6. REDUNDANCY WITH NX3030 CPU
Direct Variable
AT variable
DG_NX4010.tRedundancy.
RedCmdLoc.*
Description
Variable Bit
4 bResetNETStatisticsRemote
TRUE – This command produces an equiv-
alent action to the ResetNETStatisticsLo-
cal button on the PX2612 in the remote
PLC.
FALSE – The reset commands for the
NETA / NETB statistics in the remote PLC
wasn’t activated.
5..7 bReserved[5..7] Reserved.
Table 214: Redundancy Commands
6.6.4.3. User Information Exchanged between PLCA and PLCB
The Diagnostics and Commands Exchange Synchronization service, in each MainTask cycle, exchange the following data
structures between both PLCs, using the NETA / NETB synchronism channels:
Redundancy Diagnostics (RedDgnLoc and RedDgnRem), already described in the Redundancy Diagnostics Structure
section
Redundancy Commands (RedCmdLoc and RedCmdRem), already described in the Redundancy Commands section
User Information Exchanged between PLCA and PLCB (RedUsrLoc and RedUsrRem), which are described in this
section
The RedUsrLoc and RedUsrRem structures are simply a 128 bytes array, which utilization can be freely defined by the
user. They allow the user to transfer, each cycle, 128 bytes of information from PLCA to PLCB, and other 128 bytes from
PLCB to PLCA.
RedUsrRem is a copy from the other PLC RedUsrLoc, received through NETA / NETB. A specific PLC writes information
on RedUsrLoc, which are read in the RedUsrRem of the other PLC.
These data structures have many utilities. E.g. supposing the SCADA system is connected only to the Active PLC and it’s
desired to visualize some information from the Non-Active PLC. The Non-Active PLC can put this information in these data
structures. Among such information, for instance, might be some not mapped diagnostics in RedDgnLoc and RedDgnRem.
6.6.4.4. Modbus Diagnostics used at Redundancy
To check for failure in all MODBUS Server configured in a MODBUS Client instance, there is a specific diagnosis in each
MODBUS Client instance configured. The table below displays the diagnostics for this type of failure in a MODBUS Client
instance called MODBUS_Symbol_Client.
Variable
DG_MODBUS_Symbol_
Client.tDiag.*
Description
bAllDevicesCommFailure
TRUE – All servers configured at this
Client shows error.
FALSE – There is at least one Server con-
figured in this Client that doesn’t shows er-
ror.
Table 215: Modbus Client Diagnostic
When configured vital failure mode, this diagnostic is consulted and 3 seconds after it’s state change from FALSE to TRUE,
a switchover occurs if the other conditions for this event are satisfied.
347
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