General-Purpose I/O User Guide: Agilex™ 5 FPGAs and SoCs
ID
813934
Date
8/04/2025
Public
1. Agilex™ 5 General-Purpose I/O Overview
2. Agilex™ 5 HSIO Banks
3. Agilex™ 5 HVIO Banks
4. Agilex™ 5 HPS I/O Banks
5. Agilex™ 5 SDM I/O Banks
6. Agilex™ 5 I/O Troubleshooting Guidelines
7. GPIO FPGA IP
8. Programmable I/O Features Description
9. Document Revision History for the General-Purpose I/O User Guide: Agilex™ 5 FPGAs and SoCs
2.5.1. I/O Standard Placement Restrictions for True Differential I/Os
2.5.2. Placement Restrictions for True Differential and Single-Ended I/O Standards in the Same or Adjacent HSIO Bank
2.5.3. VREF Sources and Input Standards Grouping
2.5.4. HSIO Pin Restrictions for External Memory Interfaces
2.5.5. RZQ Pin Requirement
2.5.6. I/O Standards Implementation Based on VCCIO_PIO Voltages
2.5.7. I/O Standard Selection and I/O Bank Supply Compatibility Check
2.5.8. Simultaneous Switching Noise
2.5.9. HPS Shared I/O Requirements
2.5.10. Clocking Requirements
2.5.11. Clock Restrictions for GPIO Interfaces
2.5.12. SDM Shared I/O Requirements
2.5.13. Unused Pins
2.5.14. VCCIO_PIO Supply for Unused HSIO Banks
2.5.15. HSIO Pins During Power Sequencing
2.5.16. Drive Strength Requirement for HSIO Input Pins
2.5.17. Maximum DC Current Restrictions
2.5.18. 1.05 V, 1.1 V, or 1.2 V I/O Interface Voltage Level Compatibility
2.5.19. Connection to True Differential Signaling Input Buffers During Device Reconfiguration
2.5.20. LVSTL700 I/O Standards Differential Pin Pair Requirements
2.5.21. Implementing a Pseudo Open Drain
2.5.22. Allowed Duration for Using RT OCT
2.5.23. Single-Ended Strobe Signal Differential Pin Pair Restriction
2.5.24. Implementing SLVS-400 or DPHY I/O Standard with 1.1 V VCCIO_PIO
8.1. Programmable Pre-Emphasis
The VOD setting and the output impedance of the driver set the output current limit of a high-speed transmission signal. At a high frequency, the slew rate may not be fast enough to reach the full VOD level before the next edge, producing pattern-dependent jitter. With pre-emphasis, the output current is boosted momentarily during switching to increase the output slew rate.
Pre-emphasis increases the amplitude of the high-frequency component of the output signal and thus helps to compensate for the frequency-dependent attenuation along the transmission line. The overshoot introduced by the extra current happens only during a change of state switching to increase the output slew rate and does not ring, unlike the overshoot caused by signal reflection. The amount of pre-emphasis required depends on the attenuation of the high-frequency component along the transmission line.
Figure 52. Programmable Pre-emphasisThis figure shows the true differential output with pre-emphasis.