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APPX
Appendix 7 Processing Time
System switching time when a redundant system is used
The following shows the system switching time when the Ethernet-equipped module mounted on the control system in the
redundant system detects a communication error or cable disconnection and sends a system switching request to the control
system CPU module. System switching time is the time from communication error or cable disconnection detection to when
the control system CPU module is switched over.
■Calculation formula
The following is the formula to calculate the system switching time.
*1
*1 The meanings of the variables in the equation are as follows.
System switching cause System switching time [ms]
Communication error detection (alive check error) Tsi + (Ti (Tr + 1)) + St + Tsw
Communication error detection (ULP timeout occurrence) Ttu + St + Tsw
Disconnection detection Td + St + Tsw
Variable Meaning
Tsi Destination alive check start interval timer [ms] ( Page 260 Timer Settings for Data Communication)
Ti Destination alive check interval timer [ms] ( Page 260 Timer Settings for Data Communication)
Tr Destination alive check resend count ( Page 260 Timer Settings for Data Communication)
St 1 scan time [ms] ( MELSEC iQ-R CPU Module User's Manual (Application))
Tsw CPU module system switching time [ms] ( MELSEC iQ-R CPU Module User's Manual (Application))
Ttu TCP ULP timer value [ms] ( Page 260 Timer Settings for Data Communication)
Td Disconnection detection monitoring time [ms] ( Page 276 Redundant System Settings)
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