Discussion in 'Homework Help' started by minimugy, Mar 23, 2011.

1. ### minimugy Thread Starter New Member

Mar 2, 2011
7
0
Hello!

i've been give a problem that i am stuck on. if you can help that'd be great!

Write an equation for the following sequences (use only three variables for the right hand side): The overflow indicator V will turn off iff X is negative, Y is positive, and D is positive, or Xis positive, Y is negative, and D is negative.

so far i have,

V=X'YD + XY'D'

i was thinking it would be an exclusive or but i was told that was wrong, so if you can help me simplify this it would i would really appreciate it.

2. ### mjhilger Member

Feb 28, 2011
119
16
Have you written your truth table or karnaugh map? That would be a great place to start. Once you have that, you should be able to see how to write your equation.

3. ### minimugy Thread Starter New Member

Mar 2, 2011
7
0
I did but it gave me the same function i have above. so thats where i am stuck.

would it be wither one of the two since the two products are the exact opposite of each other?

4. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
655
When V is off, is it true or false?

5. ### minimugy Thread Starter New Member

Mar 2, 2011
7
0
I believe it is off if either of the two hit. but i need to get it to only 3 terms on the right side and i have six.

6. ### mjhilger Member

Feb 28, 2011
119
16
Your statement says that V will turn OFF iff .....

V' = X'YD + XY'D' <- is three variables X, Y, D

Or are you saying that you may only use X or X' (etc.) but not both? Not sure what you are looking for?

You cannot use XOR of 3 variables, because it would give 3 states for V', not just the 2 you are looking for.

7. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
655
Your original statement didn't say "3 terms", it said "3 variables".

8. ### minimugy Thread Starter New Member

Mar 2, 2011
7
0
well i re read the wuestion and it says 3 variable which i guess iw as confused with 3 terms or something. i felt like it only needed to be either X'YD or XY'D' to v but now i see that i only have 3 variables and i was done all along. I'm sorry about my confusion and any confusion i may have cause you. Thanks for the help!!!!

9. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
655
I was going to make the same point, but I am wondering why the stipulation "use only three variables for the right hand side", since there are only 3 variables available. How could you possibly use more?