GTS Transceiver PHY User Guide: Agilex™ 3 FPGAs and SoCs

ID 848344
Date 8/04/2025
Public
Document Table of Contents

2.6.3. System PLL

The GTS transceiver bank has one system PLL. The system PLL is the primary clock source for hard IP blocks (Ethernet MAC, PCS, FEC and PCIe) and the core interface which bridges the FPGA core and the GTS transceivers.

The system PLL has one output (C0) to feed those blocks. When you use the system PLL clocking mode, the hard IP blocks are not clocked by the PMA clock. The system PLL can also be used to clock the PMA direct mode.

You must instantiate and configure the system PLL using the GTS System PLL Clocks IP. For more information, refer to Implementing the GTS System PLL Clock IP.

The system PLL can use either of the local reference clock or regional reference clock in the GTS transceiver bank. It can also get the reference clock from four HVIO pins located in the adjacent HVIO bank.

Figure 20. System PLL Clock Network

Different interface protocols operating at different line rates can share a system PLL, except for PCIe. When multiple interface protocols share a system PLL, the protocol with the highest line rate determines the system PLL frequency, and the protocols with the lower line rates must be overclocked. The exact cadence is based on the clock; refer to Datapath Clock Cadences for the details.