Question

How are the bits of the register PSW affected if we select Bank-2 of 8051?

• A. PSW-5=0 and PSW-4=1
• B. PSW-2=0 and PSW-3=1
• C. PSW-3=1 and PSW-4=1
• D. PSW-3=0 and PSW-4=1

Hint:

Bank selection = RS1 RS0 → (PSW-4, PSW-3).

Answer 1

The Correct Option is D

Concept: In 8051, register banks are selected using PSW bits RS1 and RS0.

Step 1: PSW bits for bank selection \[ \text{RS1} = \text{PSW-4}, \quad \text{RS0} = \text{PSW-3} \]

Step 2: Bank selection table

• Bank 0 → RS1=0, RS0=0

• Bank 1 → RS1=0, RS0=1

• Bank 2 → RS1=1, RS0=0

• Bank 3 → RS1=1, RS0=1

Step 3: For Bank-2 \[ RS1 = 1,\quad RS0 = 0 \]

Step 4: Map to PSW bits \[ PSW-4 = 1,\quad PSW-3 = 0 \]

Step 5: Conclusion \[ \boxed{PSW-3 = 0 \text{ and } PSW-4 = 1} \]

Final Answer: \[ \boxed{(D)} \]