ISERDESE3 and IDDRE1 Clocking - 2023.2 English

UltraFast Design Methodology Guide for FPGAs and SoCs (UG949)

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2023.2 English

For ISERDESE3 and IDDRE1 clocking in UltraScale and UltraScale+ devices, maximum skew requirements exist between the clock and inverted clock pins. To meet the maximum skew requirements, AMD recommends using a single net for the clock and inverted clock pins when using the local inversion.

In the following figure, the left side shows a suboptimal configuration that uses the CLKOUT0B output of the MMCM. The right side of the figure shows the optimal configuration that uses the local inversion on the CLK_B and CB pins of the ISERDESE3 and IDDRE1. Using the optimal configuration guarantees that the maximum skew requirement is met while using fewer global clock resources.

Figure 1. Suboptimal to Optimal Clocking Topologies for ISERDESE3 and IDDRE1