PLC coder/ errror Message 'The FixedStepDiscrete solver cannot be used'/

Hi there, I have a state space model, with single input and 4 outputs. it is a continuous model. when I try to check PLC compatibility, it shows the error 'The FixedStepDiscrete solver cannot be used to simulate block diagram 'Subsystem' because it contains continuous states. Which solver can I use for the system, to generate IEC structured text code? any suggestions? Thanks in advance.

[dada hamid]

Please someone answer it , that's my question too.