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Logic Circuit help

Harald Kapp

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I have no idea how to test my circuit to see if it matches the truth table.
Start by writing down the truth table for your circuit's function Y=A*B + NOT C.
Then check against the truth table Laplace has given you.

And is it the And gate?
Right. That's the gate that goes to 0 when the control input is 0.

Now go on to the gate or gates that create the control signal which is 0 when A=B=C=0 ´, and only for this case.
Hint: This gate will have 1 for any other combination of A, B and C, so whenever one or more of A, B or C are 1, the output (the control signal) will be 1, too.
Oh my good, I've almost given away the solution with this hint,.
 

Madz2007

Dec 8, 2016
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A*B + NOT C

Doesnt work, I tested it for both the outputs and its not that,
 

Harald Kapp

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No, it doesn't work.
You need a function of A, B and C that gives 0 when every input is 0
Start wth two inputs only Y=A ??? B where ??? is the function you're looking for (e.g. OR, EXOR, AND, NAND, NOR ...) Which one will give 0 for A=0 and B=0?
Use the result of this function and the input C to arrive at the final control signal.
 

Madz2007

Dec 8, 2016
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Im one hour away of submitting this and i still have no idea... i think ill fail this time but if you can carry on helping it will be much appreiciated
 

Harald Kapp

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Or and and will give 00
OR will, and it wil also fulfill the other condition:
Now go on to the gate or gates that create the control signal which is 0 when A=B=C=0 ´, and only for this case.
as OR will give 1 for any of A, B or C being 1.

You now have CONTROL = A OR B OR C.
You also know that RED = NOT GREEN Except for A=B=C=0 here RED = 0, too instead of 1.
How will you use this CONTROL signal to make RED=0 ?
 

Harald Kapp

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Boolean functions do not match the gate types
This escaped my attention, I'll be forever struggling with the American way of drawing logic gates ;).
I only loked at the equation, which is unsuitable nevertheless.
 
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