AHDL BCD-to-binary converter design – in hardware description terms, when converting a multi-digit BCD value to its equivalent pure binary, is the multiplication-by-10 step implemented directly using the language’s arithmetic capability, i.e., by using a multiplication operator, or by some other construct?

Introduction / Context:
When building a Binary Coded Decimal (BCD) to pure binary converter in a hardware description language such as AHDL, a common subtask is multiplying an accumulated result by 10 as you process each new BCD digit. This question probes whether that “times ten” operation is typically realized using the language’s arithmetic operator, or whether it relies on shifts, special library calls, or type declarations.

Given Data / Assumptions:

• Source format: BCD digits, usually groups of 4 bits per decimal digit.
• Target format: unsigned binary integer able to hold the full decimal value.
• Design context: synthesizable AHDL targeting PLDs/CPLDs/FPGAs.
• Arithmetic is permitted in the HDL and mapped to hardware by synthesis.

Concept / Approach:
The textbook algorithm for multi-digit conversion iterates through digits and applies result = result * 10 + next_digit. In an HDL, “*” denotes multiplication. Synthesis tools infer the required hardware: either LUT-based multipliers or dedicated DSP blocks. While shifts and adds can also realize *10 via (x << 3) + (x << 1), the direct, intention-revealing way is to use the multiplication operator and allow the tool to optimize the precise implementation.

Step-by-Step Solution:

Verification / Alternative check:
Implementations using (x << 3) + (x << 1) are mathematically equivalent to *10 and may save resources on very small devices, but they are optional micro-optimizations. The presence of “*” remains the canonical language feature for multiplication.

Why Other Options Are Wrong:
“Shifting bits” is a technique, not the primary language construct. “A library function” is unnecessary for simple scaling. “A variable type” cannot perform arithmetic. “A clock enable signal” controls timing, not math operations.

Common Pitfalls:
Forgetting to size the accumulator wide enough; omitting unsigned/signed intent; assuming multiplication cannot be synthesized (modern tools support it well).

Final Answer:
a multiplication operator