Unused Inputs to Primitives, Megafunctions & Macrofunctions

The following rules apply to unconnected input ports on primitive, Intel® FPGA IP, and macrofunction symbols and instances.

  • Unused inputs to flipflop primitives have the following defaults:


    VCC (inactive)


    VCC (inactive)


    VCC (active)

    The data and clock inputs to flipflops and the data and ENA inputs to latches are required.

  • An unused OE input to a TRI buffer defaults to VCC (active, output enabled).
  • Unused inputs to logic primitives in Block Editor files must be connected to VCC or GND.
  • The default logic levels for unused inputs to Intel® FPGA IP, if any, are documented in the Help for each Intel® FPGA IP. There may not be a default input to some ports on Intel® FPGA IP, and failure to connect such ports will cause the Compiler to issue error messages.