2024-10-19 11:00:03 +01:00
|
|
|
---
|
|
|
|
|
tags: [logic-gates, binary, nand-to-tetris]
|
|
|
|
|
---
|
|
|
|
|
|
|
|
|
|
# Multiplexers (MUX) and demultiplexers (DMUX)
|
|
|
|
|
|
|
|
|
|
## Multiplexer
|
|
|
|
|
|
|
|
|
|
> Multiplexing is the generic term used to describe the operation of sending one
|
|
|
|
|
> or more analogue or digital signals over a common transmission line at
|
|
|
|
|
> different times or speeds.
|
|
|
|
|
|
|
|
|
|
A multiplexer selects one of several input signals and forwards ths selected
|
|
|
|
|
input to a single output line.
|
|
|
|
|
|
|
|
|
|
We have two inputs (A,B) plus a third input SEL (for "select"). Applying a value
|
|
|
|
|
to SEL toggles the output between A and B.
|
|
|
|
|
|
2024-10-20 19:50:20 +01:00
|
|
|
|
2024-10-19 11:00:03 +01:00
|
|
|
|
|
|
|
|
Multiplexers can be used to build larger circuits by connecting the output of
|
|
|
|
|
one multiplexer to the input of another. They are often used to implement data
|
|
|
|
|
selection and switching in digital systems
|
|
|
|
|
|
|
|
|
|
### Programable gates
|
|
|
|
|
|
|
|
|
|
One of the main use cases of multiplexers is to implement programmable gates.
|
|
|
|
|
These are gates where the logic can be switched. For example an ANDMUXOR gate
|
|
|
|
|
uses the SEL value to toggle the operation of a gate between AND and OR for its
|
|
|
|
|
two inputs A and B
|
|
|
|
|
|
|
|
|
|
## Demultiplexer
|
|
|
|
|
|
|
|
|
|
As the name suggests, a demultiplexer reverses the functionality of a
|
|
|
|
|
multiplexer. It receives a single input and based on the selection of the SEL
|
|
|
|
|
input it channels it to either an A or a B output.
|
|
|
|
|
|
2024-10-20 19:50:20 +01:00
|
|
|
|
2024-10-19 11:00:03 +01:00
|
|
|
|
|
|
|
|
We can think of it as a distributor of a value into one of several possible
|
|
|
|
|
channels.
|
