 Suppose 8 tri-state pins are used to control 56 LEDs through Charlieplexing, which is enough for 8 7-segment displays (without decimal points).Typically 7-segment displays are made to have a common cathode, sometimes a common anode, but without loss of generality suppose it is a common cathode.All LEDs in all 8 7-segment displays cannot be turned on simultaneously in any desired combination using Charlieplexing.