Fig. 8 Ethercat Tab --> Advanced Settings --> Behavior --> Watchdog - Beckhoff EP3356-0022 Documentation

Basics of communication
Fig. 8: EtherCAT tab --> Advanced settings --> Behavior --> Watchdog
Comments:
• The multiplier applies to both watchdogs.
• Each watchdog has its own timer setting, which together with the multiplier results in a time.
• Important: The multiplier/timer setting is loaded into the slave on start-up, if the corresponding
checkbox is ticked. If the checkbox is not ticked, no download takes place, and the ESC setting
remains unchanged.
Multiplier
Both watchdogs receive their pulses from the local terminal/box clock, divided by the watchdog multiplier.
1/25 MHz * (watchdog multiplier + 2) = 100 µs (for default setting of 2498 for the multiplier)
The standard setting of 1000 for the SM watchdog corresponds to a release time of 100 ms.
The value in multiplier + 2 corresponds to the number of basic 40 ns ticks representing a watchdog tick.
The multiplier can be modified in order to adjust the watchdog time over a larger range.
Example "Set SM watchdog"
This checkbox enables manual setting of the watchdog times. If the outputs are set and the EtherCAT
communication is interrupted, the SM watchdog is triggered after the set time and the outputs are deleted.
This setting can be used for adapting a terminal to a slower EtherCAT master or long cycle times. The
default SM watchdog setting is 100 ms. The setting range is from 0 to 65535. Together with a multiplier in a
range from 1 to 65535, this covers a watchdog period of 0 to ~170 seconds.
Calculation
Multiplier = 2498 → watchdog base time = 1 / 25 MHz * (2498 + 2) = 0.0001 seconds = 100 µs
SM watchdog = 10000 → 10000 * 100 µs = 1 second watchdog monitoring time
18 Version: 1.1.0 EP3356-0022