All user I/Os have an internal clamp diode control circuitry, as shown in the following figure. A pull-up clamp diode must not be present in the I/O circuitry if the hot-swap feature is used. The 3.3 V PCI standard requires a pull-up clamp diode and it cannot be selected if hot-swap capability is needed.
Figure 1. Internal Clamp Diode Control Circuitry
For more information about hot swapping and cold sparing applications, see the AC396: SmartFusion2 and IGLOO2 in Hot Swapping and Cold Sparing Application Note.