28-11-2012, 06:35 PM
VHDL Quick Start
VHDL-quick-start.ppt (Size: 154.5 KB / Downloads: 42)
Modeling Digital Systems
VHDL is for writing models of a system
Reasons for modeling
requirements specification
documentation
testing using simulation
formal verification
synthesis
Goal
most reliable design process, with minimum cost and time
avoid design errors!
Modeling Behavior
Architecture body
describes an implementation of an entity
may be several per entity
Behavioral architecture
describes the algorithm performed by the module
contains
process statements, each containing
sequential statements, including
signal assignment statements and
wait statements
Modeling Structure
Structural architecture
implements the module as a composition of subsystems
contains
signal declarations, for internal interconnections
the entity ports are also treated as signals
component instances
instances of previously declared entity/architecture pairs
port maps in component instances
connect signals to component ports
wait statements
Mixed Behavior and Structure
An architecture can contain both behavioral and structural parts
process statements and component instances
collectively called concurrent statements
processes can read and assign to signals
Example: register-transfer-level model
data path described structurally
control section described behaviorally