By default, models are configured to enable low-level debugging, where the simulation pauses within a time step, as soon as the condition for a breakpoint is met. When you clear this parameter, the simulation pauses at the end of the time step where the condition for a breakpoint is met.

Low-level debugging is supported only for normal mode simulations. This option has no effect on accelerator and rapid accelerator simulations.

When you enable low-level debugging, you have more options on the Debug tab for controlling how to step through the simulation.

Using the check box next to each breakpoint in the Breakpoints List, you can enable and disable individual breakpoints during and between debugging sessions. When the check box is selected, the breakpoint is active, and the simulation pauses when the condition for the breakpoint is met. When the check box is cleared, the breakpoint is inactive, and the simulation does not pause because of that breakpoint.

To enable or disable all breakpoints configured in the model, click Enable or disable all breakpoints .

The Breakpoints List contains a row for each signal breakpoint you configure in the model. Each signal breakpoint has a condition, and the simulation pauses when the signal value satisfies that condition. The condition consists of a relational operator, such as equals (=) or greater than (>), and a value. For example, for a signal breakpoint condition of > 1, the simulation pauses when the signal value is greater than one.

Signal breakpoints do not support specifying the condition using variables, expressions, or symbols such as π (pi).

Signal breakpoints are supported for only Simulink signals and are not supported for other types of signals, such as Simscape™ signals.

Signal breakpoints are supported only for real scalar signals with these data types:

These additional limitations for port value labels also apply for signal breakpoints Additional Considerations for Using Port Value Labels.

By default, no model breakpoints are configured for a model. To add the zero-crossing breakpoint to a model, on the Debug tab, click the button arrow next to Add Breakpoint and select Zero Crossing. After you add the zero-crossing breakpoint, you can enable and disable the zero-crossing breakpoint from the Breakpoints List during and between debugging sessions for the model.

When the simulation pauses due to an active zero-crossing breakpoint, the Simulink Editor opens a tab to display the subsystem or model that contains the block where the zero crossing occurred and highlights the block in green.

By default, no model breakpoints are configured for a model. To add the NaN or Inf value breakpoint to a model, on the Debug tab, click the button arrow next to Add Breakpoint and select NaN or Inf Value. After you add the NaN or Inf value breakpoint, you can enable and disable the NaN or Inf value breakpoint from the Breakpoints List during and between debugging sessions for the model.

When the NaN or Inf value breakpoint is enabled for a model, the simulation pauses when a computation results in a NaN or Inf value. NaN or Inf values can occur when the computation result is infinite or outside of the range of values supported by the machine running the simulation.

When the simulation pauses due to an active NaN or Inf breakpoint, the Simulink Editor opens a tab to display the subsystem or model that contains the block where the NaN or Inf value occurred and highlights the block in green.

Use the NaN or Inf value breakpoint to help locate the site of computational errors in a model.