DP-Watchdog

For safety reasons, it is necessary to provide systems with highly effective protection functions against incorrect parameterization or failure of the transmission equipment. PROFIBUS-DP uses monitoring mechanisms on the DP master device and on the DP slave devices. For monitoring mechanisms that are implemented as time monitoring, monitoring intervals are specified during the configuration stage for the DP system.

The DPM1 monitors the user data transfer of the slave devices with the data control timer. A separate monitoring timer is used for each assigned slave device. The time monitor triggers if a proper transfer of user data does not take place within the monitoring interval. In this case, the user is notified. If the automatic Auto-Clear mode error reaction has been activated, the DPM1 leaves the Operate state in the event of an error, supplies the outputs of the associated slave devices with safe values and switches to the Clear operating state.

A slave device carries out communication monitoring in order to detect errors in the assigned master device or the transmission link. If a slave device does not experience any data traffic with the master device assigned to it within the response monitoring interval, the slave device automatically supplies its outputs with safe values.