29 PRECAUTIONS ON PROGRAMMING
29.1 Instructions Not Available in Redundant System
505
29
■REMTO instruction
When the system switching is performed while the instruction is being executed (M101 = ON), SM1643 (ON only in one scan
after system switching (standby to control)) will turn on for one scan in the new control system and the REMTO instruction will
be executed again on the station number 10 of the network number 1. When the system switching is performed while a write
instruction such as the REMTO instruction is being executed, execution of the instruction may have been suspended before
completion of writing data to the target module. Thus, insert an interlock in the new control system to read the X signals and
buffer memory status of the target module and to determine whether or not to execute the instruction again.
• DEVICES
*1 For details on the link special relays (SB) and link special registers (SW), refer to the manuals for the network used.
*2 Change the device number according to the system.
• Program example
DEVICES Data stored
SM1643 System switching check flag (standby system to control system)
SB47
*1
Baton pass status of own station
SW0A0.9
*1
Baton pass status of each station
M100
*2
Write request
M101
*2
At instruction execution
M102
*2
ON at instruction re-execution request due to system switching
M103
*2
Completed without an error
M104
*2
Completed with an error
(1) Add an interlock circuit for determining whether or not to execute the instruction again (according to the X signals and buffer memory status of the target
module) as required.
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