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3 to 8 decoder with enable

Claraborges

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Hi, I have this image with two decoders 3 to 8 using enable, and I have this information:
E3 is the most significant
It knows if the enabling pin, when deactivated, causes all decoder views (S0 to S7) to remain at logic level 1.
And then they give a final Boolean expression and ask: what keys must be linked to obtain this expression?

I learned about the 3 to 8 decoder circuit ... but I don't know what to do with that information. How to do the exercise? I really want an explanation
 

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KlausST

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Hi,

The expression shows three parts.
For a first step just use "WXZ" ....what happens when
W= 1, X = 1, Z = 1?
Which decoder output(s) is/ are enabled?

Klaus
 

FvM

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Sure you have
XY + W + WXZ
Sure you posted the execise problem correctly, without omitting something, e.g. inversion symbols?

Term WXZ in the given expression is redundant, because it's already covered by term W. Respectively the output doesn't depend on Z, switch setting is equal for upper and lower decoder. Switch 3-7 and 11-15 should be closed.
 

KlausST

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Hi,

WXZ can be expanded to WXZY + WXZ/Y

But true, all is covered by "W" ....


Klaus
 

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