Stratix V Device Handbook: Volume 2: Transceivers

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ID 683779
Date 11/23/2021
Public
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3.4.2. Resetting the Transceiver in CDR Manual Lock Mode

The numbers in this list correspond to the numbers in the following figure, which guides you through the steps to put the CDR in manual lock mode.

  1. Make sure that the calibration is complete (rx_cal_busy is low) and the transceiver goes through the initial reset sequence. The rx_digitalreset and rx_analogreset signals should be low. The rx_is_lockedtoref is a don't care and can be either high or low. The rx_is_lockedtodata and rx_ready signals should be high, indicating that the transceiver is out of reset. Alternatively, you can start directly with the CDR in manual lock mode after the calibration is complete.
  2. Assert the rx_set_locktoref signal high to switch the CDR to the lock-to-reference mode. The rx_is_lockedtodata status signal is deasserted. Assert the rx_digitalreset signal high at the same time or after rx_set_lockedtoref is asserted if you use the user-coded reset. When the Transceiver PHY reset controller is used, the rx_digitalreset is automatically asserted.
  3. After the rx_digitalreset signal gets asserted, the rx_ready status signal is deasserted.
  4. Assert the rx_set_locktodata signal high, tLTR_LTD_Manual (minimum 15 μs) after the CDR is locked to reference. rx_is_locktoref should be high and stable for a minimum tLTR_LTD_Manual (15 μs), before asserting rx_set_locktodata. This is required to filter spurious glitches on rx_is_lockedtoref. The rx_is_lockedtodata status signal gets asserted, which indicates that the CDR is now set to LTD mode.
    The rx_is_lockedtoref status signal can be a high or low and can be ignored after asserting rx_set_locktodata high after the CDR is locked to reference.
  5. Deassert the rx_digitalreset signal after a minimum of tLTD_Manual (4 μs).
  6. If you are using the Transceiver PHY Reset Controller, the rx_ready status signal gets asserted after the rx_digitalreset signal is deasserted. This indicates that the receiver is now ready to receive data with the CDR in manual mode.
Figure 85. Reset Sequence Timing Diagram for Receiver when CDR is in Manual Lock Mode

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