Burkert Type 8644 - Manual (Page 71)

8644/phoenix - 67
S
YSTEM
D
ESCRIPTION
Entry into effect of the failsafe values
Failsafe values become valid
• there is no connection to the PLC (watchdog).
One example of this is a severed or unattached cable. If the watchdog period has lapsed without any
telegrams being received, then the substitute values is issued when the watchdog is activated.
• the control is on Stop.
No process data are being exchanged. As soon as the control indicates that it is on stop, the substitute
values is used. Various controls show their status at intervals via a broadcast.
• no process data circulation takes place following a power-up, yet the parameter telegram has already
been received.
There is the possibility that the PLC is already on RUN, but the participant is only now being switched
on. In this event the station receives a parameter and configuration telegram. However, it is not
guaranteed that the status of the control (RUN/STOP) is already know or that valid data telegrams will
follow directly. Therefore, the security values which have already been transmitted in the parameter tele-
gram are issued.
Depending on the parameter and working environment it cannot be guaranteed that the configuration
telegram will be transmitted immediately after the parameter telegram. Therefore make sure that the
planned configuration is identical to the attached configuration. You thus ensure that the security values
from the parameter telegram can be issued safely with the aid of the configuration even before
verification.
When the security values are being transmitted, the BF LED flashes. This shows that the output data
are under the control of the local slave.