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Micro Controller Interview Questions - Part 1


Write the difference between LDA and STA instruction ?

  • LDA : Load data in to Accumulator register(A) directly from the address specified with in the instruction.
  • STA : Store the contents of Accumulator register(A) to the address specified with in the instruction.

    What are the types of rotate instructions ?

  • RLC : Rotate Accumulator Left
  • RRC : Rotate Accumulator Right
  • RAL : Rotate Accumulator Left through Carry
  • RAR : Rotate Accumulator Right through Carry

    What are the operating modes of 8255 ?

  • Bit set/Reset mode
  • I/O modes
  • mode 0 : Simple input/output
  • mode 1 : Input/output with handshake
  • mode 2 : Bi-directional I/O data transfer

    What are the priority modes in 8259 ?

  • Fully nested mode
  • Special fully nested mode
  • Rotating priority mode
  • Special mask mode
  • Poll mode

    What is the use of SWAP function in 8051 ?

    SWAP A : Swap nibbles with in the Accumulator bytes. It interchanges the low and high order nibbles of the Accumulator (bits 0-3 and bits 4-7)

    What is SCON ?

  • SCON is the serial port control register , which contains not only the mode selection bits (SM0 : SM2 ,REN), but also the 9th data bit for transmit and receive (TB8 and RB8) and the serial port interrupt bits (TI and RI).
  • SM0 : Serial port mode control bit 0
  • SM1 : Serial port mode control bit 1
  • SM2 : Serial port mode control bit 2
  • REN : Receiver enable control bit
  • TB8 : Transmit bit 8
  • RB8 : Receive bit 8
  • TI : Transmit Interrupt flag
  • RI : Receive interrupt flag

    How we calculate the Baud rate for serial port in mode 0 ?

    Baud Rate = Oscillator frequency/12

    What is the significance of TXD and RXD pins in 8051 ?

  • TXD : Transmit data pin for serial port in UART mode. Clock output in shift register mode.
  • RXD : Receive data pin for serial port in UART mode. Data I/O pin in shift register mode.

    Write two examples of Register indirect Addressing modes in 8051 ?

    MOV A,@R0 ; Load thecontents pointed by R0 in A.
    ADD A,@R1 ; Add thecontents of A and thecontents pointed by R1.

    What is Accumulator Register ?

    It is an 8 : bit register. It holds a source operand and receives the result of the arithmetic instructions (Addition, Subtraction, Multiplication and Division)

    Micro Controller Interview Questions - Part 1 >>>




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