Mitsubishi QJ71LP21 Reference Manual page 355

8 TROUBLESHOOTING
Error
Code Error Contents and Cause
*1
(SD0)
• Since the standby system is in an
error or similar status in the
redundant system, the control
system cannot be switched to the
standby system.
• When an attempt was made to
execute system switching, the
control system could not be
switched to the standby system due
to a network error of the control
system.
6220
System switching cannot be executed
as the standby system or tracking
cable is faulty in a redundant system.
The following shows the reasons for
system switching on the control
system.
• System switching by SP. CONTSW
instruction
• System switching request from
network module
Switching is disabled because of a bus
6221
switching module error.
The link module mounted on the
6230 standby type CPU is the remote
master station.
*1 : Characters in parentheses ( ) indicate the special register numbers where individual information is being
stored.
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Corrective Action
Check the standby system condition.
Check the status of the standby
system and resolve the error.
This is a bus switching module
hardware fault. (Contact your local
Mitsubishi representative.)
Check the system configuration status.
MELSEC-Q
Corresponding
CPU
Q4AR
QnPRH
Q4AR
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