Article ID: 000079520 Content Type: Troubleshooting Last Reviewed: 05/16/2014

Why does the Early Power Estimator tool (EPE) report higher power than PowerPlay Power Analyzer (PPPA), when using ALTUFM_OSC in MAX II and MAX V devices?

Environment

BUILT IN - ARTICLE INTRO SECOND COMPONENT
Description

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. 

Resolution

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.

Related Products

This article applies to 3 products

MAX® II Z CPLD
MAX® V CPLDs
MAX® II CPLDs