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1. In AVR micro controllers, ADD instruction affects the status of which of the following bits of a status register?
a) Z
b) C
c) N
d) All of the mentioned

Answer: d [Reason:] ADD instruction affects the status of Z, C, N, V, H and S bits of a status register.

2. ADC instruction is used for?
a) addition of two 16 bit numbers
b) analog to digital conversion
c) automatic digital control
d) none of the mentioned

Answer: a [Reason:] ADC instruction can be used for addition of two 16 bit numbers as here two 8 bit numbers are added simultaneously along with the carry coming from the previous 8 bits. So it can be used for the addition of two 16 bit numbers.

3. AVR supports which of the following mentioned subtraction instructions?
a) SUB
b) SBC
c) SBI
d) All of the mentioned

Answer: d [Reason:] AVR supports five types of subtraction instructions. They are SUB, SBC, SBI, SBCI, SBIW.

4. What steps are involved when we subtract two numbers present at two different locations?
a) take the two’s complement of the subtrahend
b) add it to the minuend
c) invert the carry
d) all of the mentioned

Answer: d [Reason:] When we need to subtract two numbers present at two different locations then firstly we need to take the 2’s complement of the subtrahend, then we add it with the minuend and then when we invert the carry then the complete procedure of the subtraction is completed.

5. In executing subtraction based instructions, state the role of the C flag?
a) if C=1, the result is negative
b) if C=1, the result is positive
c) none of the mentioned
d) all of the mentioned

Answer: a [Reason:] If the C flag comes out to be 1, then the result is assumed to be negative and vice versa.

6. Which of the following is correct about the MUL instruction?
a) it is a byte-by- byte multiplication instruction
b) the product is stored in two registers R1 and R0
c) both of the mentioned
d) none of the mentioned

Answer: c [Reason:] MUL instruction is a byte-by-byte multiplication instruction whose result is stored in two registers R1 and R0.

7. In AVR, when is the V flag set?
a) their is a carry from D7 bit
b) their is a carry from D6 to D7 bit
c) both of the mentioned
d) any of the mentioned

Answer: d [Reason:] V(overflow flag) is set in an AVR based micro controller if their is a carry from the D7 bit of the operation or their is a carry from D6 to D7 bit of the operation.

8. To set the bits of a register R1 to 1, we must OR the contents of the register with?
a) 00H
b) 11H
c) FFH
d) 0FH

Answer: c [Reason:] To make the contents of the register R1 to 1 we must OR the contents of that register with FFH because according to Or algorithm 0+1=1 and 1+0=1.

9. CP instruction alters the value of the register?
a) true
b) false
c) none of the mentioned
d) can’t be said

Answer: b [Reason:] CP command is used to compare the contents of the two registers. It doesn’t actually alters the value of the register.

10. What is right about the ROR instruction?
a) it rotates the contents of the register left to right
b) it rotates the contents of the register from right to left
c) it rotates the contents of the register from left to right through carry
d) it rotates the contents of the register from right to left through carry