UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

cancel
Showing results for 
Search instead for 
Did you mean: 
2,801 Views
Registered: ‎07-03-2009

DCM Phase Shift for GEMAC - Negative or Positive values

I am finally at the point where I can look into the setup and hold timings of the GMII port of the GEMAC on my real hardware. The user guide for the GEMAC (ug144 - Appendix C) suggest that extensive investigation of the phase shift should be carried out.

 

I have a working system using the DCM phase shift suggested in the example UCF (PHASE_SHIFT = -32).

 

The user guide recommends "a complete sweep of phase-shift settings during your initial system test. Use only positive (0 to 255) phase-shift settings, and use a test range that covers a range of no less than 128, corresponding to a total 180 degrees of clock offset."

 

I am a little confused by this as the example UCF uses a negative number (and works), should I be using negative or positive numbers for the phase shift ?

 

Thanks

Graeme

 

 

0 Kudos