Watchdog function

Watchdog function, Index 0x80n0:05

Most EtherCAT terminals are equipped with a safety device (watchdog) that switches the outputs to a defined state, for example in case of interrupted process data traffic.

The watchdog time is set via the general TwiNCAT dialog

"Advanced Settings" -> General -> Behavior -> Watchdog -> "Set Multiplier" and "SM Watchdog":

A maximum watchdog time of 65 s is possible. Larger values are calculated modulo 65, for example 70 s would be shortened to 5 s.

Note
	General information on watchdog settings Observe the general notes on the watchdog setting.

The procedure is as follows:

• As long as the terminal is properly and regularly supplied with EtherCAT process data, it outputs them. The so-called watchdog observes this without further action; they say, "it is being brought up".
• As soon as the data stop arriving, the output value remains at the last value. The watchdog now starts to run down. If data arrive again in time, the watchdog returns to the starting value.
• If it has expired, i.e. the set time has elapsed without new data arriving, the substitute value is output.
• As soon as new data arrive, they are output again and the watchdog observes anew.

The following settings can be made for the substitute value in index 0x80n0:05:

• "Default watchdog value":
  The analog output value is set to a user-specific value. This must have been stored in "Default output" (index 0x80n0:13) beforehand and is then output in the watchdog case.
  This is the default setting with "Default output" = 0. In the watchdog case, a terminal operated in this way outputs 0.
• "Watchdog ramp":
  The user-specific value "Default output" is approached from the last valid output value as a linear ramp over a predetermined time. This time is entered via "Default output ramp" (index 0x80n0:14) in digits/ms.
• "Last output value"
  With this setting, the last valid output value is retained.