XAUI v12.3 Product Guide
138
PG053 April 6, 2016
Appendix C:
Debugging Designs
Transceiver Specific Checks
• Monitor the
mgt_codevalid[7:0]
input to the XAUI core by triggering on it using
the Vivado lab tools. This input is a combination of the transceiver RX disparity error
and RX not in table error outputs.
• These signals should not be asserted over the duration of a few seconds, minutes or
even hours. If they are frequently asserted, it might indicate an issue with the
transceiver.
• Place the transceiver into parallel or serial near-end loopback.
• If correct operation is seen in the transceiver serial loopback, but not when loopback is
performed through an optical cable, it might indicate a faulty optical module.
• If the core exhibits correct operation in the transceiver parallel loopback but not in
serial loopback, this might indicate a transceiver issue.
• A mild form of bit error rate might be solved by adjusting the transmitter Pre-Emphasis
and Differential Swing Control attributes of the transceiver.
Problems with the MDIO
See
for detailed information about performing MDIO transactions.
Things to check for:
• Ensure that the MDIO is driven properly. Check that the
mdc
clock is running and that
the frequency is 2.5 MHz or less.
• Ensure that the XAUI core is not held in reset.
• Read from a configuration register that does not have all 0s as a default. If all 0s are
read back, the read was unsuccessful. Check that the PRTAD field placed into the MDIO
frame matches the value placed on the
prtad[4:0]
port of the XAUI core.
• Verify in simulation and/or a Vivado lab tools capture that the waveform is correct for
accessing the host interface for a MDIO read/write.