What are Code Converters

In the digital domain, data or information is represented by a combination of 0’s and 1’s. A code is basically the pattern of these 0’s and 1’s used to represent the data. Code converters are a class of combinational digital circuits that are used to convert one type of code in to another. Code conversion is a widely used process used in digital systems for reasons such as enhancing security of data, reducing the complexity of arithmetic operations and thereby reducing the hardware required, dropping the level of switching activity leading to more speed of operation and power saving etc.

Some of the most prominently used codes in digital systems are Natural Binary Sequence, Binary Coded Decimal, Excess-3 Code, Gray Code, ASCII Code etc. Like any combinational digital circuit, a code converter can be implemented by using a circuitry of AND, OR and NOT gates. Designing a code converter is very easy and consists of the following steps:-

The input and the output codes are first of all written in the form of a truth table that represents the output code for every input combination. Each bit of the output code is then treated as the logical function of all the bits of the input code. For each output bit, a K-Map is drawn with respect to the input bits and the simplest logic relating the output bit to the input bits is formulated from it. This logic can be in the form of a minimum Sum of Products term or a minimum Product of Sum terms depending upon the needs of the designer. Alternatively, a canonical sum of product or product of sum term can be written for each output bit from the truth table itself and it can then be simplified using Boolean algebra. Once the most simplified logic equations are formulated for every output bit, the hardware implementation of the circuit takes place by the use of the same equations and the code converter is synthesized.

For complex codes containing a very large number of digits, computer tabulation methods are used for the simplification of logic as it becomes cumbersome beyond reach to perform the same using K-Map or Boolean algebra technique. The use of BCD to Excess-3 converter in arithmetic operational circuits to reduce the overall hardware and the use of Binary to Gray code converters to reduce switching activity are a few simple examples of the applications of Code Converters.

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