HDL design focus for multiplexers and demultiplexers In hardware description languages such as VHDL or Verilog, what is the key issue when designing MUX and DEMUX blocks?

Introduction / Context:
Writing synthesizable HDL for data routing primitives like multiplexers (MUX) and demultiplexers (DEMUX) relies on correctly expressing conditional data movement. This ensures that tools infer efficient logic consistent with the intended selection behavior.

Given Data / Assumptions:

• Target: generic MUX/DEMUX in HDL.
• We care about the central design concern that yields correct inference in synthesis.

Concept / Approach:
Both MUX and DEMUX are fundamentally conditional assignments. A MUX selects one of many inputs to drive a single output based on select lines; a DEMUX routes one input to one of many outputs. In HDL, this is captured by conditional signal assignments (if/else or case) that map select values to the proper data path with defined defaults to avoid latches.

Step-by-Step Solution:

Verification / Alternative check:
Synthesis reports should show inferred multiplexers (e.g., LUT-based mux trees) or demultiplexing gates without latches. Simulation waveforms must match truth tables.

Why Other Options Are Wrong:

• Library availability: Helpful but not the core design issue.
• Using case specifically: One way, but if/else works equally well; the key is the conditional assignment itself.
• Describing the functions: Too vague; the actionable requirement is conditional assignments tied to select inputs.

Common Pitfalls:

• Leaving out a default branch, causing latch inference.
• Mixing blocking/non-blocking assignments incorrectly in Verilog when clocked logic is added later.

Final Answer:
Assigning signals under certain conditions.