In 8085 microprocessor, assume the accumulator contains AAH and CY = 0. How many times the instruction RAL must be executed so that the accumulator reads A9H. What will be the CY bit reading at that instant?

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  1. 4 times; CY = 1
  2. 2 times; CY = 0
  3. 4 times; CY = 0
  4. 2 times; CY = 1

Answer (Detailed Solution Below)

Option 2 : 2 times; CY = 0
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RAL instruction

F1 Engineering Mrunal 13.03.2023 D38

In the 8085 Instruction set, there is a mnemonic RAL, which stands for Rotate Accumulator Left and involves the Carry flag in rotation.

In this operation, the bit which is coming out from the most significant place will be copied to the Carry flag bit and the previous carry bit will be moved to the least significant bit place of the accumulator.

Explanation

Given, AA H = 1010 1010

and CY = 0

0 1010 1010

On the first operation of the RAL command, the output, and CY flag is

1 0101 0100 

0101 0100 = 54 H 

and CY = 1

On the second operation of the RAL command, the output, and CY flag is

0 1010 1001

1010 1001 = A9 H

and CY = 0

So, the correct answer is option 2.

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