KMaps - Digital Logic (self doubt)

Question

I’m taking for an example kmaps for 3 var

 

	A’B’	A’B	AB	AB’
C’	0	1	3	2
C	4	5	7	6

(probably here we are taking CAB’ = 6

and below like AB’C =5 )

 

	A’B’	A’B	AB	AB’
C’	0	2	6	4
C	1	3	7	5

 

But how do i know which one to use and when? 
 

Comments

The scenario of your K-MAP depends on the order in which the function is given

For e.g.

1) if F(A,B,C) is given(A being the MSB and C being LSB) then the 2^nd diagram you have drawn is correct

2) if F(C,A,B) is given(C being the MSB and B being LSB) then the 1st diagram you have drawn is correct

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Suppose we are given a boolean function f(a,b,c) = Σm (2, 4, 5, 7) for a mux 4:1

I’ll use KMaps as ??

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All the above 3 maps are correct, just keep in mind what is the LSB and MSB

as it is F(A,B,C) maps has been drawn as A being MSB and C being LSB

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So if i’m asked to insert values of B at the input lines , i’ll take AC as select variables and B as data variable, that is taking the KMAP as :-

	A’C’	A’C	AC	AC’
B’	0	1	5	4
B	2	3	7	6

 

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as i said you may take anything as per your convenience

but if you want to implement it as a multiplexer then easy method will be using truth tables

A	B	C	F
0	0	0	0
0	0	1	0
0	1	0	1
0	1	1	0
1	0	0	1
1	0	1	1
1	1	0	0
1	1	1	1

 

The reduced truth table will be

A	C	F
0	0	$B$ (0 input of MUX)
0	1	0  (1 input of MUX)
1	0	$\bar{B}$  (2 input of MUX)
1	1	1  (3 input of MUX)