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 Posted: Mon Sep 10, 2018 12:23 pm

Joined: Sat Aug 25, 2018 7:21 am
Posts: 29
Hi all.
I've been brushing up my skills in electronics (mostly combinational logic) in order to facilitate my understanding of the NES PPU documentation (also I really like the topic) and for further study I think CAD tools might come in handy. I've been reading about certain tools capable of transforming truth tables in combinational circuits. However I didn't manage to get it working. I have Proteus installed. Does it have this option? If not, is there any similar software for Linux? (It's ok if I have to use Windows but I'd rather not).

PS: I know there are tools for simplifying bool logic, but I also want the resulting circuit, so I can check my own solutions and advance faster.

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 Posted: Mon Sep 10, 2018 7:13 pm

Joined: Fri Nov 19, 2004 7:35 pm
Posts: 4119
Don't remember the exact name for this, but the OR of a bunch of ANDS and NOTS will give you something which will work, though not necessarily simplified.

Example: XOR
A|B| A ^ B
------
0|0| 0
1|0| 1
0|1| 1
1|1| 0

Because there are rows for 1,0 and 0,1, you can say (A & !B) | (!A & B).

Another example:
A|B|C| A^B^C
----------------
0|0|0| 0
0|0|1| 1
0|1|0| 1
0|1|1| 0
1|0|0| 1
1|0|1| 0
1|1|0| 0
1|1|1| 1

Since any of these clauses will give you a 1, you OR them together.
(!A & !B & C) | (&A ! &B & !C) | (A & !B & !C) | (A & B & C)

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 Posted: Mon Sep 10, 2018 7:18 pm

Joined: Sun Apr 13, 2008 11:12 am
Posts: 7964
Location: Seattle
I never knew there was any option other than playing with Karnaugh maps.

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 Posted: Mon Sep 10, 2018 11:38 pm

Joined: Fri Nov 12, 2004 2:49 pm
Posts: 7647
Location: Chexbres, VD, Switzerland
Dwedit wrote:
Don't remember the exact name for this, but the OR of a bunch of ANDS and NOTS will give you something which will work, though not necessarily simplified.

The exact name for this is "minterms".
There's two ways to do it, with minterms by summing (OR-ing) AND functions, and with maxterms by ANDing OR functions.

Quote:
I never knew there was any option other than playing with Karnaugh maps.

Karnaugh maps are used to simplify the equation, so that there's less gates involved for the same work. However they are not required per-se.

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 Posted: Tue Sep 11, 2018 1:12 am

Joined: Sat Aug 25, 2018 7:21 am
Posts: 29
I think the post title wasn't clear enough, although it's detailed in the post itself. Thank you for your answers but I already know the concept of logic sufficiency and how to simplify truth tables by hand using Karnaugh maps. It's the first technique I learned. I'm looking for a software capable of automatically doing this, such as Minilog (Espresso). It would be great if Proteus had this option, as I already have this software installed. So I want to know about a software with this capability, preferably for Linux.

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 Posted: Tue Sep 11, 2018 2:12 am

Joined: Fri Nov 12, 2004 2:49 pm
Posts: 7647
Location: Chexbres, VD, Switzerland
You should look for logisim.

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 Posted: Tue Sep 11, 2018 2:34 am

Joined: Sat Aug 25, 2018 7:21 am
Posts: 29
You should look for logisim.

Thank you. That's what I was looking for. I read Multisim is a more suitable version for professional designers. I'll go with Logisim for the moment. Doesn't Proteus have logic optimization capabilities as well?

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 Posted: Tue Sep 11, 2018 5:01 am

Joined: Mon Sep 20, 2004 6:04 am
Posts: 3628
Location: Indianapolis
HastatusXXI wrote:
Doesn't Proteus have logic optimization capabilities as well?

Not that I've ever seen. Closest thing in name at least, is the "gateswap optimizer", but that's just for automatically swapping which NAND gate is used on a 7400, for example.

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 Posted: Tue Sep 11, 2018 5:25 am

Joined: Sat Aug 25, 2018 7:21 am
Posts: 29
Memblers wrote:
HastatusXXI wrote:
Doesn't Proteus have logic optimization capabilities as well?

Not that I've ever seen. Closest thing in name at least, is the "gateswap optimizer", but that's just for automatically swapping which NAND gate is used on a 7400, for example.

Ok, then. Thank you. It's kind of curious how such a complete CAD software lacks this apparently basic feature.

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