Using LogiBLOX

LogiBLOX is a tool that allows you to quickly synthesize modules for common functions such as adders, counters, and multiplexers. It allows you to create components of arbitrary bus width (e.g., a 17-bit adder) and automatically uses the best architectural resources for a particular target device family. In this optional section, you replace the ADSU4 component in the ALU schematic with a LogiBLOX adder. If you choose to leave the ALU schematic in its original form, read this section but do not make save any changes.

Creating and Instantiating a LogiBLOX Module

To replace the ADSU4 symbol with a LogiBLOX module:

1. Bring the ALU schematic into view.
   
   
2. Select the ADSU4 component.
   
   
3. Select Right Mouse Button Delete to delete the symbol from the schematic.
   
   
4. Select Libraries XILINX Libraries from the menu bar.
   
   
5. From the Xilinx Unified Libraries menu, select LogiBLOX.
   
   The Create/Modify/Instantiate LogiBLOX Symbol dialog box appears.
   
   
6. In the Symbol component field, type addsub4.
   
   This is the user-given component name for the new LogiBLOX-generated module.
   
   
7. Under Instantiate symbol, choose YES.
   
   This gives you the opportunity to place the component on the schematic immediately after LogiBLOX exits.
   
   
8. For PLD Technology, select the family to which you are targeting the design, e.g., XC4000E.
   
   The dialog box should now appear as shown in the following figure.
   
   

   Figure 9.48 Instantiate LogiBLOX Dialog Box

9. Click OK to invoke the The LogiBLOX program.
   
   In about 1 minute, the LogiBLOX Module Selector appears.
   
   
10. Set the options in this dialog box as shown in the following figure.
    
    You are making a non-registered adder/subtracter module of four bits.
    
    

    Figure 9.49 Using the LogiBLOX Module Selector

11. Click OK.
    
    Design Architect takes a minute or so to generate a symbol for this new module.
    
    
12. When the module appears on your screen, place it in the space left by the ADSU4.
    
    Do not worry about lining up pins with nets right now.
    
    
13. Arrange the surrounding nets as shown in the figure.
    
    
14. Check and save the ALU schematic.
    
    

    Figure 9.50 Adding the ADDSUB4 LogiBLOX Component