MATLAB: Do the dialog prompts use different terminology for the properties of fixed-point data in Stateflow and Simulink Fixed Point

simulink

I am using Stateflow and Simulink Fixed Point to create a fixed-point simulation. I would like a unified interface and terminology for data specification. For example, Simulink Fixed Point describes an unsigned 8-bit integer as a "uint(8), while Stateflow describes this as a "uint8".

Best Answer

The ability to use a unified user interface and terminology for fixed-point data specification is not available in Simulink Fixed Point and Stateflow.

To work around this issue, consult the Stateflow and Simulink Fixed Point documentation for the details of each interface. You can also use the "inherited" data type in Stateflow to inherit data properties from Simulink, which may remove the need to use the Stateflow fixed-point specification interface.

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MATLAB: GLOBALFIMATH has no effect for FI objects in Fixed-Point Designer (R2012b)

If no rounding method, overflow action, or fimath is used in the argument list of the FI constructor, then it will always use nearest rounding (and saturate overflow), regardless of the GLOBALFIMATH setting.

This behavior first occured in the R2009b Fixed-Point Toolbox and is documented in its release notes. The documentation for which can be found here:

https://www.mathworks.com/help/fixedpoint/getting-started-with-fixed-point-toolbox.html

_"When you create a fi object in this way in R2009b, you may get different results. As of this release, the fi constructor creates the fi object using a RoundMode of nearest and an OverflowMode of saturate. Thus, the setting of the RoundMode and OverflowMode properties of the global fimath are not used to create fi objects from floating-point values."_

The FI object uses 'nearest' and 'saturate' for being consistent with the way Simulink constructs fixed-point parameters, and to insulate it from any global settings.

The recommended way to construct a FI object that obeys the GLOBALFIMATH settings is to use the CAST function, which is available since R2013a: http://www.mathworks.com/help/releases/R2013a/matlab/ref/cast.html

The CAST function will always obey the "fimath" in force for the 'like' variable (either attached to the 'like' variable or 'globalfimath'). For example:

>> resetglobalfimath;  % To ensure a clean state
>> globalfimath('RoundingMethod', 'Floor');
>> h = cast(2.247, 'like', fi([], 0,8,1e-2,0))  % Floor rounding
h = 
      2.2400
>> globalfimath('RoundingMethod', 'Ceiling');
>> h = cast(2.247, 'like', fi([], 0,8,1e-2,0))  % Ceiling rounding
h = 
      2.2500

MATLAB: Do I receive an error when I plot matrix signals from the Fixed-Point Settings interface in Simulink 6.0 (R14)

This bug has been fixed in Release 14 Service Pack 3 (R14SP3). For previous product releases, read below for any possible workarounds:

We have verified that there is a bug in Simulink 6.0 (R14) while plotting matrix signals from the Fixed-Point Settings interface.

There are currently no known workarounds.

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Related Solutions

MATLAB: GLOBALFIMATH has no effect for FI objects in Fixed-Point Designer (R2012b)

MATLAB: Do I receive an error when I plot matrix signals from the Fixed-Point Settings interface in Simulink 6.0 (R14)

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