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Encoder in Digital Electronics, Its Designing and Logical diagram- An encoder essentially performs the reverse of a decoder function in a combinational logic circuit. The process of converting from symbols or numbers to coded format is called encoding. The encoders and decoders play an essential role in digital electronics; encoders & decoders are used to convert data from one form to another form. These are frequently used in communication system such as telecommunication, networking, etc. to transfer data from one end to the other end. Similarly, in the digital domain, for easy transmission of data, it is often encrypted or placed within codes, and then transmitted. At the receiver, the coded data is decrypted or gathered from the code and is processed in order to be displayed or given to the load accordingly.
Encoder definition in digital electronics:
A device used for the conversion of decimal into binary or it is a combination logic circuit that receives 2n or less than 2n input lines and generate n output lines.
Encoder Block diagram:
Block diagram for the 8×3 lines Encoder in digital electronics is given below.
An encoder in digital electronics is an electronic device used to convert an analogue signal to a digital signal such as a BCD code. It has a number of input lines, but only one of the inputs is activated at a given time and produces an N-bit output code that depends on the activated input. The encoders and decoders are used in many electronic projects to compress the multiple number of inputs into smaller number of outputs. The encoder allows 2 power N inputs and generates N-number of outputs. For example, in 4-2 encoder, if we give 4 inputs it produces only 2 outputs. But in this article we will talk about the 9×3 encoder.
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Designing steps for the 8×3 lines Encoder.
- Problem: Design 8×3 lines Encoder.
- The number of available inputs are 8 and outputs are 3.
- The inputs and outputs are assigned letters. Let we represent the inputs by d0, d1, d2, … d7, and the outputs are assigned the symbol letters x, y, and z.
- The Encoder truth table.
- Encoder Boolean function (simplified form)
8×3 lines Encoder Logical diagram:
As you can see the logical diagram of the 8×3 lines Encoder is very simple. The inputs d0 to d7 are connected with the three OR Gates as per the Boolean functions. The inputs d4, d5, d6, and d7 are connected with the first OR gate labeled with output x. The inputs d2, d3, d6, and d7 are connected with the 2nd OR Gate labeled with the output y. The inputs d1, d3, d5, and d7 are connected with the third OR gate labeled with z. The input d0 is not connected with any of the OR Gates.
A Priority Encoder is a circuit or an algorithm that compresses multiple binary inputs into a smaller number of outputs. The output of a priority encoder is the binary representation of the original number starting from zero of the most significant input bit. They are often used to control interrupt requests by acting on the highest priority interrupt input.
If two or more inputs are given at the same time, the input having the highest priority will take precedence. An example of a single bit 4 to 2 encoder is shown, where highest-priority inputs are to the left and “x” indicates an irrelevant value – i.e. any input value there yields the same output since it is superseded by higher-priority input. The output V indicates if the input is valid.
Priority encoders can be easily connected in arrays to make larger encoders, such as one 16 to 4 encoder made from six 4 to 2 priority encoders – four 4 to 2 encoders having the signal source connected to their inputs, and the two remaining encoders take the output of the first four as input. The priority encoder is an improvement on a simple encoder circuit, in terms of handling all possible input configurations
Larger encoders can be built from smaller encoder modules in much the same way that larger decoders can be built from smaller decoder modules. An encoder module that can be used as a building block for larger encoders must have one additional output called group- signal (GS). GS is asserted whenever EIN is asserted along with any other input signal, and it is used to form the most significant bit of the encoded output data element.
Uses of Encoder:
Encoder circuits are typically used in digital systems when a binary number that corresponds to a given input must be generated. For example, individual “call attendant” signals arising from passengers seated on an airplane could be encoded into a seat number. Priority encoders are also used when certain input signals must be dealt with in a special manner. For example, if inputs from several sources can all arrive simultaneously, a priority encoder can indicate which signal should be dealt with first.