Q. What is the time taken by one machine cycle if crystal frequency is 20MHz?

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Q. Find the number of times the following loop will be executed

MOV R6,#200
BACK:MOV R5,#100
HERE:DJNZ R5, HERE
DJNZ R6,BACK
END

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Q. What is the meaning of the instruction MOV A,05H ?

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Q. Does the two instructions mean the same?
1) BACK: DEC R0

JZ BACK

2) BACK: DJNZ RO, BACK

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Q. To initialise any port as an output port what value is to be given to it?

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Q. Which out of the four ports of 8051 needs a pull-up resistor for using it is as an input or an output port?

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Q. Which of the ports act as the 16 bit address lines for transferring data through it?

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Q. Which of the following registers are not bit addressable?

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Q. Which instruction is used to check the status of a single bit?

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Q. Which addressing mode is used in pushing or popping any element on or from the stack?

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Q. Which operator is the most important while assigning any instruction as register indirect instruction?

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Q. What is the advantage of register indirect addressing mode?

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Q. Which of the following comes under indexed addressing mode?

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Q. Is this a valid statement ?
SETB A

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Q. When we add two numbers the destination address must always be.

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Q. DAA command adds 6 to the nibble if:

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Q. If SUBB A,R4 is executed, then actually what operation is being applied?

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Q. A valid division instruction always makes:

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Q. In 8 bit signed number operations, OV flag is set to 1 if:

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Q. In unsigned number addition, status of which bit is important?

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