AR# 9468

Description

Solution

For the FROM TO constraint, two TIMEGRPs must be created: one for the destination elements and one for the source elements. To exclude a signal(s) from either theTIMEGRP for the FROM TO constraint, you can use an EXCEPT command.

For example, the syntax would look like the following:

• TIMEGRP new_srcgrp = srcgrp EXCEPT sig1;
• TIMEGRP new_destgrp = dest_grp EXCEPT sig2;

If you must apply a FROM TO TIG constraint, make sure that the TIMESPEC line contains the TIG notifier as follows:

TIMESPEC "TS_constraintA" = FROM "new_srcgrp" TO "new_destgrp" TIG;

Additional Information

• For information on how this syntax can be used to constrain block RAM halves independently, see (Xilinx Answer 6448)
• For more information on using the EXCEPT, FROM TO, TIMEGRP, and TIMESPEC constraints, see the online documentation at: http://www.xilinx.com/support/software_manuals.htm
• For more details on timing constraints, please see the Timing Constraints User Guide