Description
In Quartus® II versions 12.1 and later, you can use the QSF variable UNFORCE_MERGE_PLL_OUTPUT_COUNTER to prevent the PLL output counters from merging in Stratix® V, Arria® V, or Cyclone® V devices.
Resolution
Below is an example of the assignment being made to a PLL output counter:
set_instance_assignment -name UNFORCE_MERGE_PLL_OUTPUT_COUNTER ON -to "mypll:inst|mypll_0002:mypll_inst|altera_pll:altera_pll_i*”