Redundancy Of Profibus Dp Connection - Siemens Add 7 AddFEM Manual

AddFEM
3.3.1

Redundancy of PROFIBUS DP Connection

The PROFIBUS DP channels are absolutely equivalent. The AddFEM changes the
channels at the recognition of a DP error, sign–of–life change/error or at the receipt
of a GCCL (Global Control Clear) message. The changeover of the DP channels
from the AP is always carried out via the sign of life. The variant 6DL3100–8AC
accepts the PrmCommand for changing over the DP channels in accordance with
PROFIBUS Guideline 2.212 and makes the redundancy status available as a dia-
gnosis.
DP A
DP B
Fig. 3-6
The connection between AddFEM and the AP is configured redundantly as
PROFIBUS DP A and PROFIBUS DP B. Each AddFEM has two PROFIBUS DP
connections. The two busses operate in parallel.
The input information (Input) is always transferred in parallel to both automation
processors. The outputs of the AddFEM can theoretically only "obey" one of the
two automation processors (AP A or AP B). Either the output data of the AP A or
the output data of the AP B are output by the AddFEM. For this reason a master–
reserve changeover with regard to the outputs is necessary on the AddFEM. The
output information of the passive AP is analyzed for monitoring purposes and then
rejected.
There are various changeover criteria for the output–specific changeover. As a re-
action to a coupling failure the system always changes over to the intact interface.
In case of a total failure, meaning that messages are not received on either of the
two interfaces, zero signals are output (safety–oriented control).
AddFEM
C79000–G8076–C900–03
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AP A
AP B
OUTPUT
INPUT
Redundant PROFIBUS DP connection
Mode of Operation
DP A DP B
Changeover
after error
OUTPUT
3-13