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Numeric (Clock-Driven Logic)

Last Modified: January 12, 2018

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.

This input supports scalar values of integer and fixed-point data types.

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y

An input to this node.

This input supports scalar values of integer and fixed-point data types.

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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. This output is available when you wire unsigned numeric values to x and y.

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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overflow

A Boolean that indicates if the theoretical computed value of the sum exceeds the valid range of its data type. This output is available when you wire signed numeric values to x and y.

True This node wraps the value of sum.
False This node does not wrap the value of sum.
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Note  

If you cascade nodes, you must use unsigned versions of the nodes in the intermediate operations. Set the encoding of the final node to the encoding you want for the entire cascaded operation.

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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

Web Server: Not supported in VIs that run in a web application


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