Processes - Virginia Commonwealth University



Processes

• Processes execute concurrently.

• May include either a sensitivity list or wait statements, but not both.

o Think as if the process contains, just before the “end process,” an implicit wait statement containing the signals in the sensitivity list.

o All statements except wait statements take zero simulation time to execute.

o At start of simulation all processes execute (concurrently) and suspend when they encounter a wait statement (possibly the phantom wait at the end).

• Statements within a process execute sequentially.

• Signals are updated only when the process suspends.

o When signal assignments are encountered the next value is put on a transaction queue waiting to be assigned, but not actually assigned until after the process suspends.

• Normal variables are declared only within a process.

o Variables are local to the process and are static.

o Variable assignments are made when the statement executes.

Equivalent examples

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