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A question about the logic of certain transformations

  1. May 1, 2008 #1
    there is this table that i showed in my previos question
    now i need to implement it using 16X4 and 4 X4 proms

    here is the table:


    here is the table:


    my problem is with the #1 and the #2 components

    regarding the #1 component:
    its input is the two's complement of a certain number X
    and the output is the |X|

    i know that in order to transform a normal number into its two's complement
    we need to flip each digit and add one to the resolt

    we are required to do the oppossite thing ,so we need to subtract one
    and flip each digit
    but they did something odd (int the #1 component)

    in part A marked red they didnt transform at all the numbers
    but in part B marked blue instead of subtracting one and plipping each digit
    they found the two's complement of the input number

    regarding component #2:
    i have the same problem but here in group D they flip each digit
    were as in part C they live it as it is

    there is some logic behind that
    i cant see it??
  2. jcsd
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