Decoder used as a demultiplexer — control and data roles How can a standard decoder be used to implement a demultiplexer (DeMUX)? Choose the correct wiring approach.

Introduction / Context:
Decoders and demultiplexers are closely related. A decoder activates exactly one of many outputs based on a binary select value. A demultiplexer routes a single data input to one of several outputs based on the same kind of select value. Understanding this relationship lets you repurpose readily available decoder ICs as DeMUXes with minimal wiring changes.

Given Data / Assumptions:

• Decoder has n select inputs and 2^n outputs plus an enable.
• Demultiplexer needs n select inputs, one data input, and 2^n outputs.
• We can drive the decoder’s enable with data.

Concept / Approach:
To emulate a DeMUX, connect the binary selection lines to the decoder’s address inputs. Feed the DeMUX data signal into the decoder’s enable (or strobe) so that only the selected output reflects the data signal’s active level. The other outputs remain inactive, just as in a native DeMUX IC.

Step-by-Step Solution:

Verification / Alternative check:
Compare truth tables: with enable driven by data, the decoder energizes only the addressed output, exactly matching demultiplexing.

Why Other Options Are Wrong:

• Tying select lines HIGH or LOW ignores selection; you would get a fixed output line only.
• Tying enable LOW (or fixed) prevents data-controlled routing.

Common Pitfalls:
Forgetting that many decoders have active-LOW enables and outputs; ensure polarity matches the data signal level or add inversion as needed.

Final Answer:
using the input lines for data selection and an enable line for data input