Editing Component Logic

You can use the Block window in the FPGA Editor to modify or create component logic. See the “Block Window” figure of the “Getting Started” chapter. You can use only one block window at a time for editing; however, you can have additional block windows open for viewing.

To edit a component's internal logic, perform one of the following.

• Double click the left mouse button on a component, and then press the second to the left button in the block window's toolbar (the Begin Editing button). If it is disabled, check to make sure the edit mode is read-write.
  
  
• Select a component and select the Editblock command in the User toolbar
  
  
• Select a component and enter editblock in the Command Line toolbar
  
  

Notes on Editing a Component

• Look-up tables (LUT) and flip-flops have several check boxes associated with them. You can enable a LUT or flip-flop by selecting the appropriate check box.
  
  
• You can also specify carry mode by selecting the appropriate check box.
  
  
• Multiplexer (MUX) symbols have triangular input pins. You can click on the appropriate pin to highlight the path through that pin.
  
  
• You can create LUT equations by using attributes for the component. In the Block window, click on the Show/Hide Attributes toolbar button. Equations are a boolean representation of the logic; for example, F4 + (~F3*F2).