E-Tile Transceiver PHY User Guide

ID 683723
Date 4/01/2024
Document Table of Contents

3.1.10. Unused Transceiver Channels

Unused transceiver channels that you plan to use later must be protected in order to ensure that there is no degradation in channel performance or maximum baud rate over the period of time that they are unused. To preserve the performance of these unused transceiver channels, the Quartus® Prime software can program the unused channels so that the analog circuitry in their transmit and receive stages toggles at a low data rate. This protects the analog circuitry from the effects of applying a constant bias with no signal applied. This is accomplished by setting the transmitter to generate a PRBS sequence at a low data rate, looping back the generated PRBS sequence into the receiver, and setting the receiver to lock to the low data rate generated PRBS sequence.

Unused simplex transmitter channels do not require protection.

Unused channels can appear in these ways:
  • Unused transceiver channels in a used tile
  • Unused transceiver channels in a completely unused tile
  • Unused transceiver channels in PAM4 mode
  • Channels protected in order to enable reconfiguring from mission mode to channel protection mode and back again

In the following sections, use either the per-pin assignment or the global assignment, but not both, to protect unused transceiver channels. This is because only one of the two is applicable when compiling, with the per-pin assignment taking precedence over the global assignment.