Hot Swap

Hot Swap allows a voltage to be applied to the inputs of devices before power is present on the VDDI pins. A pull-up clamp diode must not be present in the I/O circuitry to be hot swap. GPIO supports hot swap, but HSIO does not support hot swap.

When FPGA is not powered, GPIO is in a high-impedance state (hi-Z), also known as disabled state. For GPIO configured for I/O standards requiring a VREF, the amount of current flowing into or out should be minimized for the GPIO pin so that the external VREF signal is not affected.