Xilinx 8.2i manual Cm Cover Mode, Detail Write Out Detailed MAP Report, Cm area speed balanced

Chapter 7: MAP

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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 onoff

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.

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