The prorating constraints, VOLTAGE and TEMPERATURE, provide a method for determining timing delay characteristics based on known environmental parameters. On a schematic, you can enter these constraints in any empty space. For Release 1.5 these two constraints are supported only for the XC4000XL. New speed file releases for existing architectures will support these two constraints.
This constraint allows the specification of the operating voltage. This provides a means of prorating delay characteristics based on the specified voltage.
Each architecture has its own specific range of supported voltages. If the entered voltage does not fall within the supported range, the constraint is ignored and an architecture-specific default value is used instead. The UCF syntax is as follows.
VOLTAGE=value[units]
value is an integer or real number specifying the voltage and units is an optional parameter specifying the unit of measure. V specifies volts, the default voltage unit.
This constraint allows the specification of the operating temperature which provides a means of prorating device delay characteristics based on the specified junction temperature. Prorating is a linear scaling operation on existing speed file delays and is applied globally to all delays.
Each architecture has its own specific range of valid operating temperatures. If the entered temperature does not fall within the supported range, the constraint is ignored and an architecture-specific default value is used instead. The UCF syntax is as follows.
TEMPERATURE=value[C |F| K]
value is an integer or a real number specifying the temperature. C, K, and F are the temperature units: F is degrees Fahrenheit, K is degrees Kelvin, and C is degrees Celsius, the default.
