- Ensure that the polarities of the txn/txp and rxn/rxp lines are not reversed. If they are, these can be fixed by using the
TXPOLARITY and RXPOLARITY ports of the transceiver.
- Check that the transceiver is not being held in reset or still being initialized.
The RESETDONE outputs from the transceiver indicate when the transceiver is
ready.
- 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.