Intel® Agilex™ Clocking and PLL User Guide

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ID 683761
Date 11/09/2022
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Document Table of Contents
Document Table of Contents x
1. Intel® Agilex™ Clocking and PLL Overview 2. Intel® Agilex™ Clocking and PLL Architecture and Features 3. Intel® Agilex™ Clocking and PLL Design Considerations 4. Clock Control Intel® FPGA IP Core 5. IOPLL Intel® FPGA IP Core 6. IOPLL Reconfig Intel® FPGA IP Core 7. Intel® Agilex™ Clocking and PLL User Guide Archives 8. Document Revision History for the Intel® Agilex™ Clocking and PLL User Guide
1. Intel® Agilex™ Clocking and PLL Overview x
1.1. Clock Networks Overview 1.2. PLLs Overview
2. Intel® Agilex™ Clocking and PLL Architecture and Features x
2.1. Clock Networks Architecture and Features 2.2. PLLs Architecture and Features
2.1. Clock Networks Architecture and Features x
2.1.1. Clock Network Architecture 2.1.2. Clock Resources 2.1.3. Clock Control Features
2.1.1. Clock Network Architecture x
2.1.1.1. Clock Network Hierarchy 2.1.1.2. Clock Sectors 2.1.1.3. Programmable Clock Routing
2.1.3. Clock Control Features x
2.1.3.1. Clock Gating 2.1.3.2. Clock Divider
2.1.3.1. Clock Gating x
2.1.3.1.1. Root Clock Gate 2.1.3.1.2. Sector Clock Gate 2.1.3.1.3. I/O PLL Clock Gate 2.1.3.1.4. LAB Clock Gate
2.2. PLLs Architecture and Features x
2.2.1. PLL Features 2.2.2. PLL Usage 2.2.3. PLL Locations 2.2.4. PLL Architecture 2.2.5. PLL Control Signals 2.2.6. PLL Feedback Modes 2.2.7. Clock Multiplication and Division 2.2.8. Programmable Phase Shift 2.2.9. Programmable Duty Cycle 2.2.10. PLL Cascading 2.2.11. PLL Input Clock Switchover 2.2.12. PLL Reconfiguration and Dynamic Phase Shift 2.2.13. PLL Calibration
2.2.5. PLL Control Signals x
2.2.5.1. Reset 2.2.5.2. Locked
2.2.6. PLL Feedback Modes x
2.2.6.1. Direct Compensation Mode 2.2.6.2. LVDS Compensation Mode 2.2.6.3. Source Synchronous Compensation Mode 2.2.6.4. Normal Compensation Mode 2.2.6.5. Zero-Delay Buffer Mode 2.2.6.6. External Feedback Mode
2.2.11. PLL Input Clock Switchover x
2.2.11.1. Automatic Switchover 2.2.11.2. Automatic Switchover with Manual Override 2.2.11.3. Manual Clock Switchover
2.2.13. PLL Calibration x
2.2.13.1. Power-Up Calibration 2.2.13.2. User Calibration
3. Intel® Agilex™ Clocking and PLL Design Considerations x
3.1. Guidelines: Clock Switchover 3.2. Guidelines: Timing Closure 3.3. Guidelines: Resetting the PLL 3.4. Guidelines: Configuration Constraints 3.5. Guidelines: I/O PLL Reconfiguration 3.6. Clocking Constraints 3.7. IP Core Constraints 3.8. Guideline: Achieving 5% Duty Cycle for fOUT_EXT ≥ 300 MHz Using tx_outclk Port from LVDS SERDES Intel® FPGA IP
4. Clock Control Intel® FPGA IP Core x
4.1. Release Information for Clock Control Intel® FPGA IP 4.2. Clock Control IP Core Parameters 4.3. Clock Control IP Core Ports and Signals
5. IOPLL Intel® FPGA IP Core x
5.1. Release Information for IOPLL Intel® FPGA IP 5.2. .mif File Generation 5.3. IP-XACT File Generation 5.4. IOPLL IP Core Parameters 5.5. IOPLL IP Core Ports and Signals
5.2. .mif File Generation x
5.2.1. Generating a New .mif File 5.2.2. Adding Configurations to Existing .mif File
5.3. IP-XACT File Generation x
5.3.1. Generating a New IP-XACT File
5.4. IOPLL IP Core Parameters x
5.4.1. IOPLL IP Core Parameters - PLL Tab 5.4.2. IOPLL IP Core Parameters - Settings Tab 5.4.3. IOPLL IP Core Parameters - Cascading Tab 5.4.4. IOPLL IP Core Parameters - Dynamic Reconfiguration Tab 5.4.5. IOPLL IP Core Parameters - Advanced Parameters Tab
6. IOPLL Reconfig Intel® FPGA IP Core x
6.1. Release Information for IOPLL Reconfig Intel® FPGA IP 6.2. Implementing I/O PLL Reconfiguration in the IOPLL Reconfig IP Core 6.3. IOPLL Reconfig IP Core Reconfiguration Modes 6.4. Avalon® Memory-Mapped Interface Ports in the IOPLL Reconfig IP Core 6.5. Address Bus and Data Bus Settings 6.6. Design Example
6.2. Implementing I/O PLL Reconfiguration in the IOPLL Reconfig IP Core x
6.2.1. Connectivity between the IOPLL and IOPLL Reconfig IP Cores 6.2.2. Connecting the IOPLL and IOPLL Reconfig IP Cores
6.3. IOPLL Reconfig IP Core Reconfiguration Modes x
6.3.1. .mif Streaming Reconfiguration 6.3.2. Advanced Mode Reconfiguration 6.3.3. Clock Gating Reconfiguration 6.3.4. Dynamic Phase Shift Reconfiguration
6.3.1. .mif Streaming Reconfiguration x
6.3.1.1. Recalibration Using .mif
6.3.2. Advanced Mode Reconfiguration x
6.3.2.1. Recalibration Using Advanced Mode
6.5. Address Bus and Data Bus Settings x
6.5.1. Address Bus and Data Bus Settings for Advanced Mode Reconfiguration 6.5.2. Output Clock and the Corresponding Data Bit Setting for Clock Gating Reconfiguration 6.5.3. Data Bus Setting for Dynamic Phase Shift for IOPLL Reconfig IP Core
6.5.1. Address Bus and Data Bus Settings for Advanced Mode Reconfiguration x
6.5.1.1. Data Bus Setting for Bandwidth Control and Charge Pump 6.5.1.2. Data Bus Setting for Ripplecap
6.6. Design Example x
6.6.1. Reconfiguration Option: .mif Streaming Reconfiguration Using IOPLL Reconfig IP Core 6.6.2. Reconfiguration Option: Advanced Mode Reconfiguration and Recalibration Using IOPLL Reconfig IP Core 6.6.3. Reconfiguration Option: Clock Gating Reconfiguration Using IOPLL Reconfig IP Core
1. Intel® Agilex™ Clocking and PLL Overview
2. Intel® Agilex™ Clocking and PLL Architecture and Features
3. Intel® Agilex™ Clocking and PLL Design Considerations
4. Clock Control Intel® FPGA IP Core
5. IOPLL Intel® FPGA IP Core
6. IOPLL Reconfig Intel® FPGA IP Core
7. Intel® Agilex™ Clocking and PLL User Guide Archives
8. Document Revision History for the Intel® Agilex™ Clocking and PLL User Guide

