Question

What is a demultiplexer?

Answer 1

A demultiplexer (often abbreviated as demux) is a digital logic device that takes a single input signal and channels it to one of several output lines. Essentially, it performs the reverse function of a multiplexer (mux), which takes multiple input signals and selects one to be output.

### Key Features of a Demultiplexer:

1. **Input and Output:**
   - **Single Input:** A demultiplexer has one input line.
   - **Multiple Outputs:** It has multiple output lines. The number of output lines is determined by the number of selection lines, which are used to determine which output line the input signal should be sent to.

2. **Selection Lines:**
   - **Control Signals:** Selection lines are used to choose which output line will receive the input signal. The number of selection lines determines the number of possible output lines. For example, with \( n \) selection lines, a demultiplexer can have \( 2^n \) outputs.

3. **Functionality:**
   - **Data Routing:** It routes data from a single source to one of many destinations. For instance, in a 1-to-4 demultiplexer, the single input is routed to one of the four outputs based on the binary value of the selection lines.

### Example:

Consider a 1-to-4 demultiplexer. It has:
- **1 Input Line**
- **2 Selection Lines** (which can choose among 4 outputs)
- **4 Output Lines**

Here's a truth table to illustrate how it works:

| Selection Lines | Output 0 | Output 1 | Output 2 | Output 3 |
|-----------------|----------|----------|----------|----------|
| 00              | 1        | 0        | 0        | 0        |
| 01              | 0        | 1        | 0        | 0        |
| 10              | 0        | 0        | 1        | 0        |
| 11              | 0        | 0        | 0        | 1        |

- **Selection Lines 00** route the input to **Output 0**.
- **Selection Lines 01** route the input to **Output 1**.
- **Selection Lines 10** route the input to **Output 2**.
- **Selection Lines 11** route the input to **Output 3**.

### Applications:

- **Data Distribution:** Demultiplexers are used in communication systems to distribute data from one source to multiple destinations.
- **Memory Addressing:** They help in selecting specific memory locations in computer systems.
- **Digital Signal Processing:** Used in routing signals to various processing units.

By allowing a single input to be routed to multiple outputs, demultiplexers are crucial in systems where data needs to be distributed efficiently and accurately.

Answer 2

A demultiplexer (or demux) is a digital logic device used in electronics to route a single input signal to one of several output lines. It essentially performs the reverse function of a multiplexer (mux), which routes multiple input signals to a single output line.

### How It Works

- **Input Signal**: The demultiplexer has a single input line where the signal is fed.
- **Control Lines**: It has several control lines (also known as select lines) that determine which output line the input signal will be sent to.
- **Output Lines**: The demultiplexer has multiple output lines. Based on the values of the control lines, the input signal is directed to one specific output line while all other output lines are set to zero (or in a high-impedance state).

### Basic Operation

1. **Selection**: The control lines select one of the possible output lines.
2. **Routing**: The input signal is then routed to the selected output line.
3. **Inactive Outputs**: The non-selected output lines remain inactive or in a default state.

### Example

Consider a 1-to-4 demultiplexer:
- **Input Line**: 1 input signal
- **Control Lines**: 2 control lines (allowing for 4 possible combinations)
- **Output Lines**: 4 output lines

If the control lines are set to 00, the input signal is routed to output line 0. If the control lines are set to 01, the input signal goes to output line 1, and so on.

### Applications

- **Data Routing**: Directing data to various parts of a system or different devices.
- **Communication Systems**: Channel selection in communication systems.
- **Memory Systems**: Address decoding in memory systems, where the demultiplexer selects a specific memory location.

### Practical Example

In a computer system, a demultiplexer can be used to route data from a single source to multiple destinations based on the control signals. For instance, if you have one data line and you want to send this data to one of four different devices, a demultiplexer can be used to ensure that the data is sent to the correct device according to the control signals.

### Summary

In essence, a demultiplexer allows for the selective distribution of data from a single source to multiple destinations, making it a crucial component in digital systems for managing and routing signals efficiently.