Download Structural Modeling - Computer Science - Lecture Slides and more Slides Computer Science in PDF only on Docsity!
Modeling Styles
1. Structural Modeling: As a set of interconnected
components (to represent structure),
2. Dataflow Modeling: As a set of concurrent
assignment statements (to represent dataflow),
3. Behavioral Modeling: As a set of sequential
assignment statements (to represent behavior),
4. Mixed Modeling: Any combination of the above
three.
Structural Style of Modeling
- In the structural style of modeling, an
entity is described as a set of
interconnected components.
entity HALF_ADDER is
port (A, B: in BIT; SUM, CARRY: out BIT);
end HALF_ADDER;
-- This is a comment line.
Dataflow Style of Modeling
The dataflow model for the HALF_ADDER is described
using two concurrent signal assignment statements
architecture HA_CONCURRENT of HALF_ADDER is
begin
SUM <= A xor B after 8 ns;
CARRY <= A and B after 4 ns;
end HA_CONCURRENT;
Concurrent signal assignment statements are concurrent
statements, and therefore, the ordering of these statements in an architecture body is not important.
Behavioral Style of Modeling
- The behavioral style of modeling specifies the
behavior of an entity as a set of statements that
are executed sequentially in the specified order.
- This set of sequential statements, that are
specified inside a process statement, do not
explicitly specify the structure of the entity but
merely specifies its functionality.
- A process statement is a concurrent statement
that can appear within an architecture
- A process statement, too, has a declarative part (between the keywords process and begin), and a statement part (between the keywords begin and end process).
- The statements appearing within the statement part are sequential statements and are executed sequentially.
- The list of signals specified within the parenthesis after the keyword process constitutes a sensitivity list and the process statement is invoked whenever there is an event on any signal in this list.
- In the previous example, when an event occurs on signals A, B, or ENABLE, the statements appearing within the process statement are executed sequentially.
Mixed Style of Modeling
- It is possible to mix the three modeling styles
that we have seen so far in a single architecture
body.
- That is, within an architecture body, we could
use component instantiation statements (that
represent structure), concurrent signal
assignment statements (that represent
dataflow), and process statements (that
represent behavior).