2.2.11.1. Automatic Switchover

Intel® Agilex™ I/O PLLs support a fully configurable clock switchover capability.

Figure 19. Automatic Clock Switchover Circuit Block DiagramThis figure shows a block diagram of the automatic switchover circuit in the I/O PLL.


When the current reference clock is not present, the clock sense block automatically switches to the backup clock for I/O PLL reference. You can select a clock source as the backup clock by connecting it to the inclk1 port of the I/O PLL in your design.

The clock switchover circuit sends out three status signals—clkbad0, clkbad1, and activeclock—from the I/O PLL to implement a custom switchover circuit in the logic array.

In automatic switchover mode, the clkbad0 and clkbad1 signals indicate the status of the two clock inputs. When they are asserted, the clock sense block detects that the corresponding clock input has stopped toggling. These two signals are not valid if the frequency difference between inclk0 and inclk1 is greater than 20%.

The activeclock signal indicates which of the two clock inputs (inclk0 or inclk1) is being selected as the reference clock to the I/O PLL. When the frequency difference between the two clock inputs is more than 20%, the activeclock signal is the only valid status signal.

Use the switchover circuitry to automatically switch between inclk0 and inclk1 when the current reference clock to the I/O PLL stops toggling. You can switch back and forth between inclk0 and inclk1 any number of times when one of the two clocks fails and the other clock is available.

For example, in applications that require a redundant clock with the same frequency as the reference clock, the switchover state machine generates a signal (clksw) that controls the multiplexer select input. In this case, inclk1 becomes the reference clock for the I/O PLL.

When using automatic clock switchover mode, the following requirements must be satisfied:

  • Both clock inputs must be running when the FPGA is configured.
  • The period of the two clock inputs can differ by no more than 20%.
  • The input clocks must meet the input jitter specifications and I/O standard specifications.

Glitches in the input clock may be seen as a greater than 20% difference in frequency between the input clocks.

If the current clock input stops toggling while the other clock is also not toggling, switchover is not initiated and the clkbad[0..1] signals are not valid. If both clock inputs are not the same frequency, but their period difference is within 20%, the clock sense block detects when a clock stops toggling. However, the I/O PLL may lose lock after the switchover is completed and needs time to relock.

Note: You must reset the I/O PLL using the reset signal to maintain the phase relationships between the I/O PLL input and output clocks when using clock switchover.
Figure 20. Automatic Switchover After Loss of Clock DetectionThis figure shows an example waveform of the switchover feature in automatic switchover mode. In this example, the inclk0 signal is held low. After the inclk0 signal is held low for approximately two clock cycles, the clock sense circuitry drives the clkbad0 signal high. As the reference clock signal (inclk0) is not toggling, the switchover state machine controls the multiplexer through the extswitch signal to switch to the backup clock, inclk1.


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