Enable External mode to tune and monitor a model while it runs on your hardware board. With External mode, changing a parameter value in the model on the host changes the corresponding value in the model running on the hardware. Similarly, scopes in the model display data from the model running on the hardware.
Enabling External mode adds a lightweight server to the model running on the hardware board. This server increases the processing burden upon the hardware board, which can result in an overrun condition. If you enable the Enable overrun detection check box, and the software reports an overrun, consider disabling External mode. Enabling the External mode parameter makes the following communication-related parameters visible: Set host COM port LEGO® MINDSTORMS® NXT hardware and Arduino® Mega 2560 hardware TCP/IP port (1024-65535) for BeagleBoard hardware Enabling the External mode parameter disables the Enable communication between two NXT bricks parameter LEGO MINDSTORMS NXT hardware.