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Invalid root Inport/Outport block connection


Select the diagnostic action to take if Simulink® software detects invalid internal connections to this model's root-level Output port blocks.

Category: Diagnostics


Default: none


Simulink software silently inserts hidden blocks to satisfy the constraints wherever possible.


Simulink software warns you that a connection constraint has been violated and attempts to satisfy the constraint by inserting hidden blocks.


Simulink software terminates the simulation or code generation and displays an error message.


  • In some cases (such as function-call feedback loops), automatically inserted hidden blocks may introduce delays and thus may change simulation results.

  • Auto-inserting hidden blocks to eliminate root I/O problems stops at subsystem boundaries. Therefore, you may need to manually modify models with subsystems that violate any of the constraints below.

  • The types of invalid internal connections are:

    • A root output port is connected directly or indirectly to more than one nonvirtual block port:

    • A root output port is connected to a Ground block:

    • Two root Outport blocks are connected to the same block port:

    • An Outport block is connected to some elements of a block output and not others:

    • An Outport block is connected more than once to the same element:

    • The signal driving the root output port is a test point:

    • The output port has a constant sample time, but the driving block has a non-constant sample time:

    • The driving block has a constant sample time and multiple output ports, and one of the other output ports of the block is a test point.

    • The root output port is conditionally computed, you are using Function Prototype Control or a Encapsulated C++ target, and the Function Prototype specification or C++ target specification states that the output variable corresponding to that root output port is returned by value.

Command-Line Information

Parameter: ModelReferenceIOMsg
Value: 'none' | 'warning' | 'error'
Default: 'none'

Recommended Settings

DebuggingNo impact
TraceabilityNo impact
EfficiencyNo impact
Safety precautionerror

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