The contents of the flag register after execution of the following program by…
2015
The contents of the flag register after execution of the following program by 8085 microprocessor will be
Program
SUB A
MVI B,(01)H
DCR B
HLT
- A.
(54)H
- B.
(00)H
- C.
(01)H
- D.
(45)H
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Correct answer: A
The program execution proceeds as follows:
1. SUB A: The accumulator is subtracted from itself, resulting in 0. This sets the Zero (Z) flag to 1 and Parity (P) flag to 1. The Carry (CY) flag is reset to 0, and Sign (S) flag is 0.
2. MVI B, 01H: Loads the value 01H into register B. This instruction does not affect any flags.
3. DCR B: Decrements register B to 00H. In the 8085 microprocessor, DCR does not affect the flags.
4. HLT: Halts the processor.
Final Flag Status: S=0, Z=1, AC=1, P=1, CY=0. This corresponds to the hexadecimal value 54H.
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