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

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

2.6.3.1. I/O PLL in HVIO Bank as System PLL

Below the GTS transceiver bank, there are two HVIO banks (5A/5B) that share a common I/O PLL. This I/O PLL can be used as a second system PLL, but it is limited to the PMA Direct mode in the current release of the Quartus® Prime Pro Edition software.

When you configure the GTS transceiver bank to run PCIe* and non- PCIe* protocols, you must use two system PLLs. Since there is only one system PLL in the Agilex™ 3 device, you must use the I/O PLL from the adjacent HVIO bank. As the I/O PLL support is currently limited, it is not possible to run PCIe* concurrently with other non- PCIe* protocols requiring the use the I/O PLL as a second system PLL in the same design. The I/O PLL support is planned to be expanded in a future release of the Quartus® Prime Pro Edition software.

The two HVIO banks that are adjacent to the GTS transceiver bank 1A are:
  • HVIO bank 5A
  • HVIO bank 5B
The input reference clock for the I/O PLL can come from any one of the following four pins in the HVIO banks 5A or 5B:
  • PLLREFCLK1 (5A)
  • PLLREFCLK2 (5A)
  • PLLREFCLK1 (5B)
  • PLLREFCLK2 (5B)

You must consider the following when using the I/O PLL. As the I/O PLL is different from the system PLL, you have to instantiate the I/O PLL using the IOPLL IP instead of the GTS System PLL Clocks IP . Refer to the Clocking and PLL User Guide: Agilex® 3 FPGAs and SoCs for more information. The I/O PLL in the slowest device speed grade is not capable of reaching the system PLL's maximum frequency of 1000 MHz. Refer to the device datasheet for the I/O PLL specifications. Additionally, the I/O PLL does not support the fractional mode.