Warning (332009): The launch and latch times for the relationship between source clock: and destination clock: are outside of the legal time range. The relationship difference is correct, however the launch time is set to 0.

Description

When you compile a UniPHY-based DDR3 SDRAM controller, you may get the above warning between pll_ref_clk and pll_afi_clk/pll_write_clk.

This warning is due to a non-integer ratio between the PLL reference clock frequency and the operating frequency, which forces the launch and latch edge times beyond the allowed range of time values.

Resolution

The warning can be safely ignored. If you want to avoid the warning, you can try one of these two workarounds.

Workaround 1: Add a “set_false_path” constraint between pll_ref_clk and pll_afi_clk/pll_write_clk because there is no timing path between pll_ref_clk and the PLL output clocks.

Workaround 2: Change the frequency of the PLL reference clock to get an integer ratio between the PLL reference clock frequency and the operating frequency.