Adding a Module to Your Design

To design LogiBLOX modules, follow these steps.

1. Start LogiBLOX from your third-party design tool.
   
   
2. Select a base module type.
   
   
3. Customize the module by changing the pin settings and attributes if the defaults are not what you need.
   
   
4. Place the modules in the schematic or in the HDL code and connect them to the rest of your design.
   
   

A LogiBLOX module is displayed in the Module Selector GUI as an illustration that is dynamically updated as you modify the module's fields. The LogiBLOX symbols are bundled into a library provided with your third-party design editor. The LogiBLOX library must be in your editor's library search path for you to access it. For more information, please refer to your CAE Interface User Guide.

Choosing a Module

Each LogiBLOX module can be considered a template with a base function. Refer to the “Module Descriptions” chapter for a list of these modules by function. After you have decided which module to use, start the LogiBLOX program. The Module Selector window is displayed.

When you invoke the Module Selector, the program displays the details of the last module you generated. If you are invoking the LogiBLOX program for the first time, the Module Selector displays the Accumulator's default settings.

When you modify an existing module, that module and all its characteristics are displayed for editing.

Creating a Module

The graphical illustration of the module has check-boxes next to the optional pins. If you select a box, the symbol pin is displayed and is connected to the module. If you deselect the box, the pin disappears.

Use the attribute boxes to specify the module attributes. These attributes may affect the appearance of the module. Refer to the “Module Descriptions” chapter for a description of the module pins and attributes.

To specify your module, click on the pins you want to activate and the attributes you want to add to your module. The Module Selector dynamically reveals or hides the attributes and pins that are affected by your choice.

Figure 2.6 Module Selector Window

Module Selector Window Options

Either type a name in the Module Name box to identify the module you want to create, or click on the pull-down arrow to see the list of modules that have already been created for your project. LogiBLOX uses this name to create files in which it saves the different outputs it generates for the module. If you select an existing module from the pull-down list and alter its characteristics, you must change the module name or you will overwrite the existing module. Overwriting an existing module implies that you want to update the selected module.

Note: Do not give a LogiBLOX module the same name as an existing component in the Unified Libraries.

Note: If you edit a LogiBLOX module that you have used multiple times in a design, either by repeatedly adding the same module or by copying it within the schematic tool, all copies of the module are also modified.

The Module Type box displays the type of the currently selected module. Click on the pull-down arrow to select another module type from the list of available modules.

Specify the data bus width for the module. You can use one of the predefined settings (2, 4, 8, 16, or 32) from the pull-down menu, or type in a custom bus width in the text box. Generally, the minimum value allowed is 2 and the maximum value is 64. Decimal is the only valid base. All LogiBLOX bus pins are big endian, that is, the bits in a bus width of N are numbered N-1 through 0.

The top part of the display shows a graphical illustration of the current module.

Use the check-marks to select or deselect optional pins on the symbol. For example, if you check the Overflow pin check box on the Accumulators module, the pin is automatically drawn on the symbol. Required pins, such as the Clock input pin, do not have check boxes.

Beneath the symbol image, LogiBLOX displays a list of the attributes that pertain to the module. You can assign values to particular attributes to further customize your module. To get online help for the attributes and their possible values, move the mouse pointer over the attribute, click the mouse button to move the focus, and press the F1 key.

Click OK when you have completely specified the module and are ready to insert it into your design. The program implements the module and generates the requested simulation models, component declarations, or both.

A log window is also displayed and records any errors and warnings reported by the DRC.

If the DRC completes without any errors, the Module Selector performs the following operations (depending on what you have requested in the Setup window).

• In schematic-based environments, it generates a symbol definition file (the .mod file) that describes the schematic symbol that is created for the module. It also launches the symbol generator utility with a pointer to this file.
  
  
• Instructs the schematic editor to place the symbol on the schematic or to replace the selected symbol with the new one.
  
  
• In HDL-based environments, it generates a component instantiation/declaration for inclusion in the HDL code.
  
  
• Calls the model generator to create a behavioral or gate-level simulation model for the current module.
  
  
• Calls the LogiBLOX module synthesizer to create a gate-level implementation netlist.
  
  

Click Cancel to quit the Module Selector. This operation discards any details you may have entered and leaves the project unchanged.

If you wish to change device families or output types, click Setup and make your new choices in the Setup window.

Note: You cannot change the device family after you have generated a module in the current session. To target a different device family, you must exit lbgui first and restart it.

Click User Prefs to set the editor you want to use for editing memory files. The default editor on UNIX platforms is vi. The default editor on Windows 95 and Windows NT is Wordpad.

Click Help to access the online help tool.

Editing a LogiBLOX Module

Part of the power of LogiBLOX is its ability to customize each module to represent many functions. For example, you can customize the ADD_SUB module to work as an adder only, a subtracter only, or as both an adder and a subtracter.

To customize a module, select only the LogiBLOX module control pins that are needed, specify a bus size for the module, and specify module attributes when the default modes are not the desired ones.

To customize the module using the Module Selector, use the pin connections and attribute setup fields in this dialog box.

The “Module Descriptions” chapter lists all LogiBLOX modules and the attributes that are appropriate for each module. The same attributes are described in full detail in the “Understanding Attributes” chapter.

Including the Module in the Design

After designing the module, click OK to generate the module. Next, place the module on the schematic or paste the instantiation into your HDL file.

Log Window

When you generate a module, a log window is displayed. The log window is a secondary window with scroll bars. LogiBLOX places any output messages generated by the DRC, symbol generator, model generator, and netlist generator processes in this window.

Each time you complete a module and press OK, the Module Selector calls the Design Rule Checker. If the DRC reports no errors, LogiBLOX generates the required output. If the DRC finds errors, LogiBLOX displays the error messages in the log window and the requested modules are not generated.

Connecting the Modules

This section provides information on connecting your LogiBLOX modules to the rest of your design.

Schematic Design

Insert LogiBLOX modules in your schematic and connect them with buses, nets, or both.

Note: You should specify bus widths using your CAE tool's normal mechanism. These values should match those on the module`s bus pins.

HDL File

Fill out the instantiation section of the HDL template file by indicating the module's connections to signals in your design.

Changing a Module

This section provides information on changing or copying a LogiBLOX module.

Schematic Module

To change a module that you have already placed on your schematic, select the module and invoke the Module Selector. The Module Selector displays the settings of the module that you want to edit.

Copying Modules

If you copy a module within your schematic or add repeated instances to your schematic, the original module and all of its copies share the same module configuration and simulation model.

Subsequent modifications to any one of these modules change all copies of that module.

Copying Modules from Another Design

If you choose to copy a module from another design, such as by copying an entire hierarchical module, you must invoke the GUI, regenerate the module, and then dismiss it to recreate the module and create the simulation model for that module. Alternatively, if your design includes several copied modules, you can copy the HDL files into the new project directory and reanalyze them in the new environment.

HDL Module

To complete your LogiBLOX module description, you must edit an HDL template and specify the module pin connections. Refer to the interface guide for your EDA tool for specific instructions.

After a LogiBLOX HDL module is instantiated, it must be modified with the Module Selector. By invoking the LogiBLOX GUI in standalone mode, you can load the previous module's details and modify them with new edits.