Re: [理工] [計組]logic gate

[BenLinus (班)]

※ 引述《doggingg (doggingg)》之銘言：
: Use AND,OR,NOT to design a two-bit binary adder/subtractor.
: Give the examples to show that your answer worked correctly.

[X=0 作加法, X=1則作減法, X要當carry_in]

A - B = A + (-B) = A + (~B + 1)    所以X當carry_in

  A   B       Sum     Carry_out
 a1a0b1b0   X=0  X=1   X=0
  0 0 0 0   0 0  0 0    0
  0 0 0 1   0 1  1 1    0
  0 0 1 0   1 0  1 0    0
  0 0 1 1   1 1  0 1    0
  0 1 0 0   0 1  0 1    0
  0 1 0 1   1 0  0 0    0
  0 1 1 0   1 1  1 1    0
  0 1 1 1   0 0  1 0    1
  1 0 0 0   1 0  1 0    0
  1 0 0 1   1 1  0 1    0
  1 0 1 0   0 0  0 0    1
  1 0 1 1   0 1  1 1    1
  1 1 0 0   1 1  1 1    0
  1 1 0 1   0 0  1 0    1
  1 1 1 0   0 1  0 1    1
  1 1 1 1   1 0  0 0    1

不知道有沒有手殘 orz


Sum0 = a0 xor (b0 xor X) xor X

Sum1 = a1 xor (b1 xor X) xor carry_in (即從bit0來的carry_out)

Cout = (a1 and b1) or (carry_in and [a1 xor b1])


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◆ From: 114.43.195.103
※ 編輯: BenLinus        來自: 114.43.195.103       (02/11 14:41)
推 doggingg:謝謝大大  我懂囉
推 doggingg:在請問一下，它的布林函式長怎樣?Cin跟Cout還有Sum
※ 編輯: BenLinus        來自: 114.43.195.103       (02/11 17:16)
→ BenLinus:用打的反而有點亂orz
推 doggingg:謝謝大大熱心回答