GATE EC 2017 Set 1 — Question 45
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Digital Circuits → Computer Organization → Machine Instructions & Addressing
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Question
The following FIVE instructions were executed on an 8085 microprocessor.The Accumulator value immediately after the execution of the fifth instruction is
MVI A, 33H
MVI B, 78H
ADD B
CMA
ANI 32H
Correct answer
(B) 10H
Solution
Let's trace the execution of the 8085 microprocessor instructions:
A =
B =
A = A + B
A =
In decimal:
In hexadecimal:
A =
A =
Current A =
Complemented A =
A =
A = A AND
Current A =
Immediate data =
&
-------------
A =
1.
The Accumulator (A) is loaded with the immediate data MVI A, 33H (Move Immediate to Accumulator):33H.A =
33H (binary: 0011 0011)2.
Register B is loaded with the immediate data MVI B, 78H (Move Immediate to Register B):78H.B =
78H (binary: 0111 1000)3.
The content of Register B is added to the content of the Accumulator. The result is stored in the Accumulator.ADD B (Add Register B to Accumulator):A = A + B
A =
33H + 78HIn decimal:
In hexadecimal:
A =
ABH (binary: 1010 1011)4.
The content of the Accumulator is complemented (1's complement). Each bit is inverted.CMA (Complement Accumulator):A =
Current A =
1010 1011Complemented A =
0101 0100A =
54H (binary: 0101 0100)5.
The content of the Accumulator is logically ANDed with the immediate data ANI 32H (AND Immediate with Accumulator):32H. The result is stored in the Accumulator.A = A AND
32HCurrent A =
54H (binary: 0101 0100)Immediate data =
32H (binary: 0011 0010) Performing bitwise AND:0101 0100 (A)&
0011 0010 (32H)-------------
0001 0000 The result is 0001 0000 in binary, which is 10H in hexadecimal.A =
10HTherefore, the Accumulator value immediately after the execution of the fifth instruction is 10H.The final answer is Continue learning with Success Tracker
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