This change has been incorporated into the documentation in Release 2011a (R2011a). For previous releases, read below for any additional information:
This is an issue when using the model reference block in accelerator mode. When you make the simulation mode for the referenced model to be "Accelerator", you are making the parameters, numerator and denominator tunable. The model reference code generated for this model has instances where we divide by the first element of the denominator array. Once you make a parameter tunable in code generation, we don't run any of the checks to make sure valid values are entered. Please refer to the the article Limitations on Accelerator Mode Referenced Models-> Run time checks
from the following link-
<http://www.mathworks.com/help/releases/R2011a/toolbox/simulink/ug/bqonbts-1.html#brazo0s-1_1>
To workaround this issue atleast one of the below options needs to be exercised:
1. Normal simulation mode for the referenced model
2. Avoid specifying a leading zero for the denominator matrix as it is redundant to have them.
