Answers Database

How to specify TIMESPECs


Record #1069

Product Family:  Software

Product Line:  FPGA Core

Problem Title:
How to specify TIMESPECs


Problem Description:
How to specify TIMESPECs


Solution 1:

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 predefin
ed "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 :

<Timespec_name>=FROM:<group1>:TO:<group2>=<delay>

example:
TS01=FROM:FFS:TO:FFS=20MHz
TS02=FROM:TNM1:TO:PADS=30NS
TS03=FROM:TIMEGRP1:TO:FFS=AUTO

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

TIMESPEC="TS04=FROM:PADS:TO:FFS=100KHZ";

Nanoseconds are the default units for specifying delay times in TS attribute.  O
ther 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 accura
cy.

Please consult chapter 4 of the Development System User Guide Vol. 1 or page 4-5
2 and 4-53 of the Libraries Guide for more details on Timespecs.



End of Record #1069