Standby Master Function - Mitsubishi Electric MELSEC-Q Series User Manual

8.2.5

Standby master function

If the master station goes down due to an error in a CPU module, power supply, or others, switching the control to the
standby master station (a backup station for the master station) continues data link. This function is used not to stop
the entire system even if the master station goes down.
(1) Types of the standby master function
The standby master function can be categorized into three types as listed below.
Function
Master station switching function
Master station duplex function
Data link start function using a
*2*3
standby master station
*1 A standby master station does not start data link until the master station starts up.
*2 Configure the same system for the master station and standby master station (same modules connected, parameters,
and program).
*3 Before using this function, check the version of the master/local module. (
(2) Operation of the standby master function
The following are the operations of the master station and standby master station of when the master station goes
down. The following figure shows the operation until a failed master station goes back to normal after the standby
master station starts to operate as a master station and data link is continued.
Controlling: Controlling the data link of the CC-Link system
Standby status: Standing by in case the station controlling the data link of the CC-Link system becomes faulty.
Data link control by the master station
Master station
Controlling
Cyclic transmission
Master station
Cyclic transmission
*1 When the master station goes down and the standby master station starts to take in control of data link, the station
number of the standby master station becomes 0.
When the master station goes
down, the standby master
station operates as a master
station to continue data link.
Remote device station
Station number 2
The number of occupied stations: 2
Cyclic transmission
Remote device station
Station number 2
The number of occupied stations: 2
Cyclic transmission
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When a failed master station
becomes normal again, it
return as a standby master
station.
×
Intelligent device station
Station number 4
The number of occupied stations: 1
Cyclic transmission
Intelligent device station
Station number 4
The number of occupied stations: 1
Cyclic transmission
CHAPTER 8 FUNCTIONS
: Enabled, ×: Disabled
When only a standby master
station is started up, it starts
data link as a master station.
*1
×
*1
×
Page 399, Appendix 6 (2))
Standby master station
Station number 1
The number of occupied stations: 1
Standby status
Standby master station
1
Station number 1 0
Controlling
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