltage, the maximum undistorted output voltage amplitude of the integrated operational amplifier, such as F007, when the power supply voltage is plus or minus 15V, Uopp is plus or minus 12V.
    3. Differential mode input resistance Rid. The differential mode input resistance Rid of the integrated operational amplifier is the equivalent resistance seen from the two input terminals of the integrated operational amplifier. It reflects how much current the integrated op amp draws from the signal source. Define Rid=Uid/Iid. The larger the differential mode input resistance Rid, the better, the differential mode input resistance Rid of an ideal op amp→∞.
    4. Output resistance R0. The output resistance of the integrated op amp is the internal resistance of the equivalent signal source seen from the output end of the op amp to the op amp. The smaller the output resistance of the integrated operational amplifier, the better, the output resistance of the ideal operational amplifier is R0→∞.
    5. The common mode rejection ratio KCMR. The KCMR of the integrated operational amplifier is the same as the definition of the differential amplifier circuit, that is, the ratio of the differential mode voltage gain to the common mode voltage gain. Commonly expressed in decibels, that is, KCMR=20㏒∣Aud/Auc∣(db) The larger the common mode rejection ratio of the integrated op amp, the better the ideal op amp KCMR→∞.
    6. The maximum common mode input voltage amplitude uicm. When the common-mode input voltage applied between the two input terminals of the integrated operational amplifier exceeds a certain value, the operational amplifier cannot work normally, and this fixed value is the maximum common-mode input voltage. F007’s uicm=12V7, the maximum differential mode input voltage amplitude uidm When the differential mode input voltage applied between the two input terminals of the integrated op amp exceeds a certain value, the normal input performance of the input stage is destroyed. This certain value is called Maximum differential mode input voltage amplitude uidm. The uidm of F007 = positive and negative 30V8, the input offset voltage Uio The input offset voltage Uio reflects the input polarity symmetry of the integrated operational amplifier and the quality of the potential configuration at all levels. In static state, the input voltage is not equal to 0. To make Uo=0, a compensation voltage must be added between the two input terminals, that is, the input offset voltage. The Uio of F007 is about 2mv. The smaller the input offset voltage of the integrated op amp, the better. When the ideal op amp tends to 09 and the input bias current IIB is static, the DC current values ​​of the two input terminals are IB1 and IB2 respectively. The input bias current is defined as the average value of the two. The Iib of F007 is about 200 nA. The lower the input bias current of the integrated op amp, the better. The ideal op amp tends to 010, and the input offset current IIo. The difference between the DC currents of the two input terminals at static state is called the input offset current, IIo=IB1-IB2.F007 IIo is about 100Na. The smaller the input offset current of the integrated op amp, the better, the ideal op amp tends to be 0.11, open loop gain bandwidth. The corresponding frequency bandwidth when the open-loop differential mode voltage gain of the op amp drops to 1/root sign 2 times of the DC gain (-3db) is called the -3db open-loop gain bandwidth of the op amp, and is represented by BW. The frequency bandwidth at which the open-loop voltage gain of the op amp drops to one is called the unity gain bandwidth, and is represented by BWG. The open-loop gain bandwidth of an ideal op amp is infinite. Slew rate (slew rate) SR, which is defined as the maximum rate of change of the output voltage under the rated output voltage of the op amp, that is, SR=∣du0/dt∣max. It reflects the op amp’s response to high-speed changing signals. The slew rate of an ideal op amp is infinite.

    What is the role of the interrupt enable register?

    The keyboard interrupt enable register is used to set whether to open the keyboard interrupt function of the 8 pins of port A. Clearing a bit to 0 disables the keyboard interrupt of this pin. Writing 1 allows the corresponding pin to be used as a keyboard interrupt and allows its interrupt request. At the same time, the internal pull-up resistor corresponding to the pin is also turned on.

    What are the restrictions on the waiting mode?

    When all of the following five conditions are met, if the WAIT instruction is executed, the microcontroller will immediately generate a low-voltage detection interrupt and return from the wait mode.

    1.The CM02 bit of the CM0 register is “1” (stop the peripheral function clock). 2. The VC27 bit of the VCR2 register is “1” (the low voltage detection circuit is valid). 3. The D40 bit of the D4INT register is “1” (low voltage detection interrupt is enabled). 4. D41 bit is “1” (use low voltage detection interrupt for return from wait mode). 5. When the input voltage of the VCC1 pin rises to above Vdet4 (the VCl3 bit of the VCR1 register is “1”), and the input voltage of the VCC1 pin drops below Vdet4, it transitions to the standby mode. Returns from wait mode when it rises above Vdet4. At this time, if the VCl3 bit is “0” (VCCl < Vdet4), the wait instruction must be executed.

    What is a duplexer?

    Duplexer: It combines two or more signals into a common channel or medium to increase transmission efficiency. It allows the transmitter to work on one frequency and the receiver to work on another frequency, sharing a pair of antennas to reduce the interaction and fading of different RF signals.


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