Xilinx Constraints Guide

Chapter 1: Constraint Types
Relative Location (RLOC) Constraints
The RLOC constraint groups logic elements into discrete sets.
• You can define the location of any element within the set relative to other elements
in the set, regardless of eventual placement in the overall design.
• For example, if RLOC constraints are applied to a group of eight flip-flops organized
in a column, the mapper maintains the columnar order and moves the entire group
of flip-flops as a single unit.
• In contrast, absolute LOC constraints constrain design elements to specific locations
on the FPGA die with no relation to other design elements.
Placement Constraints
• AREA_GROUP
• BEL
• LOC
• LOCATE
• Prohibit
• RLOC
• RLOC_ORIGIN
• RLOC_RANGE
• USE_RLOC
Constraints Guide
16 www.xilinx.com UG625 (v. 13.2) July 6, 2011