Siemens 6MD662, Руководство пользователя

Страница: 23 / 86

Redundant PROFIBUS DP interface
23
SIPROTEC PROFIBUS DP - Bus mapping 6MD662/3/4
C53000-L1840-B011-03
•
If no indication changes were transmitted in the event list during a number of bus
cycles then the message block number remains unchanged in its value during this
time.
The same last transmitted message block number is transferred repeatedly until
new entries in the event list also effect changes to the message blocks that are
transferred, thereby incrementing the message block number.
Buffer overflow A set bit indicates an overflow of the event list buffer.
The buffer overflow bit is reset following acknowledgement of the current transmitted
message blocks if no new buffer overflow occurred in the meantime.
Message lost This bit is only used with activated redundancy function (otherwise always = 0).
If a reset of one of the PROFIBUS DP modules occurs then the module restarts with
an empty event list. If entries were contained before in the event list of this module
then after the module restart there exists an inconsistency between the event lists of
the two PROFIBUS DP modules in the device.
Also during the device start-up it may happen that one of the modules is updated and
operational before the other one and just at this time an indication change is transmit-
ted to the modules. But this indication change then only is entered in the event list of
the already operational module.
Such an inconsistency of the event lists is recognized during module start-up using
inter-module communication (RedCom).
If there are event list entries on the partner module which are not contained in the own
event list then the bit “Message lost” is set.
This bit automatically is reset if
•
the PROFIBUS DP master connected to this module is in PRIMARY state and has
read and acknowledged an event list entry,
•
both event lists are consistent again because all additional entries of the partner
module were read.
1.4.1.2 Control_I_1 byte
Control byte for the redundancy function.
Reference Standard mapping 3-3, ref. to chap. 3.2.4
Standard mapping 3-4, ref. to chap. 5.2.4
Bit assignment
Figure 1-5 Control byte “Control_I_1” (input direction)
Control_I_1
reserved = 0
0 1 2 3 4 5 6 7 Bit position
Meaning
Slave Prim
ar
y
Slav
e B
a
c
k
up
T
o
g
g
le bit
s
co
nf
irm
a
tion