Why does the TimeQuest timing analyzer ignore set_clock_groups constraints?

Description

Due to an error in the Quartus® II software version 11.1 SP2 and earlier, the TimeQuest timing analyzer may ignoreset_clock_groups constraints if they are written with backslashes (""):

set_clock_groups -asynchronous -group {clk_A} -group {clk_B} -group {clk_C}

This may result in timing paths reported even though the paths have been cut using the set_clock_groupsconstraint.

Resolution

To work around this problem, delete the "\" and create the constraint in one line in your Synopsys Design Constraints file (.sdc). For example, modify the previous constraint as follows:

set_clock_groups -asynchronous -group {clk_A} -group {clk_B} -group {clk_C}

This error is scheduled to be fixed in a future release of the Quartus II software.