Mitsubishi Q12PRHCPU - Page 246

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6.2 Redundant System Network Overview
6.2.2 MELSECNET/H Remote I/O network
6
REDUNDANT SYSTEM NETWORKS
(8) Detecting Configuration Mismatch for the Remote I/O Station in the
Master Station and Sub-master Station
When a disconnection occurs in the system connected to the MELSECNET/H
multiplexed remote I/O network, the accessible remote I/O stations might be different
between the control system (master station) and standby system (sub-master station).
In this case, as control cannot be continued after system switching, the "UNIT LAY.
DIFF. (error code: 6036)" stop error (specific to the standby system in the backup
mode) occurs in order to prevent system switching.
The abovementioned operation, i.e., checking whether the accessible remote I/O
stations for the master station and sub-master station are identical, is called the
"network separation check".
The "UNIT LAY. DIFF" occurs in the MELSECNET/H multiplexed remote I/O network
that uses optical cables, when a disconnection occurs simultaneously at the following
locations.
• Between the master station and sub-master station
• Other than above location
In the diagram below, the "UNIT LAY. DIFF" occurs when a disconnection occurs
simultaneously at point A and any of point B to D.
Table6.2 shows the transmission possibilities when a disconnection occurs at Point A
only and when a disconnection occurs simultaneously at Point A and Point C.
:Possible, :Not Possible
Diagram 6.18 Error Detection at Cable Disconnection
Table6.2 Transmission Possibilities when Disconnection Occurs at Point A and Point C
At Point A Only At Points A and C
System A CPU
Module
System B CPU
Module
System A CPU
Module
System B CPU
Module
1 Station
2 Stations
3 Stations
Control system
Standby
system
Tracking cable
MELSECNET/H Remote I/O network
Remote I/O station
(station No. 3)
Remote I/O station
(station No. 2)
Multiplexed Remote
Master Station
(station No. 0)
UNIT LAY. DIFF.
(When Point A and any of
Point B-D are simultaneously
disconnected)
Multiplexed Remote
Sub-master Station
(station No. 1)
Point A
Point C
Point D Point B