Keypad HDL encoder data path: The output data bus represents a 4-bit code for the pressed key, formed by combining the row and column information produced by the scanning encoder. Evaluate this description.

Introduction / Context:Matrix keypads interface naturally to digital logic by scanning rows and columns. The intersection of an active row and a detected column is mapped to a key code. Many designs present this as a 4-bit output suitable for numeric or hexadecimal keypads.

Given Data / Assumptions:

• A ring counter or sequencer asserts one row/column at a time.
• Sense lines read back the column/row that closed via the pressed key.
• An encoder maps the row/column pair into a single 4-bit code.

Concept / Approach:The encoder performs combinational mapping: for a given row_i and col_j detection, it outputs a constant 4-bit value representing key i,j. Debounce logic ensures stable capture; a data-ready or valid signal can flag that the 4-bit code is meaningful.

Step-by-Step Solution:Scan rows/columns via sequencer.Detect active intersection when a key shorts a row to a column.Feed row/column lines to a priority encoder or LUT that outputs a 4-bit code.Latch code and assert data-valid; release on key-up and resume scanning.

Verification / Alternative check:Simulation shows deterministic mapping from (row,col) to the 4-bit code; hardware testing confirms correct values on the data bus for each key.

Why Other Options Are Wrong:It is not limited to hexadecimal layouts; any 4-bit mapping is possible. Analog multiplexers are unnecessary for pure digital scanning. Gray code is optional; most keypads use straightforward binary/BCD coding.

Common Pitfalls:Ghosting without diodes in multi-key press scenarios; inadequate debounce; mismatched row/column mapping tables.

Final Answer:Correct