Components / Plexers
Demultiplexer (DEMUX) in Logisim
Routes a single data input D to the selected output Y[S] while driving all unselected outputs to 0.
| Library | Plexers |
|---|---|
| Type name | Demultiplexer |
| Pins and defaults | in0 D (-40, 0), sel S (-20, bottom), out0..out(2^S-1) Y0..Yn (0, y), width 1..32, selectBits 1..4 |
How the DEMUX Works in Logisim
A Demultiplexer (DEMUX) performs the inverse operation of a Multiplexer: it takes a single data input (D) on the left and routes its value to whichever of the 2^S output lines (Y0, Y1, ...) is addressed by the bottom Select input (S).
All unselected output lines are driven to 0. If the Select input S is left floating (Z) or receives an error (E), every output pin on the Demultiplexer outputs E.
Tip: Tying the data input D of a 1-bit Demultiplexer to a Constant 1 makes it behave identically to a one-hot Decoder.
DEMUX Pins & Pinout
| Pin | Direction | Width | Location & Role |
|---|---|---|---|
| in0 (D) | Input (Left edge) | 1–32 bits | Located at (-40, 0). Data signal to route to the chosen output. |
| sel (S) | Input (Bottom edge) | 1–4 bits (selectBits) | Located at x = -20 on the bottom edge. Binary index of the target output line. |
| out0 .. out(2^S-1) (Y0..Yn) | Output (Right edge) | 1–32 bits | Located at x = 0 from top (Y0) to bottom. Output Y[S] = D; all other outputs = 0. |
DEMUX Truth Table & Behavior
| Select (S) | Data (D) | Output Y0 | Output Y1 |
|---|---|---|---|
| 0 | D | D | 0 |
| 1 | D | 0 | D |
| Z or E | Any | E | E |