isolation cell
Beginner
A tiny gate that holds a wire steady while the part of the chip feeding it is switched off.
Novice
A small gate placed on a wire leaving a block that can be switched off. While the block is off, its outputs drift to random values; the isolation cell holds the wire at a fixed 0 or 1 so those values can’t confuse the parts still running.
Expert
Inserted per UPF on domain crossings and powered from the receiving or always-on supply. Its enable must be asserted before power-down and released only after power-up completes.
Explained in Personal and edge devices (Industries).