Xilinx Constraints Guide

Chapter 4: Xilinx Constraints
USE_LUTNM (Use LUTNM)
Architecture Support
Applicable Elements
Propagation Rules
The USE_LUTNM (Use LUTNM) constraint:
• Is an advanced mapping and placement constraint.
• Turns LUTNM (Lookup Table Name) on or off for a specific element or section
of a set.
Applies to FPGA devices. Does not apply to CPLD devices.
Applies to instances or macros that are members of sets.
It is illegal to attach USE_LUTNM to a net.
Syntax Examples
The following examples show how to use this constraint with particular tools or
methods. If a tool or method is not listed, you cannot use this constraint with it.
Values
• TRUE
Turns on the constraint for a specific element
• FALSE
Turns off the constraint for a specific element
The default is TRUE.
Schematic Syntax
• Attach to a member of a set
• Attribute Name
USE_LUTNM
• Attribute Values
See Values section above.
VHDL Syntax
Declare the VHDL constraint as follows:
attribute USE_LUTNM: string;
Specify the VHDL constraint as follows:
attribute USE_LUTNM of entity_name: entity is “{TRUE|FALSE}”;
For more information about basic VHDL syntax, see VHDL Attributes.
Constraints Guide
310 www.xilinx.com UG625 (v. 13.2) July 6, 2011