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  • Ten Daily Electronic Common Sense-Section 134

    Briefly describe the bit arbitration technology of CAN?

    CAN’s non-destructive bit arbitration technology is different from general arbitration technology.
    In general arbitration technology, when two or more units start to transmit messages at the same time, when a bus access conflict occurs, all messages will avoid waiting. The message will not be transmitted to the bus until it detects that the bus is idle. This mechanism will cause a waste of computer time on the bus and greatly reduce real-time performance. Sometimes important information is delayed.
    The CAN bus uses the “carrier monitoring, multi-master control/collision avoidance” (CSMA/CA) communication mode. As long as the bus is free, any unit can start sending messages. If two or more units start transmitting messages at the same time, there will be a bus access conflict.
    This conflict can be resolved by using bit-wise arbitration of the identifier. The arbitration mechanism ensures that neither the message nor the time is lost. When a data frame and a remote frame with the same identifier are sent at the same time, the data frame takes precedence over the remote frame.
    During arbitration, each transmitter compares the level of the transmitted bit with the monitored bus level. If the levels are the same, the unit can continue to transmit. If what is sent is a “recessive” (logic 1) level and what is monitored is a “dominant” (logic 0) level, then this unit has lost arbitration and must exit the sending state.

    What are the main electrical parameters of the antenna?

    The electrical parameters of the antenna mainly include the efficiency, effective length, frequency bandwidth, input impedance, gain coefficient, polarization direction and pattern of the antenna.

    4500 series chip function:

    Remarks for model device name:
    CD45014 input double AND gate and 2 input NOR gate
    CD4502 Selectable 3-State Output Hex Inverter/Buffer
    CD4503 six non-inverting tri-state buffers
    CD4504 Six Voltage Converter
    CD4506 Dual 2-Input Scalable NOR Gate
    CD4508 dual 4-bit latch D-type flip-flop
    CD4510 can preset BCD code up/down counter
    CD4511BCD latch, 7-segment decoding, driver
    CD4512 Octal Data Selector
    CD4513BCD latch, 7-segment decoding, driver (blanking)
    CD4514 4-bit latch, 4-16-wire decoder
    CD45154-bit latch, 4-16-wire decoder
    CD4516 can preset 4-bit binary up/down counter
    CD4517 dual 64-bit static shift register
    CD4518 dual BCD synchronous plus counter
    CD4519 four-bit AND-OR selector
    CD4520 dual 4-bit binary synchronous up counter
    CD452124 stage frequency divider
    CD4522 can preset BCD synchronous 1/N counter
    CD4526 can preset 4-bit binary synchronous 1/N counter
    CD4527BCD Ratio Multiplier
    CD4528 Dual Monostable Flip-Flops
    CD4529 Dual Quad/Single Octal Analog Switch
    CD4530 dual 5-input dominant logic gate
    CD453112 bit parity checker
    CD45328 Bit Priority Encoder
    CD4536 Programmable Timer
    CD4538 Precision Dual Monostable
    CD4539 Dual Quad Data Selector
    CD4541 programmable oscillator/timer
    CD4543BCD seven-segment latch decoding, driver
    CD4544BCD seven-segment latch decoding, driver
    CD4547BCD seven-segment decoding/high current driver
    CD4549 function approximation register
    CD4551 Quad 2-Channel Analog Switch
    CD4553 three-digit BCD counter
    CD4555 Duo-Binary Four-Select One Decoder/Separator
    CD4556 duo-binary four-select-one decoder/separator
    CD4558BCD eight-segment decoder
    CD4560″N”BCD Adder
    CD4561 “9” complement
    CD4573 Quad Programmable Operational Amplifier
    CD4574 Quad Programmable Voltage Comparator
    CD4575 Dual Programmable Op Amp/Comparator
    CD4583 Dual Schmitt Trigger
    CD4584 six Schmitt triggers
    CD45854 bit numerical comparator
    CD45998 bit addressable latch
    CD221004×4×1 crosspoint switch

    What are the characteristics of photoelectric switches?

    The photoelectric switch is characterized by small size, high speed, non-contact, and it is easy to combine with TTL, MOS and other circuits.

    What is the detection limit?

    Detection limit: refers to the lowest concentration of ions that can be detected by ISE.

    What are the characteristics of three-phase sinusoidal AC?

    1. The frequency of the sinusoidal alternating current of each phase is the same;
    2. The maximum value of the sinusoidal alternating current of each phase is the same;
    3. The phase difference of each phase of sinusoidal alternating current is l20. Their analytical formulas are:
      • eu=Emsino)t
      • ev=Emsin(cot-120.)
      • ew=Emsin(cot 120.)
    4. The sum of sinusoidal AC electromotive force of each phase is zero at any time, that is eIf ev ew=0 .

    What are the three ways to self-test?

    1. Power-on self-test
    2. Periodic self-test
    3. Keying self-test

    What are the reasons for the change in strain gauge resistance due to changes in ambient temperature?

    There are two reasons for the change in the resistance of the strain gauge due to changes in the ambient temperature:
    One is that the metal sensitive grid resistance of the strain gauge itself changes with temperature;
    The second is that the additional deformation of the strain gauge due to the difference in the linear expansion coefficient of the test piece material and the sensitive grid material causes the resistance to change.

    What is a discrete solution?

    The discrete solution is a power management system implemented with a discrete IC that limits the battery voltage to 3.3V.

    What is the basic workflow of an RFID system?

    The reader sends a radio frequency signal of a certain frequency.
    When the device enters the working area of the transmitting antenna, an induced current is generated in the electronic tag, and the energy obtained is activated;
    The electronic tag sends its own code and other information through the built-in transmitting antenna;
    The receiving antenna of the system receives the carrier signal sent by the electronic tag, and transmits it to the reader through the antenna regulator.
    The reader demodulates and decodes the received signal, and sends it to the background main system for related processing;
    The main system judges the legitimacy of the label according to the logical operation, makes corresponding processing and control for different settings, and sends out command signals to control the action of the actuator.


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