Mitsubishi Electric MELSEC iQ-R Series User Manual page 404

■Asynchronous tracking mode
In the asynchronous tracking mode, the control system starts the next scan without waiting for notifications of data reception/
reflection completion from the standby system.
Unlike the synchronous tracking mode, the scan time is not affected by waiting time for data reception/reflection completion.
When the standby system does not receive the tracking data from the control system, the standby system starts the next
scan.
Ex.
When the CPU module of the control system is in the RUN state and the CPU module of the standby system is in the STOP
state (in a redundant system without extension base units
Scan time of the control system CPU module
I/O refresh
Control system
CPU module
I/O refresh
(input only)
Standby system
CPU module
Scan time of the standby system CPU module
*1 If the constant scan is used, waiting time for the constant scan is generated.
*2 In a redundant system with redundant extension base unit, the processing order in the scan is different ( Page 81 In redundant
mode), but the operation is the same as in a configuration with main base units only.
In the control system, the scan time is extended by the following tracking send processing time.
Item
(1) Tracking send (2) Waiting for completion of tracking
processing
(3) Sending tracking data
In the standby system, the scan time increases by the following tracking receive processing time.
Item
(5) Tracking receive (6) Waiting for tracking data reception
processing
(7) Reflecting tracking data
■When the mode is switched from the asynchronous tracking mode to the synchronous
tracking mode
When the mode is switched from the asynchronous tracking mode to the synchronous tracking mode, the standby system
receives the tracking data twice in one scan. Therefore, the scan time of the standby system is extended by the following time.
Scan time of the standby system: Standby system scan time  2 + Control system scan time
26 REDUNDANT FUNCTION
402
26.3 Tracking Transfer
END
(1)
(3)
MAIN
(2)
Tracking data
(6) (6) (6)
END END END
data reflection
*2
)
END
*1
MAIN
(4)
(2)
Data Data
received reflected
(6) (7)
(5)
END
Description
After receiving a notification of the reflection completion from the standby system, the
control system sends the tracking data.
When a notification of reflection completion is not arrived (4), the control system does not
send tracking data in the scan.
The control system sends the tracking data. After completing the send, the control system
starts another END processing without waiting for a notification of receive completion from
the standby system.
Description
The standby system receives the tracking data from the control system. When the standby
system does not receive the tracking data, the standby system starts the next scan.
After receiving the tracking data, the standby system notifies the control system of the
receive completion and reflects the tracking data.
The standby system reflects the tracking data. After the reflection completion, the standby
system notifies the control system of the reflection completion and starts the next scan.
*1
MAIN
(2)
(6) (6) (6)
END END END
END
(1)
(3)
*1
Tracking data
(6)
END END