Filter
Top Products
134 www.xilinx.com Development System Reference Guide
Chapter 7: MAP
R
The default packfactor value is 100%. This value applies if you do not specify the –c option,
or enter the –c option without a packfactor value.
Processing a design with the –c 0 option is a good way to get a first estimate of the number
of CLBs required by your design.
–cm (Cover Mode)
–cm {area | speed | balanced}
The –cm option specifies the criteria used during the cover phase of MAP. In this phase,
MAP assigns the logic to CLB function generators (LUTs). Use the area, speed, and
balanced settings as follows:
• The area setting makes reducing the number of LUTs (and therefore the number of
CLBs) the highest priority.
• The behavior of the speed setting depends on the existence of user-specified timing
constraints. For the design with user-specified timing constraints, the speed mode
makes achieving timing constraints the highest priority and reducing the number of
levels of LUTS (the number of LUTs a path passes through) the next priority. For the
design with no user-specified timing constraints, the speed mode makes achieving
maximum system frequency the highest priority and reducing the number levels of
LUTs the next priority. This setting makes it easiest to achieve timing constraints after
the design is placed and routed. For most designs, there is a small increase in the
number of LUTs (compared to the area setting), but in some cases the increase may be
large.
• The balanced setting balances the two priorities – achieving timing requirements and
reducing the number of LUTs. It produces results similar to the speed setting but
avoids the possibility of a large increase in the number of LUTs. For a design with
user-specified timing constraints, the balanced mode makes achieving timing
constraints the highest priority and reducing the number of LUTS the next priority.
For the design with no user-specified timing constraints, the balanced mode makes
achieving maximum system frequency the highest priority and reducing the number
of LUTs the next priority.
The default setting for the –cm option is area (cover for minimum number of LUTs).
–detail (Write Out Detailed MAP Report)
This option writes out a detailed MAP report. The option replaces the
MAP_REPORT_DETAIL environment variable.
–equivalent_register_removal (Remove Redundant Registers)
–equivalent_register_removal on|off
With this option on, any registers with redundant functionality are examined to see if their
removal will increase clock frequencies. This option is available for Virtex-4 designs. By
default, this option is on.
Note:
This option is available only when “–global_opt (Global Optimization)” is used.