Clocking and PLL User Guide: Agilex™ 5 FPGAs and SoCs

ID 813671
Date 7/25/2024
Public
Document Table of Contents

5.2.2. IOPLL IP Core Parameters - Settings Tab

Table 9.   IOPLL IP Core Parameters - Settings Tab for Agilex™ 5 Devices
Parameter Value Description
PLL Auto Reset On or Off Automatically self-resets the PLL on loss of lock.
Create a second input clk ‘refclk1’ On or Off Turn on to provide a backup clock attached to your PLL that can switch with your original reference clock.
Second Reference Clock Frequency 16 Selects the frequency of the second input clock signal. The default value is 100.0 MHz. The minimum and maximum value is dependent on the device used.
Create an ‘active_clk’ signal to indicate the input clock in use On or Off Turn on to create the activeclk output. The activeclk output indicates the input clock which is in use by the PLL. Output signal low indicates refclk and output signal high indicates refclk1.
Create a ‘clkbad’ signal for each of the input clocks On or Off Turn on to create two clkbad outputs, one for each input clock. Output signal low indicates the clock is working and output signal high indicates the clock is not working.
Switchover Mode Automatic Switchover, Manual Switchover, or Automatic Switchover with Manual Override Specifies the switchover mode for design application. The IP supports three switchover modes:
  • If you select the Automatic Switchover mode, the PLL circuitry monitors the selected reference clock. If one clock stops, the circuit automatically switches to the backup clock in a few clock cycles and updates the status signals, clkbad and activeclk.
  • If you select the Manual Switchover mode, when the control signal, extswitch, changes from logic high to logic low, and stays low for at least three clock cycles, the input clock switches to the other clock. The extswitch can be generated from FPGA core logic or input pin.
  • If you select Automatic Switchover with Manual Override mode, when the extswitch signal is high, it overrides the automatic switch function. As long as extswitch remains low, further switchover action is blocked. To select this mode, your two clock sources must be running and the frequency of the two clocks cannot differ by more than 20%. If both clocks are not on the same frequency, but their period difference is within 20%, the clock loss detection block detects the lost clock. The PLL most likely drops out of lock after the PLL clock input switchover and needs time to lock again.
Enable access to I/O Bank clock ports On or Off This options enables the IOPLL's I/O bank clock ports. The ports are exported instead of outclks, and can be configured through corresponding outclk settings (the outclks that correspond to periphery ports are indicated in the 'Output Clocks' section). The clock ports can be connected to one LVDS only.
Enable access to the PLL DPA output port On or Off Turn on to enable the PLL DPA output port.
Enable access to PLL external clock output port On or Off Turn on to enable the PLL external clock output port.
Specifies which outclk to be used as extclk_out[0] source C0C3 (I/O bank) Specifies the outclk port to be used as extclk_out[0] source.
Specifies which outclk to be used as extclk_out[1] source C0C3 (I/O bank) Specifies the outclk port to be used as extclk_out[1] source.
16 This parameter is only available when Create a second input clk 'refclk1' is turned on.