On Wed, 17 Oct 2001, Bernard Ebinu wrote:
> Hi Dr. Amaral,
>
> I have a question about how mulitplexer's work. For example in slide 20
> of lecture 7 you ask the question implement the function
> F(R,S,T) = R'S' + RT
>
> First of all, what do you mean by implement the above function.
Bernard:
It means that you are expected to create a logic box that has
three inputs and one output and that the logic value of the output
is dictated by the function above.
>From what you have learned in class, you know that there are many
ways to implement the function above. For instance you can implement
it using two two-input AND, one two-input OR, and two INVERSORS.
You could also rewrite the function as:
F(R,S,T) = ((R'S' + RT)')' = ((R'S')'(RT)')' = ((R+S)'(R'+T'))'
and you could use one two-input NOR, one two-input OR, one two-input NAND,
and two INVERSORS.
... you got the idea.
> From my
> understanding a multiplexer would assign to the output, one of the input
> values depending on what R and S are in this case. How does this knowlege
> ( right or wrong ) apply to the question asked. If you could further
> explain a mux that would be great.
> Thanks for your time,
You can also use a multiplexer (instead of the collections of gates
listed in the two solutions above) to implement F(R,S,T), if you
examine the slides you will see that all you have to do is to expand
the function into full terms, and to select two of the inputs to be
the control inputs of the multiplex. Then you can figure out what
you need to put in the data inputs of the multiplex so that you obtain
the behaviour prescribed in the output.
Does this helps?
Cheers,
Nelson
/
\ / / Jose Nelson Amaral - amaral@cs.ualberta.ca
) / ( Associate Professor
/ / \ Dept. of Computing Science - University of Alberta
( / ) Edmonton, Alberta, Canada, T6G 2E8
\ O / Phone: (780)492-5411 Fax: (780)492-1071
\ / http://www.cs.ualberta.ca/~amaral
`----'
This archive was generated by hypermail 2.1.3 : Wed Nov 21 2001 - 15:50:12 MST