8085 Microprocessor Questions
8085 Microprocessor Questions
1. What are the various
registers in 8085?
Answer- Accumulator register, Temporary register,
Instruction register, Stack Pointer, Program Counter are the various registers
in 8085.
2. In 8085 name the 16-bit
registers?
Answer- Stack pointer and Program counter all have 16
bits.
3. What are the various
flags used in 8085?
Answer- Sign flag, Zero flag, Auxiliary flag, Parity
flag, Carry flag.
4. What is Stack Pointer?
Answer- Stack pointer is a special purpose 16-bit
register in the Microprocessor, which holds the address of the top of the
stack.
5. What is a Program counter?
Answer- Program counter holds the address of either
the first byte of the next instruction to be fetched for execution or the
address of the next byte of a multi-byte instruction, which has not been
completely fetched. In both cases, it gets incremented automatically one by
one as the instruction bytes get fetched. Also Program register keeps the
address of the next instruction.
6. Which Stack is used in
8085?
Answer- LIFO (Last in First Out) stack is used in
8085. In this type of Stack the last stored information can be retrieved first.
7. What happens when HLT
instruction is executed in the processor?
Answer- The Micro Processor enters into Halt-State and
the buses are tri-stated.
8. What is meant by a bus?
Answer- A bus is a group of conducting lines that carrier’s
data, address, & control signals.
9. What is Tri-state logic?
Answer- Three Logic Levels are used and they are High,
Low, High impedance state. The high and low are normal logic levels & the high
impedance state is electrical open circuit conditions. Tri-state logic has a
third line called enable line.
10. Give an example of one
address microprocessor?
Answer- 8085 is a one address microprocessor.
11. In what way interrupts
are classified in 8085?
Answer- In 8085 the interrupts are classified as
Hardware and Software interrupts.
12. What is Hardware
interrupts?
Answer- TRAP, RST7.5, RST6.5, RST5.5, INTR.
13. What is Software
interrupts?
Answer- RST0, RST1, RST2, RST3, RST4, RST5, RST6,
RST7.
14. Which interrupt has the
highest priority?
Answer- TRAP has the highest priority.
15. Name 5 different
addressing modes?
Answer- Immediate, Direct, Register, Register
indirect, Implied addressing modes.
16. How many interrupts are
there in 8085?
Answer- There are 12 interrupts in 8085.
17. What is the clock frequency
for 8085?
Answer- 3 MHz is the maximum clock frequency for 8085.
18. What is the RST for the
TRAP?
Answer- RST 4.5 is called TRAP.
19. In 8085 which is called
a High order / Low order Register?
Answer- Flag is called as Low order register &
Accumulator is called as High order Register.
20. What are input &
output devices?
Answer- Keyboards, Floppy disks are examples of
input devices. The printer, LED / LCD display, CRT Monitor are examples of
output devices.
21. Can an RC circuit be
used as the clock source for 8085?
Answer- Yes, it can be used; if an accurate clock
frequency is not required. Also, the component cost is low compared to LC or
Crystal.
22. Why crystal is a
preferred clock source?
Answer- Because of high stability, large Q (Quality
Factor) & the frequency that doesn’t drift with aging. Crystal is used as a
clock source most of the time.
23. Which interrupt is not
level-sensitive in 8085?
Answer- RST 7.5 is a raising edge-triggering
interrupt.
24. What does the Quality factor
mean?
Answer- - The Quality factor is also defined, as Q. So
it is a number, which reflects the lossless of a circuit. The higher the Q, the
lower are the losses.
25. What are
level-triggering interrupts?
Answer- - RST 6.5 & RST 5.5 are level-triggering
interrupts.
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