Processes and Sequential Statements

Abstract

The primary concurrent statement in VHDL is a process statement. A number of processes may run at the same simulated time. Within a process, sequential statements specify the step-by-step behavior of the process, or, essentially, the behavior of an architecture. Sequential statements define algorithms for the execution within a process or a subprogram. They belong to the conventional notions of sequential flow, control, conditionals, and iterations in the high level programming languages such as Pascal, C, or Ada. They execute in the order in which they appear in the process. In an architecture for an entity, all statements are concurrent. The process statement is itself concurrent statement. It can exist in an architecture and define regions in the architecture where all statements are sequential.