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Redundant PROFIBUS DP interface
1.6.3
Event list at redundancy
Summary of the
event list's
principle
36
Note:
• The PRIMARY state from the master can only be received by the slave if PROFI-
BUS DP master and slave are in data exchange because the master state is trans-
mitted in the cyclic data messages (byte "Control_O_1", ref. to chap. 1.4.1.4).
This also means:
• A slave module never can become PRIMARY if it is not in data exchange with
the master.
• A communication interruption of the PRIMARY channel always includes a redun-
dancy switchover to BACKUP because the PRIMARY state from the master then
is not received any more.
• Only one slave module has the PRIMARY state even if both PROFIBUS DP mas-
ters are PRIMARY at the same time.
• When a slave module after a redundancy switchover becomes PRIMARY then the
output data at this time are regarded as changed and will be passed on to the
SIPROTEC device.
• If there is an error in the RedCom communication, then both slave modules behave
independently and both modules also can become PRIMARY.
An error in the RedCom communication or in one of the modules can be detected
by the master using extended diagnosis data (ref. to chap. 1.4.2, bit "HW-Defect").
Every redundant PROFIBUS DP of the SIPROTEC devices also contains an event list
for transmission of indications with time stamp.
The mechanism for reading event list entries as well as the event list data types are
described in the manual "SIPROTEC Communication module, PROFIBUS DP - Com-
munication profile", chap. "Event list via PROFIBUS DP".
This chapter contains additional information which has to be observed if the event list
is used in redundant communication systems.
The event list is a ring buffer
cation which has to be transmitted via PROFIBUS DP also is entered with an identifi-
cation, the current value and the time stamp into the event list buffer.
In the cyclic input telegram to the master, an area for the transmission of three event
list entries is reserved.
If there are entries in the event list ring buffer then the (max. three) oldest entries are
copied in the input telegram and the sequence number in the "Control_I" byte (ref. to
chap. 1.4.1.1) is incremented.
The master now recognizes with the new sequence number that new event list entries
were sent. After that, it evaluates the entries and acknowledges the reading by copy-
ing the sequence number in the "Control_O" byte of the output telegram (ref. to chap.
1.4.1.3).
1. The size of the ring buffer (max. number of entries in the event list) can be defined in the
range of 10 to 1000 during configuration of the bus specific parameters in DIGSI.
The default value is 500.
1
which exists on each module. Every change of an indi-
SIPROTEC PROFIBUS DP - Bus mapping 6MD662/3/4
C53000-L1840-B011-03
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