Integrated Circuits Used 74LS90 Procedure Add IC 74LS90 into ICBase-2 (74LS90).Connect Pin-14 (Output) of ICBase-2 (74LS90) to VCC Port.Connect GND Port to Pin-7 (Input) of ICBase-2 (74LS90).Connect Input-15 to Pin-3 (Input) of ICBase-2 (74LS90).