How to use a 8-bit multiplexer

Thread Starter

yjpang84

Joined Sep 10, 2006
1
Guys im desperate..

this is the qn: Z is a boolean function of 3 input variables A,B and C. If A=C; else Z=0.

Design and draw a clearly labelled diagram to implement Z using only one 8-bit multiplexer.

i don't even understand the question. please enlighten. :confused:
 

thingmaker3

Joined May 16, 2005
5,084
What happened to "then?" Is the "then" supposed to be "Z=1?" Is B a "red herring" variable?

I would contact the instructor to see if there is a typo.
 

rishid

Joined Oct 24, 2005
8
Truth table for this is:
A B C | Z
0 0 0 | 1
0 0 1 | 0
0 1 0 | 1
0 1 1 | 0
1 0 0 | 0
1 0 1 | 1
1 1 0 | 0
1 1 1 | 1

Then I think you just use A,B,C as the select bits in the 8bit mux and draw either 1 or 0's as in puts depedning on the value of Z for the specific mux input
 

hgmjr

Joined Jan 28, 2005
9,029
I think you are going to need to incorporate a 4-input "OR" gate into which you will need to feed the appropriate outputs of the mux to complete the implementation.

hgmjr
 

Papabravo

Joined Feb 24, 2006
13,559
No need for the 4-input gate. The single output of the mux is all you need. The select inputs A, B, and C "select" one of the constant inputs to route to the output. It could hardly be simpler.
 

hgmjr

Joined Jan 28, 2005
9,029
My bad. Papabravo is correct. I was thinking of 3-in / 1-of-8 out decoder when I recommended an OR gate.

hgmjr
 

Papabravo

Joined Feb 24, 2006
13,559
It's an easy mistake to make without a diagram. Although I have known about this technique since I was an undergraduate, I have never had occasion to use it in a career that has spanned nearly four decades.
 
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