Integrated Circuits Used 74LS90 Procedure Add IC 74LS90 into ICBase-1 (74LS90).Add IC 74LS90 into ICBase-2 (74LS90).Connect Pin-5 (VCC) of ICBase-1 (74LS90) to VCC Port.Connect Pin-19 (Input & Output) of ICBase-1 (74LS90) to GND Port.