Hi Dave, The IODELAY_CTRL block need to be clocked at 200MHz +/- 10MHz. From the datasheet it is not clear whether you can clock the IODELAY block at a different frequency - it just states that the average tap delay at 200MHz is 78ps. I'm not sure what the effect would be if you clocked it at 100MHz, but let us know what your experience is.
Regards, Henno On Thu, Aug 1, 2013 at 7:20 AM, David MacMahon <[email protected]>wrote: > I noticed that the QDR controller on ROACH2 clocks the IODELAY delay > adjustments at 200 MHz (i.e. sys_clk2x). Is there any advantage to running > that at 200 MHz rather than at 100 MHz (i.e. sys_clk)? It seems that > startup calibration might take twice as long at 100 MHz, but that's > probably not a significant amount of time and it would ease the timing > requirements thereby simplifying place and route. > > Would it be as simple as changing the "PORT div_clk = sys_clk2x" line(s) > of the qdr_controller instance(s) in system.mhs to use "sys_clk" instead of > "sys_clk2x"? > > Thanks, > Dave > > > -- Kind regards, Henno Kriel Digital Back End: Hardware Team Manager MeerKAT Digitiser: System Architect SKA South Africa Third Floor The Park Park Road (off Alexandra Road) Pinelands 7405 Western Cape South Africa Latitude: -33.94329 (South); Longitude: 18.48945 (East). (p) +27 (0)21 506 7300 (p) +27 (0)21 506 7365 (direct) (f) +27 (0)21 506 7375 (m) +27 (0)84 504 5050
