Encoder vs. decoder fundamentals How does an encoder differ from a decoder in digital systems?

Introduction / Context:
Encoders and decoders are complementary combinational circuits widely used in selection, addressing, and display systems. Being able to state their core function succinctly is key to choosing the correct device for a given signal-routing or code-translation task.

Given Data / Assumptions:

• An N-to-n encoder maps a 1-of-N active input into an n-bit code, typically with n = log2(N).
• An n-to-2^n decoder maps an n-bit binary input to one active output line among 2^n outputs.
• Some devices include enable inputs and priority handling but their basic roles remain as above.

Concept / Approach:
An encoder compresses the identity of one active line among many into a compact binary word. Conversely, a decoder expands a binary word into a single asserted output among many. Remember: encoder = many-to-few (coding), decoder = few-to-many (selection).

Step-by-Step Solution:

Verification / Alternative check:
Truth tables in datasheets confirm the many-to-few vs few-to-many roles. Simulation of simple cases (e.g., I5 HIGH on an encoder) yields output 101 for Y2..Y0.

Why Other Options Are Wrong:

• Decoder outputs a binary code (B): Backwards—decoders expand, encoders compress.
• Decoder compresses an n-bit word (C): Also backwards.
• Encoder drives all outputs HIGH on invalid inputs (D): Not generally true; behavior depends on device (some assert a validity or priority output instead).

Common Pitfalls:
Confusing enable polarity or priority behavior with the fundamental translation direction; mixing up tri-state output multiplexers with decoders.

Final Answer:
The output of an encoder is a binary code for 1-of-N input.