7-bit binary adder/subractor . how ?

wolvzzz

New Member

• Oct 3, 2012

• #1

this is the Logic diagram inside a 7483 4-bit binary adder/subractor ..


View attachment 67720


hopefuLLy .. somebody wouLd be abLe to give me the equivaLent circuit for a 7-bit inputs


a very big big big thanks in advance pro's .. hehehe




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Last edited: Oct 3, 2012

MikeMl

Well-Known Member

Most Helpful Member

• Oct 3, 2012

• #2

That chip is cascadable to any width in multiples of 4 bits. Why not just use two of them? heh heh

 

Last edited: Oct 3, 2012

wolvzzz

New Member

• Oct 3, 2012

• #3

reaLLy ? can you give me the equivaLent cascaded circuit using 2 7483 ? knowing that ,, maybe I can derive that thing using onLy basic Logic gates . I want to impLement it that way because our task is to design a 7-bit binary adder/subractor without using any speciaL kind of ic .. hehehe


- the mini caLcuLator

View attachment 67729





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Last edited: Oct 3, 2012

MikeMl

Well-Known Member

Most Helpful Member

• Oct 3, 2012

• #4

Can't you just cascade 7 . Subtraction implies complementing one of the two inputs, and putting a one to the carry-in of the low order adder.

 

Last edited: Oct 3, 2012

wolvzzz

New Member

• Oct 5, 2012

• #5

copy ^_^








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wolvzzz

New Member

• Oct 5, 2012

• #6

finaLLy .. i made to design the 7 bit adder using the Logic Ly simuLator .. hehehehehe

View attachment 67764 ..


and now with a subtactor . assuming .. when M is Low then ADD , when High then SUBTRACT

if im not mistaken .. can i just XOR the B's with M as a new input for the second operand ? im not too sure though







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Last edited: Oct 5, 2012

MikeMl

Well-Known Member

Most Helpful Member

• Oct 5, 2012

• #7

Xor (or maybe its XNor) the seven bits you want to subtract. Wire the subtract control signal M to all seven Xors. Assuming you are doing twos-complement, then the subtract control signal M also goes to the carry-in of the low order full adder.

Ones complement: to negate a number, complement every bit.
Twos complement: to negate a number, complement every bit, and add one.

 

Last edited: Oct 5, 2012