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1. Agilex™ 5 Clocking and PLL Overview
2. Agilex™ 5 Clocking and PLL Architecture and Features
3. Agilex™ 5 Clocking and PLL Design Considerations
4. Clock Control Intel® FPGA IP Core
5. IOPLL Intel® FPGA IP Core
6. Document Revision History for the Clocking and PLL User Guide: Agilex™ 5 FPGAs and SoCs
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
3.1. Guidelines: Clock Switchover
3.2. Guidelines: Timing Closure
3.3. Guidelines: Resetting the PLL
3.4. Guidelines: Configuration Constraints
3.5. Clocking Constraints
3.6. IP Core Constraints
3.7. Guideline: Achieving 5% Duty Cycle for fOUT_EXT ≥ 300 MHz Using tx_outclk Port from LVDS SERDES Intel® FPGA IP
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2.2.11. PLL Input Clock Switchover
The clock switchover feature allows the I/O PLL to switch between two reference input clocks. Use this feature for clock redundancy or for a dual-clock domain application where a system turns to the redundant clock if the previous clock stops running. The design can perform clock switchover automatically when the clock is no longer toggling or based on a user control signal, extswitch.
Agilex™ 5 I/O PLLs support the following clock switchover modes:
- Automatic switchover—the clock sense circuit monitors the current reference clock. If the current reference clock stops toggling, the reference clock automatically switches to inclk0 or inclk1 clock.
- Manual clock switchover—clock switchover is controlled using the extswitch signal. When the extswitch signal goes from logic high to logic low, and stays low for at least three clock cycles for the inclk being switched to, the reference clock to the I/O PLL is switched from inclk0 to inclk1, or vice-versa.
- Automatic switchover with manual override—this mode combines automatic switchover and manual clock switchover. When the extswitch signal goes low, it overrides the automatic clock switchover function. If the extswitch signal is low, further switchover action is blocked.
Note: The fabric-feeding PLL located in HVIO block does not support clock switchover feature.