E-Tile Transceiver PHY User Guide

ID 683723
Date 9/30/2022
Public
Document Table of Contents

3.1.7.1. Internal Serial Loopback Path

The internal serial loopback path sets the CDR to recover data from the serializer instead of the receiver serial input pin.

The transmitter buffer sends data normally, but internal serial loopback takes the data before the buffer.

It is implemented completely on-chip and does not require any connector on the serial path. This loopback path is enabled independently of the TX buffer enablement.

The E-tile transceiver channel also supports external connectivity where you have to connect the TX differential outputs to the RX differential inputs. This external connection must consist of a transmission path with 100 Ω differential mode impedance. Mission mode is a form of external connection where the data source is something other than the E-tile transmitter. For example, a BERT or other device's TX is providing data to the E-tile receiver.

Note: Currently, only the PRBS31/PRBS31Q patterns are supported in internal serial loopback mode.
Figure 56. Internal Serial Loopback Path

For more details on Register Read/Write support and programming, refer to PMA Register Map and PMA Attribute Codes to configure these parameters.

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