Short Question And Answer Microprocessor Set-11

1. What is data transfer instructions?
The data transfer instructions copy data from one source in to a destination without modifying the content of the source.

2. Give the flow chart symbols?
Rectangle: represents a process
Arrow: indicates the direction Represents a predefined process Represents beginning or end  Represents a decision making

3. What are the notations used in the 8085 instructions?
R = 8085 8-bit register
M=memory register
Rs = Register source
Rd = register destination
Rp = register pair

4. What is JNC 16-bit address?
It change the program sequence to the location specified by the 16-bit Address if the carry flag is reset

5. Give the instructions that perform the logical operations?

  • AND, OR, Exclusive-OR
  • Rotate
  • Compare
  • Complement

6. What is a three-byte instruction?
In a three-byte instruction, the first byte specifies the Opcode, and the following two bytes specifies the 16- bit address.

7. Define a program?
A program is a sequence of instructions written to tell the computer to perform a specific function.

8. Define ASCII code?
ASCII code is a 7-bit code that represents both decimal numbers, alphabets. Extended ASCII is an 8-bit code.

9. What is STA in data transfer instruction?
Copy the data from the accumulator in the memory location specified by the 16-bit address

10. What is an IN instruction?
This is a 2-byte instruction. It accepts data from the input port specified in the second byte.

12. What is an OUT instruction?
This is a 2-byte instruction. It sends the content of the accumulator to the output port specified in the second byte.

13. Give the difference between JZ and JNZ?
JZ change the program sequence to the location specified by the 16-bit address if the zero flag is set
JNZ change the program sequence to the location specified by the 16-bit address if the zero flag is reset.

14. What is CMA?
Complements the data in the accumulator.

15. What is CALL instruction?
CALL instruction change the sequence to the location of a subroutine.

16. How is the instruction set classified?
The instruction set is classified in three groups according to the word size:

  1. 1-byte instruction
  2. 2-byte instruction
  3. 3-byte instruction

17. Why the number of out ports in the peripheral-mapped I/O is restricted to 256
The number of output ports in the peripheral I/O is restricted to 256 ports because the operand of the OUT instruction is 8-bits; it can have only 256 combinations

18. If an input and output port can have the same 8-bit address how does the 8085
differentiate between the ports?
In The 8085 differentiates between the input and output ports of the same address by the control signal. The input port requires the RD and the output port requires the WR signal.

19. What are the control signals necessary in the memory mapped I/O?
RD, WR, I/O (low)

20. Why a latch is used for the output port and a tri-state buffer is used for the input
A latch is necessary to hold the output data for display. The input data byte is obtained by enabling a tri-state buffer and placed in the accumulator.