For the Kintex-7 GTX IBERT core generated in 13.3 and earlier, the reference clock for the lowest numbered Kintex-7 GTX in a quad is used to generate the user clocksfor other GTs in the samequad.
For example, if channel 0 and channel 3 of a GTX_QUADare selected with two different reference clocks driving each of the channels, then the IBERT core will use MGTREFCLK0 to generate the user clocks for both GTX channels. This could cause channel 3 of the GTX_QUAD tonotwork properly.
The user clock generation for each transceiver should be independent for each reference clock enabled. Because of this issue, incorrect TXUSRCLKs will be generated which might lead to link failure.
This issue only affects the Kintex-7 GTX IBERT design when generated in version 13.3 and earlier.The issue is to be addressed in version 13.4 of the tools.
Currently, the only work-around is to ensure that all 4 GTs in a QUAD use the same reference clock so that the proper TXUSRCLK is generated for all 4 channels in a QUAD.If this is not possible, 2 different IBERT designs will need to be generated so that you can test the transceivers with the appropriate reference clock.One design will use the first reference clock for all 4 transceivers in the quad, and the second design will use the second reference clock for all 4 transceivers in the quad.