Integrated Circuits Used 74LS90 Procedure Add IC 74LS90 into ICBase-1 (74LS90).Add IC 74LS90 into ICBase-2 (74LS90).Connect GND Port to Pin-6 (Input) of ICBase-1 (74LS90).Connect GND Port to Pin-7 (Input) of ICBase-1 (74LS90).