BCD to Excess-3 code converter

The availability of a large variety of codes for the same discrete information results in the use of different codes by different digital systems. It is sometimes necessary to use the output of one system as the input of another. A conversion circuit must be inserted between two such systems. Thus a BCD to Excess-3 code converter is a circuit that makes the two systems compatible even though each uses a different binary code.

The following example illustrates the conversion of BCD to Excess-3 code. It shows the input in BCD and the output in Excess-3. The four input combinations from 10 to 15 never occur and therefore they don’t care about combinations.