8085 Microprocessor MCQ

101. How many times will the following loop be executed?

              LXI B, 0010 H
LOOP: DCX B
MOV A, B
ORA C
JNZ LOOP

Select the correct answer using the code given below:

1. 10
2. 100
3. 16
4. 15

102. Read the following assembly language program segment of the 8085 microprocessor:

LXIH, 2501 H

MOV A, L

ORI F0 H

MOV L, A

MOV A, H

ANI F0 H

MOV H, A

HLT

What are the contents of A, H and L registers after executing the above set of instructions in sequence?

1. Contents of A, H and L registers are 25, 20 and F1, respectively
2. Contents of A, H and L registers are 05, 25 and 01, respectively
3. Contents of A, H and L registers are 20, 20 and F1, respectively
4. Contents of A, H and L registers are 25, 05 and 01, respectively

103. On execution of the following segment 0f instructions in sequence

MVI A, 91H
XRI 91 H

Which one of the following is correct?

1. Content of accumulator is 00 H. Carry, Auxiliary Carry and Zero flag set to 0, 1 and 0, respectively.
2. Content of accumulator is 91 H. Carry, Auxiliary Carry and Zero flag set to 0, 0 and 1, respectively.
3. Content of accumulator is 00 H. Carry, Auxiliary Carry and Zero flag set to 0, 0 and 1, respectively.
4. Content of accumulator is 91 H. Carry, Auxiliary Carry and Zero flag set to 0, 1 and 0, respectively.

104. Consider the following statements:

1. Indirect addressing is not possible for mapped I/O port addresses
2. Pointers can not be used to access memory-mapped I/O addresses
3. Fewer machine instructions can be used with I/O mapped I/O addressing as compared to memory mapped I/O addressing
4. With an 8085 microprocessor, one can access at the most 512 devices with unique addresses using I/O mapped I/O addressing

Which of these statements are correct?

1. 1, 2 and 3
2. 2 and 4
3. 3 and 4
4. 1 and 3

105. The contents of memory locations 2000 H, 2001 H and 2002 H are AAH, BBH and CCH respectively. What are the contents of H and L registers after executing the following instructions in sequence?

LXI H, 2001 H
LHLD 2001 H

Select the correct answer using the codes given below:

1. Contents of H and L registers are 20 H and 01 H, respectively
2. Contents of H and L registers are AAH and BBH, respectively
3. Contents of H and L registers are BBH and CCH, respectively
4. Contents of H and L registers are CCH and BBH, respectively

106. The following sequences of instructions are executed by an 8085 microprocessor:

1000        LXI SP, 27FF
1003        CALL 1006
1006        POPH

What are the contents of the stack pointer (SP) and the HL register pair on completion of execution of these instructions?

1. SP = 27 FF, HL = 1003
2. SP = 27 FD, HL = 1003
3. SP = 27 FF, HL = 1006
4. SP = 27 FD, HL = 1006

107. INR instruction of 8085 does not affect carry flag. Which of the following is correct about INR instruction?

1. Overflow cannot be detected
2. Overflow can be detected
3. If a programme requires overflow to be detected, ADD instruction should be used instead of INR
4. It can be used to increase the contents of the BC register pair

108. Consider the following 8085 instructions:

ANA A, ORA A, XRA A, SUB A, CMP A.

Now, consider the following statements:

1. All are arithmetic and logic instructions
2. All cause the accumulator to be cleared irrespective of its original contents
3. All reset the carry flag
4. All of them are 1-byte instructions

Which of these statements is/are correct?

1. 1, 2, 3 and 4
2. 2 only
3. 1, 2 and 4
4. 1,3 and 4

109. Consider the program given below, which transfer a block of data from one place in memory to another:

       MVI C, 0B H

       LXI H, 2400 H

       LXI D, 3400 H

L1: MOV A, M

       STAX D

       INR L

       INR E

       DCR C

       JNZ L1

What is the total number of memory accesses (including instruction fetches) carried out?

1. 118
2. 140
3. 98
4. 108

110. Consider the following statements about register indirect addressing:

1. It helps in writing code that executes faster
2. It helps in writing compact code
3. It allows reuse of memory CPU data transfer instruction
4. It is essential for stack operations

Which of these statements are correct?

1. 1, 3 and 4
2. 1, 2 and 4
3. 2,3 and 4
4. 1,2 and 3