VHDL execution model inside a process block In VHDL, how are the statements written between BEGIN and END within a process executed (i.e., what is their evaluation order)?

Introduction / Context:
VHDL has two execution domains: concurrent statements at the architecture level and sequential statements inside processes, procedures, and functions. Designers must understand this distinction to predict signal updates and avoid simulation/synthesis mismatches.

Given Data / Assumptions:

• The focus is on statements placed between BEGIN and END of a process.
• We are not referring to concurrent statements outside a process.
• Standard VHDL semantics apply (signal assignment scheduling, delta cycles, etc.).

Concept / Approach:
Within a process, statements execute in program order, one after another, as if in a conventional programming language. Although signal updates may take effect after delta cycles, the evaluation order of statements themselves is sequential. Outside processes, statements are concurrent and conceptually active at all times.

Step-by-Step Solution:

Verification / Alternative check:
Compare with architecture-level concurrent statements (e.g., conditional signal assignments) which are evaluated concurrently; this contrast reinforces that process internals are sequential.

Why Other Options Are Wrong:

• Constantly/Simultaneously: describe concurrent behavior, not process internals.
• Concurrently: correct for architecture statements, not for statements inside a process.

Common Pitfalls:
Expecting sequential variable-like behavior for signals without accounting for delta cycles; mixing up concurrent architecture code with sequential process code.

Final Answer:
Sequentially