Estimate Fan-In to Assign Output Pins

• Try to guess the fan-in (list of inputs or registers) contributing to the realization of each output

• Use this to assign output pins in appropriate LABs

  • The maximum number of signals that feed each LAB from the PIA is 36 (MAX 7000) / 33 (MAX 9000)
    • Maximum 36 input pins / registers(from other macrocells)
    • For each signal from the PIA chosen, both the true and the inverted form are available in the LAB
  • This will avoid having a fan-in greater than 36 into a LAB
    • Prevents compilation errors; saves resources

• Outputs / LABs fed by more than 36 inputs / registers will only compile if Multi-Level Synthesis = ON

  • More macrocells will be needed for the design to break up the fan-in

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