Specifications

CHAPTER 2: DESIGN ENTRY
USING ALTERA MEGAFUNCTIONS
ALTERA CORPORATION INTRODUCTION TO QUARTUS II ■ 53
Instantiation by Inference
EDA synthesis tools automatically recognize certain types of HDL code and
infer the appropriate megafunction.You can directly instantiate memory
blocks (RAM and ROM), DSP blocks, shift registers, and some arithmetic
components in Verilog HDL or VHDL code. The EDA tool then maps the
logic to the appropriate Altera megafunction during synthesis.
Using the Clear Box Methodology
In the black box flow, an EDA synthesis tool treats Altera megafunctions and
LPM functions as black boxes. As a result, the EDA synthesis tool cannot
fully synthesize and optimize designs with Altera megafunctions, because
the tool does not have a full model or timing information for the function.
Using the clear box flow, you can use the MegaWizard Plug-In Manager to
create a fully synthesizeable Altera megafunction or LPM function for use
with EDA synthesis tools.
The following steps describe the basic flow for using clear box
megafunctions with EDA synthesis tools:
1. Use the MegaWizard Plug-In Manager to create and parameterize the
megafunction or LPM function. Make sure you turn on Generate a
Clearbox body in the MegaWizard Plug-In Manager.
2. Use the Verilog or VHDL design file generated by the MegaWizard
Plug-In Manager to instantiate the function in the EDA synthesis tool.
3. Perform synthesis and optimization of the design in the EDA synthesis
tool.
Using of the clear box methodology generally results in slower simulation
times in EDA simulation tools (but not the Quartus II Simulator), due to the
level of detail (timing information and device resources used) that is
included with a clear box megafunction or LPM function. In addition,
specific device details are included in the clear box megafunction or LPM
function, so that to use a different device for the design, the clear box
function needs to be regenerated for the new device.