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AR# 36357

11.4-14.7 MAP -global_opt - unroutable net when using on MIG designs

Description

The MAP -global_opt (Global Optimization) option sometimes causes an unroutable situation when invoking physical synthesis on MIG v3.4-v3.8 designs.

This can result in the following Route warning message during PAR:

WARNING:Route:436 - The router has detected an unroutable situation for one or more connections. The router will finish the rest of the
design and leave them as unrouted. The cause of this behavior is either an issue with the placement or unroutable placement constraints.
To allow you to use FPGA editor to isolate the problems, the following is a list of (up to 10) such unroutable connections:
Unroutable signal: <signal_name>
...

Solution

When using the "-global_opt" option the actual connectivity within some of the P-side I/O sites used for the signal dqs_p_iodelay changes.

This results in an unroutable situation where there is no route inside the I/O site to route to the N-side I/O site.

Turning "-global_opt" OFF will prevent the unroutable situation from occurring.

Synplify Pro users may run into timing violations when turning off "-global_opt".

The timing violations can be avoided if you turn off the "-read_constraint_file" option in Synplify Pro.
AR# 36357
Date Created 06/23/2010
Last Updated 09/09/2014
Status Active
Type General Article
Devices
  • Virtex-6 LXT
Tools
  • ISE Design Suite - 14
  • ISE Design Suite - 13
  • ISE Design Suite - 11
IP
  • MIG