AHDL BCD→binary conversion detail In an AHDL design of a BCD-to-binary converter, how is multiplication by 10 typically implemented efficiently at the logic level?

Introduction / Context:
BCD-to-binary converters often need to multiply intermediate values by 10 when building positional weights (tens, hundreds). In hardware description languages like AHDL, designers prefer structures that map to fast, small hardware rather than generic arithmetic that may infer larger multipliers.

Given Data / Assumptions:

• Target operation is multiply by 10.
• Implementation is in AHDL for synthesis to logic.
• Hardware efficiency is desired (few LUTs/gates, short delay).

Concept / Approach:

Multiplying by 10 can be decomposed into shifts and adds: 10 * X = (8 * X) + (2 * X) = (X << 3) + (X << 1). Shift operations are wiring (bit-reindexing) with essentially zero logic cost, and addition uses small carry chains. This approach avoids inferring a general-purpose multiplier, which would be overkill for constant-factor multiplies used in BCD conversion pipelines.

Step-by-Step Solution:

Verification / Alternative check:

Resource and timing reports from synthesis show fewer logic elements compared to a generic “* 10” operator (if that operator infers a multiplier). Simulation waveforms confirm functional equivalence for all input cases.

Why Other Options Are Wrong:

• Library multiplication function or explicit “*” operator: works functionally but may infer larger multiplier blocks, wasting area.
• Integer types: a data type choice, not a hardware technique; does not perform the multiplication itself.

Common Pitfalls:

• Forgetting to handle BCD digit carries properly when aggregating tens/hundreds.
• Neglecting bit growth after shifts; ensure adequate vector width.

Final Answer:

By using the shifting of bits