Question

Consider the following flags of 8085 affected by the instruction SUB B: A. Sign flag B. Carry flag C. Zero flag D. Parity flag

• A. A, B, C and D
• B. A, B and C only
• C. B and D only
• D. C and D only

Hint:

Arithmetic instructions affect all flags in 8085.

Answer 1

The Correct Option is A

Concept: SUB instruction in 8085 affects all condition flags.

Step 1: Sign flag Indicates MSB of result. \[ \Rightarrow \text{Affected} \]

Step 2: Carry flag Indicates borrow in subtraction. \[ \Rightarrow \text{Affected} \]

Step 3: Zero flag Set if result is zero. \[ \Rightarrow \text{Affected} \]

Step 4: Parity flag Depends on number of 1s. \[ \Rightarrow \text{Affected} \] \[ \therefore \text{All flags affected} \]