Answers Database
How to specify TIMESPECs
Record #1069
Product Family: Software
Product Line: XACT FPGA
Product Part: ppr
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 m
ay be specified either in the schematic primitive, TIMESPEC, or within a constraints (CST) file. Tim
especs 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 :
<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 TIMESPEC= 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. Other typical units a
re :
- 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 Li
braries Guide for more details on Timespecs.
End of Record #1069 - Last Modified: 03/19/98 19:05 |
