Assertion–Reason (8085 Microprocessor): The 8085 has an on-chip oscillator with an inbuilt crystal; therefore, a crystal oscillator is preferred for frequency stability.

Introduction / Context:
This assertion–reason item tests factual knowledge of the Intel 8085 microprocessor clocking scheme and the general principle of using crystal oscillators for frequency stability in digital systems and microcontrollers.

Given Data / Assumptions:

• Assertion (A): 8085 has an on-chip oscillator with an inbuilt crystal.
• Reason (R): Crystal oscillators are preferred for frequency stability.
• Understanding of 8085 clock pins X1 and X2 and the need for an external timing element.

Concept / Approach:
The Intel 8085 includes an on-chip clock generator/amplifier stage that requires an external crystal, ceramic resonator, or LC network connected to pins X1 and X2. The 8085 does not contain an 'inbuilt crystal' inside the chip package. Separately, it is a well-established fact that crystal oscillators provide superior frequency stability compared to RC oscillators, hence are generally preferred where timing accuracy matters.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets and standard texts show 8085 requires an external crystal (typically 6.144 MHz or similar) at X1/X2. The internal stage merely sustains oscillation; it does not house the crystal element.

Why Other Options Are Wrong:

Common Pitfalls:

Final Answer: