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HS=X⊕Y= X·Y+X ·Y CO=X·Y. Return. Next. 5.10 Adders, Subtractor and ALUs. Half Adders and Full Adders. Half adder , adds two 1-bit operands x and y, producing a 2-bit sum. The low-order bit of the sum may be named HS (half sum), and the high-order bit may be named CO (carry out).
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HS=X⊕Y= X·Y+X ·Y CO=X·Y Return Next 5.10 Adders, Subtractor and ALUs • Half Adders and Full Adders • Half adder, adds two 1-bit operands x and y, producing a 2-bit sum. The low-order bit of the sum may be named HS (half sum), and the high-order bit may be named CO (carry out)
S=X⊕Y⊕CIN =X·Y·CIN+X·Y·CIN+X·Y·CIN+X·Y·CIN Return Back Next 5.10 Adders, Subtractor and ALUs • Full adder, Besides the addend-bit inputs x and y, a full adder has a carry-bit input, CIN. And two output bits, S and COUT. COUT=X·Y+X·CIN+Y·CIN (p431 Figure 5-86)
Return Back 5.10 Adders, Subtractor and ALUs • Ripple Adders • Two binary words, each with n bits,can be added using a ripple adder----a cascade of n full-adder stages, each of which handles one bit. • A ripple adder is slow, the total worst-case delay is tADD=tXYCout+(n-2) ·tCinCout+tCinS (p432 Figure 5-87)