• Variables are used and declared in a process however it cannot be used to communicate between processes.
• Variable assignments are done immediately and are executed sequentially.
• Variables may or may not represent physical wires.
• Signal assignments are done at the end of process.
• Signals represent physical wires in the circuit.
• Use variables in combinational processes because there is less simulation overhead.
• Order dependency
– Signal assignments are order independent.
– Variable assignments are order dependent.
– Signal assignments under a clocked process are translated into registers.
– Variable assignments under a clocked process may or may not be translated into registers.
Signals or Variables
Hardware inferred
Same process with order of statements changed
Hardware inferred
Hardware modeling examples “For loop”
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