Table Of Contents

Unsigned (Clock-Driven Logic)

Version:
    Last Modified: September 10, 2016

    Implements an adder-subtractor that operates on bit patterns. You can cascade and pipeline AddSub nodes to achieve higher throughput rates.

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    carry in/inverted borrow in

    A Boolean that determines whether this node accounts for an additional least-significant bit (LSB).

    True Adds one extra LSB to x + y when sub? is False. Computes xy normally when sub? is True.
    False Subtracts one extra LSB from xy when sub? is True. Computes x + y normally when sub? is False.

    Default: False

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    bypass x

    A Boolean that determines whether this node ignores the value you wire to x.

    True This node uses a value of 0 instead of the value you wire to x.
    False This node uses the value you wire to x.

    Use this Boolean to remove x from the expression this node calculates. For example, use this Boolean to return –y instead of xy.

    Default: False

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    sub?

    A Boolean that determines whether this node performs subtraction or addition. Use this Boolean to change the operation of this node programmatically.

    True The node calculates x - y.
    False The node calculates x + y.

    Default: False

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    x

    An input to this node. If x is a fixed-size Boolean array, the first array element represents the least-significant bit (LSB) and the last element represents the most-significant bit (MSB).

    This input supports scalar Boolean values and arrays of Boolean values.

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    y

    An input to this node. If y is a fixed-size Boolean array, the first array element represents the LSB and the last element represents the MSB.

    This input supports scalar Boolean values and arrays of Boolean values.

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    carry out/inverted borrow out

    A Boolean that indicates whether the data type of sum cannot represent the result of an unsigned addition operation.

    True The data type of sum cannot represent the result of an unsigned addition operation.
    False The data type of sum cannot represent the result of an unsigned subtraction operation.

    In this situation, this node wraps the value of sum. If you cascade this node, you can use this output to specify whether a downstream node carries or borrows a value. To specify that a downstream node uses this value, wire carry-out/inverted borrow-out to the carry-in/inverted borrow-in input of the downstream node.

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    sum

    The result this node computes. The result depends on not only the values of x and y but also the values of any Boolean inputs. This node applies the Wrap overflow mode to sum in the following situations:

    • sub? is True and carry out/inverted borrow out returns False
    • sub? is False and carry out/inverted borrow out returns True

    Where This Node Can Run:

    Desktop OS: none

    FPGA: All devices


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