Programmable input delay on ARRIA II GX

Thanks, FvM.

As I understand it that would take a PLL which I would rather avoid

if the functionality comes cheaper.

Looking at the IOE structure there is "programmable delay" but I am guessing

by your comments that this is not _dynamically_ programmable and hence that

would be why it would not show up in altiobuf megafunction params.

Data rate is slow enough at 250MHz DDR LVDS such that I only really

need the dynamic behavior initially for convenience so perhaps I just do a bunch

of builds <tick-tock> with the "fixed" "programmable delay" varied and find my happy place.

Sound good?

Cos

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As I understand it that would take a PLL which I would rather avoid if the functionality comes cheaper.

Looking at the IOE structure there is "programmable delay" but I am guessing

by your comments that this is not _dynamically_ programmable and hence that

would be why it would not show up in altiobuf megafunction params.

Data rate is slow enough at 250MHz DDR LVDS such that I only really

need the dynamic behavior initially for convenience so perhaps I just do a bunch

of builds <tick-tock> with the "fixed" "programmable delay" varied and find my happy place.

--- Quote End ---

Cosmo,

Quartus II will do a good job inserting IODelays. I'm dabbling (not really) with a similar set-up. I'm using Cyclone IV though which is different than Arria II GX where the DDR registers are built into the IO-ring and the compiler can't add extra routing delay. But I recompiled (QII9.1sp2) my code for Arria II GX and ended up with a really small hold violation of 7 ps for the Fast model only. But I have a skew of 500 ps on the input data at a 240 MHz frequency, you may have a smaller skew and meet timing. After compilation in the Fitter Report -> Resource Section -> Delay Chain Summary you can see what the compiler added.

Thanks, josyb, yes, I just noticed that looking at the results using

"Locate in Resource Property Editor" for the lvds nodes through Assignment Editor.

Checking the Fitter Report is much easier. :)

That's pretty handy dandy and explains why things just worked since i had

already specified my input timing in sdc file.

Thanks all!

Cos