NPTEL Digital Circuits Week 11 Assignment Answers 2024

1. How many flags are there in 8085 microprocessors?

a) 3
b) 5
c) 7
d) 6

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2. The clock frequency of an 8085 microprocessor is 5 MHz. If the time required to execute an instruction is 1.6 us, then the number of T-states needed for executing the instruction is

a) 1
b) 6
c) 7
d) 8

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3. Which of the following is not a valid 8085 instruction?

a) LDAX B
b) LDAX H
c) LDAX D
d) INRM

Answer :-

4. What is the accumulator content after the execution of following instructions?

MVI A, 55h
RLC
RLC
RLC

a) 55h
b) AAh
c) A8h
d) 8Ah

Answer :-

5. What will happened to the contents of the stack pointer (SP) in 8085 after a PUSH instruction is executed?

a) The contents of stack pointer incremented by 2
b) The contents of stack pointer decremented by 2
c) The contents of stack pointer incremented by 1
d) The contents of stack pointer decremented by 1

Answer :-

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7. The contents of a register (B) and accumulator (A) of 8085 microprocessor are 49H and 3AH respectively. The contents of A and the status of carry flag (CY) and sign flag (S) after executing SUB B instruction are

a) A = F1, CY = 1, S = 1
b) A = 0F. CY = 1, S = 1
c) A = F0, CY = 0, S = 0
d) A = 1F. CY = 1, S = 1

Answer :-

8. What is the content of the accumulator after the execution of the program? (Assume 8085 flag register is initially reset).

MVI A, F2h
RRC
MOV B. A
RAL
RAL
ADD B
RAR

a) AEh
b) 2Eh
c) 5Dh
d) 2Ch

Answer :-

9. An 8085 executes the following instructions
2710 LXI H, 1234h
2713 DAD H
2714 PCHL
All the addresses and constants are in hexa decimal. Let PC be the contents of the program
counter and HL be the contents of HL register pair just after executing PCHL. Which of the following statements is correct?

a) PC = 2715H and HL = 2468H
b) PC = 1234H and HL = 2715H
c) PC = 2468H and HL = 2468H
d) PC = 2668H and HL = 2715H

Answer :-

10. What are the contents of accumulator after the following program executed?

LXI B, 0400 H
LOOP: DCR B
MOV A, C
ORA B
JNZ LOOP

а) 01Н
b) 02H
с) 03Н
d) 00H

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11. Which of the following register is NOT a general purpose register?

a) B
b) C
c) D
d) A

Answer :-

12. The Accumulator contains OFBh and B contains 12h. What are the contents of A and B after the given instruction is executed?

ORA B
a) A = 10h, B = 0Dh
b) A = 0FBh, B = 12h
c) A = 12h, B = 0FBh
d) A = 13h. B = 16h

Answer :-

13. In an 8085 processor, suppose the accumulator content is OFH and the carry flag is 0. What will be the content of the accumulator after RAR and RRC instructions?

A) Both cases contents of accumulator is 87H
B) Both cased contents of accumulator is 07H
C) RAR —> 07H, RRC —> 87H
D) RAR →> 87H, RRC —> 07H