Consult the port list section for a description of the diagnostic signals that are available to debug the RX.
This signal indicates that the receiver has detected and locked to the word boundaries as defined by a 01 or 10 control or data header. This is the first step to ensure that the 10G/25G Ethernet Subsystem IP is functioning normally.
A bad FCS indicates a bit error in the received packet. An FCS error could be due to any number of causes of packet corruption such as noise on the line.
A local fault indication can be locally generated or received. Some causes of a local fault are:
- block lock not complete
- high bit error rate
- overflow or underflow
If the Ethernet packets are being transmitted properly according to IEEE Std. 802.3, there should not be RX errors. However, the signal integrity of the received signals must be verified first.
To aid in debug, a local loopback can be performed with the signal
ctl_local_loopback when the Include AXI4-Lite enable option is
selected. Otherwise, a local loopback is performed with signal
gt_loopback_in for a non-AXI4-Lite configuration. This connects the TX SerDes to the RX SerDes,
effectively bypassing potential signal integrity problems. The transceiver is placed
into "PMA loopback," which is fully described in the transceiver product guide. In
this way, the received data can be checked against the transmitted packets to verify
that the logic is operating properly.