what do you call this device?

[j3Riks]

for example i have an 8 I/O ports microcontroller and i have to monitor 4 ICs with each having 8 I/O ports. how do i switch from the 4 ICs?

 

[panic mode]

it's called multiplexer but in order to make it work you will need at least two more I/O on your microcontroller.

 

[j3Riks]

but a multiplexer only has one output port. what i need is something that has at least 8 output ports and multiple input ports.

you see if i use a multiplexer i still need to switch so many times just to cover all the pins of the ICs. what i want to do in my program is read the port of the MCU just ones, for example if P0 is = 0100 1001 do this " " ....if i use a multiplexer i need to read the I/O port of the MCU one at a time and at the same time controlling the selector pin of the multiplexer.

 

[diode]

What ICs are exatly the "4 ICs" ?

Many ICs have enable and circuit select pins that are meant exatly for this purpose...