RTU

The RTU heartbeat point, if defined, is updated once a second and cycles from a value of 1 to 60 during normal operation. If the interface is gracefully shutdown, the value of the RTU heartbeat point is set to 0.

If the RTU is deemed to be in a state that requires its link to be reset, the associated heartbeat point is set to the Unit Down digital state. For a TCP connection, the interface puts the RTU in a needs link reset state when the there is no valid socket connection established to the RTU. For a serial connection, the needs reset link state is determined if the serial port is in a fault state or if the RTU does not respond to requests from the interface in the allotted amount of time specified for the RTU.