How do I constrain the osc output pin for ALTUFM megafunctions?

To constrain the optional osc output pin on ALTUFM_NONE, ALTUFM_I2C, ALTUFM_SPI, and ALTUFM_PARALLEL megafunctions, use either of the following methods:

• Constrain the clock automatically by using the derive_pll_clocks command. Note that in addition to creating generated clocks for PLL outputs, the derive_pll_clocks command also creates clock constraints for internally-generated clocks.
• Constrain the clock manually by using the following command:
  create_clock -period 181.818 -name <name> <hierarchical path to ufm_block>|osc
• Although actual output frequency may vary, constraining the osc pin to 181.818 ns (5.5 MHz) ensures the clock is analyzed at its minimum possible period (maximum possible frequency).