Modeling with a process
The statements encapsulated inside a process are executed in sequence.
For successful synthesis, we only use process for two purpose:
Describe routing structures with if and case statements,
construct templates for memory elements(discussed later).
porcess(sensitivity_list) begin sequential statement; sequential statement; ... end process.
The sensitivity_list is a list of signals to which the process responds. For example, all the input signal of a combinational circuit should be included in this list.
Sequential signal assignment statement
sig <= value_expression;
This statement must be encapsulated inside a process.
process(a,b) begin c <= a and b; c <= a or b; end process;
is the same as
c <= a or b;