Xilinx Constraints Guide

Example
(* KEEPER = “TRUE” *) DEFAULT
For more information about basic Verilog syntax, see Verilog Attributes.
UCF Syntax
DEFAULT constraint_name;
Accepted constraint_names for DEFAULT are:
• KEEPER
• FLOAT
• PULLDOWN
• PULLUP
UCF Syntax Example
DEFAULT KEEPER = TRUE;
XCF Syntax
BEGIN MODEL “entity_name”
DEFAULT constraint_name [attribute_value] ;
END;
Accepted constraint_names for DEFAULT are:
• KEEPER
• FLOAT
• PULLDOWN
• PULLUP
Accepted attribute_values depend on the attribute type.
XCF Syntax Example
BEGIN MODEL “my_design”
DEFAULT keeper = TRUE;
END;
NCF Syntax
Same as UCF syntax.
PlanAhead Syntax
Chapter 4: Xilinx Constraints
For more information about using the PlanAhead software to create constraints, see
Floorplanning the Design in the PlanAhead User Guide (UG632). See PlanAhead in this
Guide for information about:
• Defining placement constraints
• Assigning placement constraints
• Defining I/O pin configurations
• Floorplanning and placement constraints
Constraints Guide
UG625 (v. 13.2) July 6, 2011 www.xilinx.com 97