E-Tile Transceiver PHY User Guide

ID 683723
Date 4/01/2024
Document Table of Contents Reverse Parallel Loopback Path

The reverse parallel loopback path sets the transmitter buffer to transmit data fed directly from the CDR recovered data.

When in reverse parallel loopback mode, the reference clock source of the received data stream must be the same reference clock that the transceiver channel receives (0ppm difference between the transmit and receive frequencies).

Additionally, the TX and RX bit rate/reference clock ratio and width mode register settings must be set to the same value to ensure proper operation of the reverse parallel loopback.

Using an external instrument, data is fed to the RX buffer, and the deserialized parallel data stream of the receiver is looped back as the parallel data input stream for the transmitter.

Figure 56. Reverse Parallel Loopback Path