Burkert Type 8644 - Manual (Page 83)

8644/phoenix - 79
S
YSTEM
D
ESCRIPTION
In the profibus, broadcast messages indicate the status of the PLC.
CPU313C-2 DP for example is a CPU that displays its status to other participants in the network via
broadcasts of this type. The DPV1 field bus node decides on the basis of these reports whether process
data values or security values should be issued.
The DPV1 field bus node initially starts with the security values after the parameter telegram has been
received. If it receives a broadcast, the security values are either retained or converted to process data
operation, according to the status of the PLC.
If no broadcast is sent, the option of data exchange without broadcast operate is relevant. The option not to
have the device wait for the broadcast from the control can be set in the parameter telegram. In this event,
the process data exchange is recorded following parameterization and configuration on receipt of the first
data telegram.
Control stop example:
The control stop is displayed via a broadcast from the CPU313C-2 DP. The security values are cut in
immediately. If the PLC does not display the control stop or if the data exchange without
broadcast operate
option is not activated, the security values are triggered when the watchdog time lapses. The previous
process data remain valid until that point.
Analysis of the broadcast is adjustable for the DPV1 field bus node in bit 5 of the control byte (parameter
telegram, byte 11, see
Parameter telegram section).
Data Exchange and Global Command Operate