Xilinx V2.1 - Manual (Page 83)

Math 83
Xilinx Blocks
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AddSub
The Xilinx AddSub block implements an adder/subtractor.
The operation can be fixed (Add or Subtract) or changed
dynamically under control of the
sub mode signal.
Block Parameters Dialog Box
The block parameters dialog box can be invoked by double-clicking the icon in your
Simulink model.
Figure 3-55: AddSub block parameters dialog box
Parameters specific to the AddSub block are:
•
Mode : specifies the block operation to be Addition, Subtraction, or Addition/
Subtraction. When Addition/Subtraction is selected, the block operation is
determined by the
sub input port, which must be driven by a 1-bit unsigned
signal. When the sub input is 1, the block performs subtraction. Otherwise, it
performs addition.
•
Implement with Xilinx Smart-IP Core : when checked, the System
Generator will implement the block as a LogiCORE. Otherwise, it is implemented
as a synthesizable VHDL module.
Other parameters used by this block are explained in the Common Parameters section
of the previous chapter.
Xilinx LogiCORE
If the Implement with Xilinx Smart-IP Core checkbox is selected on the
parameters dialog box, and if the output width is in the range of 1 to 256, the block