Specifications

CHAPTER 1: DESIGN FLOW
DESIGN METHODOLOGIES & DESIGN PLANNING
30 ■ INTRODUCTION TO QUARTUS II ALTERA CORPORATION
Design Methodologies & Design
Planning
When you are creating a new design, it is important to consider the design
methodologies the Quartus II software offers. For example, the LogicLock
feature offers the ability to use top-down or bottom-up design
methodologies, top-down incremental compilation design flows, and block-
based design flows. You can use these design flows with or without EDA
design entry and synthesis tools.
Top-Down versus Bottom-Up Design
Methodologies
In the top-down design flow, there is only one output netlist for the entire
design, which may allow you to perform optimization across design
boundaries and hierarchies for the entire design, and is often simpler to
manage.
In the bottom-up design methodology, there are separate netlists for each
design module. This functionality allows you to compile each module
separately and apply different optimization techniques to each module.
Modifications to individual modules do not affect the optimizations to other
modules. The bottom-up design methodology also facilitates the reuse of
design modules in other designs.
Top-Down Incremental Compilation
Flow
The top-down incremental compilation flow allows you to preserve design
performance and save compilation time by reusing previous compilation
results and ensuring that only the parts of the design that have been
modified are recompiled. The top-down incremental compilation flow can
help you to improve timing by allowing you to change the placement of only
the critical elements of the design while processing the other design
partitions, or allowing you to specify the placement only for designated
portions of the design so that the Compiler can automatically optimize the
rest of the design.