LVDS SERDES Transmitter / Receiver IP Cores User Guide

ID 683062
Date 12/15/2017
Public
Document Table of Contents

1.5.2.2. DPA PLL Calibration in Arria II and Stratix IV Devices and Later

Starting with the Arria II device and the production versions of Stratix IV devices, DPA PLL calibration is implemented for each receiver channel independently using delay elements in the LVDS receiver path. Anytime the rx_reset port is deasserted for a receiver channel, the DPA circuitry is reset, and the calibration and locking process begins. The DPA circuitry in an LVDS receiver can reset at any time without impacting other LVDS receivers sharing the same PLL.

  1. The following events occur during the DPA calibration process:
  2. The ALTLVDS_RX IP core counts 256 data transitions, then inserts delay elements on the LVDS receiver data path to skew the clock and data relationship.
  3. The ALTLVDS_RX IP core counts 256 data transitions, then removes the delay elements on the LVDS receiver data path, restoring the original clock to data relationship.
  4. The ALTLVDS_RX IP core counts 256 data transitions, and then asserts the rx_dpa_locked signal.

With the Stratix IV production devices, you can choose to use the DPA PLL calibration method to be backward compatible with Stratix III and Stratix IV ES devices by turning on Enable PLL calibration in the ALTLVDS_RX parameter editor. If you turn off Enable PLL calibration in the ALTLVDS_RX parameter editor, the receiver IP core uses delay elements in the receiver data path.

Arria II devices always use the DPA calibration method using delay elements in the receiver data path.