Binary Subtraction Circuits

Recall that (R)2 = (P)2 - (Q)2

= (P)2 + (-Q)2

= (P)2 + [Q]2

= (P)2 + (Q)2? + 1

For an SN7483 adder

(?)2 = (A)2 + (B)2 + (C0)2 (4.39)

where ? = ?4?3?2?1, A = A4A3A2A1, and B = B4B3B2B1

If C0 = 0, A = P, and B = Q, then (?)2 = (P)2 + (Q)2 .

If C0 = 1, A = P, and B = Q?, then (?)2 = (P)2 - (Q)2 .

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