Multiplexer
Multiplexer: the select lines S pick one of several data inputs and pass it to Y.
Function table (2-bit example)
| S1 | S0 | Y |
|---|---|---|
| 0 | 0 | I0 |
| 0 | 1 | I1 |
| 1 | 0 | I2 |
| 1 | 1 | I3 |
Pins
Data inputs I0, I1… on the left; select lines S along the bottom (higher number = higher bit); output Y on the right. Use + / − to change the number of select bits.
How to use it
A signal-controlled selector switch. It can also implement any truth table: wire each row's output value to Iₖ and the variables to S.
Usage example
The four data inputs I0–I3 go on the left and the select lines S1 S0 underneath. S1 S0 = 10 (that's 2) selects I2, so Y equals I2.
Common mistakes
Mind the order: S1 is the high bit, so S1S0 = 10 selects I2.