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FPGA Schematic Design Step Guide FPGA Schematic Design Step Guide
ispLEVER 5.1 Documentation
1
FPGA Schematic Design
Step Guide
Schematic design is a powerful design method to help illustrate your design
hierarchy and signal interconnect. The ispLEVER 5.1 software supports
schematic/VHDL and schematic/Verilog HDL entries for FPGAs, including
LatticeECP/EC, LatticeXP, LatticeSC, and MachXO device families.
Schematic Design Tools
The Lattice Schematic Editor, Symbol Editor, and Library Manager allow you
to capture your design with a combination of schematics, FPGA library
macros, or HDL modules. Hierarchy is established by instantiating a symbol
from a customer symbol produced by the IPexpress or your own RTL module.
The following lists the major schematic tools included in ispLEVER.
Schematic Editor a graphical editor for placing library symbols, adding
attributes, and wiring connections
Symbol Editor a graphical editor for creating and modifying library
symbols
Library Manager a graphical interface to collect library symbols
Hierarchy Navigator a graphical tool to explore schematic/HDL design
hierarchy
Design Steps
This section shows the major design steps that are specific for an FPGA
schematic design. Steps are as follows:
Create a new project. First you need to create a new FPGA design
project and select schematic/VHDL or schematic/Verilog as your design
entry type.
Create a schematic symbol from the IPexpress or an HDL module. A
schematic is mainly comprised of symbols, wires, and attributes. In this
step, youll learn how to create a symbol (
*.sym
) from the IPexpress or
from an existing Verilog or VHDL module. These symbols can later be
added to your schematic design source.
Instantiate design modules. In this step, youll add the schematic
symbols you created in the prior step into a schematic (
*.sch
) and then
add necessary wires, I/O makers, etc. to complete the schematic.
Note
In FPGA schematic designs, the lowest-level sources must be VHDL or Verilog
modules. FPGA Schematic Design Step Guide
ispLEVER 5.1 Documentation
2
Edit net attributes. After finishing the schematic, you can apply net
attributes. Net attributes include IO configuration and pin lock attributes.
You can apply them to a net from or to the external signals.
Create an HDL template from a schematic symbol. You can use the
Symbol Editor to create a Verilog or VHDL template from a schematic
symbol. These templates can later be imported into the project as the
lower-level sources.
Create an HDL simulation model from a schematic. You can create a
Verilog or VHDL simulation model from a schematic file (
*.sch
)
depending on your design source type. The model will be used to perform
functional simulation on the schematic design project.
Simulate a Schematic. This step shows you how to perform functional
and timing simulation on your FPGA schematic design.
Create a New Project
Using the Project Navigators Project Wizard, you can create a new
schematic design targeting an FPGA device. The Wizard will guide you
through the steps of specifying project name and location, choosing design
entry type and synthesis tool, as well as selecting a target device.
To create a new project:
1. In the Project Navigator, choose File > New Project.
2. In the first dialog of Project Wizard, do the following:
Under Project Name, enter a name for your project. The default
project name is
Untitled
.
Under Location, click ... to open the Browse for Folder dialog box.
Browse for the desired location, or click New Folder to create a new
directory to place the new project, and then click OK. Note that you
should not place more than one project in the same directory.
Under Design Entry Type, select Schematic/VHDL or Schematic/
Verilog HDL.
Under Synthesis Tools, choose a synthesis tool.
Click Next.
3. In the Select Device dialog box, select the desired FPGA device family
and a specific device within that family. Then choose the options you want
for that device. When you finish, click Next.
4. In the Add Source dialog box, click Next. You can add design sources
later.
5. In the Project Information dialog box, make sure the project settings are
correct and then click Finish.
The new FPGA schematic design project is created and displayed in the
Project Navigator. FPGA Schematic Design Step Guide
ispLEVER 5.1 Documentation
3
Create a Schematic Symbol from the IPexpress or an HDL
Module
Schematic symbols (
*.sym
) are generally created from the IPexpress or from
an existing HDL module.
To create a schematic symbol from the IPexpress:
1. Run the IPexpress and configure the module or IP core.
2. In the configuration tab, click Generate.
The IPexpress writes a new schematic symbol file (
*.sym
) into your
project directory using the interface ports defined by your module.
