Mitsubishi Electric MELSEC iQ-R Series User Manual page 176

• Program example
(0) Save the ON/OFF status of SM1636 (Previous control system identification flag) to 'System B restart flag' since SM1636 is on during only one scan
after the operating status of the CPU module has changed to RUN.
(3) Execute the subroutine program (P100) while 'System B restart flag' is on.
Jump to the END instruction not to execute the user program while 'System B restart flag' is on.
(41) Terminate the main routine program.
(57) Start measuring the timeout time (ten seconds (Timer limit setting: 100ms)) for the startup of previous control system.
Execute the SP.CONTSW instruction when the data link status of the network modules in the system B is normal and no system switching requests are
received from them. Wait until the information in SD1646 (System switching request status from a network module of the other system) is updated
(Two seconds). Check SD1646 for the system switching request status from the network modules in the system B.
Enable the manual system switching after the network module communications in the system B have been established successfully.
Execute the system switching instruction.
Turn off 'System B restart flag'.
Turn off 'System B restart flag' as well when the timeout time (ten seconds) has elapsed, because system switching is not performed and the CPU
module proceeds to the next scan to execute the user program while the system A remains as the control system. (The timeout time (ten seconds)
needs to be adjusted depending on the system configuration and environment.)
(79) Terminate the subroutine program.
■Precautions
In the user program, SM402 (After RUN, ON for 1 scan only) and SM403 (After RUN, OFF for 1 scan only) cannot be used
because the system switching instruction (SP.CONTSW) takes several scans to complete the processing. Use other devices
instead. For example, use an alternative device to SM402 to turn it ON on the rising edge of SM1636 (Previous control system
identification flag) and make it turn off after the first execution of the user program. Make an alternative device to SM403 to
turn on at the head of the next scan following the falling edge of the alternative device to SM402.
11 BASIC CONCEPT OF REDUNDANT SYSTEM
174
11.6 System Determination
User program