8051 clock input pins Pins XTAL1 and XTAL2 of the 8051 are used to connect an external crystal or oscillator source. Choose the correct statement.

Introduction / Context:
The system clock determines instruction timing for 8051 microcontrollers. Classic 8051 devices provide two pins, XTAL1 and XTAL2, to interface with a crystal resonator or an external clock source. Properly understanding these pins is essential for board level hardware design and reliable timing.

Given Data / Assumptions:

• Standard 8051 pinout with XTAL1 and XTAL2 dedicated to the oscillator network.
• External components may include a crystal and load capacitors or a clock module.
• Reset and GPIO functions are on other pins, not on XTAL1 or XTAL2.

Concept / Approach:

XTAL1 is typically the input to the internal inverting amplifier, and XTAL2 is the output. A crystal connected across XTAL1 and XTAL2 with capacitors to ground can sustain oscillation. Alternatively, a single ended external clock can be injected on XTAL1 according to the device data sheet.

Step-by-Step Solution:

Verification / Alternative check:

Oscilloscope measurements at XTAL2 show oscillation when configured with a crystal. Serial communication accuracy also verifies proper clocking.

Why Other Options Are Wrong:

False: contradicts the standard 8051 design.

XTAL1 only for GPIO: incorrect; these pins serve the oscillator function.

XTAL2 as reset: reset is on a separate pin named RST.

Common Pitfalls:

Using incorrect load capacitors, long traces causing startup issues, and injecting clock levels that violate input requirements.

Final Answer:

True