Points To Note When Using Standby Master Function - Mitsubishi Electric M800VW Series Programming Manual

M800V/M80V Series PLC Programming Manual (2/2)
16 External PLC link
16.1 CC-Link

16.1.4.3 Points to Note When Using Standby Master Function

(1) Only one standby master station resides in a single data link system.
(2) The total number of stations is 64, including standby master station.
(3) If a master station error is detected in the initial state (before parameter communication starts), switching to the standby
master station won't be carried out.
(4) The data link control is automatically transferred to the standby master station in the event of the master station's failure,
but refreshing cyclic data won't be instructed.
Thus, give this instruction using the sequence program. For the instruction timing, refer to "16.1.4.4 ON/OFF Timings of
Link Special Relays (SB) Relating to Standby Master Function".
After the instruction, the information before the master station failure is output to each station.
(5) When the data link is being controlled by the standby master station, the master station's parameters cannot be updated.
(6) The error (error code: B39A) occurs at the standby master station if there is a difference between the standby master sta-
tion's station number setting (*1) and the number set with the master station's parameter "Standby master station No.".
If this error has occurred, change the master station's parameter setting, or change the station No. setting switch of the
standby master station, and then reset the standby master station.
(*1) If master station or standby master station is NC, the said parameter is "#24001+40(n-1) station No." and
"#24010+40(n-1) STBY master st".
("n" means channel No.)
(7) If you detach the master station's terminal block and then attach it again without turning OFF the power while the master
station is controlling data link, both the master and standby master stations operate as master stations, which will result in
an error (error code: BBC5). ("ERR." LED flashes)
(8) When the data link control is transferred to the standby master station at the master station's failure, the "ERR." LED of
the standby master station flashes.
(This is because the station No. of the standby master station will change from the one set with a parameter to zero and
the standby master station becomes absent. Data link itself is normally performed.)
To avoid this, set the standby master station to be an error cancel station.
(When NC is master station, the parameter to change is "#24126+15(n-1) set rsvd sta".)
("n" indicates n-th connected station.)
However, if you set the station to be an error cancel station, other errors can't be detected. Therefore, use it with caution.
(9) Among the data sent from (the station operating as) the master station to (the station operating as) the standby master
station, the point number and range of devices that will be saved by the sequence program may differ according to the
system used.
In the case of the example in "When master station controls data link" in the section "16.1.4.2 Overview of Link Data
Transmission When Standby Master Function Is in Use", the above-mentioned devices are in the shaded areas between
RX20 and RX5F.
931 IB-1501668-B