I'm using a Lattice FGPA IceStick with the newer IceCube2 programming environment and the Diamond 3.0 programming tool. The 'iCEstick LED Rotation' example runs OK but when I attempt to enable the PLL, the example stops working. By 'stops working', I mean that upon download the LEDs don't blink and appear to be in an intermediate state as if configured as inputs. The problem remains after removing the PLL. No help found on Lattice's site.
When configuring the PLL, it appears as if IceCube2 decides to use a different constraint file located in the impl directory instead of the constraint directory. Check the constraint editor and make sure the pin assignments have not changed. If necessary, modify and LOCK the pin assignments in the Pin Constraints Editor in IceCube2.
The pin assignments change every time a new project is chosen in icecube2 and not just when configuring the PLL. And there doesn't seem to be a way around this. It probably is an icecube2 error and not a Diamond Programmer error. (I use Diamond 3.4 programmer.)
If an existing project is chosen in icecube2, where the pins were previously LOCKED, then there is no need to change the constraints again.