Page 104 - DCAP108_DIGITAL_CIRCUITS_AND_LOGIC_DESIGNS

Unit 6: Implementation of Combinational Logic Circuit

Notes
Example: Here is an abbreviated truth table for the demultiplexer. We could have given

the full table since it has only 16 rows, but we will use the same convention as for the multiplexer
where we abbreviated the values of the data inputs.

a2 a1 a0 d | x7 x6 x5 x4 x3 x2 x1 x0

0 0 0 c | 0 0 0 0 0 0 0 c
0 0 1 c | 0 0 0 0 0 0 c 0
0 1 0 c | 0 0 0 0 0 c 0 0
0 1 1 c | 0 0 0 0 c 0 0 0
1 0 0 c | 0 0 0 c 0 0 0 0
1 0 1 c | 0 0 c 0 0 0 0 0
1 1 0 c | 0 c 0 0 0 0 0 0
1 1 1 c | c 0 0 0 0 0 0 0
Here is one possible circuit diagram for the demultiplexer:
Figure 6.14: Circuit Diagram of Demultiplexer

You must complete internal configruation of multiplexing before making the
multiplexing process in any application, otherwise it may be failed.

6.3 Code Converters

The purpose of the decoder and encoder circuits is to convert from one type of input encoding to
a different output encoding. For example, a 3-to-8 binary decoder converts from a binary number
on the input to a one-hot encoding at the output. An 8-to-3 binary encoder performs the opposite
conversion. There are many other possible types of code converters. One common example is a
BCD-to-7-segment decoder, which converts one binary-coded decimal (BCD) digit into information

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