RapidIO Intel FPGA IP User Guide

ID 683884
Date 9/15/2021
Public
Document Table of Contents

4.2.1.2. Reference Clock

The reference clock signal drives the transceiver and the Physical layer. By default, this clock is called clk in the generated IP core. Platform Designer (Standard) allows you to export the clk signal with a name of your choice.

The reference clock, clk, is the incoming reference clock for the transceiver’s PLL. The frequency of the input clock must match the value you specify for the Reference clock frequency parameter. The transceiver PLL converts the reference clock frequency to the internal clock speed that supports the RapidIO IP core baud rate.

The RapidIO parameter editor lets you select one of the supported frequencies. The selection allows you to use an existing clock in your system as the reference clock for the RapidIO IP core.

Note: You must drive the external transceiver TX PLL pll_refclk0 input clock from the same source from which you drive the RapidIO IP core clk input clock.

This source must be within ±100 ppm of its nominal value, to ensure the difference between any two devices in the RapidIO system is within ±200 ppm.

Figure 8. Reference Clock in a variation other than Intel® Arria® 10 and Intel® Cyclone® 10 GX RapidIO IP Core

The above figure shows how the transceiver uses the reference clock in variations other than Intel® Arria® 10 and Intel® Cyclone® 10 GX. In Intel® Arria® 10 and Intel® Cyclone® 10 GX variations, clk is the reference clock only for the RX PLL. The reference clock for the TX PLL is an input signal to the TX PLL IP core that you connect to the RapidIO IP core.

The PLL generates the high-speed transmit clock and the input clocks to the receiver high-speed deserializer clock and recovery unit (CRU). The CRU generates the recovered clock (rxclk) that drives the receiver logic.

For more information about the supported frequencies for the reference clock in your RapidIO variation, refer to the relevant device handbook.