Interfacing parallel data to serial equipment Which device is commonly used to convert between a system’s parallel data format and an external serial format?

Introduction / Context:
Many microprocessors and microcontrollers natively handle parallel data on internal buses, but external links (RS-232/TTL serial, UART-over-USB bridges, etc.) are serial. A specialized interface converts between these formats reliably and with timing control.

Given Data / Assumptions:

• Parallel data inside the host system (e.g., CPU bus or memory-mapped I/O).
• Serial link to external equipment (asynchronous serial).
• Need framing, start/stop bits, optional parity, and baud-rate generation.

Concept / Approach:
A UART is designed to serialize parallel bytes into asynchronous serial frames and to deserialize incoming serial frames into parallel bytes. It handles timing via baud-rate generators and often provides buffers/FIFOs for reliable data transfer.

Step-by-Step Solution:
Identify requirement: parallel-to-serial and serial-to-parallel conversion for asynchronous links.Select device class providing framing and baud control: UART.Therefore, the correct interface choice is a UART.

Verification / Alternative check:
Microcontroller datasheets list on-chip UARTs explicitly for serial communication. External bridge ICs (e.g., USB-UART) use the same concept, confirming the role of UARTs in parallel/serial interfacing.

Why Other Options Are Wrong:

• Key matrix: Input scanning hardware, not a serial interface.
• Memory chip: Storage, not a parallel/serial conversion interface.
• Series-in, parallel-out register: Converts serial to parallel but lacks framing/baud control and reverse direction.

Common Pitfalls:

• Confusing simple shift registers with full serial communication interfaces; shift registers do not manage asynchronous framing or baud rates.
• Overlooking the need for parity, start, and stop bits in many serial protocols.

Final Answer:
UART (Universal Asynchronous Receiver/Transmitter)