What is the cause of the error message "FIMATH mismatch:Property 'ProductWordLength'" here?

I get the error message

FIMATH mismatch:Property 'ProductWordLength': 16 ~= 32

from the following action code in a state transition table:

 y = fi(10,0,32,10,'ProductMode','SpecifyPrecision','ProductWordLength',32,'ProductFractionLength',10)^x;

where x is defined as:

fixdt(0,8,5)

y is defined as:

fixdt(0,32,10)

The 16 seems to come frome the native number of bits in the hardware implementation details.

Following to this. Is there a short way to just calculate 10^x in the precision of y in StateFlow?

Answer 1

[Yash]

Hi Torsten,

The error you're encountering suggests a mismatch in the "ProductWordLength" property when performing the computations. The fi object you are creating for "y" specifies a ProductWordLength of 32, but somewhere in the computation, a ProductWordLength of 16 is being used, likely due to the default fimath settings or hardware constraints.

To calculate (10^x) with the precision of "y" in Stateflow, you can ensure the fimath properties are consistent across your calculations. Here's a way to do this:

1. Define a consistent fimath object: Create a fimath object with the desired properties and apply it to all fixed-point operations.
2. Use the fimath object in your computation: Ensure that your calculations are using this fimath object.

Here's an example of how you can achieve this:

% Define the value of x (example value, replace with actual input)
x_value = 3; % Example: x = 3

% Create a fixed-point object for x with the specified type
x = fi(x_value, 0, 8, 5);

% Define a fimath object with consistent properties for the calculation
myFimath = fimath('ProductMode', 'SpecifyPrecision', ...
                  'ProductWordLength', 32, ...
                  'ProductFractionLength', 10, ...
                  'SumMode', 'SpecifyPrecision', ...
                  'SumWordLength', 32, ...
                  'SumFractionLength', 10);

% Set the fimath property of x
x.fimath = myFimath;

% Create a fixed-point object for the base number 10
base = fi(10, 0, 32, 10, 'fimath', myFimath);

% Calculate 10^x with the precision of y
y = base^x;

% Display the result
disp(['10^', num2str(x_value), ' = ', num2str(y)]);

10^3 = 1000

Adjust the "x_value" to your specific needs or ensure that "x" is correctly defined elsewhere in your code. This approach should help resolve the fimath mismatch error and allow you to compute (10^x) using the desired precision.