Integrated Circuits Used 74LS90 Procedure Add IC 74LS90 into ICBase-1 (74LS90).Connect Pin-10 (Input & Output) of ICBase-3 to Input-9.Connect VCC Port to Pin-20 (Input) of ICBase-1 (74LS90).Connect GND Port to Pin-7 (Input) of ICBase-1 (74LS90).