Trouble generating MEX/ C code for a function containing DSP System object constructor

Hi,

I am trying to generate a MEX file and C code for a function, but its failing and giving the following error:

   codegen genNCO -args {F0}
??? Cannot compute constant value for argument #4 for this System object constructor. All arguments to the constructor of this System object must be constants for code generation. One way to supply a constant value is to pass it to the main function using Simulink non-tunable parameters (for MATLAB Function block) or coder.newtype('constant',...) (for MATLAB Coder).

Error in ==> genNCO Line: 43 Column: 12
Code generation failed: Open error report.
Error using codegen

The function genNCO is defined as:

function y_NCO = genNCO(F0)
%#codegen

Points = 2^13;
Fs =  250e3;
Ts = 1/Fs;
minSFDR = 80; 
dphi = pi/2; 
Nacc = 13;
Nqacc = ceil((minSFDR-12)/6);
phIncr = round(F0*Ts*2^Nacc);
phOffset = 2^Nacc*dphi/(2*pi);%2^Nacc*dphi/(2*pi);
NaccType = numerictype([],Nacc);

% Declare System objects as persistent
persistent hnco;

% Initialize persistent System objects only once. Do this with 'if isempty(persistent variable).' This condition will be false after the first time. 

if isempty(hnco)
  hnco = dsp.NCO('PhaseIncrementSource', 'Property',...
      'PhaseIncrement', phIncr,...
      'PhaseOffset', phOffset,...
      'NumDitherBits', 4,...
      'NumQuantizerAccumulatorBits', Nqacc,...
      'SamplesPerFrame', Points,...
      'CustomAccumulatorDataType', NaccType);

end

y_NCO = step(hnco);
y_NCO = double(y_NCO.');

I also tried defining values needed by hnco as follows:

Nacc = coder.newtype('double',13);%ceil(log2(1/(df*Ts)));
Nqacc = coder.newtype('double',ceil((minSFDR-12)/6));
phIncr = coder.newtype('double',round(F0*Ts*2^Nacc));
phOffset = coder.newtype('double',2^Nacc*dphi/(2*pi));%2^Nacc*dphi/(2*pi);
NaccType = coder.newtype('embedded.fi',numerictype([],Nacc1));

but it didn't help and the build fails.

Can someone tell me how to pass these values to hnco as to have a successful build for MEX and C- code? Thanks.