8051 reset input — which active-HIGH pin resets the microcontroller when driven HIGH for a proper pulse width? Select the correct pin name used to reset a standard 8051.

Introduction / Context:
Knowing the hardware reset pin is fundamental for designing power-on reset, manual reset buttons, and watchdog circuits. The 8051 uses a dedicated active-HIGH reset input pin with a defined minimum pulse width requirement.

Given Data / Assumptions:

• Classic 8051 pinout nomenclature
• Active-HIGH reset behavior
• Separate control pins exist for PSEN, EA, ALE, etc.

Concept / Approach:
The standardized name of the reset pin on an 8051 is RST. Driving RST HIGH for at least the specified duration (while oscillator is running) resets the CPU, clears certain SFRs to default, and restarts execution at the reset vector 0000H.

Step-by-Step Solution:

Verification / Alternative check:
Vendor datasheets consistently label the pin as RST. PSEN is Program Store Enable (for external code fetch), not reset. EA selects internal/external code fetch.

Why Other Options Are Wrong:

• RESET/RSET: common informal names, but not the official 8051 pin label.
• PSEN: code memory read strobe, not reset.
• EA: external access select, not reset.

Common Pitfalls:

• Assuming RESET text on schematics maps 1:1 to 8051 pin names; always check the datasheet label.

Final Answer:
RST