Agilex™ 5 ES Device Errata and User Guidelines

ID 825514
Date 12/09/2024
Public
Document Table of Contents

2.5.8. TX user clock output does not work for a certain range of VCO frequencies

Description

The o_tx_clkout and o_tx_clkout2 ports have an issue when selecting "TX User Clock" as the source. Depending on the data rate, the user clock is driven by either the slow, medium, and fast PLLs. The medium speed PLL, which has a VCO output frequency range of between 10.5 to 13.5 GHz, cannot drive the user clock, which causes the user clock output to be in an incorrect frequency. Therefore, do not use the user clock when the data rate requires the usage of the medium speed PLL. Data rates such as 3.125 Gbps or 6.25 Gbps require the medium speed PLL frequency of 12.5 GHz.

You can check the data rates that are affected by using the GTS PMA/FEC Direct PHY IP. as follows:

  • Set the required "PMA data rate".
  • Select the reference clock frequency.
  • Check the stated VCO frequency. The message pane shows if "TX_PLL_MED" is selected.

If the VCO frequency is between 10.5 to 13GHz, or "TX_PLL_MED" is written in the info message, you cannot use the user clock.

Workaround

The word clock is not impacted by this issue, and can be used when data rates require the medium speed PLL be used.