Description

1. What is the use of the -xe switch in MAP and PAR?
   
   
2. Where can I find documentation for similar switches and optimizations?
    
   

Solution

The -xe switch drives the placer and router to use extensive algorithms to achieve a placed and routed design. 

This is very runtime sensitive and can cause long run times. 

The Tool will try to achieve a proper placement and routing when there are timing violations or unroutable nets.

MAP:

The -xe option is available when running timing-driven packing and placement with the -timing option, and sets the extra effort level.

Syntax : -xe effort_level

effort_level can be set to n (normal) or c (continue). 

When -xe is set to c, MAP continues to attempt to improve packing until little or no improvement can be made.

PAR:

Use this option to set the extra effort level.

Syntax: -xe n|c

• n (normal) tells PAR to use additional runtime intensive methods in an attempt to meet difficult timing constraints.
  If PAR determines that the timing constraints cannot be met, then a message is issued explaining that the timing cannot be met and PAR exits.
   
• c (continue) tells PAR to continue routing even if PAR determines the timing constraints cannot be met.
  PAR continues to attempt to route and improve timing until little or no timing improvement can be made.

Note Use of extra effort c can result in extremely long runtimes.
To use the -xe option, you must also set the -ol (Overall Effort Level) option to high or have the -pl (Placer Effort Level) option and -rl (Router Effort Level) option set to high.

For information on similar switches and optimizations  refer to the command line user guide: http://www.xilinx.com/support/documentation/sw_manuals/xilinx13_2/devref.pdf