Xilinx Constraints Guide

Chapter 4: Xilinx Constraints
TEMPERATURE (Temperature)
The TEMPERATURE (Temperature) constraint:
• Is a timing constraint.
Architecture Support
• Allows the specification of the operating junction temperature.
• Provides a means of prorating device delay characteristics based on the specified
temperature.
Prorating is a scaling operation on existing speed file delays and is applied globally to
all delays. Newer devices may not support TEMPERATURE prorating until the timing
information (speed files) are marked as production status.
Each architecture has its own specific range of valid operating temperatures. If the
entered temperature does not fall within the supported range, TEMPERATURE is
ignored and an architecture-specific worst-case value is used instead. Also note that the
error message for this condition does not appear until static timing.
• Spartan®-3A
• Spartan-3E
• Virtex®-4
• Virtex-5
Applicable Elements
Propagation Rules
Applies globally to the entire design.
This constraint is a design element constraint. Any attachment to a net is illegal.
Syntax
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.
UCF and NCF Syntax
TEMPERATURE=value [C |F| K];
where
value
• is a real number specifying the temperature
• C, K, and F are the temperature units
– F is degrees Fahrenheit
– K is degrees Kelvin
– C is degrees Celsius (default)
The following statement specifies that the analysis for everything relating to speed file
delays assumes a junction temperature of 25 degrees Celsius.
TEMPERATURE=25 C;
Constraints Guide
274 www.xilinx.com UG625 (v. 13.2) July 6, 2011