CODE CONVERTERS

The availability of a large variety of codes for the same discrete elements of information results in the use of different codes by different systems. Therefore a conversion circuit is inserted between the two systems, if each uses different codes for the same information.
Hence, a “code converter” is a logic circuit which changes data presented in one type of binary code to another type of binary code. It makes two systems compatible even though each uses a different binary code.

The following are some of most commonly used code converters.

(i) BCD-to-binary
(ii) Binary-to-BCD
(iii) Binary-to-gray-code
(iv) Gray-code-to-binary
(v) BCD to Excess-3
(vi) Excess-3 to BCD

ENCODERS

Encoder is a combinational circuit, whose inputs are decimal digits (or) alphabetic characters (or) familiar numbers (or) symbols and outputs are the coded representation of those inputs.
An encoder has ‘m’ input lines and ‘n’ output lines, where m ≤ 2n. It is assume that only one input has a value of 1 at any given time.

Encoders can be designed with both active high and active low signals.

Octal-to-Binary Encoder

Octal ⇒ 8 symbols (symbols 0 to 7)
m = 8. So, 2n ≥ 8 ⇒ n ≥ 3

DECODERS

Decoder is a combinational circuit, which converts the coded binary information into symbols (or) numbers. It performs the reverse operation of an encoder. It has ‘n’ inputs and ‘m’ outputs lines.

At a time one output line will be active based on an input combination.

2 × 4 Decoder (with active high inputs and active high outputs)