Xilinx Blockset Overview
Precision
The fundamental computational mode in the Xilinx Blockset is arbitrary precision fixed point arithmetic. Most blocks give you the option of choosing the precision, i.e. the number of bits and binary point position.
By default, the output of Xilinx blocks is full precision; that is, sufficient precision to represent the result without error. Most blocks have a
Number of Bits
When you have specify
Binary Point
You will also be asked to specify how many bits are to the right of the binary point (i.e., the size of the fraction). The binary point position must be between zero and the number of bits in the number’s container.
Overflow and Quantization
When
The Xilinx fixed point data type supports several options for
In the case of quantization, the options are to round to the nearest representable value or to the value farthest from zero if there are two equidistant nearest representable values, or to truncate the data (i.e., discard bits to the right of the least significant bit).
It is important to realize that whatever option is selected, the generated HDL model and Simulink model will behave identically.
Override with Doubles
An Override with Doubles message appears on many Xilinx Blocks, with some variations. Variations are:
Override Computation with Doubles
Override Constant with Double
Override Output with Doubles
Override Storage with Doubles
Most Simulink blocks use double precision floating point signals and arithmetic. However, when such a signal passes through Xilinx Gateway In block, it is converted to a fixed point signal. Later, when passing through a Xilinx Gateway Out block, the signals are converted back into double precision floating point.
Common Options in Block Parameters Dialog Box | 21 |