Dmux

[jonzzzsat]

I have partial understanding of how to deduce the chip implementation. But I am still uncertain of how to use the algebra well.

K-maps or canonical forms I have tried to make sense of.

here goes:

in=Not(sel)AND(a)OR       so      0=(0.a)      
in=(sel)AND(b)                so      1=(1.b)

I don't know if this is right, but I intuit this kind of thing evolves as you work it out;

so I deduced outputs: (a=o)(b=1)  and this mean two Or chips must feed outputs a and b;

I further deduced 3 And chips and 3 Not chips but I can't go any further, I tried to implement but I got a poor result and I don't know how to fix it up.

Incidentally, I nearly solved it with 2 Not and 1 Xor; I was only line 2 output incorrect. (but I didn't know where to go from there?

And another question: do you rely on the pin, input and output indications step by step as you test(and guess)? or must you rely on the algebra, how do these two forms relate?  

 

[WBahn]

jonzzzsat wrote

I have partial understanding of how to deduce the chip implementation. But I am still uncertain of how to use the algebra well.

K-maps or canonical forms I have tried to make sense of.

here goes:

in=Not(sel)AND(a)OR       so      0=(0.a)      
in=(sel)AND(b)                so      1=(1.b)

You seem to be confusing inputs and outputs. In the DMux, you have an input signal called 'in', and input signal called 'sel', and two output signals called 'a' and 'b'. So your logic equations should be of the form

a = some logic involving 'sel' and 'in'

[jonzzzsat]

a=Not(sel)ANDNOT(in)OR(in)
b=(sel)ANDNOT(in)OR(in)

from this:

[(sel)ORNOT(sel)]
Not(in)OR(in)
a or b

I have been examining the truth tables for clues, and I've tried a number of implementations , but none of my ideas are working.  

[WBahn]

jonzzzsat wrote

a=Not(sel)ANDNOT(in)OR(in)
b=(sel)ANDNOT(in)OR(in)

You are cramming too many operations together without indicating what order they are done in. Is the first one

a=(Not(sel) AND NOT(in)) OR(in)

or is it

a=Not(sel) AND (NOT(in) OR(in))

Very different things. Don't make people guess.

from this:

[(sel)ORNOT(sel)]
Not(in)OR(in)
a or b

Where is this coming from?

Any signal OR'ed with the NOT of itself is always True. Think about it.

I have been examining the truth tables for clues, and I've tried a number of implementations , but none of my ideas are working.

What truth tables? What implementations have you tried? What about them isn't working?

Again, don't make people guess. We are not mind readers.

Think about what it is you want a DMux to do. Focus on each output separately -- they are separate logic problems.

If the 'sel' input is equal to 0, you want the 'a' output to be whatever the 'in' input is, otherwise you want the 'a' output to be 0.

If the 'sel' input is equal to 0, you want the 'b' output to be 0, otherwise you want the 'b' output to be whatever the 'in' input is.

[jonzzzsat]

I watched some internet tutorials, but still my understanding of mathematics is inadequate; I'll work on that. But in my previous thoughts I reasoned two And chips could give different 'a' and 'b' outputs; because 1 and 1 will give 1; and 1 and 0 will give 0. And I thought there's got to be a Not chip to make this happen. But I wasn't creative enough to wire it.

But the thing that I now understand is you can apply the truth tables to the input values, to get a start on the implementation. I had the right idea from the outputs back, but not from the inputs forward.

I had an over complicated idea of the input values.  

[WBahn]

I can't tell for sure whether you got it implemented or not? If so, great -- congratulations. If not, please describe what your present implementation looks like and how it is behaving.