Device Family: Arria V GT, Arria V GX, Arria V GZ, Arria V ST, Arria V SX, Cyclone V E, Cyclone V GT, Cyclone V GX, Cyclone V SE, Cyclone V ST, Cyclone V SX, Stratix V E, Stratix V GS, Stratix V GT, Stratix V GX
Type: Answers
Area: Component


Last Modified: August 31, 2016
Version Found: v12.0

How do I set the PLL compensation targets for the Altera_PLL megafunction?

Description

You will see the following warning in the Quartus® II fitter report if a PLL does not have a compensated clock specified:

 

Warning (177007): PLL(s) placed in location <PLL location> do not have a PLL clock to compensate specified - the Fitter will attempt to compensate all PLL clocks

                Info (177008): <instance_name> altera_pll:altera_pll_i|general[0].gpll~FRACTIONAL_PLL

Workaround/Fix

The way to specify a compensated clock target (which can be done directly in the ALTPLL megafunction GUI), is to make a “Match PLL Compensation Clock” assignment.  The syntax of the PLL clock node has to be specific in order for it to be saved in the Assignment Editor.  Filter on *outclk_wire* in a post compilation filter in the node finder.

For example:

example:inst|example_0002:example_inst|altera_pll:altera_pll_i|outclk_wire[0]

Where outclk_wire[0] corresponds to C0 in the Altera_PLL instance.