8031 vs. 8051 — key architectural difference Which statement correctly distinguishes the 8031 from the 8051?

Introduction / Context:
The 8031 and 8051 are closely related; however, one is intended for systems with external program memory while the other includes on-chip program ROM. Recognizing this difference helps when selecting parts for cost or board-space constraints.

Given Data / Assumptions:

• Baseline Intel 8051 family definitions.
• 8031 and 8051 share CPU core, timers, serial port, and interrupts.
• Difference centers on on-chip program memory.

Concept / Approach:
The classic 8051 contains on-chip program ROM (originally mask ROM, later flash in derivatives). The 8031 is the ROM-less counterpart, requiring external program memory connected to the PSEN, ALE, and Port 0/Port 2 buses.

Step-by-Step Solution:

Verification / Alternative check:
Any standard pinout diagram shows the 8031 using external program memory signals; 8051 can also use external program memory but additionally includes internal ROM.

Why Other Options Are Wrong:

• No interrupts: incorrect; 8031 has interrupts.
• The 8051 is ROM-less: opposite of the truth.
• Extra 64 bytes claim: not the key differentiator between these part numbers.

Common Pitfalls:
Confusing RAM size differences in derivatives with the presence/absence of on-chip program memory.

Final Answer:
The 8031 is ROM-less.