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Within the TIMESPEC primitive, you use the following syntax to specify timing requirements between specific end points.
TSidentifier=FROM source_group TO dest_group delay
TSidentifier=FROM source_group delay
TSidentifier=TO dest_group delay
Unspecified FROM or TO, as in the second and third syntax statements, implies all points.
The From-To statements are TS attributes that reside in the TIMESPEC primitive. The parameters source_group and dest_group must be one of the following.
Predefined groups consist of FFS, LATCHES, RAMS, or PADS and are discussed in the “Using Predefined Groups” section. TNMs are introduced in the “Creating User-Defined Groups Using TNMs” section. TIMEGRP symbols are introduced in the “Creating New Groups from Existing Groups” section.
Note: Keywords, such as FROM, TO, and TS appear in the documentation in upper case; however, you can enter them in the TIMESPEC primitive in either upper or lower case. You cannot enter them in a combination of lower and upper case.
The delay parameter defines the maximum delay for the attribute. Nanoseconds are the default units for specifying delay time in TS attributes. You can also specify delay using other units, such as picoseconds or megahertz.
Refer to the “Specifying Time Delay in TS Attributes” section later in this chapter for more information on time delay. The delay can be a function of another TIMESPEC (TS01*2).
The following examples illustrate the use of From-To TS attributes.
Schematic syntax in TIMESPEC primitive
TS01=FROM FFS TO FFS 30
TS_OTHER=FROM PADS TO FFS 25
TS_THIS=FROM FFS TO RAMS 35
TS_THAT=FROM PADS TO LATCHES 35
UCF syntax
TIMESPEC TS01=FROM FFS TO FFS 30;
TIMESPEC TS_OTHER=FROM PADS TO FFS 25;
TIMESPEC TS_THIS=FROM FFS TO RAMS 35;
TIMESPEC TS_THAT=FROM PADS TO LATCHES 35;
You can place TS attributes containing From-To statements in either of two places: in the TIMESPEC primitive on the schematic as discussed in this chapter or in a constraints (UCF) file.