Quartus II Settings File Reference Manual - Altera

Chapter 4: Analysis & Synthesis Assignments 4–127
MUX_RESTRUCTURE
MUX_RESTRUCTURE
Type
Allows the Compiler to reduce the number of logic elements required to implement
multiplexers in a design. You can use this option if your design contains buses of
fragmented multiplexers. This option restructures multiplexers more efficiently for
area, allowing the design to implement multiplexers with a reduced number of logic
elements.
The following three settings are available:
■ On—Allows the Compiler to minimize your design area. This setting decreases
logic element usage but may negatively affect design clock speed (f MAX).
■ Off—Multiplexer restructuring is disabled in the design. This setting does not
decrease logic element usage and does not affect design clock speed (f MAX).
■ Auto—Allows the Quartus II software to determine whether multiplexer
restructuring should be enabled. The Quartus II software uses other synthesis
settings, for example, the Optimization Technique option, to determine if
multiplexer restructuring should be applied to the design. This setting decreases
logic element usage but may negatively affect design clock speed ( fMAX).
The Restructure Multiplexers option works on entire trees of multiplexers.
Multiplexers may arise in different parts of the design through VHDL or Verilog
constructs such as “if”, “case”, or “?:”. When multiplexers from one part of the design
feed multiplexers in another part of the design, trees of multiplexers are formed. The
Restructure Multiplexers option identifies buses of multiplexer trees that have a
similar structure. Multiplexer buses occur most often as a result of multiplexing
together vectors in Verilog, or array types such as STD_LOGIC_VECTOR in VHDL.
When turned on, the Restructure Multiplexers option optimizes the structure of each
multiplexer bus for the target device to reduce the overall number of logic elements
used in the design.
You can use this option as a project-wide option, or assigned to a design entity.
This option defaults to Auto.
Enumeration
■ Auto
■ Off
■ On
Device Support
This setting can be used in projects targeting the following device families:
■ Arria GX
■ Arria II GX
■ Arria II GZ
■ Arria V
June 2012 Altera Corporation Quartus Settings File
Reference Manual