matlab的simulink中出现警告VariableStepDiscrete' instead of solver 'ode45'

在simulink中自己构建了一个DSPBuilder的文件，仿真时出现如下警告：

Warning: The model 'MM_chaos_text1_simple' does not have continuous states, hence Simulink is

using the solver 'VariableStepDiscrete' instead of solver 'ode45'. You can disable this
diagnostic by explicitly specifying a discrete solver in the solver tab of the Configuration
Parameters dialog, or by setting the 'Automatic solver parameter selection' diagnostic to 'none'

in the Diagnostics tab of the Configuration Parameters dialog 

意思是说你的model里面不连续，应该使用VariableStepDiscrete仿真模式，而不是ode45模式。
有两种更改方法：
1、在该model的工具栏上选择simulation，再选择并进入configuration parameters界面，从solver里面设置，type设置为variable-step，solver设置为discrete；
2、或者在Diagnostics子菜单里将'Automatic solver parameter selection' 设置为none。