For interfacing an Intel 8086 microprocessor to a 16-bit Analog-to-Digital Converter (ADC), which peripheral interface chip is most appropriate?

Introduction:
Interfacing an 8086 with an external 16-bit ADC requires general-purpose parallel I/O lines to read conversion results and control the ADC (start/End-of-Conversion). This question tests knowledge of standard Intel 82xx peripherals.

Given Data / Assumptions:

• CPU: 8086 (16-bit).
• Peripheral: 16-bit ADC (parallel data output assumed).
• Candidate devices: 8259 (PIC), 8255 (PPI), 8253 (timer), 8251 (USART).

Concept / Approach:

The 8255 Programmable Peripheral Interface provides three 8-bit ports configurable for input/output strobes. It is commonly used to interface digital sensors/ADCs/DACs by mapping data lines and control signals to its ports. By contrast, the 8259 handles interrupts, the 8253 provides timers/counters, and the 8251 is for serial communication – none of which directly provide the parallel I/O needed to read a 16-bit ADC bus (two ports can be combined for 16 bits).

Step-by-Step Solution:

Verification / Alternative check:

Textbook interfacing examples pair 8255 with ADC/DAC devices for parallel data transfer.

Why Other Options Are Wrong:

8259 – interrupt controller; 8253 – timing only; 8251 – serial I/O; none directly supply the needed parallel ports.

Common Pitfalls:

Confusing the role of timers/interrupts with data-path I/O; overlooking the need to read two 8-bit halves for a 16-bit word.

Final Answer:

8255