8051 external memory capacity: “Up to 65K bytes of external code memory and 65K bytes of external data memory can be added to any 8051 family member.” Assess the statement.

Introduction / Context:
The 8051 architecture supports separate program (code) and external data address spaces, each conventionally 64 KB (65536 bytes). Understanding this separation is essential when interfacing ROM/Flash and RAM to the microcontroller.

Given Data / Assumptions:

• Program space: addressed via PSEN and the code fetch bus.
• External data space: addressed via MOVX instructions.
• Address width: 16 bits for each space → 0x0000 to 0xFFFF.

Concept / Approach:
Because the 8051 uses separate control strobes and instructions for code fetch (PSEN) versus external data (MOVX with RD/WR), the two spaces can each be expanded to the full 64 KB dictated by 16-bit addressing. Internally, ports P0 and P2 provide the multiplexed address/data bus (AD0–AD7) and high address lines (A8–A15).

Step-by-Step Solution:

Verification / Alternative check:
Reference hardware designs: 8031 (ROMless 8051) routinely pairs with 64 KB EPROM/Flash for code and separate 32–64 KB SRAM for data, demonstrating independent expansion limits.

Why Other Options Are Wrong:

• Incorrect / conditional options: Limit capacity unnecessarily; the constraint is 16-bit address width and bus multiplexing, not device variant (most share the same bus scheme).

Common Pitfalls:
Confusing internal data memory (128 or 256 bytes) with external data memory; assuming shared unified memory instead of Harvard-like separation in the MCS-51 architecture.

Final Answer:
Correct