Can someone double check my K-map equation?

WBahn

Joined Mar 31, 2012
26,398
Sorry, didn't realise. Would you like me to repost them?
If you wouldn't mind, but it's certainly not necessary. Just post them here in the future. Try to make the file sizes less than 200KB (less than 50KB is highly preferred and usually achievable). If you scale the image to be between 300 and 500 pixels wide it will embed in the post easily and display well on most monitors (smartphones aside).

I made a comment about halfway up saying i screwed up a couple values, this is the same problem still.
Okay -- well the first thing we need to do is make sure that your K-map is correct. In your original post you just presented a K-map as a given. I seem to recall that at some point you mentioned that it was for a particular signal line of a seven segment decoder, but I didn't review it to see if it was correct because it wasn't indicated if it was active HI or active LO, so I just accepted that it was correct at face value. Are you sure it is correct, now?

Which part do you want me to show work on? The equation?
Enough so that I can follow what you did, not just see where you ended up.

I'll be back in the lab in an hour and 45 mins or so if you need me to show something with the circuits but I'll only have like an hour and a half before this is due once i get there.
That's always a problem with on-line forums -- they are not very responsive in the crunch. I have lots of work to do, too, and I can't guarantee that I will even be available during any particular window of time.
 

WBahn

Joined Mar 31, 2012
26,398
Kmap looks good. Equation was (WXYZ)' + W'X'YZ + W'X + WX'Y'
Using Demorgans i got
(WXYZ)(WX')(WXY'Z')(W'XY)
Do you really believe that these are equivalent?

Let's do a simple sanity check.

In order for your second form to be true, ALL of the factor must be true, correct?

That means that (WXYZ) must be true which means that W, X, Y, and Z, must ALL be true.

But for any of the other factors, at least one of the signals must be false. For instance, for (WX') to be true, X must be false. So for your second form, X must both be true and it must be false at the same time, which is not possible, and hence your second form can never be true.

Always, always, ALWAYS ask if your answer makes sense!
 

Thread Starter

SumTingWong

Joined Jan 22, 2015
22
Do you really believe that these are equivalent?

In order for your second form to be true, ALL of the factor must be true, correct?

That means that (WXYZ) must be true which means that W, X, Y, and Z, must ALL be true.

But for any of the other factors, at least one of the signals must be false. For instance, for (WX') to be true, X must be false. So for your second form, X must both be true and it must be false at the same time, which is not possible, and hence your second form can never be true.
I believe it's possible to simplify but it gets it down to such a small equation that it doesn't seem right? (WX(YZY'Z'))(WX')(W'XY) = (WX)(WX')(W'XY) = (W)(W'XY)?
 
Top