System Switching Time When A Redundant System Is Used - Mitsubishi Electric MELSEC iQ-RJ71EN71 User Manual

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.
System switching cause
Communication error detection (alive check error)
Communication error detection (ULP timeout occurrence)
Disconnection detection
*1 The meanings of the variables in the equation are as follows.
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)
APPX
390
Appendix 7 Processing Time
*1
System switching time [ms]
Tsi + (Ti  (Tr + 1)) + St + Tsw
Ttu + St + Tsw
Td + St + Tsw