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  2. Adder (electronics) - Wikipedia

    en.wikipedia.org/wiki/Adder_(electronics)

    The sum-output from the second half adder is the final sum output of the full adder and the output from the OR gate is the final carry output (). The critical path of a full adder runs through both XOR gates and ends at the sum bit . Assumed that an XOR gate takes 1 delays to complete, the delay imposed by the critical path of a full adder is ...

  3. Adder–subtractor - Wikipedia

    en.wikipedia.org/wiki/Adder–subtractor

    This works because when D = 1 the A input to the adder is really A and the carry in is 1. Adding B to A and 1 yields the desired subtraction of B − A. A way you can mark number A as positive or negative without using a multiplexer on each bit is to use an XOR gate to precede each bit instead. The first input to the XOR gate is the actual ...

  4. XOR gate - Wikipedia

    en.wikipedia.org/wiki/XOR_gate

    In certain situations, the inputs to an OR gate (for example, in a full-adder) or to an XOR gate can never be both 1's. As this is the only combination for which the OR and XOR gate outputs differ, an OR gate may be replaced by an XOR gate (or vice versa) without altering the resulting logic. This is convenient if the circuit is being ...

  5. Logic gate - Wikipedia

    en.wikipedia.org/wiki/Logic_gate

    A logic circuit diagram for a 4-bit carry lookahead binary adder design using only the AND, OR, and XOR logic gates. A logic gate is a device that performs a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output.

  6. Carry-lookahead adder - Wikipedia

    en.wikipedia.org/wiki/Carry-lookahead_adder

    The XOR is used normally within a basic full adder circuit; the OR is an alternative option (for a carry-lookahead only), which is far simpler in transistor-count terms. For the example provided, the logic for the generate and propagate values are given below. The numeric value determines the signal from the circuit above, starting from 0 on ...

  7. Carry-skip adder - Wikipedia

    en.wikipedia.org/wiki/Carry-skip_adder

    A carry-skip adder [nb 1] (also known as a carry-bypass adder) is an adder implementation that improves on the delay of a ripple-carry adder with little effort compared to other adders. The improvement of the worst-case delay is achieved by using several carry-skip adders to form a block-carry-skip adder.

  8. Kogge–Stone adder - Wikipedia

    en.wikipedia.org/wiki/Kogge–Stone_adder

    An example of a 4-bit Kogge–Stone adder is shown in the diagram. Each vertical stage produces a "propagate" and a "generate" bit, as shown. The culminating generate bits (the carries) are produced in the last stage (vertically), and these bits are XOR'd with the initial propagate after the input (the red boxes) to produce the sum bits. E.g., the first (least-significant) sum bit is ...

  9. Majority function - Wikipedia

    en.wikipedia.org/wiki/Majority_function

    A majority gate returns true if and only if more than 50% of its inputs are true. For instance, in a full adder, the carry output is found by applying a majority function to the three inputs, although frequently this part of the adder is broken down into several simpler logical gates.