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82 Xilinx Development System
Xilinx System Generator v2.1 Reference Guide
Block Parameters Dialog Box
The block parameters dialog box can be invoked by double-clicking the icon in your
Simulink model.
Figure 3-54: Accumulator block parameters dialog box
Parameters specific to the block are:
• Number of Bits (output width): specifies the output width which must
match the input width. If the data input does not match the output width, an error
is reported.
• Overflow: specifies behavior on internal overflow to be Wrap, Saturate, or flag as
an Error.
• Operation: This is a list of two choices: add and subtract. This determines
whether the block is adder or subtractor based.
• Feedback Scaling: specifies the feedback scale factor to be one of the
following:
1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, or 1/256.
• Reset to input: when selected, the output of the accumulator is loaded by the
data on input port b whenever the accumulator is reset. When not selected, the
output of the accumulator is reset to 0.
The type of the output is the same as that of the input. The block always has a latency
of 1.
Other parameters used by this block are explained in the Common Parameters section
of the previous chapter.
Xilinx LogiCORE
The block always uses the Xilinx LogiCORE Accumulator V5.0. The data width must
be between 1 and 258, inclusive.
The Core datasheet can be found on your local disk at: