Mitsubishi Electric MELSEC iQ-R Series User Manual page 49

Setting method
Set the standby master station in the "Add New Module" window or "Station Type" in "Required Settings". ( Page 56
Station Type)
Precautions
■The number of standby master stations
One standby master station can be connected in one system.
■Data link control of a standby master station
When a master station goes down, data link control is automatically switched to a standby master station. Note that an
instruction to refresh cyclic data is not issued. Use a link special relay (SB) and link special register (SW) to issue a refresh
instruction. ( Page 49 Link special relay (SB) areas and link special register (SW) areas)
After the instruction is issued, information before a master station error is detected is output to each station.
■Change in the module parameter settings of the master station
While data link is performed by a standby master station, the module parameter settings of the master station cannot be
changed.
■Station number setting for a standby master station
If the station number of the standby mater station differs from that is set in "Network Configuration Settings" under "Basic
Settings" of the master station, an error (error code: B39A) occurs in the standby master station. If an error has occurred,
reset the CPU module of the standby master station after changing the module parameter settings of the master station or
changing the station number of the standby master station.
■If the terminal block of a master station is removed while the master station is controlling data
link
If the terminal block of a master station is removed without powering off the master station and reconnected, both of the
master station and standby master station will perform master operation because the right of controlling data link is transferred
to the standby master station; therefore, communications cannot be normally performed.
By powering off the master station and reconnecting the terminal block and powering on the master station, the master station
is reconnected as standby master station operation; therefore, communications can be normally performed.
■The status of an LED when data link control is switched to a standby master station
When the master station goes down and the standby master station starts to take in control of data link, the ERR. LED on the
standby master station flashes. The station number of the standby master station is changed from the one set in the module
parameters to the station number 0, and the standby master station is regarded that it is not connected. Data link is normally
performed.
To prevent this situation, set the standby master station as an error invalid station.
■Number of points and range of devices to save data using a program
The points and range of devices where data from a master station (station operating as a master station) to a standby master
station (station operating as a standby master station) are saved using a program vary depending on the system.
■If an error is detected in the master station in the initial status (before data link is started)
Data link control is not transferred to the standby master station and data link is not started. (This applies only to the master
station switching function and master station duplex function.)
■When the data link startup function by standby master station is used
• Parameters and program set in the master station and standby master station
Set the same module parameters and program in the master station and standby master station. If not, the operation is not
guaranteed.
• Line test
When the data link start function by a standby master station is used, a line test cannot be executed using the mode setting.
Use an engineering tool to execute a line test. ( Page 106 Line test)
1 FUNCTIONS
1.3 Standby Master Function
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