When using the ALTUFM_OSC megafunction in MAX® II or MAX V devices, the EPE and Quartus® II PPPA power results may vary significantly, if the oscena port is hardcoded to ‘1’ in user logic.
PPPA does not consider the connectivity between devices and so the oscena=‘1’ will be ignored during power analysis. The EPE has an oscillator enable setting which is set to '1' by default and as a result, PPPA power numbers will be much lower than in the EPE.
This issue is not of concern when the oscena pin is tied to a physical input pin as it is possible to easily set the toggle rate to a desired value.
To set the oscena port\'s toggle rate in PPPA, follow the instructions below :
- Locate the oscena port in Technology Map Viewer.
- Copy the net name that it is connected to exactly as it’s written in the Viewer into the Assignment Editor.
- Note that if oscena was tied to ‘1,’ the fitter will invert the signal and tie the node to ~GND. If oscena was tied to ‘0,’ the fitter will invert the signal and tie the node to VDD. In this case oscena=’1’, so an inversion is implemented and oscena becomes an active low signal tied to ~GND, which will be the net name in this case.
- Set the Assignment Name to Power Static Probability. Since this is an active low signal, set 0 as the Value.
When you run PPPA, the numbers should now closely match the EPE.