A multiplexer (MUX) is a device that accepts data from one of many input sources for transmission over a common shared line. To achieve this the MUX has several data lines and a single output along with data-select inputs, which permit digital data on any one of the inputs to be switched to the output line. The logic symbol for a 1-of-4 data selector/multiplexer is shown in Figure 2-13, and its associated table listed in Table 2-14.
Figure 2-13 Logic symbol for 1-of-4 multiplexer
Data Select Inputs |
Input Selected |
|
S1 |
S0 |
|
0 |
0 |
D0 |
0 |
1 |
D1 |
1 |
0 |
D2 |
1 |
1 |
D3 |
Table 2-14 Operation of 1-of-4 Multiplexer
Note that if a binary zero appears on the data-select lines then data on input line D0 will appear on the output. Thus, data output Y is equal to D0 if and only if S1=0 and S0=0
Similarly, the data output is equal to D1, D2 and D3 for 
,
and
, respectively. Thus the total multiplexer logic
expression, formed from ORing terms is
The implementation of this equation is as shown in Figure 2-14.
Figure 2-14 Logic circuit for 1-of-4 multiplexer
Copyright © Adrian Als , 1999
This page was last modified: Wednesday, April 12, 2000