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AR# 1069

5.x PPR - How to specify TIMESPECs


How to specify TIMESPECs


Timespecs are the way to communicate to PPR specific timing parameters for your design. Timespecs may be specified either in the schematic primitive, TIMESPEC, or within a constraints (CST) file. Timespecs may be specified between predefined "global" groups specified below or between groups defined by TNMs or TIMEGRPs.

Using Predefined Groups :

FFS - CLB or IOB flip-flops
LATCHES - Input latches only;not latches from function generators
PADS - Input/output pads
RAMS - For XC4000/E/EX RAM primatives

Syntax :



If you are specifying timespecs in a contraints file you will need to add TIMESPEC= to the begining of the statement :


Nanoseconds are the default units for specifying delay times in TS attribute. Other typical units are :

- NS for nanoseconds
- MHZ for megahertz
- US for microseconds
- KHZ for kilohertz
- AUTO minimizes delays along certain paths without specifying a spec

XNFPrep converts all units to nanoseconds and rounds to the nearest 0.1ns accuracy.

Please consult chapter 4 of the Development System User Guide Vol. 1 or page 4-52 and 4-53 of the Libraries Guide for more details on Timespecs.
AR# 1069
Date Created 08/31/2007
Last Updated 03/22/2000
Status Archive