# Multiplexer

#### hoomun

Joined Oct 8, 2004
5
hi, im supose to complete the design of " A'B'CD'+A'B'CD+A'BC'D'+A'BC'D+AB'C'D+AB'CD'+AB'CD+ABCD " or simplifed ver of it " A'BC'+AB'D+B'C+ACD " with a multiplexer and then build the circut at uni any idea on how to do this? ( i have multisim software aswell )

cheers

#### hoomun

Joined Oct 8, 2004
5
Originally posted by hoomun@Oct 8 2004, 03:41 PM
hi, im supose to complete the design of " A'B'CD'+A'B'CD+A'BC'D'+A'BC'D+AB'C'D+AB'CD'+AB'CD+ABCD " or simplifed ver of it " A'BC'+AB'D+B'C+ACD " with a multiplexer and then build the circut at uni any idea on how to do this? ( i have multisim software aswell )

cheers
[post=2835]Quoted post[/post]​

any 1?

#### Battousai

Joined Nov 14, 2003
141
Originally posted by hoomun@Oct 9 2004, 12:57 AM
any 1?
[post=2844]Quoted post[/post]​
Ok well begin by simplifying the expression with boolean algebra:

A'B'CD'+A'B'CD+A'BC'D'+A'BC'D+AB'C'D+AB'CD'+AB'CD+ABCD
------------------ =========== ------------------ ==========

The underlined can be grouped together:

A'B'C(D'+D)+A'BC'(D'+D)+AB'C'(D+D')+ACD(B'+B)

Since X+X' = 1 because when X=0, X'=1 and vice versa, this results in:

A'B'C+A'BC'+AB'C'+ACD
-------------- ========

Now factor the underlined and you get:

A'(B'C+BC')+A(B'C'+CD)

Now what is a mux?

A mux is just a selector. It selects between two inputs, X and Y based on the value of a select variable S.

Let's take the B'C+BC' statement.

Let's arbitrarily pick B as the select variable. If B=0, then BC'=0 and B'C=C. Likewise if B=1, then B'C=0, and BC'=C'.

I think you should be able to take it from there. I believe the entire solution will require three muxes.

#### hoomun

Joined Oct 8, 2004
5
Originally posted by Battousai@Oct 10 2004, 03:23 AM
Ok well begin by simplifying the expression with boolean algebra:

A'B'CD'+A'B'CD+A'BC'D'+A'BC'D+AB'C'D+AB'CD'+AB'CD+ABCD
------------------  =========== ------------------  ==========

The underlined can be grouped together:

A'B'C(D'+D)+A'BC'(D'+D)+AB'C'(D+D')+ACD(B'+B)

Since X+X' = 1 because when X=0, X'=1 and vice versa, this results in:

A'B'C+A'BC'+AB'C'+ACD
--------------  ========

Now factor the underlined and you get:

A'(B'C+BC')+A(B'C'+CD)

Now what is a mux?

A mux is just a selector. It selects between two inputs, X and Y based on the value of a select variable S.

Let's take the B'C+BC' statement.

Let's arbitrarily pick B as the select variable. If B=0, then BC'=0 and B'C=C. Likewise if B=1, then B'C=0, and BC'=C'.

I think you should be able to take it from there. I believe the entire solution will require three muxes.
[post=2848]Quoted post[/post]​

hi thanks for the reply but i got a diff simplified ans from urs. as i staed in above it was

A'BC'+AB'D+B'C+ACD (i used multisim!)

now if i put that in the truth table and not worry about the equation ill get this
from troth table:

0
0
1
1
1
1
0
0
0
1
1
1
0
0
0
1

E0= 0
E1=1
E2=0
E4=D
E5=1
E6=0
E7=D

now i used 74151N

actually heres what i got in attachment, but it dosent work?! where did i go wrong?! (is the way i did the mux right?)

sorry about the balck and green line i forgot to put them in.
now the truth table i get from this mux is:

0
0
0
1
1
1
0
0
1
1
1
1
0
0
0
1

what did i do wrong can u guys see what went wrong my head dosent work any more!!!

#### sayan_nit

Joined Sep 18, 2004
2
Originally posted by hoomun@Oct 9 2004, 03:57 AM
any 1?
[post=2844]Quoted post[/post]​

u first make the truth table from the given function,then draw the implementation table.encircle the min terms.take any one of(A,B,C,D)as data i/p line & the other 3 as select i/p's.then, it's easy na?  #### arvind

Joined Nov 4, 2004
18
hi,
u can use a 16 to 1 mux, give the four conrol inputs as
s0 A
s1 B
s2 C
s3 D

and keep the other inputs at following logic values,

e0 0
e1 0
e2 1
e3 0
e4 1
e5 1
e6 0
e7 0
e8 0
e9 1
e10 1
e11 0
e12 1
e13 1
e14 0
e15 1
ur purpose will be solved
ps: keep the mux in enable mode         