Decoder and Multiplexer

2023. July 31

encoding, for computer

decoding, for human

Decoder

1. Key Features and Working of a Decoder:

1) a decoder has 'n' input lines and 2^n output lines

2) input to the decoder is a binary code represented by 'n' bits. Each input combination uniquely selects one of the output lines.

3) Only one output line will be active (high) at a time on the binary code applied to the input.

4) The decoder's truth table is based on the binary representation of the input lines and their corresponding outputs.

* 3-to-8 Decoder example

2. Applications of Decoders

1. Memory Address Decoding: In computer memory systems, decoders are used to convert the binary memory address to a specific memory location. This enables the selection of particular memory cell from a large memory array.

2. Digital Display Systems: In digital display applications, such as 7-segment displays, decoders are used to convert binary-coded input to the corresponding display segments' activation.

3. Control Signal Decoding: Decoders are used in control systems to interpret binary control signals and activate specific devices or perform specific actions based on the input code.

4. Demultiplexing: In data routing, decoders are used to demultiplex a single input line to one of several output lines based on the input code.

5. Instruction Decoding: In microprocessors, decoders are used to interpret instruction codes and generate control signals for executing various instructions.

Encoder

1. Key Features and Working of an Encoder:

1) An encoder has 'n' input lines and 'm' output lines. The number of output lines is generally smaller than the number of input lines.

2) The encoder produces a binary code at the output, representing the active input line

3) Only one input line should be active (high) at a time an encoder. If multiple input lines are active, the encoder will prioritize one of them.

2. Application of Encoders

1) Priority Encoding: Encoders are used to encode multiple inputs into a priority-encoded format. In applications where only the highest-priority input needs to be encoded, and the rest are ignored, priority encoders are utilized.

2) Address Encoding: In memory systems, encoders are used for memory address encoding, converting the binary address lines into a compact binary code used to select a specific memory location. 

3) Data Transmission: Encoders are used in digital communication systems to encode data for transmission over communication channels

4) Digital Control Systems: Encoders are used in digital systems to encode the states of sensors, switches, or other input devices into a binary code.