Specifications

CHAPTER 9: TIMING CLOSURE
USING LOGICLOCK REGIONS TO ACHIEVE TIMING CLOSURE
170 ■ INTRODUCTION TO QUARTUS II ALTERA CORPORATION
of modules. You can use the LogicLock feature on individual nodes, for
instance, by assigning the nodes along the critical path to a LogicLock
region.
Successfully improving performance by using LogicLock regions in a design
requires a detailed understanding of the design’s critical paths. Once you
have implemented LogicLock regions and attained the desired performance,
back-annotate the contents of the region to lock the logic placement.
Soft LogicLock Regions
LogicLock regions have predefined boundaries and nodes assigned to a
particular region always reside within the boundary or LogicLock region
size. Soft LogicLock regions can enhance design performance by removing
the fixed rectangular boundaries of LogicLock regions. With the soft region
property enabled, the Fitter attempts to place as many assigned nodes in the
region as close together as possible, and has the added flexibility of moving
nodes outside the soft region to meet a design’s performance requirement.
Path-Based Assignments
The Quartus II software enables you to assign specific source and
destination paths to LogicLock regions, allowing for easy grouping of
critical design nodes into a LogicLock region. You can create path-based
assignments with the Paths dialog box, by dragging and dropping critical
paths from the Timing Analyzer section of the Report window and the
Timing Closure floorplan into LogicLock regions.
The Paths dialog box allows you to specify a path by identifying a source
and destination node and using wildcards when identifying nodes. You can
click List Nodes to determine how many nodes will be assigned to the
LogicLock region. You open this dialog box by clicking Add Path or double-
clicking in the Contents tab of the LogicLock Region Properties dialog box,
or by double-clicking on a path in the Timing Closure floorplan. See
Figure 5.