Overview

The two main concurrent statements are the following.

• Process statements
  
  A process statement defines a process. Processes are composed of sequential statements (see the “Sequential Statements” chapter), but processes themselves are concurrent statements. All processes in a design execute concurrently. However, at any given time only one sequential statement is interpreted within each process. A process communicates with the rest of a design by reading or writing values to and from signals or ports declared outside the process.
  
  
• Block statements
  
  

A block statement defines a block. Blocks are named collections of concurrent statements, optionally using locally defined types, signals, subprograms, and components.

VHDL provides two concurrent versions of sequential statements; concurrent procedure calls and concurrent signal assignments.

The component instantiation statement references a previously defined hardware component.

Finally, the generate statement creates multiple copies of any concurrent statement.