# Logic gate into boolean equation

Discussion in 'Electronic Basics' started by Jibbed, Nov 17, 2003.

1. ### JibbedGuest

Hi,
Hope this is the right group for this.

I've made a big circuit in digital works that makes a 7 Segment digital
display count from 0 to 9. I now have to make the Boolean equations from the
circuit. One for each segment.

Here is the first segment (8kb):
http://www.magic-carpet.freeserve.co.uk/thb/digi_circuit.GIF

Would it be:
_ _ _ _ _ _ _ _ _ _
SEG A = A B C D + A B C D + A B C D

Or is that total crap?!

TIA,
Jon

2. ### petrus bitbyterGuest

Jon,

It is not total crap, but it's not correct either. Besides, the negation
lines do not come through on the right place. Below I use a notation that
fits better in a typed text.

SEG A = /(/A * /B * /C * D + /A * B * /C * /D + /A * B * C * /D)

Re-reading your equation and shifting the negation lines a little bit, I
guess it's the same that you (want to) write.

petrus

3. ### JibbedGuest

Hi peter,
Thanks! That was what I was looking for! Never seen it written like that but
it does makes sense to me, sort of confirmed what I'd hoped. I had the
original
equation I made from the truth table which had an OR instead of a NOR that I
changed it to. I was hoping that I could just "NOT" the whole equation which
it seems like I can do.

But, I need it written in the form I have it written, which I'm hoping would
be:

http://www.magic-carpet.freeserve.co.uk/thb/equation.GIF

(note the absence of a line immediately above the OR (+). Correct?)

Anyway you've been lots of help. I just need to get cracking on the rest of
the segments now!...

Regards,
Jon

5. ### JibbedGuest

Phew! Good to hear.

Thanks,
Jon

6. ### petrus bitbyterGuest

Jon,

It's correct. The way I initially learned to write it, but, as I said, not
easy to type. Modern logic developing programs tend to use the "!" for the
NOT, "|" for the OR and "&" for the AND. Learned from the C language. You'll
met them when you continue to study digital developement.

Succes,

petrus