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Registered: ‎02-08-2021

CLKREQ on B65 L3N for a xcku040sfva784-1-i is transitioning low without any constrains but unused pins to PULLNONE.

Hi there,

I am observing a strange behaviour on a Trenz module.

I have a PCIe x4 interface in B225 as part of the Kintex Ultrscale DMA IP, with B65-L3N connected to CLKREQ in the PCIe slot, but without any constrain for it.

I have this constrain in the main xdc:

set_property BITSTREAM.CONFIG.UNUSEDPIN PULLNONE [current_design]

For some reason, that signal pulls down after programming.

Is that possible? I see that the PCIe core in the DMA does not manage CLKREQ at all, so I was wondering how can that be.

We only have two FET isolators in the line (one on each side of the connector), no pullups or downs.


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