Short Question And Answer Microprocessor Set-10

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1. List the addressing modes of 8051?

  • Direct addressing
  • Register addressing
  • Register indirect addressing.
  • Implicit addressing
  • Immediate addressing
  • Index addressing
  • Bit addressing

2. Write about CALL statement in 8051?
There are two subroutine CALL instructions. They are

  1. LCALL (Long CALL)
  2. ACALL (Absolute CALL)

Each increments the PC to the 1st byte of the instruction & pushes them in to the stack.

3. Write about the jump statement?
There are three forms of jump. They are LJMP (Long jump)-address 16 AJMP (Absolute Jump)- address 11 SJMP (Short Jump)-relative address

4. Write program to load accumulator, DPH, &DPL using 8051?
MOV A, #30
MOV DPH, A
MOV DPL, A

5. Write a program to find the 2’s complement using 8051?
MOV A, R0
CPL A
INC A

6. Write a program to subtract the contents of R1 of Bank0 from the contents of R0 of Bank2.
MOV PSW, #10
MOV A, R0
MOV PSW, #00
SUBB A, R1

7. Write a program to add 2 8-bit numbers using 8051?
MOV A,#30H
ADD A, #50H

8. Explain the 16-bit registers DPTR and SP of 8051.
DPTR: DPTR stands for data pointer. DPTR consists of a high byte (DPH) and a low byte (DPL). Its function is to hold a 16-bit address. It may be manipulated as a 16-bit data register or as two independent 8-bit registers. It serves as a base register in indirect jumps, lookup table instructions and external data transfer.SP: SP stands for stack pointer. SP is a 8- bit wide register. It is incremented before data is stored during PUSH and CALL instructions. The stack array can reside anywhere in onchip RAM. The stack pointer is initialized to 07H after a reset. This causes the stack to begin at location 08H.

9. What is mean by microcontroller?
A device which contains the microprocessor with integrated peripherals like memory, serial ports,
parallel ports, timer/counter, interrupt controller, data acquisition interfaces like ADC, DAC is called
microcontroller.

10. Explain DJNZ instructions of Intel 8051 microcontroller?
a) DJNZ Rn, rel Decrement the content of the register Rn and jump if not zero.
b) DJNZ direct, rel Decrement the content of direct 8-bit address and jump if not zero.

11. What is the function of NEU?
The numeric execution unit executes all the instructions including arithmetic, logical transcendental, and data transfer instructions. The numeric execution unit executes all the numeric processor instructions while the control unit (CU) receives, decodes instructions, reads and writes memory operands and executes the 8087 control instructions.

12. Give the disadvantages of bus window technique?
The numeric execution unit executes all the instructions including arithmetic, logical transcendental, and data transfer instructions. The numeric execution unit executes all the numeric processor instructions while the control unit (CU) receives, decodes instructions, reads and writes memory operands and executes the 8087 control instructions.

13. What is swapping out?
A portion of the program or important partial results required for further execution may e saved back on
secondary storage to make the physical memory free for further execution of another required portion
of the program. This is called ‘swapping out’ of the executable program.

14. Name the five interrupt sources of 8051.
External hardware interrupt 0 (INT 0), External hardware interrupt 1 (INT 1), Timer 0 interrupt (TF0),
timer 1 interrupt (TF1) and serial communication interrupt (R1 & T1).

15. What is baud rate in 8051?
The Baud Rate is determined based on the oscillator’s frequency when in mode 0 and 2. In mode 0, the baud rate is always the oscillator frequency divided by 12. This means if you’re crystal is 11.059Mhz, mode 0 baud rate will always be 921,583 baud. In mode 2 the baud rate is always the oscillator frequency divided by 64, so a 11.059Mhz crystal speed will yield a baud rate of 172,797.

16. Define microcomputer?
A computer that is designed using a microprocessor as its CPU. It includes microprocessor, memory and I/O.

17. Define ROM?
A memory that stores binary information permanently. The information can be read from this memory but cannot be altered.

19. What is an ALU?
The group of circuit that provides timing and signals to all operation in the computer and controls data flow.

20. What are the four primary operations of a MPU?
1. Memory read
2. Memory write
3. I/O read
4. I/O write