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Simulation behavior for denormal numbers


Specify the desired behavior for denormal results from arithmetic operations. Denormal numbers are any non-zero numbers whose magnitude is smaller than the smallest normalized floating-point number (see realmin). Some hardware targets flush denormal results from arithmetic operations to zero. You can emulate this behavior by setting the parameter to Flush To Zero (FTZ).


Default: Gradual Underflow

Gradual Underflow

Denormal numbers are used in the results from arithmetic operations. This setting is supported by all simulation modes.

Flush To Zero (FTZ)

Emulates flush-to-zero behavior for denormal numbers. This setting flushes denormal results from arithmetic operations to zero. This setting is not supported during normal mode simulation.


In model reference systems, you can simulate a top-level model using gradual underflow with any simulation mode. Models referenced by the top-level model can simulate the flush-to-zero behavior only if the instance of the referenced model uses an accelerated simulation mode and has the Simulation behavior for denormal numbers parameter set to Flush to zero (FTZ).

Command-Line Information

Parameter: DenormalBehavior
Value: 'GradualUnderflow' | 'FlushToZero'
Default: 'GradualUnderflow'


This parameter requires a Fixed-Point Designer™ license.

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