To create a schematic symbol from an existing HDL module:
1. In the Project Navigator, add the HDL module to your Schematic/VHDL or
Schematic/Verilog project.
2. In the Sources window, select the HDL source. In the Processes window,
double-click Generate Schematic Symbol.
The Project Navigator writes a new schematic symbol file (
*.sym
) into the
project directory using the interface ports defined by your HDL module.
Note that if you prefer to use the Parameter Configuration File (
*.lpc
) as the
source in your project, you may add the related HDL file temporarily to your
project to create a schematic symbol.
Once a symbol is created, you can modify it in the Symbol Editor.
Instantiate Design Modules
You can insert the symbol you created into a schematic (
*.sch
).
To add a symbol to a schematic:
1. If you have not already done so, open or create a schematic file (
*.sch
).
2. In the Schematic Editor, press F2 or choose Add > Symbol to open the
Symbol Libraries dialog box.
The Library box displays all the available symbol library paths. The
symbols you created for the project are stored in the
[Local]
path.
3. In the Library box, select the desired path. In the Symbol box, select the
symbol you wan to add to your schematic. The symbol is attached to your
mouse cursor.
4. Click the left mouse button to drop the symbol to the desired location in
your schematic.
You can continue to place the same symbol by clicking the left mouse
button, or select a new symbol to add. When you finish, close the Symbol
Libraries dialog box.
After placing the symbols, you can add necessary wires and I/O markers to
complete the schematic. FPGA Schematic Design Step Guide
ispLEVER 5.1 Documentation
4
Set a User Symbol Library
As mentioned in the above procedure, the
symbols you created for the project are by default stored in the
[Local]

path. You can also set a user symbol library (
*.lib
) to store the user
symbols that are commonly used. Then, when you want to insert symbols to a
schematic, you can select your user library and add the symbols within it to
your schematic.
To set a user symbol library:
1. In the Project Navigator, choose Window > Library Manager.
2. In the Library Manager, choose File > New to create a new library file
(
*.lib
)
3. Choose Edit > Add Symbol(s).
4. In the Add Symbols to Library dialog box, browse for the symbol (
*.sym
)
you want to add to the user library, and then select it. You can select more
than one symbol at a time by using the SHIFT and CTRL keys on your
keyboard.
5. Click Open. The Library Manager copies the symbol(s) into the current
library. The original symbols still exist and may be deleted if so desired.
6. Choose File > Save As to save the new library with a specific name.
7. In the Project Navigator, choose Options > User Defined Symbol
Libraries Configuration.
8. In the dialog box, click the New icon. A new line is displayed in the list box.
9. Click the ... button to the right of the new line to open the Select User
Defined Symbol Library dialog box. Navigate to the user library you just
created, and then click Open.
10. Click OK to close the Set User Defined Symbol Libraries dialog box.
Now you have completed setting your user library. Next time when you
open the Schematic Editor and choose Add > Symbol, youll see your
user library listed in the Symbol Libraries dialog box. You can select the
user library and then choose any symbol included in the library to add to
your schematic.
Edit Net Attributes
After completing your schematic file (
*.sch
), you can set IO configuration
and pin lock attributes for the net from or to the external signals.
To add a net attribute to a schematic:
1. In the Schematic Editor, make sure the schematic file you want to work
with is open.
2. Choose Edit > Attribute > Net Attribute to open the Net Attribute Editor
dialog box.
3. On the schematic, select the net you want to add attribute for.
The net name and default net attributes for Lattice FPGA design appear in
the dialog box. FPGA Schematic Design Step Guide
ispLEVER 5.1 Documentation
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4. To assign a device pin to the selected net, select
LOC=
in the dialog box,
type in the desired pin name in the text box, and press Enter. The net is
locked to the pin.
To apply a certain IO configuration to the selected net, select the desired
attribute, type in the value, and press Enter. The new attribute value is
applied.
5. You can continue to edit net attributes the same way. When you finish,
close the Net Attribute Editor dialog box.
Create an HDL Template from a Schemat