Design an 8-input to 3-bit binary decoder and explain its working using block diagram.

Q.) Design an 8-input to 3-bit binary decoder and explain its working using block diagram.

 Subject: Digital Systems

A binary decoder is a combinational circuit that converts binary information from n coded inputs to a maximum of 2^n unique outputs. They are used in a variety of applications, including data multiplexing and data demultiplexing, seven segment displays, and memory address decoding.

In this case, we are designing an 8-input to 3-bit binary decoder. This means we have 8 unique inputs and we want to decode them into 3-bit binary outputs.

Here is a step-by-step approach to designing an 8-input to 3-bit binary decoder:

  1. Identify the Inputs and Outputs: The inputs are 8 unique signals (let's call them I0 to I7) and the outputs are 3-bit binary codes (let's call them O0, O1, and O2).

  2. Create the Truth Table: The truth table for an 8-input to 3-bit binary decoder is as follows:

Inputs Outputs
I0 000
I1 001
I2 010
I3 011
I4 100
I5 101
I6 110
I7 111

  1. Design the Logic Circuit: The logic circuit for this decoder can be designed using AND, OR, and NOT gates. Each output is connected to an AND gate. The inputs to the AND gates are the inputs to the decoder and their complements. The specific connections depend on the desired output for each input.

  2. Create the Block Diagram: The block diagram for this decoder would have 8 input lines and 3 output lines. Each input line would be connected to the AND gates as described in the previous step. The outputs of the AND gates would be the outputs of the decoder.

Here is a simplified block diagram:

I0 ------------------ AND ---- O0
                      /  \
I1 ------------------ AND ---- O1
                      /  \
I2 ------------------ AND ---- O2
                      /  \
I3 ------------------ AND
                      /  \
I4 ------------------ AND
                      /  \
I5 ------------------ AND
                      /  \
I6 ------------------ AND
                      /  \
I7 ------------------ AND
  1. Explain the Working: The decoder works by activating the AND gate that corresponds to the current input. For example, if I3 is the current input, the AND gate for O1 and O2 will be activated, producing the output 011. All other AND gates will be deactivated, producing a 0 output.

In conclusion, an 8-input to 3-bit binary decoder can be designed using basic logic gates. The decoder takes one of 8 inputs and produces a 3-bit binary output corresponding to the input. The design can be represented using a truth table and a block diagram.