Near-end PMA Loopback:
The near-end PMA loopback for GTH Transceivers is currently not supported by the IBERT tool, but it can be selected by setting the followingattributes manually through the "DRP Settings" tabin IBERT:
It is important to note here thatthough PMA_LPBK_CTRL_LANE<n>[1:0] attributeis perGTH lane,the SLICE_CFG and LANE_AMON_SEL are not lane specific attributes,but affect all four lanes in a Quad. Therefore, all four transceivers in aQuadare placed in near-end PMA loopback mode when these attributes are set to these values. This feature is to be addressed in a future version of the IBERT tool.
Near-end PCS Loopback:
The near-end PCS loopback can be selected from the pull-down menu in the IBERT tool. IBERT sets the following bit to enable the near-end PCS loopback when selected from the menu.
Far-end PMA Loopback:
Far-end PMA loopback is supported in GTH Transceivers, but far-end PCS loopback is not supported. The"Far-end PCS" in the IBERT tool is incorrectly labeled (it is actually far-end PMA loopback), and selecting this option only sets the PCS_MODE<n> bit to 'b. The other attribute PCS_RESET<n> is not set correctly either.This feature is to be addressed in a future revision of the IBERT tool.
The far-end PMA loopback can be selected correctly by setting the above attributes manually through the "DRP Settings" tab in IBERT.