Cyclic Data Retention Time For System Switching In A Redundant System - Mitsubishi Electric MELSEC Q Series Reference Manual

7.5
Cyclic Data Retention Time for System Switching in a
Redundant System
This section gives calculation formulas for cyclic data retention time that is taken when a system switching occurs in a
redundant system.
(1) When the control system power supply module is faulty or powered off or
when the control system CPU is faulty or reset
(a) When a redundant system is the control station and "System switching time of
Redundant CPU (Tsw) < Control station switching time (Csw)" is met
Th = Csw+ SS [ms]
Th: Cyclic data retention time
Tsw: System switching time of Redundant CPU
Csw: Control station switching time = 20 + Constant link scan set value (
SS: Sequence scan time of Redundant CPU
*1 For details, refer to the following.
QnPRHCPU User's Manual (Redundant System)
Control station
Station No.1
System A 1
CPU scan time
Data sent from
0)
station No.1 to
another station
Control system
System A
System B Standby system
Normal station
Station No.2
System B
CPU scan time
Data sent from
station No.2 to
another station
Data received
at another
station from
station No.1 or 2
262
Communication error station
Power
down
1)
Standby system
Control system
System switching time
Control station
switching time
2
Cyclic transmission
delay time
0)
Cyclic data retention time
*1
*1
Sub-control station
4
3
3)
Cyclic transmission delay time
3)
1)
Page 201, Section 6.3.6 (1))
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