VHDL storage semantics: Evaluate the claim “When we want to remember a value in VHDL, it must be stored in a VARIABLE.” Decide whether this statement correctly reflects how synthesis infers storage (registers/latches).

Introduction / Context:
Understanding how VHDL models storage is essential for writing synthesizable code. Designers often confuse VHDL variables with hardware registers. This item checks whether a remembered (stored) value must be implemented with a VARIABLE, or whether SIGNAL-based coding in clocked processes is the normal route for storage inference.

Given Data / Assumptions:

• Synthesizable storage (flip-flops/latches) is typically inferred from SIGNAL assignments within processes using clock/enable conditions.
• VARIABLEs in synthesizable processes can be used for intermediate calculations but do not inherently imply hardware storage unless their usage and process structure force it.
• Asynchronous or synchronous resets, and edge detection, are commonly expressed around SIGNAL-based processes.

Concept / Approach:
In synthesizable VHDL, storage inference comes from the presence of clocked processes (if rising_edge(clk)) and signal assignment patterns that require state to be held between clock events. VARIABLES are convenient for temporary values in a process activation, while SIGNALs represent wires and registers across delta cycles and clock edges. Registers are created because of the sequential semantics and clock conditions, not because a VARIABLE is used.

Step-by-Step Solution:

Verification / Alternative check:
Synthesis reports list inferred registers from SIGNAL assignments under clocked conditions, confirming that VARIABLES are not mandatory to “remember” values.

Why Other Options Are Wrong:
“Correct” reverses standard synthesis practice. “Applies only in testbenches” and “Applies only with shared variables” are misleading edge cases that do not define storage inference rules.

Common Pitfalls:
Confusing simulation convenience of VARIABLES with actual hardware registers; forgetting that registers arise from edge-guarded SIGNAL assignments and required state retention.

Final Answer:
Incorrect