How do I debug Matlab NCO HDL Optimized in loop error?

I have a simulink file set up as follows:

With a simple state transistion chart:

with the NCO settings as follows:

When I attempt to compile the model, I get the following error:

"Dimensions of the input port 1 are unknown for MATLAB System block "myfile/NCO HDL Optimized1". This can happen when the input port is in a loop, is driven by a Ground block or a source with unspecified dimensions, or if the input port has unconnected signal lines. Consider adding a Signal Specification block with specified dimensions in front of the input port."

I've tried fiddling with the inc port data type converter but have been unable to get rid of the error and searching doesn't seem to bring up much information. However it will work if I remove the state chart.

What debugging steps should I take?

Can anyone explain this error?

What does the question mark denote on the simulink diagram?

Answer 1

[Bharath Venkataraman]

The NCO block is unable to determine the data types of its inputs. Please put in a Signal Specification block in front of the increment input and specify the datatype, size ([1 1] is scalar) and complexity.

Answer 2

[Kiran Kintali]

Can you please try making the chart "Moore" machine?

Thanks

[Lee Thomas]

Thanks, I get an error saying that state actions are not allowed in Moore charts (e.g. "entry")