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Microprocessor Interview Questions and Answers
What is Program counter?
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 the cases
it gets incremented automatically one by one as the instruction bytes get
fetched. Also Program register keeps the address of the next instruction.
What is the RST for the
TRAP?
RST 4.5 is called as TRAP.
What are level-triggering
interrupt?
RST 6.5 & RST 5.5 are level-triggering interrupts.
Which interrupt is not
level-sensitive in 8085?
RST 7.5 is a raising edge-triggering interrupt.
What are Software
interrupts?
RST0, RST1, RST2, RST3, RST4, RST5, RST6, RST7.
What are the various flags
used in 8085?
Sign flag, Zero flag, Auxiliary flag, Parity flag, Carry flag.
In 8085 name the 16 bit
registers?
Stack pointer and Program counter all have 16 bits.
What is Stack Pointer?
Stack pointer is a special purpose 16-bit register in the Microprocessor, which
holds the address of the top of the stack.
What happens when HLT
instruction is executed in processor?
The Micro Processor enters into Halt-State and the buses are tri-stated.
What does Quality factor
mean?
The Quality factor is also defined, as Q. So it is a number, which reflects the
lossness of a circuit. Higher the Q, the lower are the losses.
How many interrupts are
there in 8085?
There are 12 interrupts in 8085.
What is Tri-state logic?
Three Logic Levels are used and they are High, Low, High impedance state. The
high and low are normal logic levels & high impedance state is electrical open
circuit conditions. Tri-state logic has a third line called enable line.
Which interrupt has the
highest priority?
TRAP has the highest priority
What are Hardware
interrupts?
TRAP, RST7.5, RST6.5, RST5.5, INTR
Can an RC circuit be used as
clock source for 8085?
Yes, it can be used, if an accurate clock frequency is not required. Also, the
component cost is low compared to LC or Crystal
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