40- and 100-Gbps Ethernet MAC and PHY MegaCore Function User Guide

ID 683114
Date 6/15/2022
Public
Document Table of Contents

4. Debugging the 40GbE and 100GbE Link

If you are experiencing difficulties bringing up your 40‑100GbE IP core link in hardware, Altera suggests that you begin debugging at the most basic level, with word lock. Then, consider higher level issues.

The following steps should help you identify and resolve common problems that occur when bringing up a 40‑100GbE IP core link:

  1. Establish word lock—The RX lanes should be able to achieve word lock even in the presence of extreme bit error rates. If unable to achieve word lock, check the transceiver clocking and data rate configuration. Check for cabling errors such as the reversal of the TX and RX lanes. Check the clock frequency monitors.

    To check for word lock: Clear the PHY_FRAME_ERROR register by writing the value of 1 to the PHY_SCLR_FRAME_ERROR regiseter at offset 0x324, and then read the PHY_FRAME_ERROR regster at offset 0x323. If the value is non-zero then the IP core has probably not yet achieved, or has lost, word lock.

  2. Establish the alignment marker lock—Virtual lane alignment marker lock requires a moderate quality transceiver connection. If the lock is completely absent, recheck the alignment marker period. If the lock is intermittent, recheck the transceiver physical connection and analog settings.

    To check for alignment marker lock: Check the value of the rx_pcs_ready signal or read bit [0] of the PHY_RXPCS_STATUS register at offset 0x326. The value of 1 on the signal or in the register bit indicates the RX PCS is fully aligned.

  3. Establish lane integrity—When operating properly, the lanes should not experience bit errors at a rate greater than roughly one per hour per day. Bit errors within data packets are identified as FCS errors. Bit errors in control information including IDLE frames generally cause errors in XL/CGMII decoding. The bit interleaved parity (BIP) mechanism is a diagonal parity computation that enables tracing a protocol error back to a physical lane.
  4. Verify packet traffic—The Ethernet protocol includes automatic lane reordering so the higher levels should follow the PCS. If the PCS is locked, but higher level traffic is corrupted, there may be a problem with the remote transmitter virtual lane tags.
  5. Tuning—You can adjust analog parameters to minimize any remaining bit error rate. IDLE traffic is representative for analog purposes.