1. Agilex™ 7 FPGA M-Series Clocking and PLL Overview
2. M-Series Clocking and PLL Architecture and Features
3. M-Series Clocking and PLL Design Considerations
4. Clock Control Intel® FPGA IP Core
5. IOPLL Intel® FPGA IP Core
6. I/O PLL Reconfiguration Using EMIF Calibration IP
7. Agilex™ 7 Clocking and PLL User Guide: M-Series Archives
8. Document Revision History for the Agilex™ 7 Clocking and PLL User Guide: M-Series
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
2.2.6.6. External Feedback Mode
In external feedback (EFB) mode, the output of the M counter (fbout) feeds back to the PLL fbin input (using a trace on the board) and becomes part of the feedback loop. EFB mode is only supported for I/O bank I/O PLL, not supported for fabric-feeding I/O PLL.
One of the dual-purpose external clock outputs becomes the fbin input pin in this mode. The external feedback input pin, fbin is phase-aligned with the clock input pin. Aligning these clocks allows you to remove clock delay and skew between devices.
In EFB mode, you must use the same I/O standard on the input clock, feedback input, and clock outputs.
Figure 16. Example of Phase Relationship Between the PLL Clocks in EFB Mode