Burkert Type 8644 - Manual (Page 72)

68 - 8644/phoenix
S
YSTEM
D
ESCRIPTION
The watchdog checks the receipt of telegrams within a pre-set, maximum time. If no valid telegram is
received during this time, the security settings on the slave become active. These concern the output
modules in particular. A failsafe value is issued as a substitute value.
This also means that communication with the master has ceased (e.g. cable disruption). When the
communication between master and slave has been restored, the slave must start up normally (with
parameterization and configuration telegram). This ensures the re-alignment of the local configuration and
the configuration deposited on the PLC.
There are the options to activate/de-activate the watchdog and, when the watchdog is activated, to
parameterise the time. In doing so the values can be set between 0 (no monitoring) and 650 s in steps of at
least 10 ms. A series of configuration tools takes over the setting for the user, since selecting the
monitoring time can also become more complex (e. g. due to cycle times that depend on the network as
whole).
In STEP7 the watchdog monitoring is activated / de-activated in the HW config. under DP slave properties:
Illustration:
Activating the
watchdog
The duration of the watchdog is set as follows:
Network settings / DP master system properties / Properties / Network settings / bus parameters
Watchdog