Encoder

Encoder:

An encoder is a digital circuit that performs the inverse operation of decoder.

An encoder has 2*n input lines and n output lines.

In encoder the output lines generate the binary code corresponding to the input value.

Decimal to BCD encoder:

The decimal to BCD encoder, usually has ten input lines and four poutput lines.

The decoder decimal data act as the input for encoder and encoded BCD output is available on the four output lines.

Decimal value	Input									Output
	1	2	3	4	5	6	7	8	9	D	C	B	A
0	1	1	1	1	1	1	1	1	1	1	1	1	1
1	0	1	1	1	1	1	1	1	1	1	1	1	0
2	X	0	1	1	1	1	1	1	1	1	1	0	1
3	X	X	0	1	1	1	1	1	1	1	1	0	0
4	X	X	X	0	1	1	1	1	1	1	0	1	1
5	X	X	X	X	0	1	1	1	1	1	0	1	0
6	X	X	X	X	X	0	1	1	1	1	0	0	1
7	X	X	X	X	X	X	0	1	1	1	0	0	0
8	X	X	X	X	X	X	X	0	1	0	1	1	1
9	x	x	x	X	x	x	X	x	0	0	1	1	0

 

Priority Encoder:

A priority encoder is an encoder circuit that includes the priority function.

In priority encoder, if two or more input are equal to 1 at the same time, the input having the highest priority will take precedence.

Input				Output
D0	D1	D2	D3	Y1	Y0	v
0	0	0	0	x	x	0
1	0	0	0	0	0	1
X	1	0	0	0	1	1
X	X	1	0	1	0	1
x	X	x	1	1	1	1

 

Octal to binary encoder:

It has eight input one for each octal digit. And three output that generate the corresponding binary code.

Input								Output
D0	D1	D2	D3	D4	D5	D6	D7	A	B	C
1	0	0	0	0	0	0	0	0	0	0
0	1	0	0	0	0	0	0	0	0	1
0	0	1	0	0	0	0	0	0	1	0
0	0	0	1	0	0	0	0	0	1	1
0	0	0	0	1	0	0	0	1	0	0
0	0	0	0	0	1	0	0	1	0	1
0	0	0	0	0	0	1	0	1	1	0

 

 

Encoder IC’s:

IC number	Function
74147	Decimal to BCD
74184	8-i/p priority encoder.

 

 

 

 

 

UNIT 2 COMBIATIONAL CIRCUIT

Review of Boolean Theorem

Introduction to combinational logic circuit

Representation of logic function

Karnaugn map(k-Map)

Multiplexer

Demultiplexer

Decoders

Encoder

Code converters