A PROCESS statement contains sequential statements but is itself a concurrent statement within an architecture. An independent sequential process represents the behavior of some portion of a design. The body of a process is a list of sequential statements. See Processes.

The sequential statements in the process are executed in order, commencing with the beginning of simulation. After the last statement of a process has been executed, the process is repeated from the first statement, and continues to repeat until suspended. Processes can be suspended with a WAIT statement. The WAIT statement is a versatile statement that lets you suspend a process for a specific period of time, Boolean condition to occur, or/and an event to occur on a signal. The optional sensitivity list is equivalent to providing a WAIT ON statement and causes the process to be suspended. A process cannot have both a sensitivity list as well as a WAIT ON statement. See WAIT Statement.

[label_name:]

PROCESS [(sensitivity_list)]

…local declarations

BEGIN

…sequential statements

END PROCESS [label_name];

sensitivity_list

List of signal names separated by a comma. The list represents a set of signals to which the WAIT statement within the process is sensitive.

If no sensitivity list is defined, a WAIT statement within the process must be specified.

local declarations

Declarations declare data types, constants, signals, files, components, attributes, subprograms, and other information used in the model description.

sequential statements

Statements that are executed in the order in which they appear, that define algorithms for the execution of a subprogram or process.

clock <= NOT clock AFTER 10 us;

PROCESS (clock) -- sensitivity list consists of clock

VARIABLE num_events : INTEGER := 0;

BEGIN

num_events := num_events + 1;

END PROCESS;