The 20-sim tool-wrapper FMU uses 20-sim and its simulator to simulate the model. To exchange input and output signals between 20-sim and the FMI master (co-simulator), you will need to extend your model with special variables that can be set or read by the FMI master. These variables are the co-simulation inputs and outputs. They can be defined in the model in an equation section called externals:
real global export mycosimOutput;
real global import mycosimInput;
To make it possible to set or read a parameter by the co-simulation engine, it should be marked as 'shared':
// shared design parameters
real mycosimParameter ('shared') = 1.0;
The next step is to export a tool-wrapper FMU for the prepared model. See FMU Export for the details.