Xilinx Constraints Guide

Chapter 1: Constraint Types
Predefined Group Examples
From-To statements enable you to define timing specifications for paths between
predefined groups. The following examples are TS constraints that are entered in
the UCF. This method enables you to easily define default timing specifications, as
illustrated by the following examples.
Following is a UCF syntax example.
TIMESPEC "TS01"=FROM FFS TO FFS 30;
TIMESPEC "TS02"=FROM LATCHES TO LATCHES 25;
TIMESPEC "TS03"=FROM PADS TO RAMS 70;
TIMESPEC "TS04"=FROM FFS TO PADS 55;
TIMESPEC "TS01" = FROM BRAMS_PORTA TO BRAMS_PORTB(gork*);
For BRAMS_PORTA and BRAM_PORTB, the specification TS01 controls paths that begin
at any A port and end at a B port, which drives a signal matching the pattern gork*.
BRAMS_PORTA and BRAMS_PORTB Examples
Following are additional examples of BRAMS_PORTA and BRAMS_PORTB.
NET "X" TNM_NET = BRAMS_PORTA groupA;
The TNM group groupA contains all A ports that are driven by net X. If net X is traced
forward into any B port inputs, any single-port block RAM elements, or any Select RAM
elements, these do not become members of groupA.
NET "X" TNM_NET = BRAMS_PORTB( dob* ) groupB;
The TNM group groupB contains each B port driven by net X, if at least one output on
that B port drives a signal matching the pattern dob*.
INST "Y" TNM = BRAMS_PORTB groupC;
The TNM group groupC contains all B ports found under instance Y. If instance Y is
itself a dual-port block RAM primitive, then groupC contains the B port of that instance.
INST "Y" TNM = BRAMS_PORTA( doa* ) groupD;
The TNM group groupD contains each A port found under instance Y, if at least one
output on that A port drives a signal matching the pattern doa*.
TIMEGRP "groupE" = BRAMS_PORTA;
The user group groupE contains the A ports of all dual-port block RAM elements. This
is equivalent to BRAMS_PORTA ( * ).
TIMEGRP "groupF" = BRAMS_PORTB( mem/dob* );
The user group groupF contains all B ports, which drives a signal matching the pattern
mem/dob*.
A predefined group can also carry a name qualifier. The qualifier can appear any place
the predefined group is used. This name qualifier restricts the number of elements
referred to. The syntax is:
predefined group (name_qualifier [ name_qualifier ])
name_qualifier is the full hierarchical name of the net that is sourced by the primitive
being identified.
Constraints Guide
10 www.xilinx.com UG625 (v. 13.2) July 6, 2011