74F382 4-Bit Arithmetic Logic Unit

user4787732

My teacher asked me to build the 74F382 4-Bit Arithmetic Logic circuit. and after explain it to him I read your PDF, and to be honest I´m a little bit confusing. Look up in the truth Table I noticed some information: An, Bn ( This is the n´s variation,right? Like: A0,A1,A2,A3). So, if the first sentence is correct I would like to ask something: In the PDF, Function (B-A), second line.If Bn is zero and An is one, how it exit to 0111, i didn´t get it. Other question: If Cn is zero how Cn+4 blow up to 1. By the way, i´ve been looking the table and didn´t get some others outputs. Am I need to build up the truth table frist,and then, the circuit,right? Could you please taught me this truth table? Or send me some material that could help me? Thank you.

PDF LINK https://www.engineering.uiowa.edu/sites/default/files/ees/files/NI/pdfs/00/95/DS009529.pdf

ba.mirror.garr.it/.../traditional_logic_integrated_circuits.pdf <<<<<<<<<<<<<<<< ANOTHER PDF LINK

over 9 years ago

0 ShreyasRao over 9 years ago

TI__Guru 61970 points

hello user,

are you using the device , I see this is obsolete device listed on our website ?
you are right about the 'n' representing the 4 bits for A and B.
It seems that they are doing a two's complement version , but I may be wrong, I can check into that.
I would suggest you to trace back the functional block diagram for the output Fn.

0 user4787732 over 9 years ago in reply to ShreyasRao

Prodigy 110 points

my professor asked me to use logisim

0 Clemens Ladisch over 9 years ago

Guru 316510 points

TI's offical datasheet is available from the website.

I do not see the values you mentioned in the line number you mentioned.
Please specify all inputs for the case you want to discuss.

0 user4787732 over 9 years ago in reply to Clemens Ladisch

Prodigy 110 points

pdf www.engineering.uiowa.edu/.../DS009529.pdf page 3- truth table function B-A , the second sequence Cn An Bn L L H ,if B is 1 and A is 0, why the result is 0111. There is some others sequences that I didn´t get it,in fuction B-A for example,there is a lot of sequences that does not make sense

0 Clemens Ladisch over 9 years ago in reply to user4787732

Guru 316510 points

As shown on page 2, for subtraction, C_n is the inverted carry input.

So in this case, B = 1111, A = 0000, carry = 1, so B−A−carry = 1110.

0 user4787732 over 9 years ago in reply to Clemens Ladisch

Prodigy 110 points

but, how abaou the 3º line, fuction B-A. A=1111 B=0000 C=0 and the result is 0000. How to explain this stuff? IT is not OVR

0 Clemens Ladisch over 9 years ago in reply to user4787732

Guru 316510 points

Explain what exactly? Why do you think that the result should not be 0, or that OVR should be set?

0 user4787732 over 9 years ago in reply to Clemens Ladisch

Prodigy 110 points

0000 -1111, I ca not borrow any number. Sorry if there is a formula that i don´t remember.

0 Clemens Ladisch over 9 years ago in reply to user4787732

Guru 316510 points

What do you mean with "cannot borrow"? With C_n=L, you must borrow.

The OVR flag is defined on page 1 of the datasheet, and is identical with the Wikipedia description of the overflow flag.

0 user4787732 over 9 years ago in reply to Clemens Ladisch

Prodigy 110 points

got it, B-A, 0000-1111, B +(-A), in C2, 0000 + 0000,right ? But how about build up the circuit using logisim? Is there a way to create it faster,or it is necessary to create line per line? If you click in circuit´s analise you can determinate the inputs (12) and the outputs(6), but when you try to create karnaugh´s map there is 2^12 possible combinations,in short, how can I create the circuit in a faster way using logsim.

0 user4787732 over 8 years ago in reply to user4787732

Prodigy 110 points

hi,does anyone know what exactly is these 2 red segments that is bounded with ANDs and NORs?

page 69(PDF reader) 425(original).

0 Clemens Ladisch over 8 years ago in reply to user4787732

Guru 316510 points

These red things do not appear to have any meaning.

0 user4787732 over 8 years ago in reply to user4787732

Prodigy 110 points

guys, I was looking to a solution,but I just found more questions,pick up the PDF and go to page 69(PDF reader) 425(original). On the diagram you can see the input S(0,1,2),under a blue dashed line, there is some logic and by the way you will see that there is 5 lines that get out from the blue dashed line. This 5 lines are connected with S(0,1,2) and determinate the logic operation. If you look to the picture again you will see another part of this CI, the operator A3,B3( defined on the picture by 3). There is 7 ANDs, the 4´s that are united define,each, 2 logic lines that must be used to get in a result and defines all types of possible combination(~A3 B3, A3 B3 , ~B3 A3, ~B3 ~A3). And the 3´s that are united shows the same thing,except that it does not show the possibility A3 B3, WHY? What does this 7 ANDs represent on the circuit?
PDF LINK>>>>>>>>>>>>>>>>>> ba.mirror.garr.it/.../traditional_logic_integrated_circuits.pdf

0 Clemens Ladisch over 8 years ago in reply to user4787732

Guru 316510 points

I do not understand your question. These logic gates are needed to compute the result. Without them, the result would not be correct.

0 user4787732 over 8 years ago in reply to Clemens Ladisch

Prodigy 110 points

What I want to ask is : what does the 7 ANDs Door represent to the circuit. What the function? What is the result,what it represents?

0 user4787732 over 8 years ago in reply to user4787732

Prodigy 110 points

Hi,everyone. I´m still with problems,this circuit is soo big,please,help. I have already done the logic diagram by it all, but, I need to understand the line`s function, line by line, what daes it do. If I take XNOR,for example, what is going to happen. Why 7 ANDs are in this place. Things like this, is there someone that could help me? If there is not, is there a way to find all this answers by myself? What way?Thank you.

Here is the link : www.engineering.uiowa.edu/.../DS009529.pdf

0 Clemens Ladisch over 8 years ago in reply to user4787732

Guru 316510 points

If I take XNOR,for example, what is going to happen.

There is no XNOR gate. (And this is a TI forum. How do you expect anybody to help you if you don't refer to the TI datasheet?)

Why 7 ANDs are in this place.

Because they are needed to select the appropriate signals from the possible combinations of the function select inputs.

I need to understand the line`s function, line by line

The logic diagram appears to be the result of some circuit minimization algorithm. So the function of all lines can be best described as "this implements the behaviour defined in the function table".

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74F382 4-Bit Arithmetic Logic Unit